JP6028509B2 - Semiconductor laser device - Google Patents

Description

  The present invention relates to a semiconductor laser device using an edge-emitting semiconductor laser element having a photonic crystal.

  The inventors of the present application have proposed a semiconductor laser element using a photonic crystal (Patent Document 1, Non-Patent Document 1, etc.). Such a surface-emitting type semiconductor laser device has an epoch-making feature that laser beams can be emitted simultaneously in two directions at a time. In addition, by supplying a driving current to the driving electrodes divided into a plurality, it is possible to emit a laser beam in two directions for each driving electrode. If the period of the photonic crystal located directly under each drive electrode is made different, the emission angle of the laser beam pair will be different for each drive electrode. Furthermore, according to Non-Patent Document 1, continuous beam direction control can be performed by providing subdivided drive electrodes, allowing current to flow simultaneously through a plurality of drive electrodes, and changing the current balance.

JP 2009-76900 A

Taketaka Kurosaka et al., "On-Chipbeam-steeringphotonic-crystal lasers", Nature Photonics, vol. 4, pp.447-450, 2010

  However, practical applications are limited in the case of a semiconductor laser element that simultaneously emits laser beams in two directions. On the other hand, in the case of a semiconductor laser element that emits a laser beam in a predetermined direction, that is, in a structure that can emit a laser beam in a predetermined direction for each drive electrode, the drive current supplied to each drive electrode is switched. Further, the laser beam can be scanned by changing the drive current balance. In this case, the semiconductor laser element can be applied to various conventionally used laser beam deflecting devices. If the number of laser beams is increased, the laser beam deflecting device can constitute a high-definition laser beam scanning device.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a semiconductor laser device that emits a laser beam in a predetermined direction and can change the emission direction. .

  As a result of intensive studies, the present inventors have found that the lower cladding layer, the upper cladding layer, the active layer interposed between the lower cladding layer and the upper cladding layer, the active layer and the upper and lower claddings formed on the substrate. A photonic crystal layer interposed between at least one of the layers, and a plurality of drive electrodes for supplying drive electrodes to the plurality of regions of the active layer, wherein the plurality of regions of the active layer are on the light emitting end face The inventors have conceived semiconductor laser elements that are parallel and are arranged side by side in the first direction in which the active layer extends, and in which the emission directions of the laser beams emitted from the light emission end faces are different from each other. According to this semiconductor laser element, it is possible to emit a laser beam in a predetermined direction and change the emission direction.

  In the semiconductor laser element, the emission direction of the laser beam with respect to the light emission end face is different for each emission position of the laser beam on the light emission end face. For this reason, when the conventional cylindrical lens or toroidal lens etc. were used as a collimating lens in order to collimate the emitted laser beam, it became clear that the following new problems existed. That is, the focal length varies depending on the emission direction with respect to the light emission end face, and it is difficult to ensure equivalent collimating characteristics for all emitted laser beams. As the emission direction with respect to the light emission end face increases, the optical path length between the emission position of the laser beam on the light emission end face and between the lenses increases. For this reason, collimated light can be obtained only with a laser beam emitted from a specific emission position and having a specific emission angle. Further, the height in the vertical direction of the collimated light emitted from the collimating lens also varies depending on the emission direction with respect to the light emission end face.

  Therefore, the present inventors have further studied earnestly about a configuration for ensuring equivalent collimation characteristics regardless of the laser beam emission direction, and the laser beam emitted while setting the direction of the emitted laser beam as a predetermined direction. The inventors have arrived at a semiconductor laser device capable of switching the beam direction and ensuring the same collimating characteristics.

  A semiconductor laser device according to the present invention is a semiconductor laser device comprising an edge-emitting semiconductor laser element and a collimating lens that collimates a laser beam emitted from the semiconductor laser element. A lower cladding layer, an upper cladding layer, an active layer interposed between the lower cladding layer and the upper cladding layer, and an active layer interposed between at least one of the upper and lower cladding layers. A plurality of drive electrodes for supplying a drive current to a plurality of regions located in a first direction parallel to the light emission end face and extending in the first direction in the active layer in the active layer; A plurality of laser beams are emitted in different directions from positions corresponding to a plurality of regions on the light emitting end face, and the collimating lens is disposed on the light emitting end face. The front surface and the rear surface have curvatures in the cross section including the first direction and the optical axis so that the optical path lengths from the respective positions corresponding to the plurality of regions to the front main plane are equal, and the collimating lens is formed from the semiconductor laser element. The plurality of emitted laser beams are refracted and emitted in a plane parallel to the thickness direction of the semiconductor laser element.

  In the semiconductor laser device according to the present invention, the emission direction of the laser beam with respect to the light emission end face is different for each emission position of the laser beam on the light emission end face (positions corresponding to a plurality of regions on the light emission end face). The front surface and the rear surface have a curvature in the cross section including the first direction and the optical axis so that the collimating lens has the same optical path length from each position corresponding to a plurality of regions on the light emitting end surface to the front main plane. Therefore, when each laser beam emitted from the semiconductor laser element is incident on the collimating lens, it is refracted in a plane parallel to the thickness direction of the semiconductor laser element, and the width in the thickness direction of the semiconductor laser element is uniform. It is emitted as a plurality of parallel lights. Therefore, in the present invention, the same collimating characteristic can be ensured for each laser beam regardless of the laser beam emission direction.

The collimating lens has a refractive index n, a front radius of curvature R ₁ , and a rear radius of curvature R ₂ ,
F (θ) = {(n−1) × (1 / R ₁ + 1 / R ₂ )} ⁻¹
The front curvature radius R ₁ and the rear curvature radius R ₂ may be set so that the focal length F (θ) represented by the following formula is constant.

  In the collimating lens, the curvatures of the front surface and the rear surface in the cross section including the first direction and the optical axis are constant, the optical path length from each position corresponding to a plurality of regions on the light emitting end surface to the front main plane, and the collimating lens The focal length may be substantially the same. In particular, even when the radius of curvature of the front surface and the rear surface of the collimating lens in the cross section including the first direction and the optical axis is larger than the size of the semiconductor laser element, each laser beam is independent of the laser beam emission direction. Can ensure the same collimating characteristics.

The center of curvature of the front surface and the rear surface in the cross section including the first direction and the optical axis is located at the center in the first direction of the semiconductor laser element, and the coordinate axis parallel to the first direction is defined as X from the center of curvature of the front surface and the rear surface The coordinate axis perpendicular to the light emitting end face is the Y axis, the width of the semiconductor laser element in the X-axis direction is W, and the angle θ formed by the laser beam with respect to the normal of the light emitting end face is the semiconductor laser element Is 0 at the center in the first direction and increases toward the end of the semiconductor laser element in the X-axis direction, and the maximum value of the angle θ at the end of the semiconductor laser element in the X-axis direction is θ _max . Sometimes, the position y ₀ in the Y-axis direction of the light emitting end surface with respect to the center of curvature is
y ₀ <W / (2 × tan θ _max )
And the angle θ at position x along the X axis is
θ = atan (x / y ₀ )
The collimating lens has a focal length F (θ) with respect to an angle θ when the optical path length between the center of curvature of the front and rear surfaces and the front main plane is OP,
F (θ) = OP−y ₀ × (1 + tan ² θ) ^1/2
May be defined based on Even when the radius of curvature of the front and rear surfaces of the collimating lens in the cross section including the first direction and the optical axis is close to the size of the semiconductor laser element, the same collimation is achieved for each laser beam regardless of the laser beam emission direction. Characteristics can be secured.

The collimating lens has y ₀ × ((1 + tan ² θ) ^1/2 −1) in the radial direction of the curvature of the front and rear surfaces of the front main plane.
It may be positioned away from the semiconductor laser element only.

When the position of the semiconductor laser element in the X-axis direction is away from the origin, the position of the semiconductor laser element in the X-axis direction and the angle θ formed by the laser beam with respect to the normal of the light emitting end face are not proportional. There is drowning. Therefore, the front main plane is y ₀ × ((1 + tan ² θ) ^1/2 −1) in the radial direction of the curvature of the front and rear surfaces.
By being positioned away from the semiconductor laser element only, it is possible to ensure the same collimating characteristics with each laser beam regardless of the laser beam emission direction.

  The active layer includes a first region and a second region as a plurality of regions, and the plurality of drive electrodes provide a first drive electrode for supplying a drive current to the first region, and a drive current to the second region. A longitudinal direction of the first drive electrode is inclined with respect to the normal of the light emitting end face when viewed from the thickness direction of the semiconductor laser element, and the photonic The region corresponding to the first region of the crystal layer has first and second periodic structures in which the arrangement periods of the different refractive index portions having different refractive indexes from the surroundings are different from each other, and the first and second periodic structures When two or more laser beams form a predetermined angle with respect to the longitudinal direction of the first drive electrode when viewed from the thickness direction of the semiconductor laser element according to the difference of the reciprocal number of each arrangement period in the semiconductor laser element, Of these laser beams One toward the end face is set so that the refraction angle is less than 90 degrees with respect to the light exit end face, and at least one other towards the light exit end face is set so as to satisfy the total reflection critical angle condition with respect to the light exit end face. The longitudinal direction of the second drive electrode is inclined with respect to the normal of the light emitting end face when viewed from the thickness direction of the semiconductor laser element, and corresponds to the second region of the photonic crystal layer Has third and fourth periodic structures in which the arrangement periods of the different refractive index portions having different refractive indices from the surroundings are different from each other, and the difference between the reciprocal numbers of the respective arrangement periods in the third and fourth periodic structures. Accordingly, when viewed from the thickness direction of the semiconductor laser element, two or more laser beams forming a predetermined angle with respect to the longitudinal direction of the second drive electrode are generated inside the semiconductor laser element, At the light exit end Is set so that the refraction angle is less than 90 degrees with respect to the light exit end face, and at least one other towards the light exit end face is set so as to satisfy the total reflection critical angle condition with respect to the light exit end face, The difference of the reciprocal number of each arrangement period in the first and second periodic structures may be different from the difference of the reciprocal number of each arrangement period in the third and fourth periodic structures.

  In this case, by supplying a drive current to the drive electrode, two or more laser beams are generated inside the semiconductor laser element. One of the generated laser beams toward the light emitting end surface has a refraction angle of less than 90 degrees with respect to the light emitting end surface, and at least one other toward the light emitting end surface satisfies the total reflection critical angle condition with respect to the light emitting end surface. Fulfill. For this reason, the direction of the laser beam emitted simultaneously can be set to a predetermined one direction. The difference between the reciprocal numbers of the respective array periods in the first and second periodic structures is different from the difference between the reciprocal numbers of the respective array periods in the third and fourth periodic structures. Therefore, the laser beam emission direction can be switched depending on which electrode of the plurality of drive electrodes is supplied with the drive current.

The semiconductor laser element generates a plurality of laser beams, and outputs the generated plurality of laser beams in the same direction, and a plurality of laser beams output from the oscillation unit in the same direction in different directions. A deflecting unit that deflects and emits light from the light emitting end surface, and the oscillation unit includes a lower cladding layer, an upper cladding layer, an active layer, and a first photonic crystal layer as a photonic crystal layer And a plurality of drive electrodes, the deflection unit includes a second photonic crystal layer, and the first photonic crystal layer has a different refractive index different from that of the surrounding region over a region corresponding to the plurality of regions. The second photonic crystal layer has a periodic structure in which the arrangement periods of the different refractive index portions having different refractive indexes from the surroundings are different for each region corresponding to a plurality of regions. Have It may be.

  In this case, the first photonic crystal layer has a periodic structure in which the arrangement period of the different refractive index portions is the same over a region corresponding to a plurality of regions. A laser beam is output in the same direction for each electrode. Since the second photonic crystal layer has a periodic structure in which the arrangement period of the different refractive index portions is different for each region corresponding to a plurality of regions, the deflection unit outputs the same direction from the oscillation unit. Each laser beam is deflected in different directions and emitted from the light emitting end face. In the semiconductor laser device, the oscillation unit and the deflection unit are separated, and the first photonic crystal layer has a periodic structure in which the arrangement period of the different refractive index portions is the same over a region corresponding to a plurality of regions. Have. For this reason, the oscillation threshold is constant for each laser beam, and stable operation can be realized.

  The second photonic crystal layer causes interference that weakens light transmitted in the same direction as the output direction of the laser beam from the oscillating unit for each region corresponding to the plurality of regions, and the laser beam from the light emitting end surface. Interference that reinforces the light diffracted in the emission direction of the light may be generated. In this case, the deflecting unit can surely deflect each laser beam output in the same direction from the oscillating unit in a different direction and emit it from the light emitting end face.

  According to the present invention, it is possible to provide a semiconductor laser device capable of emitting a laser beam in a predetermined direction and changing the emission direction.

It is a schematic perspective view which shows the structure of a semiconductor laser apparatus. It is a longitudinal cross-sectional view of a semiconductor laser element. It is a top view of a semiconductor laser element. It is a top view inside an element for explaining a progress state of a laser beam inside a semiconductor laser element. It is a top view of the photonic crystal area | region which has a single periodic structure. It is a top view of the photonic crystal area | region which has a single periodic structure. It is a top view of the photonic crystal area | region which has a some periodic structure. It is a top view of a photonic crystal region group having a plurality of photonic crystal layer regions having a plurality of periodic structures. It is a top view of the photonic crystal layer which has a photonic crystal region group. It is a graph which shows the incident angle and outgoing angle of a laser beam with respect to deflection angle (delta) theta from a reference direction (it depends on the difference of the reciprocal of the period in each photonic crystal region). It is a top view of the different refractive index part (structure) of various shapes. It is a figure which shows the structure of a laser beam deflection | deviation apparatus. It is a figure for demonstrating the structure of a collimating lens. It is a figure for demonstrating the structure of a collimating lens. It is a figure for demonstrating the modification of a collimating lens. It is a figure for demonstrating the structure of a collimating lens. It is a figure for demonstrating the structure of a collimating lens. It is a figure which shows a semiconductor laser element. It is a diagram for demonstrating the design example of a collimating lens. It is a diagram for demonstrating the design example of a collimating lens. It is a graph for demonstrating the design example of a collimating lens. It is a diagram for demonstrating the design example of a collimating lens. It is a longitudinal cross-sectional view of a semiconductor laser element. It is a top view inside a semiconductor laser element. A vector from the origin O to the point P (βx, βy) in the xy coordinate system. It is a graph which shows the direction of the main light wave in xy coordinate system. It is a top view inside an element explaining the main light wave in active layer 3B. FIG. 4A is a plan view of a diffraction grating layer 4 ′ having a periodic structure, and FIG. 6B is a cross-sectional view in the XZ plane. It is a graph which shows the relationship between laser beam emission angle (refraction angle) (theta) 3, stripe angle (theta), and period (LAMBDA). It is a chart which shows the data used for a graph. It is sectional drawing of the partial area | region of a semiconductor laser element. It is a top view of a photonic crystal layer. 1 is a schematic perspective view of a semiconductor laser device according to an embodiment. FIG. 34 is a diagram showing a cross-sectional configuration along the line XXXIV-XXXIV of the semiconductor laser element shown in FIG. 33. FIG. 34 is a diagram showing a cross-sectional configuration along the line XXXV-XXXVX of the semiconductor laser element shown in FIG. 33. FIG. 34 is a plan view of the semiconductor laser element shown in FIG. 33. It is a top view of a 1st photonic crystal layer. It is a top view which shows the modification of a 1st photonic crystal layer. It is a top view of a 2nd photonic crystal layer. It is a schematic perspective view of the semiconductor laser element which concerns on the modification of this embodiment. 41 is a diagram showing a cross-sectional configuration of the semiconductor laser element shown in FIG. 40. FIG. FIG. 41 is a plan view of the semiconductor laser element shown in FIG. 40. It is a top view of a 1st photonic crystal layer. It is a top view of a 2nd photonic crystal layer.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  FIG. 1 is a schematic perspective view showing the configuration of the semiconductor laser device.

  The semiconductor laser device LD1 includes a semiconductor laser element 10A and a collimating lens 20. The semiconductor laser element 10A is an edge emitting semiconductor laser. The semiconductor laser element 10A emits a laser beam in a predetermined direction from the light emission end face LES with a configuration described in detail later. The collimating lens 20 collimates the laser beam emitted from the semiconductor laser element 10A.

  In the following description, the direction parallel to the light emitting end face LES and extending the active layer of the semiconductor laser element 10A is referred to as a first direction. A coordinate axis parallel to the first direction is taken as an X axis, a direction perpendicular to the light emitting end face LES is taken as a Y axis, and a direction perpendicular to the direction in which the active layer extends is taken as a Z axis. In order to represent the emission direction of the laser beam LB, an angle θ formed by the laser beam LB with respect to the normal line N of the light emission end face LES is used.

  Next, the semiconductor laser element 10A will be described in detail.

  FIG. 2 is a longitudinal sectional view of the semiconductor laser element, and FIG. 3 is a plan view of the semiconductor laser element.

  The semiconductor laser element 10A includes a lower clad layer 2, a lower light guide layer 3A, an active layer 3B, an upper light guide layer 3C, a photonic crystal layer 4, an upper clad layer 5, and a contact layer 6 which are sequentially formed on the semiconductor substrate 1. It has. On the back side of the semiconductor substrate 1, an electrode E <b> 1 is provided on the entire surface, and on the contact layer 6, a plurality of drive electrodes E <b> 2 are provided. In the drawing, five drive electrodes E <b> 2 are simply shown, but actually more drive electrodes E <b> 2 are provided on the contact layer 6.

The surface on the contact layer 6 other than the formation region of the drive electrode E2 is covered with the insulating film SH. The insulating film SH can be formed from, for example, SiN or SiO ₂ .

The materials / thicknesses of these compound semiconductor layers are as follows. Note that an intrinsic semiconductor having an impurity concentration of 10 ¹⁵ / cm ³ or less has no conductivity type. In addition, the density | concentration when an impurity is added is 10 < ¹⁷ > -10 < ²⁰ > / cm < ³ >. Further, the following is an example of the present embodiment. If the configuration includes the active layer 3B and the photonic crystal layer 4, the material system, film thickness, and layer configuration are flexible. The upper light guide layer 3C includes two layers, an upper layer and a lower layer.
Contact layer 6: P-type GaAs / 50 to 500 nm
Upper clad layer 5: P-type AlGaAs (Al _0.4 Ga _0.6 As) /1.0 to 3.0 μm
Photonic crystal layer 4:
Basic layer 4A: GaAs / 50 to 400 nm
Buried layer (different refractive index portion) 4B: AlGaAs (Al _0.4 Ga _0.6 As) / 50 to 400 nm
Upper light guide layer 3C:
Upper layer: GaAs / 10-200 nm
Lower layer: p-type or intrinsic AlGaAs / 10 to 100 nm
Active layer 3B (multiple quantum well structure):
AlGaAs / InGaAs MQW / 10-100nm
Lower light guide layer 3A: AlGaAs / 0 to 300 nm
Lower clad layer 2: N-type AlGaAs / 1.0 to 3.0 μm
・ Semiconductor substrate 1: N-type GaAs / 80 to 350 μm

  For example, AuGe / Au can be used as the material of the electrode E1, and Cr / Au or Ti / Au can be used as the material of the electrode E2.

  The light guide layer can be omitted.

In the manufacturing method in this case, the growth temperature of AlGaAs by the MOCVD method is 500 ° C. to 850 ° C. In the experiment, 550 to 700 ° C. is adopted, and TMA (trimethylaluminum) is used as the Al raw material during growth and TMG ( Trimethylgallium) and TEG (triethylgallium), AsH _{3 (} arsine) as the As raw material, Si ₂ H ₆ (disilane) as the raw material for N-type impurities, and DEZn (diethylzinc) as the raw material for P-type impurities Can do.

  When a current is passed between the upper and lower electrodes E1, E2, a current flows in a region R immediately below one of the electrodes E2, this region emits light, and the laser beam LB is output at a predetermined angle from the side end surface of the substrate. (See FIG. 3). Which laser beam LB is emitted is determined depending on which of the drive electrodes E2 is supplied with the drive current.

  The planar shape of the semiconductor laser element is a rectangle. When an XYZ three-dimensional orthogonal coordinate system is set, the thickness direction is the Z axis, the width direction is the X axis, and the direction perpendicular to the light emitting end face LES is the Y axis. . In the XY plane, the extending longitudinal direction of each drive electrode E2 forms an angle φ with respect to a straight line parallel to the Y axis. That is, the longitudinal direction of the drive electrode E2 is inclined with respect to the normal line (Y axis) of the light emitting end face LES of the semiconductor laser element when viewed from the thickness direction of the semiconductor laser element. The drive electrode E2 extends from the position of the light emitting end face LES toward the opposite end face, but is interrupted halfway without completely traversing the semiconductor laser element.

  FIG. 4 is a plan view of the inside of the device for explaining the progress of the laser beam inside the semiconductor laser device.

  The laser beam is generated in the active layer 3 </ b> B, but the light that exudes from the active layer 3 </ b> B is affected by the adjacent photonic crystal layer 4. A periodic refractive index distribution structure is formed in the photonic crystal layer 4. As a result of diffraction by this photonic crystal layer, a laser beam indicated by wave number vectors k1 to k4 is generated inside the active layer 3B. The wave vector is a vector whose direction is the normal direction of the wave front (that is, the wave propagation direction) and whose magnitude is the wave number. The laser beams with wave number vectors k1 and k2 are directed toward the light emitting end face LES, and the laser beams with wave number vectors k4 and k3 are directed in the opposite direction.

  The laser beams of the wave number vectors k1 and k2 travel at an angle of ± δθ with respect to the B direction that forms an angle φ with a straight line parallel to the Y axis in the XY plane. The B direction is the direction in which the drive electrode E2 extends. The A direction is a direction perpendicular to the B direction in the XY plane. A coordinate system obtained by rotating the XYZ orthogonal coordinate system by φ around the Z axis is defined as an xyz orthogonal coordinate system. In this case, the A direction coincides with the positive x-axis direction, and the B direction coincides with the negative y-axis direction. The laser beams of the wave number vectors k1 and k2 enter the light emission end face LES and attempt to exit to the outside. The incident angles are θ1 and θ2, respectively. The refraction angle of the laser beam having the wave vector k1 is θ3. θ3 is smaller than 90 degrees. That is, the incident angle θ2 of the laser beam having the wave number vector k2 is equal to or greater than the total reflection critical angle, and total reflection occurs at the light emitting end face LES and is not output to the outside. On the other hand, the incident angle θ1 of the laser beam with the wave vector k1 is less than the total reflection critical angle, and is transmitted to the outside through the light emitting end face LES. Θ4 is an angle formed by the traveling direction of the laser beam totally reflected on the light emitting end face LES and the negative Y-axis direction, and is 90 degrees or more.

  Note that the photonic crystal layer 4 is formed of a plurality of photonic crystal regions 4R.

  FIG. 5 is a plan view of the photonic crystal region 4R having a single periodic structure.

  A photonic crystal is a nanostructure whose refractive index changes periodically, and can strengthen or diffract light of a specific wavelength in a specific direction according to the period. By using this diffraction for light confinement and as a resonator, a laser can be realized. The photonic crystal layer 4 of the present embodiment includes a basic layer 4A and a buried layer (different refractive index portion) 4B periodically embedded in the basic layer 4A.

  In this embodiment, a plurality of holes H are periodically formed in the basic layer 4A made of the first compound semiconductor (GaAs) having the zinc flash structure, and the second compound semiconductor (having the zinc flash structure and having the second compound semiconductor ( The photonic crystal layer 4 is formed by growing a buried layer 4B made of (AlGaAs). Of course, since the photonic crystal is formed, the refractive index of the first compound semiconductor is different from that of the second compound semiconductor. In the present embodiment, the refractive index of the second compound semiconductor is lower than that of the first compound semiconductor. Conversely, the refractive index of the first compound semiconductor may be lower than that of the second compound semiconductor. .

  The different refractive index portions 4B, which are buried layers, are aligned along the A direction and the B direction to form a two-dimensional periodic structure. Here, the pitch between the different refractive index portions 4B in the A direction is a1, and the pitch between the different refractive index portions 4B in the B direction is b1. In addition, a1 = b1 may be sufficient. As a planar shape of each different refractive index portion 4B in the AB plane, a rectangle is shown in the figure, but the planar shape of the different refractive index portion 4B is not limited to this.

  FIG. 6 is a plan view of a photonic crystal region 4R having a single periodic structure different from FIG.

  The different refractive index portions 4B, which are buried layers, are aligned along the A direction and the B direction to form a two-dimensional periodic structure. Here, the pitch between the different refractive index portions 4B in the A direction is a2, and the pitch between the different refractive index portions 4B in the A direction is b2. Note that the relationship of a2> a1 is satisfied. As a planar shape of each different refractive index portion 4B in the AB plane, a rectangle is also shown in the figure, but the planar shape of the different refractive index portion 4B is not limited to this.

  FIG. 7 is a plan view of the photonic crystal region 4R having a plurality of periodic structures.

  That is, the photonic crystal region 4R includes the periodic structure shown in FIG. 5 and the periodic structure shown in FIG. 6 in a single photonic crystal region 4R, and has a period a1 and a period a2. Yes. In addition, the figure shows that both periods in the B direction are set to b2 (= b1).

In the case of such a structure, δθ in FIG. 4 is determined in accordance with the difference between the reciprocal of the period a1 (1 / a1) and the reciprocal of a2 (1 / a2). That is, by determining the periods a1 and a2, it is possible to determine the traveling direction of the laser beam indicated by the wave number vectors k1 and k2. Note that δθ = sin ⁻¹ (δk / k), δk = | π {(1 / a1) − (1 / a2)} |, and k = 2π / λ. λ is the wavelength of the laser light in the semiconductor laser element, and k is the wave number of the laser light in the semiconductor laser element.

In the case of this embodiment, the inequalities to be satisfied by the parameters θ1 and θ2 and the equivalent refractive index n _dev of the light in the semiconductor laser element are as follows.

0 ≦ θ1 <sin ⁻¹ (1 / n _dev )

θ2 ≧ sin ⁻¹ (1 / n _dev )

In consideration of the fact that the entire photonic crystal is tilted as in the present invention, equations to be satisfied by the respective parameters are as follows.
δθ = φ−sin ⁻¹ (sin θ3 / n _dev )
δk = (2π / λ ₀ ) sin {φ−sin ⁻¹ (sin θ3 / n _dev )}
b1 = b2 = b ₀ / √ (1-sin ² δθ)
a1 = 1 / {(δk / 2π) + (1 / b1)}
a2 = 1 / {(1 / b2)-(δk / 2π)}

B ₀ is a reference period with respect to the B direction (the alignment direction of the lattice points (the arrangement direction of the different refractive index portions)), and is, for example, about 290 nm.

That is, φ is the inclination of the arrangement direction (B direction) of the different refractive index portions with respect to the direction perpendicular to the light emitting end face LES, θ3 is the laser beam emission angle, n _dev is the equivalent refractive index of light in the semiconductor laser element, When a drive current is supplied to the first and second drive electrodes, the resonance wavelengths of the laser beams generated in the first and second regions of the active layer immediately below the first and second drive electrodes are the same. In the first, second, third, and fourth periodic structures (described later), the period b1, b2 is √ {1-sin ² (φ−sin ⁻¹ ) with respect to one of the directions along the basic translation vector. (Sin θ3 / n _dev ))}. By changing the setting of the cycle, the emission angle θ3 can be changed.

The total reflection critical angle θc when the total reflection condition of the laser beam of the wave vector k2 is satisfied is given by θc = sin ⁻¹ (1 / n _dev ). In this example, φ = 18.5 °, θ2 > Θc = 17.6 °.

  FIG. 8 is a plan view of a photonic crystal region group 4G having a plurality of photonic crystal layer regions 4R having a plurality of periodic structures. The photonic crystal layer regions 4R are arranged in alignment along the A direction.

  The leftmost photonic crystal layer region 4R is the region Δ1, the second photonic crystal layer region 4R is the region Δ2, the second photonic crystal layer region 4R is the region Δ3, and the fourth photonic crystal layer region 4R is The region Δ4 and the fifth photonic crystal layer region 4R are defined as a region Δ5. For convenience, Δ1 to Δ5 also indicate parameters of the reciprocal of the above period.

  In the region Δ1, the different refractive index portions 4B are arranged in the A direction so as to satisfy the cycle a1 and the cycle a2 shown in FIG. 7, and the different refractive index portions 4B are arranged in the B direction at the cycle b2.

  Similarly, in the region Δ2, the different refractive index portions 4B are arranged in the A direction so as to satisfy the cycle a1 and the cycle a3, and the different refractive index portions 4B are arranged in the B direction at the cycle b2.

  In the region Δ3, the different refractive index portions 4B are arranged in the A direction so as to satisfy the cycle a1 and the cycle a4, and the different refractive index portions 4B are arranged in the B direction at the cycle b2.

  In the region Δ4, the different refractive index portions 4B are arranged in the A direction so as to satisfy the period a1 and the period a5, and the different refractive index portions 4B are arranged in the B direction at the period b2.

  In the region Δ5, the different refractive index portions 4B are arranged in the A direction so as to satisfy the cycle a1 and the cycle a6, and the different refractive index portions 4B are arranged in the B direction at the cycle b2. However, the relationship of a1 <a2 <a3 <a4 <a5 <a6 is satisfied.

  If it demonstrates using a general formula, area | region (DELTA) N (N is a natural number) is arranged from left to right in order with small value of N along A direction, and within area | region (DELTA) N, period a1 in A direction, The different refractive index portions 4B are arranged so as to satisfy the cycle a (N + 1), and the different refractive index portions 4B are arranged in the B direction at the cycle b2, so that aN <a (N + 1) is satisfied.

  As a result, the laser beam can be emitted in different directions according to the difference in the reciprocal of the period.

  FIG. 9 is a plan view of a photonic crystal layer having the photonic crystal region group 4G.

  In the photonic crystal layer 4, the regions Δ1 to Δ5 are sequentially arranged along the A direction. The longitudinal direction of each region Δ1 to Δ5 coincides with the B direction (longitudinal direction of the drive electrode E2). When a drive current is selectively supplied to each drive electrode E2 (a drive voltage is applied between the electrode E1 and a specific electrode E2), laser beams are emitted in different directions from the light emission end face LES (FIG. 3).

  FIG. 10 is a graph showing the incident angle and the outgoing angle of the laser beam with respect to the deflection angle δθ from the reference direction (B direction) (depending on the difference in the reciprocal of the period in each photonic crystal region).

When the difference in the reciprocal of the period increases and the angle δθ increases, the difference between the incident angles θ1 and θ2 increases, and the refraction angle (emission angle) of the laser beam indicated by the k1 vector decreases from 90 ° to 0 °. φ = 18.5 °, and δθ was changed from 0 ° to 18.5 °. The equivalent refractive index n _dev of light in the semiconductor laser element was 3.3. By adjusting the angle δθ, the target laser beam emission angle can be adjusted in a wide range. On the other hand, in the laser beam indicated by the k2 vector, regardless of the value of δθ, since θ2 always exceeds the total reflection critical angle, total reflection always occurs and is not output to the outside.

  FIG. 11 is a plan view of various refractive index portions (structures) 4B having various shapes.

  In the above, a rectangular (A) shape is shown as the shape in the AB plane (XY plane) of the different refractive index portion 4B, but this may be a square (B), an ellipse or a circle (C), It can also be an isosceles or equilateral triangle (D). In addition to the direction of the triangle (D), the base is parallel to the A direction (D), the base is parallel to the B direction (E), and the triangle shown in (D) is rotated 180 degrees (F) You can also Any figure can be rotated and the ratio of dimensions can be changed. Note that the distance between the centers of gravity of each figure can be used as the arrangement period of these figures.

  Note that, when the two periodic structures are overlapped, a difference in the number of holes due to a difference in the period causes a difference in diffraction intensity between the two periodic structures. In order to reduce this, the shape length in the A direction is multiplied by a1 / b1 for the structure of the period a1, and the shape length in the A direction is multiplied by a2 / b2 (= b1) for the structure of the period a2. It is effective to do.

  In the above-described embodiment, when the number of drive electrodes E2 is one, a semiconductor laser element that can output only a beam in a single direction is configured. As long as the number of drive electrodes E2 is plural, a laser beam deflecting device can be configured.

  Next, an example of the collimating lens 20 will be described in detail with reference to FIGS. 13 and 14. 13 and 14 are diagrams for explaining the configuration of the collimating lens. 13 and 14, the origin O of the XYZ coordinate system is defined so as to be located on the light emitting end face LES of the semiconductor laser element 10A and at the center of the semiconductor laser element 10A in the X-axis direction. FIG. 13 is a top view of the collimating lens, and FIG. 14 is a vertical sectional view of the collimating lens in the radial direction r.

  The collimating lens 20 has a front surface 20a facing the semiconductor laser element 10A, and a rear surface 20b from which the collimated laser beam LB is emitted. As shown in FIG. 13, the collimating lens 20 is parallel to the light emitting end face LES and the front surface 20a in a cross section (cross section parallel to the XY plane) including the active layer 3B extending direction (X axis direction) and the optical axis OA. The curvature of the rear surface 20b is constant. In this example, a thin lens is used as the collimating lens 20.

When the curvature radii of the front surface 20a and the rear surface 20b in the cross section parallel to the XY plane of the collimator lens 20 are sufficiently larger than the size of the semiconductor laser element 10A, the emission position (light emission end surface) of each laser beam LB on the light emission end surface LES. The positions corresponding to the plurality of regions R in LES can be approximated to be the same. Therefore, in FIG. 13, the radius of curvature of the front surface 20a is represented by _RC with the origin O as the center of curvature. The radius of curvature of the rear surface 20b is represented by R _C + d, where the origin O is the center of curvature and the thickness of the collimating lens 20 is d.

Focal length F of the collimating lens 20 (theta _out) is the refractive index of the collimating lens 20 is n, the front radius of curvature as R _1, the rear-side radius of curvature when the R _2,
F (θ _out ) = {(n−1) × (1 / R ₁ + 1 / R ₂ )} ⁻¹
It is represented by In the collimating lens 20, so that the focal length F (θ _out) is constant, the front radius of curvature R ₁ and the rear radius of curvature and R ₂ are set.

Emission position of the laser beam LB at the light emitting end face LES (in this example, at a point approximated (FIGS. 13 and 14, the origin O)) optical path length to the front principal plane P _M from (the optical path length of the laser beam LB ) And the focal length F (θ _out ) match. Thereby, when each laser beam LB emitted from the semiconductor laser element 10A is incident on the collimating lens 20, as shown in FIG. 14, it is refracted in a plane parallel to the thickness direction of the semiconductor laser element 10A. It is emitted as a plurality of parallel lights having the same width in the thickness direction of the semiconductor laser element 10A. In actual semiconductor laser device 10A, since the emission position x of the laser beam LB at the light emitting end face LES differ, the optical path length from the exit location of the laser beam LB at the light emitting facet LES to the front principal plane P _M, the focal The distance F (θ _out ) substantially coincides with the distance F (θ _out ). In this example, the front principal plane P _M and the rear side principal plane is coincident with the main plane.

When a dielectric (for example, a coding film formed on the light emitting end face LES) is inserted between the semiconductor laser element 10A and the collimating lens 20, the laser beam LB passes through the dielectric, so that the laser beam LB The optical path length L (θ _out ) increases. Therefore, it is necessary to design the collimating lens 20 so that the optical path length of the laser beam LB taking into account the increased optical path length and the focal length F (θ _out ) substantially coincide.

The vertical cross-sectional shape of the collimating lens 20 in the radial direction r is not limited to the shape shown in FIG. If the collimating lens 20 has a shape in which the optical path length from the emission position of each laser beam LB to the front main plane on the light emission end face LES substantially coincides with the focal length F (θ _out ), FIG. The vertical cross-sectional shape shown in FIG.

From the above, in the present embodiment, in the semiconductor laser element 10A, the light of the laser beam LB for each emission position of the laser beam LB on the light emission end face LES (position corresponding to the plurality of regions R on the light emission end face). Even when the emission direction (emission angle θ _out ) with respect to the emission end face is different, the same collimating characteristic can be ensured for each laser beam LB regardless of the emission angle θ _out of the laser beam LB.

  Next, another example of the collimating lens 20 will be described with reference to FIGS. Also in this example, a thin lens is used as the collimating lens 20.

As shown in FIG. 16, in this example, the front surface 20 a in a direction parallel to the light emitting end face LES and extending in the active layer 3 </ b> B (X-axis direction) and the cross-section including the optical axis OA (cross-section parallel to the XY plane) The center of curvature of the rear surface 20b is defined to be located at the center of the semiconductor laser element 10A and the semiconductor laser element 10A in the X-axis direction. The Y axis is a coordinate axis perpendicular to the light emitting end face LES. In this example, as compared with the examples shown in FIGS. 13 and 14, the radii of curvature of the front surface 20a and the rear surface 20b in the cross section parallel to the XY plane of the collimating lens 20 approach the size of the semiconductor laser device 10A. Yes. As shown in FIG. 17, the front principal plane P _M and the rear side principal plane is coincident with the main plane.

As shown in FIG. 18, the width of the semiconductor laser element 10A in the X-axis direction is W. The angle (outgoing angle) θ _out formed by the laser beam LB with respect to the normal line of the light emitting end face LES is 0 at the center in the X-axis direction of the semiconductor laser element 10A and in the X-axis direction of the semiconductor laser element 10A. It gets bigger as you go to the edge. The maximum value of the emission angle θ _out at the end in the X-axis direction of the semiconductor laser element 10A is θ _max . In this case, the position y ₀ in the Y-axis direction of the light emitting end surface with respect to the center of curvature (the origin O) of the front surface 20a and the rear surface 20b is:
y ₀ <W / (2 × tan θ _max )
It is prescribed based on. The exit angle θ _{out at} position x along the X axis is
θ _out = atan (x / y ₀ )
It is prescribed based on. In FIG. 18, locations corresponding to the region R (regions with hatching) are schematically shown.

Collimator lens 20, the focal length F against the emission angle θ _out (θ _out) is the optical path length of the center of curvature of the front surface 20a and rear surface 20b (the origin O) and the front principal plane _{P M} when the OP,
F (θ _out ) = OP−y ₀ × (1 + tan ² θ _out ) ^1/2
It is prescribed based on. Accordingly, the focal length F (θ _out ) with respect to the emission angle θ _out is preferably set to be equal to or less than the value represented by “OP−y ₀ × (1 + tan ² θ _out ) ^1/2 ”.

  Next, a specific design example of the collimating lens 20 will be described with reference to FIGS. Here, the collimating lens 20 shown in FIGS. 16 to 18 is used.

In this design example, as the size of the semiconductor laser element 10A, the length (width) in the X-axis direction is set to 1 mm, and the length in the Y-axis direction is set to 0.5 mm. Optical path length OP of the center of curvature of the front surface 20a and rear surface 20b (the origin O) and the front principal plane _{P M} is set to 2 mm. The maximum emission angle θ _max is set to 60 °. Position _{y 0} in the Y-axis direction of the light emitting end face against the center of curvature of the front surface 20a and rear surface 20b (the origin O) is set to 0.2 mm. Side curvature radius _{R 2} after the collimator lens 20 is set to 2 mm. The refractive index n of the collimating lens 20 is set to 1.5.

In the semiconductor laser device 10A, it is assumed that the emission angle θ _out is deflected at intervals of 5 ° between 0 ° and 60 °. At this time, the emission position x (mm) of each laser beam LB on the light emission end face LES with respect to the emission angle θ _out is
x = y ₀ tan θ _out
Is obtained. The results are shown in FIG. FIG. 19 is a diagram illustrating the relationship between the exit angle and the exit position for explaining a design example of the collimator lens.

As can be seen from Figure 16, in this design example, in the range emission angle theta _out is 0 ° to 40 °, the output position x Togaryaku proportional of the laser beam LB at the emission angle theta _out and the light emitting end face LES ing. Thus, the emission positions x, that is, the regions R can be arranged at equal intervals in the range where the emission angle θ _out is 0 ° to 40 °. When the emission angle θ _out exceeds 40 °, the emission angle θ _out and the emission position x are not proportional.

The focal length F (θ _out ) and the front side curvature radius R ₁ of the collimating lens 20 with respect to the emission angle θ _out are:
F (θ _out ) = OP−y ₀ × (1 + tan ² θ _out ) ^1/2
F (θ _out ) = {(n−1) × (1 / R ₁ + 1 / R ₂ )} ⁻¹
Is obtained. The results are shown in FIGS. FIG. 20 is a diagram showing the relationship between the emission angle and the front curvature radius for explaining a design example of the collimating lens. FIG. 21 is a chart showing calculated values of the emission position, the focal length, and the front curvature radius with respect to the emission angle for explaining a design example of the collimating lens.

As can be seen from FIG. 21, the focal length F (θ _out ) becomes shorter as the outgoing angle θ _out becomes larger, and therefore the front curvature radius R ₁ decreases as the outgoing angle θ _out increases. When the emission angle θ _out is 60 ° of the maximum emission angle θ _max , the focal length F (θ _out ) is reduced by 11% compared to when the emission angle θ _out is 0 °. Therefore, when the emission angle theta _out is 60 °, the height of the parallel light collimated emitted by the collimator lens 20 (collimated light) (the width in the direction perpendicular to the XY plane), the emission angle theta _out 0 It is reduced by about 11% compared to when it is at ° Thus, the height of the collimated light changes according to the emission angle θ _out .

In order to obtain collimated light having substantially the same height, it is conceivable to use the semiconductor laser element 10A within a range where the change in the focal length F (θ _out ) with respect to the emission angle θ _out is small. In this design example, when the semiconductor laser element 10A is used in the range where the emission angle θ _out is 0 ° to 40 °, the change in the collimated light height is 3.4%. If the change in collimated light height is about 3.4%, the change can be ignored in actual use.

The exit angle θ _out can also be obtained by changing the position of the front main plane P _M (main plane in the present design example) of the collimating lens 20 in accordance with the change in the focal length F (θ _out ) with respect to the exit angle θ _out. Regardless, collimated light having substantially the same height can be obtained. That is, the main plane is y ₀ × ((1 + tan ² θ _out ) ^1/2 −1) in the radial direction r of the curvature of the front surface 20a and the rear surface 20b.
Only the semiconductor laser device 10A is positioned away from the semiconductor laser device 10A (see FIG. 22). Or, the main plane _{P M} is,
α (θ _out ) = (OP−y ₀ ) / (OP−y ₀ (1 + tan ² θ _out ) ^1/2 )
The position is multiplied by α (θ _out ) represented by In any case, the same collimating characteristic can be reliably ensured for each laser beam LB irrespective of the emission direction (emission angle θ _out ) of the laser beam. In FIG. 22, a state where the main plane (front main plane P _M ) is moved away is indicated by a solid line.

In the above design example, the front curvature radius R ₁ is obtained under the condition that the rear curvature radius R ₂ is constant, but the present invention is not limited to this. Under the terms of the front radius of curvature R ₁ is constant, the rear-side radius of curvature R ₂ may be obtained.

  In addition, although the example using the one photonic crystal layer 4 was demonstrated above, you may comprise this using the two photonic crystal layers 4. FIG.

  FIG. 23 is a longitudinal sectional view of the semiconductor laser device.

  The only difference from that shown in FIG. 2 is that a second photonic crystal layer 4 'is provided between the cladding layer 2 and the light guide layer 3A (active layer 3B). The second photonic crystal layer 4 ′ includes a basic layer 4 A ′ made of the same material as the first photonic crystal layer 4 and a different refractive index portion 4 B ′.

  When the photonic crystal layer 4 shown in FIG. 2 is a first photonic crystal layer, the photonic crystal layer 4 has a refractive index distribution structure having a single periodic structure shown in FIG. The second photonic crystal layer 4 ′ has a refractive index distribution in which the single periodic structure with the period a2 shown in FIG. It has a structure. That is, when the overlap of the photonic crystal layers 4 and 4 ′ is seen from the thickness direction of the semiconductor laser element, the regions Δ1 to Δ5 are aligned along the A direction as shown in FIG. Will be. Even in the case of such a structure, the same effects as the structure shown in FIG. 2 can be obtained by setting each parameter as described above.

  In the case of manufacturing such a structure, after the formation of the clad layer 2, the same manufacturing method as that for the first photonic crystal layer 4 is performed (however, the growth is stopped when the different refractive index portion 4B is formed). Then, after that, each layer after the light guide layer 3A may be manufactured in the same manner as described above.

  Further, the second photonic crystal layer 4 ′ having the same structure as the first photonic crystal layer 4 including two refractive index periodic structures is used in place of the first photonic crystal layer 4. However, the same effect can be obtained.

  As described above, the semiconductor laser element described above is an edge-emitting semiconductor laser element, and includes a lower cladding layer 2, an upper cladding layer 5, a lower cladding layer 2 and an upper surface formed on a substrate 1. Photonic crystal layers 4 and 4 interposed between the active layer 3B (which may include a light guide layer) interposed between the cladding layer 5 and the active layer 3B and at least one of the upper and lower cladding layers. , And a first drive electrode E2 for supplying a drive current to the first region R of the active layer 3B (a region immediately below one drive electrode E2). The longitudinal direction of the first drive electrode E2 is a semiconductor When viewed from the thickness direction of the laser element, it is inclined with respect to the normal line (Y axis) of the light emitting end face LES of this semiconductor laser element and corresponds to the first region R of the photonic crystal layers 4 and 4 ′. Area Δ1 is the surrounding and refraction Have different first and second periodic structures in which the arrangement periods of the different refractive index portions are different from each other, and the difference between the reciprocals of the arrangement periods (a1, a2) in the first and second periodic structures. Accordingly, when viewed from the thickness direction of the semiconductor laser element, two laser beams forming a predetermined angle (δθ) with respect to the longitudinal direction (B direction) of the first drive electrode E2 are generated inside the semiconductor laser element, Only one of these laser beams is set to satisfy the total reflection condition, and the other refraction angle θ3 is set to be less than 90 degrees.

  That is, in the edge-emitting laser element, with respect to light emission by supplying a drive current to the first drive electrode E2, the incident angle θ of one laser beam inside the laser element to the light emitting end face is set to be equal to or greater than the total reflection critical angle. Thus, the laser beam can be prevented from being output to the outside. Since the refraction angle θ3 of the other laser beam is less than 90 degrees, the laser beam can be output to the outside through the light emitting end face.

  The semiconductor laser device according to an aspect of the present invention further includes a second drive electrode E2 for supplying a drive current to the second region R of the active layer 3B (a region immediately below the second drive electrode E2). When viewed from the thickness direction of the semiconductor laser element, the longitudinal direction (B direction) of the second drive electrode E2 is inclined with respect to the normal line (Y axis) of the light emitting end face LES of the semiconductor laser element, The region Δ2 corresponding to the second region of the photonic crystal layer has third and fourth periodic structures in which the arrangement periods of the different refractive index portions having different refractive indices from the surroundings have the third and fourth periodic structures, respectively. According to the difference of the reciprocal of each of the arrangement periods (a1, a3) in the periodic structure of 4, when viewed from the thickness direction of the semiconductor laser element, a predetermined angle δθ is set with respect to the longitudinal direction of the second drive electrode E2. Two laser beams formed are semiconductor lasers Only one of these laser beams generated inside the laser beam is set so as to be totally reflected at the light emitting end face, and the other refraction angle θ3 is set to be less than 90 degrees, and the first and second periods are set. The difference of the reciprocal number of each arrangement period (a1, a2) in the structure is different from the difference of the reciprocal number of each arrangement period (a1, a3) in the third and fourth periodic structures.

  In the edge-emitting laser element, with respect to light emission by supplying a drive current to the second drive electrode E2, the incident angle of the one laser beam inside the laser element to the light emission end face is set to a total reflection critical angle or more. The laser beam can be prevented from being output to the outside. Since the refraction angle of the other laser beam is less than 90 degrees, the laser beam can be output to the outside through the light emitting end face.

  It should be noted that the same effect is obtained with respect to the third and subsequent drive electrodes E2 from the left.

  Here, in the regions within the photonic crystal layers 4 and 4 ′ corresponding to the respective drive electrodes, the difference in the reciprocal of the arrangement period of the different refractive index portions 4 </ b> B (exit direction determining factor) is different. The difference value determines the laser beam emission direction. Therefore, since the value of the difference (exiting direction determining factor) is different in both regions, the emitting direction of the laser beam is the region Δ1 corresponding to the first drive electrode E2 and the region Δ2 corresponding to the second drive electrode E2. So it will be different. One of the pair of laser beams generated in each region is incident on the light emitting end face with a total reflection critical angle or more, and thus is not emitted to the outside. Therefore, by switching the supply of the drive current to each drive electrode, it becomes possible to output only one direction of laser beam in different directions.

  In this embodiment, a photonic crystal having a different period is based on a square lattice having a period (b1, b1) in the A direction and the B direction, and a rectangular lattice having a period (a1, b1) as the first periodic structure. Although the case of a rectangular lattice with a period of (a2, b1) has been described as the second periodic structure, it is of course possible to use a structure in which the periods in the A direction are different from each other based on a triangular lattice.

  FIG. 24 is a plan view of the inside of the element shown by inverting the top and bottom of the plan view shown in FIG. 4 and slightly changing the refraction angle θ3 of the emitted beam. The same applies to FIG.

  The xyz orthogonal coordinate system is a coordinate system obtained by rotating the XYZ orthogonal coordinate system around the Z axis by an angle + φ, and the + x direction coincides with the + A direction and the + y direction coincides with the −B direction. The arrangement of the photonic crystal hole patterns is inclined by an angle φ with respect to the light emitting end face. As shown in the figure, the angle formed by the reflection direction of the wave vector k2 (the laser beam traveling direction of the wave vector k2 ′) and the light emitting end face LES is θ2 ′, and the reflection direction of the laser beam of the wave vector k1 (the laser of the wave vector k1 ′). The angle formed between the beam traveling direction) and the light exit end face LES is defined as θ3 ′.

  In the embodiment described above, the laser beam having the wave number vector k2 is set so as to be totally reflected at the light emitting end face LES so that the number of laser beams emitted from the element is one. However, if the power of the laser beam can be reused inside the device, the energy conversion efficiency from electric energy to the laser beam is considered to increase. Therefore, the conditions under which the reflected laser beam Y2 'can be reused are examined. The laser beams (main light waves) corresponding to the wave number vectors k1, k2, k3, k4, k1 ′, and k2 ′ are Y1, Y2, Y3, Y4, Y1 ′, and Y2 ′, respectively. Also assume that the vector is shown. In addition, an angle formed between the X axis and the main light wave Y4 is θt, and an angle formed between the X axis and the main light wave Y3 is θr.

Each parameter θt, θr, θ2 ′, θ3 ′ satisfies the following relational expression. Β ₀ , β ₁ , and β ₂ mean a basic reciprocal lattice vector in the B direction, a basic reciprocal lattice vector in the A direction of the first periodic structure, and a basic reciprocal lattice vector in the A direction of the second periodic structure, respectively. [Beta] ₀ = 2 [pi] / b1 (= b2), [beta] ₁ = _{2 [} pi] / a1, [beta] ₂ = _{2 [} pi] / a2, [Delta] [beta] = [beta] _{2- [} beta] ₁ , and [alpha] = [beta] ₀ / [Delta] [beta].

The angle θr will be described. As shown in FIG. 25, in the xy coordinate system, a vector from the origin O to the point P (βx, βy) is given by an angle θβ = tan ⁻¹ (βy / βx) formed with the x axis. It is done. Here, [theta] t in θβ, βx = (1/2) × Δβ, as [beta] y = beta _0, since it is the case of adding the angle phi, is given by equation (1). The remaining parameters are calculated in the same manner and are given by equations (2) to (4).
θt = tan ⁻¹ (2α) + φ (1)
θr = 180 ° −tan ⁻¹ (2α) + φ (2)
θ2 ′ = tan ⁻¹ (2α) −φ (3)
θ3 ′ = 180 ° −tan ⁻¹ (2α) −φ (4)

  In the absence of any additional structure, in order for the totally reflected main light wave Y2 ′ to contribute to laser light resonance, the angle θ2 ′ of the main light wave Y2 ′ needs to match the angle θt (θ2 ′). = Θt). In this case, φ = 0. Further, the angle θ3 ′ and the angle θr of the reflected main light wave Y1 ′ need to coincide with each other (θ3 ′ = θr). In this case, φ = 0. On the other hand, in order to totally reflect one of the two main light waves Y1 and Y2, it is necessary that φ ≠ 0. Therefore, when total reflection is performed so that the number of output beams becomes one, the main light wave reflected by the light emitting end face cannot be effectively contributed to the laser light resonance.

  Therefore, an additional structure that can use reflected light is examined.

  FIG. 26 is a graph showing the directions of main light waves in the xy coordinate system. The x axis in the xy coordinate system is rotated by an angle φ with respect to the X axis.

In order to make the main light wave Y2 ′ as reflected light coincide with the main light wave Y4 subjected to resonance, the direction of the light wave Y2 ′ may be rotated by an angle 2φ. The coordinates of the tip P4 of the vector indicating the main light wave Y4 in the xy coordinate system are (Δβ / 2, β ₀ ), and the coordinates of the tip P2 ′ of the vector indicating the main light wave Y2 ′ are coordinates obtained by rotating this by −2φ. It is.

On the other hand, in the XY coordinate system, the coordinates (Δβ / 2, β ₀ ) of the vector Y4 (tip P4) in the xy coordinate system are converted into coordinates (XA, YA) rotated by + φ, and the vector Y2 ′ The coordinates are converted into coordinates (XB, YB) obtained by rotating the coordinates of the vector Y4 in the xy coordinate system by −φ.
(XA, YA) = (Δβ cos φ / 2−β ₀ sin φ, Δβ sin φ / 2 + β ₀ cos φ) (5)
(XB, YB) = (Δβ cos φ / 2 + β ₀ sin φ, −Δβ sin φ / 2 + β ₀ cos φ) (6)

If there is a reciprocal lattice vector equal to the vector ΔY, the main light wave Y2 ′ is coupled to the main light wave Y4. That is, the vector Y4 is obtained by adding the vector ΔY to the vector Y2 ′. The vector ΔY is expressed as follows. If a new periodic structure having a reciprocal lattice vector equal to the vector ΔY is additionally employed, the totally reflected light wave Y2 ′ can be contributed to resonance.
ΔY = (XA−XB, YA−YB) = (− 2β ₀ sinφ, Δβsinφ)

  In this new periodic structure, it is preferable that the different refractive index portions are arranged in a stripe shape. The stripe-shaped periodic structure has a high anisotropy of the optical coupling coefficient and can reduce the influence of the resonance state Y1 and Y2.

  FIG. 27 is a plan view of the inside of the element for explaining main light waves in the active layer 3B.

  The line of intersection between the XY plane and the light emitting end face LES coincides with the X axis. When the above-described vector ΔY exists, the wave vector of the light wave Y2 'having the tip at the coordinate P2' is converted into the wave vector of the light wave Y4 having the tip at the coordinate P4. Let L be a straight line perpendicular to the vector ΔY. The new periodic structure may be set so that the light wave travels in a direction perpendicular to the straight line L in the active layer 3B. In order to control the traveling direction of the light wave in the active layer 3B, the pattern of the diffraction grating layer optically coupled thereto is controlled. In FIG. 14 described above, upper and lower photonic crystal layers (diffraction grating layers) 4, 4 'are provided. In the case of such a structure, a photonic crystal layer that achieves the above-described total reflection is produced in the upper diffraction grating layer 4, and the new periodic structure for using reflected light for resonance is formed in the diffraction grating layer 4. (Of course, these periodic structures may be produced by superimposing one or both layers).

  FIG. 28A is a plan view of a diffraction grating layer 4 ′ having a periodic structure that gives the vector ΔY, and FIG. 28B is a cross-sectional view in the XZ plane.

  The diffraction grating layer 4 'includes a basic layer 4A' and a different refractive index portion 4B 'extending in a stripe shape along the straight line L in the XY plane, and these refractive indexes are different. The different refractive index portions 4B 'are periodically embedded in the basic layer 4A'. As a result, a striped periodic refractive index distribution structure is formed in the diffraction grating layer 4 ′, and functions as a diffraction grating layer in which light waves travel in the direction of ΔY. By changing the ratio of the width of the basic layer 4A ′ along the direction perpendicular to the straight line L to the period Λ of the periodic structure, the intensity of diffraction by the stripe-shaped periodic refractive index distribution structure is changed. I can do it. The length L2 of the reciprocal lattice vector of ΔY in the reciprocal lattice space, the period Λ, and the angle θ formed by the straight line L and the X axis are given as follows.

L2 = {(2β ₀ sin φ) ² + (Δβ sin φ) ² } ^1/2 (7)
Λ = 2π / L2
= 1 / {( ² sin φ / a _y ) ² + ((1 / a _II −1 / a _I ) sin φ) ² } ^1/2 (8)
θ = θt−φ
= Tan ^-1 (2α)
= Tan ⁻¹ {(2 / a _y ) / (1 / a _II −1 / a _I )} (9)

Β ₀ = 2π / a _y , β ₁ = 2π / a _I , β ₂ = 2π / a _II , a _y is the period in the B direction, a _I is the period in the A direction of the first periodic structure, a _II shows the period in the A direction of the second periodic structure.

  FIG. 29 is a graph showing the relationship between the laser beam emission angle (refraction angle) θ3, the stripe angle θ, and the period Λ, and FIG. 30 is a chart showing data used in this graph. The vertical axis of the θ (°) data is shown on the left side of the graph, and the vertical axis of the Λ (nm) data is shown on the right side of the graph.

  It can be seen that as the laser beam emission angle θ3 increases, the stripe angle θ increases and the period Λ decreases. In the graph, when the angle θ3 is increased from 0 ° to 70 °, the angle θ increases from 84.27 ° to 89.54 °, and the period Λ decreases from 486.08 nm to 463.43 nm. However, it is within the practically feasible numerical range.

  In FIG. 23, when a periodic pattern for total reflection is formed in both photonic crystal layers 4 and 4 ′, a diffraction grating layer having a new periodic structure that gives the above ΔY separately from these. 4 ″ (the structure is the same as that of the diffraction grating layer 4 ′ in the case of FIG. 28) can be formed between the upper cladding layer 5 and the diffraction grating layer 4 (FIG. 31A). A diffraction grating layer 4 ″ having a new periodic structure (the structure is the same as that of the diffraction grating layer 4 ′ in FIG. 28) may be formed between the lower cladding layer 2 and the diffraction grating layer 4 ′ (FIG. 31). (B)). As described above, in the above example, the diffraction grating structure that contributes to resonance by coupling the laser beam reflected by the light emitting end face with the laser beam that resonates inside the active layer by satisfying the total reflection critical angle condition (see FIG. 28, the diffraction grating layer of FIG. 31). In this case, energy use efficiency is increased.

  FIG. 32 is a plan view of the photonic crystal layer 4 having various periodic structures. In any photonic crystal layer 4, the different refractive index portions 4B are periodically embedded in the basic layer 4A. 32A shows a square lattice, FIG. 32B shows a rectangular lattice, FIG. 32C shows a triangular lattice, and FIG. 32D shows a face-centered rectangular lattice. As described above, in the photonic crystal layer 4, two periodic structures having different periods are included so as to overlap in one photonic crystal layer 4, or in the two photonic crystal layers 4, 4 ′. A configuration in which each is included and overlapped in plan view is employed. In these figures, examples of each periodic structure before superposition are shown, and two types of periodic structures are arranged so as to overlap each other so that the directions of the respective basic translation vectors (indicated by arrows) coincide.

  Specifically, in the photonic crystal layer 4 of FIG. 32A, the different refractive index portions 4B are arranged at the lattice point positions of the square lattice. A square lattice has a shape in which squares are arranged without gaps, and the length a of one side of a square constituting one lattice is equal to the length b of the other side. In other words, the horizontal arrangement period a of the different refractive index portions 4B is equal to the vertical arrangement period b. Here, the arrow in the figure represents the basic translation vector of the lattice. Even if the pattern is translated by a linear sum of integral multiples of these basic translation vectors, it overlaps the original pattern. That is, this lattice system has a translational symmetry defined by this basic translation vector.

  In the photonic crystal layer 4 of FIG. 32B, the different refractive index portions 4B are arranged at the lattice point positions of the rectangular lattice. The rectangular lattices having different vertical and horizontal lengths are shapes in which rectangles are arranged without gaps, and the length a of one side of a rectangle constituting one lattice is different from the length b of the other side. In other words, the horizontal arrangement period a of the different refractive index portions 4B is different from the vertical arrangement period b. Here, the arrow in the figure represents the basic translation vector of the lattice. Even if the pattern is translated by a linear sum of integral multiples of these basic translation vectors, it overlaps the original pattern. That is, this lattice system has a translational symmetry defined by this basic translation vector.

  In the photonic crystal layer 4 of FIG. 32C, the different refractive index portions 4B are arranged at the lattice point positions of the triangular lattice. The triangular lattice is a shape in which triangles are arranged without gaps, and the length of the bases of the triangles constituting one lattice is a, and the height is b. When the triangle is an equilateral triangle, in other words, the length a of the base is the horizontal arrangement period a of the different refractive index portions 4B, and the vertical arrangement period b is √2 times a. Here, the arrow in the figure represents the basic translation vector of the lattice. Even if the pattern is translated by a linear sum of integral multiples of these basic translation vectors, it overlaps the original pattern. That is, this lattice system has a translational symmetry defined by this basic translation vector.

  In the photonic crystal layer 4 of FIG. 32D, the different refractive index portions 4B are arranged at the lattice point positions of the face-centered rectangular lattice. The face-centered rectangular lattice is a lattice additionally provided with a lattice point at the center position in each lattice of the rectangular lattice, and the rectangular lattice itself is formed by arranging rectangles without gaps. Here, the arrow in the figure represents the basic translation vector of the lattice. Even if the pattern is translated by a linear sum of integral multiples of these basic translation vectors, it overlaps the original pattern. That is, this lattice system has a translational symmetry defined by this basic translation vector.

  As described above, the A axis is inclined with respect to the X axis, and these are not parallel. In other words, the photonic crystal layer 4 described in FIGS. 2 to 12 and FIGS. 23 to 32 has a different refractive index portion in the photonic crystal layer 4 when viewed from the thickness direction of the semiconductor laser element. 4B is arranged at a lattice point position of the lattice structure, and the direction of the basic translation vector (A axis, B axis) of the lattice structure is a direction (X axis) parallel to the light emitting end face LES (see FIG. 4). Is different. In this case, one laser beam can satisfy the total reflection critical angle condition by setting the inclination to a certain value or more.

  The lattice structure of the photonic crystal layer, when viewed from the thickness direction, is a square lattice and a rectangular lattice, a rectangular lattice and a rectangular lattice, a triangular lattice and a face-centered rectangular lattice, a face-centered rectangular lattice and a surface. It can be constituted by a combination of a square lattice, a rectangular lattice, a triangular lattice, or a face-centered rectangular lattice, such as a centered rectangular lattice. That is, it is possible to configure a single grating as described above by combining gratings having different pitches in one direction.

  When the above-described square lattice (FIG. 32A) and the square lattice (FIG. 32B) are overlapped, the photonic crystal layer 4 (or 4, 4 ′) has a tetragonal lattice and a rectangular lattice of crystals. A period of one axial direction of the hole lattice is a1, a period of the axial direction perpendicular to the one axis is b1, a period of one axial direction of the rectangular lattice is a2, When the period in the axial direction orthogonal to one of the axes is b2, a1 = b1, a1 ≠ a2, and b1 = b2 can be satisfied. In this case, a standing wave state is formed in the photonic crystal layer surface by oblique light waves that are not orthogonal to each other, and the angle formed by the oblique light waves changes according to the difference between a1 and a2.

  When two rectangular lattices (FIG. 32B) are overlapped, the photonic crystal layer 4 (or 4, 4 ′) includes the crystal structures of the first and second rectangular lattices. , The period of one axial direction of the first rectangular lattice is a1, the period of the axial direction orthogonal to the one axis is b1, the period of one axial direction of the second rectangular lattice is a2, When the period in the axial direction orthogonal to the axis is b2, a1 ≠ a2 and b1 = b2 can be satisfied. In this case, a standing wave state is formed in the photonic crystal layer surface by oblique light waves that are not orthogonal to each other, and the angle formed by the oblique light waves changes according to the difference between a1 and a2.

  When two face-centered rectangular lattices (FIG. 32D) are overlapped, the photonic crystal layer 4 (or 4, 4 ′) has a crystal structure of the first and second face-centered rectangular lattices. The period of one axial direction of the first face-centered rectangular lattice is a1, the period of the axial direction orthogonal to the one axis is b1, and one axis of the second face-centered rectangular lattice is If the period in the direction is a2 and the period in the axial direction orthogonal to the one axis is b2, a1 ≠ a2 and b1 = b2 can be satisfied. In this case, a standing wave state is formed in the photonic crystal layer surface by oblique light waves that are not orthogonal to each other, and the angle formed by the oblique light waves changes according to the difference between a1 and a2.

  One face-centered rectangular lattice can be a triangular lattice. The triangular lattice is a special case in which the angle formed by the basic translation vectors forming the lattice of the face-centered rectangular lattice is 60 degrees.

  As shown in FIG. 2, the semiconductor laser element 10A includes a region (first region, second region...) R immediately below the drive electrode of the active layer 3B. The different refractive index portion 4B of the photonic crystal layer corresponding to the first region R of the active layer 3B and the different refractive index portion 4B of the photonic crystal layer corresponding to the second region R of the active layer 3B are the first region. The laser beams output from R and the second region R can be set to have different shapes when viewed from the thickness direction of the semiconductor laser element so that the refraction angles of the laser beams are different and the intensities are matched. In other words, the size of the hole (different refractive index portion) is changed so that the diffraction intensities of a plurality of photonic crystals are the same. Since the intensity is the same, it can be easily applied to electronic devices such as laser printers and radars.

  For example, the hole (different refractive index portion) changes the length along the direction along the basic translation vector having a different period. Specifically, in the first region R, the dimension of the different refractive index portion 4B along the direction in which the arrangement periods of the different refractive index portions 4B in the first periodic structure and the second periodic structure are different (for example, the B axis) is In the second region R, the different refractive index portions along the direction in which the arrangement periods of the different refractive index portions 4B in the third and fourth periodic structures are different (for example, the B axis) are different depending on the positions along the different directions. The dimension of 4B changes according to the position along the said different direction. As a result, the diffraction intensities in the first periodic structure and the second periodic structure, or the diffraction intensities in the third periodic structure and the fourth periodic structure can be made uniform, and the oscillation can be stabilized.

  The laser beam deflection apparatus shown in FIG. 12 includes a semiconductor laser element 10A and a drive current supply circuit 11 that selectively supplies a drive current to an electrode group E2 including a first drive electrode and a second drive electrode. . By controlling the supply of the drive current, the emission of the laser beam LB can be controlled. Here, the drive current supply circuit 11 can further include means for changing the ratio of the drive current supplied to each electrode E2 of the electrode group. That is, in FIG. 12, reference numerals SW1 to SW5 indicate amplifiers with switches, and the amplifiers can control the magnitude of the drive current supplied from the power supply circuit 11A. In this case, the control circuit 11B can control the ratio of the drive current supplied to each electrode E2 by controlling the gain of each amplifier.

  In addition, the period along the basic translation vector in the first periodic structure in the first region R can be continuously changed as the third periodic structure in the second region R is approached. In this case, there is an effect that reflection can be prevented from occurring at the interface between the photonic crystals having different periods.

  In the laser beam deflection apparatus shown in FIG. 12, it is preferable that the wavelengths of the laser beams output from the active layer immediately below each electrode E2 are the same. This is because when the laser beam is scanned by a mirror or the like, the wavelengths of the laser beams before and after the deflection are the same. Therefore, when a drive current is supplied to the first and second drive electrodes E2, the resonances of the laser beams generated in the first region R and the second region R of the active layer immediately below the first and second drive electrodes E2, respectively. It is preferable to set so that the wavelengths are the same.

That is, the periodic structure (first periodic structure, second periodic structure) superimposed in the first region R and the periodic structure (third periodic structure, fourth periodic structure) superimposed in the second region R are as follows: Meet the relationship.
For example, when considering a structure composed of a combination of a rectangular lattice and a rectangular lattice, the following relational expression is obtained.
b11 = b21 = b ₀ / √ (1-sin ² δθ1)
δθ1 = φ−sin ⁻¹ (sin θ31 / n _dev )
b12 = b22 = b ₀ / √ (1-sin ² δθ2)
δθ2 = φ−sin ⁻¹ (sin θ32 / n _dev )

  However, the B-axis direction period of the first rectangular lattice superimposed in the first region R is b11, the B-axis direction period of the second rectangular lattice is b21, and the beam emission angle of the first region R is θ31. The period of the first rectangular lattice superimposed in the second region R in the B-axis direction is b12, the period of the second rectangular lattice in the B-axis direction is b22, and the beam emission angle of the second region R is θ32 It was.

  Although the above shows a combination of a rectangular lattice and a rectangular lattice, the same applies to other lattice systems.

  Note that the above-described laser beam deflection apparatus can be miniaturized because the element itself has a deflection function, and high reliability and high speed can be expected. Since it is small in size, it is expected to be used as a laser knife or a photodynamic therapy (PDT) light source incorporated in a portable device or incorporated in a medical capsule endoscope. Of course, the application to the display by a large-sized laser scanning is also considered. Since the stray light of the laser beam is not output to the outside, an improvement in reliability is expected.

  Next, a modification of the semiconductor laser element included in the semiconductor laser device LD1 will be described with reference to FIGS.

  Similar to the semiconductor laser element 10A, the semiconductor laser element 10B is an edge-emitting semiconductor laser element. As shown in FIGS. 33 to 36, the semiconductor laser device 10B includes a semiconductor substrate 1, a lower cladding layer 2, a lower light guide layer 3A, an active layer 3B, an upper light guide layer 3C, a photonic crystal layer 4, and an upper cladding. A layer 5, a contact layer 6, an electrode E1, and a plurality of drive electrodes E2 are provided. FIG. 33 is a schematic perspective view of the semiconductor laser device. FIG. 34 is a diagram showing a cross-sectional configuration of the semiconductor laser element taken along line XXXIV-XXXIV. FIG. 35 is a diagram showing a cross-sectional configuration along the line XXXV-XXXV of the semiconductor laser element. FIG. 36 is a plan view of the semiconductor laser device.

  A part of the surface on the contact layer 6 is covered with an insulating film SH. A plurality of electrode pads EP are disposed on the insulating film SH.

  The planar shape of the semiconductor laser element 10B is a rectangle. When an XYZ three-dimensional orthogonal coordinate system is set, the thickness direction is the Z axis, the width direction is the X axis, and the direction perpendicular to the light emitting end surface LES is the Y axis. To do. In the XY plane, the extending longitudinal direction of each drive electrode E2 is parallel to a straight line parallel to the Y axis.

  The upper surface of the contact layer 6 (the surface on which the insulating film SH is formed) is viewed from the light emitting end surface LES side in the Y-axis direction when viewed from the thickness direction of the semiconductor laser element 10B, and the first region 6a, the second region 6b, And the third region 6c. The second region 6b is located between the first region 6a and the third region 6c in the Y-axis direction. Each region 6a6b, 6c extends in the X-axis direction. The insulating film SH is disposed on the third region 6 c of the contact layer 6.

  The plurality of drive electrodes E2 are juxtaposed in the X-axis direction in the second region 6b when viewed from the thickness direction of the semiconductor laser element 10B. Each drive electrode E2 has a rectangular shape. Specifically, each drive electrode E2 has a rectangular shape with the long side in the Y-axis direction. That is, the plurality of drive electrodes E2 are juxtaposed in the short side direction of the drive electrode E2. When viewed from the thickness direction of the semiconductor laser element 10B, the longitudinal direction of the drive electrode E2 is parallel to the normal line (Y axis) of the light emitting end face LES of the semiconductor laser element 10B.

  When a current is passed between the upper and lower electrodes E1, E2, a current flows through a region R immediately below one of the electrodes E2, and the region R emits light. The plurality of drive electrodes E2 supply a drive current to a plurality of regions R located in parallel with the light emitting end face LES and extending in the active layer 3B, that is, in the X-axis direction, in the active layer 3B.

  As shown in FIGS. 35 and 36, each electrode pad EP is electrically connected to the corresponding drive electrode E2 through a wiring W1 disposed on the insulating film SH. The number of drive electrodes E2 and the number of electrode pads EP are the same. In the present embodiment, the plurality of electrode pads EP are arranged in a plurality of rows along the X-axis direction. The plurality of electrode pads EP are located above the third region 6c. In the present embodiment, each electrode pad EP has a square shape. 33 and 34, the wiring W1 is not shown.

  In the present modification, the photonic crystal layer 4 includes a first photonic crystal layer 41 and a second photonic crystal layer 43. That is, the first photonic crystal layer 41 and the second photonic crystal layer 43 include a basic layer 4A and a plurality of embedded layers (different refractive index portions) 4B periodically embedded in the basic layer 4A. Each has. The first photonic crystal layer 41 and the second photonic crystal layer 43 are located in the same layer, and the second photonic crystal layer 43 is closer to the light emitting end face LES than the first photonic crystal layer 41. positioned. The shape of the burying layer 4B in the XY plane may be a rectangle, a square, an ellipse, or a circle, or an isosceles triangle or an equilateral triangle, as shown in FIGS.

  FIG. 37 is a plan view of the first photonic crystal layer.

The first photonic crystal layer 41 is located below the plurality of drive electrodes E2. In the first photonic crystal layer 41, when viewed from the thickness direction, the buried layer 4B is disposed at each lattice point (Γ point) constituting a square lattice. That is, the buried layer 4B is aligned in the X-axis direction and the Y-axis direction to form a two-dimensional periodic structure. As a result, the first photonic crystal layer 41 has a periodic structure in which the arrangement period of the buried layers 4B is the same over a region corresponding to the plurality of regions R. The period C1 in the alignment direction of the buried layer 4B is:
λ ₀ / n ₁
Is set to λ ₀ is the wavelength of the laser light in vacuum. n ₁ is an equivalent refractive index of light in the first photonic crystal layer 41.

  The laser beam is generated in the active layer 3B, but the light oozing out from the active layer 3B is affected by the adjacent first photonic crystal layer 41. In the first photonic crystal layer 41, a periodic refractive index distribution structure as shown in FIG. 37 is formed. As a result of diffraction by the first photonic crystal layer 41, a laser beam is generated in the direction indicated by the arrow in FIG. Since the first photonic crystal layer 41 has a periodic structure in which the arrangement period of the buried layer 4B is the same over a region corresponding to the plurality of regions R, the laser is emitted from each region R in the same direction. A beam is output. In the present embodiment, a laser beam directed in the Y-axis direction, that is, toward the light emitting end surface LES is used.

  The arrangement of the buried layer 4B in the first photonic crystal layer 41 is not limited to the arrangement shown in FIG. 37, and may be the arrangement shown in FIGS.

In FIG. 38A, the buried layer 4B is disposed at each M point of the square lattice. The buried layer 4B is inclined in the X axis direction and the Y axis direction by 45 degrees and is aligned in two directions orthogonal to each other. The period C2 in the alignment direction of the buried layer 4B is:
²⁻¹ / ² × λ ₀ / n ₁
Is set to Also in this case, the traveling direction of the main light wave is a direction along the X-axis direction and the Y-axis direction, as indicated by arrows in the drawing.

In FIG. 38B, the buried layers 4B are respectively arranged at the Γ points of the triangular lattice. The period C3 of the buried layer 4B is
λ ₀ / n ₁
Is set to In this case, the traveling direction of the main light wave is the direction of 60 ° intervals indicated by arrows in the figure. In FIG. 38C, the embedded layer 4B is disposed at each point J of the triangular lattice. The period C4 of the buried layer 4B is
2 × 3 ^−1/2 × λ ₀ / n ₁
Is set to In this case, the traveling direction of the main light wave is the direction of 60 ° intervals indicated by arrows in the figure.

  In this modification, the lower clad layer 2, the lower light guide layer 3A, the active layer 3B, the upper light guide layer 3C, the first photonic crystal layer 41, the upper clad layer 5, and the plurality of drive electrodes E2 serve as the oscillation unit. Configure. The oscillation unit generates a plurality of laser beams and outputs the generated plurality of laser beams in the same direction.

  FIG. 39 is a plan view of the second photonic crystal layer.

Also in the second photonic crystal layer 43, the buried layer 4B constitutes a two-dimensional periodic structure. The plurality of buried layers 4B in the second photonic crystal layer 43 are arranged at lattice point positions of a predetermined lattice structure. In this predetermined lattice structure, the angle φ formed by the two basic translation vectors is the angle (exit angle) formed by the direction orthogonal to one basic translation vector of the predetermined lattice structure and the laser beam emission direction, θ _out1. As
φ = tan ⁻¹ {sin θ / ( ² cos ² (θ _out1 / 2))}
Meet.

The period C5 of the lattice point in the direction along one basic translation vector of the lattice structure of the buried layer 4B in the second photonic crystal layer 43 is:
λ ₀ / (n ₂ × sin θ _out1 )
Meet. The period C6 of the lattice points in the direction orthogonal to one basic translation vector of the lattice structure of the buried layer 4B in the second photonic crystal layer 43 is as follows when m is an arbitrary natural number:
(2m-1) × λ ₀ / (2n ₂ )
Meet. n ₂ is an equivalent refractive index of light in the second photonic crystal layer 43.

  The angle φ formed by the two basic translation vectors (or the interval between the buried layers 4B in the X-axis direction) changes continuously as shown in FIG. 39 according to the position in the X-axis direction. That is, the second photonic crystal layer 43 has the above-described periodic structure in which the arrangement period of the buried layer 4B is different for each region corresponding to the plurality of regions R. The second photonic crystal layer 43 constitutes a deflection unit that deflects a plurality of laser beams output in the same direction from the oscillation unit in different directions and emits them from the light emitting end face by the periodic structure.

The second photonic crystal layer 43 causes, in each region corresponding to the plurality of regions R, interference that weakens light transmitted in the same direction as the output direction of the laser beam from the oscillating unit, and the light emitting end surface LES. Intensive interference is generated for the light diffracted in the laser beam emission direction from the laser beam. In the second photonic crystal layer 43, when viewed in the thickness direction, the buried layer 4B has an equal interval (same as in the Y-axis direction, that is, the same direction as the laser beam output direction from the oscillation unit). Arranged in an array period). The period of the buried layer 4B in the Y-axis direction is such that m is an arbitrary natural number,
(2m-1) × λ ₀ / (2n ₂ )
Is set to The period of the buried layer 4B in the X-axis direction parallel to the light emission end face LES is:
λ ₀ / (n ₂ × sin θ)
Is set to

  As described above, in the present modification, the first photonic crystal layer 41 has a periodic structure in which the arrangement period of the buried layers 4B is the same over a region corresponding to the plurality of regions R. From the unit, a laser beam is output in the same direction for each of the plurality of drive electrodes E2. Since the second photonic crystal layer 43 has a periodic structure in which the arrangement period of the buried layer 4B is different for each region corresponding to the plurality of regions R, the deflection unit outputs the same in the same direction. The laser beams thus produced are deflected in different directions and emitted from the light emitting end face LES.

  In this modification, in the semiconductor laser element 10A, the oscillation unit and the deflection unit are separated, and the first photonic crystal layer 41 extends over a region corresponding to the plurality of regions R, and the arrangement period of the buried layers 4B is the same. It has a periodic structure. For this reason, the oscillation threshold is constant for each laser beam, and stable operation can be realized.

  The second photonic crystal layer 43 causes interference that weakens light transmitted in the same direction as the output direction of the laser beam from the oscillation unit in each region corresponding to the plurality of regions R, and from the light emitting end surface LES. Interference that reinforces the light diffracted in the laser beam emission direction. Thereby, the deflecting unit can surely deflect each laser beam output in the same direction from the oscillation unit in a different direction and emit the laser beam from the light emitting end surface.

  Next, the configuration of the semiconductor laser element 10C according to a new modification will be described. FIG. 40 is a schematic perspective view of the semiconductor laser device. FIG. 41 is a diagram showing a cross-sectional configuration of the semiconductor laser element. FIG. 42 is a plan view of the semiconductor laser device.

  As shown in FIGS. 40 to 42, the semiconductor laser device 10B according to this modification also includes a semiconductor substrate 1, a lower cladding layer 2, a lower light guide layer 3A, an active layer 3B, an upper light guide layer 3C, and a photonic crystal. A layer 4 (first and second photonic crystal layers 41 and 43), an upper cladding layer 5, a contact layer 6, an electrode E1, a plurality of drive electrodes E2, and a plurality of electrode pads EP are provided.

  As shown in FIGS. 40 and 42, in the XY plane, the extending longitudinal direction of each drive electrode E2 forms an angle γ with respect to a straight line parallel to the Y axis. That is, the longitudinal direction of the drive electrode E2 is inclined with respect to the normal line (Y axis) of the light emitting end face LES of the semiconductor laser element when viewed from the thickness direction of the semiconductor laser element.

  FIG. 43 is a plan view of the first photonic crystal layer.

  In the first photonic crystal layer 41, the buried layer 4B is aligned in the x-axis direction and the y-axis direction to form a two-dimensional periodic structure. The xyz orthogonal coordinate system is a coordinate system obtained by rotating the XYZ orthogonal coordinate system by an angle γ around the Z axis. That is, the buried layer 4B is arranged at each lattice point (Γ point) constituting a square lattice in the xyz orthogonal coordinate system. The light generated in the active layer 3B is diffracted by the first photonic crystal layer 41, and as a result, is output as a laser beam directed in the direction indicated by the arrow in FIG. The laser beam toward the light emitting end surface LES is output in the y-axis direction, that is, in a direction inclined by an angle γ from the Y-axis direction.

  FIG. 44 is a plan view of the second photonic crystal layer.

In the second photonic crystal layer 43, an angle φ formed by two basic translation vectors in the xyz orthogonal coordinate system is
φ = tan ⁻¹ {sin θ / ( ² cos ² (θ _out1 / 2))}
And the period of the lattice point in the direction along one basic translation vector of the lattice structure of the buried layer 4B in the second photonic crystal layer 43 is
λ ₀ / (n ₂ × sin θ _out1 )
And the period of the lattice point in the direction orthogonal to one basic translation vector of the lattice structure of the buried layer 4B in the second photonic crystal layer 43 is m as an arbitrary natural number,
(2m-1) × λ ₀ / (2n ₂ )
Meet.

  Therefore, also in the present modification, the first photonic crystal layer 41 has a periodic structure in which the arrangement period of the buried layer 4B is the same over a region corresponding to the plurality of regions R. The laser beam is output in the same direction (a direction rotated by an angle γ around the Z axis from the laser beam output direction in the above-described embodiment) for each of the plurality of drive electrodes E2. Since the second photonic crystal layer 43 has a periodic structure in which the arrangement period of the buried layer 4B is different for each region corresponding to the plurality of regions R, the deflection unit outputs the same in the same direction. The laser beams thus produced are deflected in different directions and emitted from the light emitting end face LES. In this modification, a laser beam is emitted also in a direction orthogonal to the light emission end face LES.

  Also in this modified example, in the semiconductor laser element 10B, the oscillation threshold is constant for each laser beam, and stable operation can be realized. In addition, the deflecting unit can surely deflect each laser beam output from the oscillating unit in the same direction in different directions and emit the laser beam from the light emitting end surface.

  The preferred embodiments of the present invention have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  In the semiconductor laser elements 10A to 10C, the drive electrodes are supplied to two adjacent drive electrodes E2 in the direction in which the plurality of drive electrodes E2 are arranged, and the two layers in the active layer 3B are viewed in the thickness direction of the semiconductor laser elements 10A to 10C. A laser beam may be generated in a region located between the two drive electrodes E2.

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Lower clad layer, 3B ... Active layer, 4 ... Photonic crystal layer, 4B ... Different refractive index part (buried layer), 5 ... Upper clad layer, 10A-10C ... Semiconductor laser element, 20 ... Collimating lens, 41 ... first photonic crystal layer, 43 ... second photonic crystal layer, E2 ... drive electrode, LB ... laser beam, LD1 ... semiconductor laser device, LES ... light emitting end face.

Claims (13)

A semiconductor laser device comprising: an edge-emitting semiconductor laser element; and a collimating lens that collimates a laser beam emitted from the semiconductor laser element,
The semiconductor laser element is
A lower cladding layer formed on the substrate;
An upper cladding layer;
An active layer interposed between the lower cladding layer and the upper cladding layer;
A photonic crystal layer interposed between the active layer and at least one of the upper and lower cladding layers;
A plurality of drive electrodes for supplying a drive current to a plurality of regions in the active layer that are parallel to the light emitting end face and aligned in the first direction in which the active layer extends;
A plurality of laser beams are emitted in different directions from each position corresponding to the plurality of regions on the light emitting end face,
The collimating lens is
The front surface and the rear surface have a curvature in the cross section including the first direction and the optical axis, so that the optical path lengths from the respective positions corresponding to the plurality of regions in the light emitting end surface to the front main plane are equal, The collimating lens refracts and emits a plurality of laser beams emitted from the semiconductor laser element in a plane parallel to the thickness direction of the semiconductor laser element ,
The collimating lens, the refractive index is n, the front radius of curvature as R _1, the rear-side radius of curvature when the R _2,
F (θ) = {(n−1) × (1 / R ₁ + 1 / R ₂ )} ⁻¹
The front curvature radius R ₁ and the rear curvature radius R ₂ are set so that the focal length F (θ) represented by the following formula is constant .
A semiconductor laser device. In the collimating lens, the curvatures of the front surface and the rear surface in the cross section including the first direction and the optical axis are constant, respectively.
The optical path length from each position corresponding to the plurality of regions on the light emitting end surface to the front main plane and the focal length of the collimating lens are substantially the same.
The semiconductor laser device according to claim 1 . The center of curvature of the front surface and the rear surface in the cross section including the first direction and the optical axis is located at the center in the first direction of the semiconductor laser element, and the center of curvature of the front surface and the rear surface is used as an origin. The coordinate axis parallel to one direction is the X axis, the coordinate axis perpendicular to the light emitting end face is the Y axis, the width of the semiconductor laser element in the X axis direction is W, and the laser beam is normal to the light emitting end face. Is 0 at the center of the semiconductor laser element in the first direction and increases toward the end of the semiconductor laser element in the X-axis direction, and the X-axis of the semiconductor laser element is increased. When the maximum value of the angle θ at the end in the direction is θ _max
The position y ₀ in the Y-axis direction of the light emitting end surface with respect to the center of curvature is
y ₀ <W / (2 × tan θ _max )
And the angle θ at position x along the X axis is
θ = atan (x / y ₀ )
Stipulated based on
The collimating lens has a focal length F (θ) with respect to an angle θ when the optical path length between the center of curvature of the front and rear surfaces and the front main plane is OP.
F (θ) = OP−y ₀ × (1 + tan ² θ) ^1/2
Stipulated based on
The semiconductor laser device according to claim 1 . A semiconductor laser device comprising: an edge-emitting semiconductor laser element; and a collimating lens that collimates a laser beam emitted from the semiconductor laser element,
The semiconductor laser element is
A lower cladding layer formed on the substrate;
An upper cladding layer;
An active layer interposed between the lower cladding layer and the upper cladding layer;
A photonic crystal layer interposed between the active layer and at least one of the upper and lower cladding layers;
A plurality of drive electrodes for supplying a drive current to a plurality of regions in the active layer that are parallel to the light emitting end face and aligned in the first direction in which the active layer extends;
A plurality of laser beams are emitted in different directions from each position corresponding to the plurality of regions on the light emitting end face,
In the collimating lens, the front surface and the rear surface have a curvature in a cross section including the first direction and the optical axis so that the optical path lengths from the respective positions corresponding to the plurality of regions on the light emitting end surface to the front main plane are equal. The collimating lens refracts and emits a plurality of laser beams emitted from the semiconductor laser element in a plane parallel to the thickness direction of the semiconductor laser element ,
The center of curvature of the front surface and the rear surface in the cross section including the first direction and the optical axis is located at the center in the first direction of the semiconductor laser element, and the center of curvature of the front surface and the rear surface is used as an origin. The coordinate axis parallel to one direction is the X axis, the coordinate axis perpendicular to the light emitting end face is the Y axis, the width of the semiconductor laser element in the X axis direction is W, and the laser beam is normal to the light emitting end face. Is 0 at the center of the semiconductor laser element in the first direction and increases toward the end of the semiconductor laser element in the X-axis direction, and the X-axis of the semiconductor laser element is increased. when the maximum value of the angle theta in the end in the direction is theta _max,
The position y ₀ in the Y-axis direction of the light emitting end surface with respect to the center of curvature is
y ₀ <W / (2 × tan θ _max )
And the angle θ at position x along the X axis is
θ = atan (x / y ₀ )
Stipulated based on
The collimating lens has a focal length F (θ) with respect to an angle θ when the optical path length between the center of curvature of the front and rear surfaces and the front main plane is OP.
F (θ) = OP−y ₀ × (1 + tan ² θ) ^1/2
Stipulated based on
A semiconductor laser device. In the collimating lens, the front main plane is y ₀ × ((1 + tan ² θ) ^1/2 −1) in the radial direction of the curvature of the front and rear surfaces.
Only located away from the semiconductor laser element,
The semiconductor laser device according to claim 3 or 4 , wherein The active layer includes a first region and a second region as the plurality of regions,
The plurality of drive electrodes include a first drive electrode for supplying a drive current to the first region, and a second drive electrode for supplying a drive current to the second region,
The longitudinal direction of the first drive electrode is inclined with respect to the normal of the light emitting end face when viewed from the thickness direction of the semiconductor laser element,
The region corresponding to the first region of the photonic crystal layer has first and second periodic structures in which arrangement periods of different refractive index portions having different refractive indexes from the surroundings are different from each other,
A predetermined angle with respect to the longitudinal direction of the first drive electrode when viewed from the thickness direction of the semiconductor laser element according to the difference between the reciprocals of the arrangement periods of the first and second periodic structures. 2 or more laser beams are generated inside the semiconductor laser element, and one of these laser beams toward the light emitting end face is set to have a refraction angle of less than 90 degrees with respect to the light emitting end face. And at least one further toward the light exit end face is set to satisfy a total reflection critical angle condition with respect to the light exit end face,
The longitudinal direction of the second drive electrode is inclined with respect to the normal of the light emitting end face when viewed from the thickness direction of the semiconductor laser element,
The region corresponding to the second region of the photonic crystal layer has third and fourth periodic structures in which arrangement periods of different refractive index portions having different refractive indexes from the surroundings are different from each other,
A predetermined angle with respect to the longitudinal direction of the second drive electrode when viewed from the thickness direction of the semiconductor laser element according to the difference between the reciprocals of the arrangement periods in the third and fourth periodic structures. 2 or more laser beams are generated inside the semiconductor laser element, and one of these laser beams toward the light emitting end face is set to have a refraction angle of less than 90 degrees with respect to the light emitting end face. And at least one other toward the light exit end face is set so as to satisfy a total reflection critical angle condition with respect to the light exit end face,
The difference between the reciprocal numbers of the array periods in the first and second periodic structures is different from the difference between the reciprocal numbers of the array periods in the third and fourth periodic structures.
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is a semiconductor laser device. The semiconductor laser element generates a plurality of laser beams, and outputs a plurality of generated laser beams in the same direction, and a plurality of laser beams output in the same direction from the oscillation unit in different directions. And a deflecting unit that deflects the light to exit from the light exit end face,
The oscillation unit includes the lower cladding layer, the upper cladding layer, the active layer, a first photonic crystal layer as the photonic crystal layer, and the plurality of drive electrodes,
The deflection unit includes a second photonic crystal layer,
The first photonic crystal layer has a periodic structure in which the arrangement period of different refractive index portions having different refractive indexes from the surroundings is the same over the region corresponding to the plurality of regions,
The second photonic crystal layer has a periodic structure in which the arrangement period of the different refractive index portions having different refractive indexes from the surroundings is different for each region corresponding to the plurality of regions.
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is a semiconductor laser device. The second photonic crystal layer causes, in each region corresponding to the plurality of regions, interference that weakens light transmitted in the same direction as the output direction of the laser beam from the oscillation unit, and the light emission Intensifying interference that diffracts the light diffracted in the laser beam exit direction from the end face,
The semiconductor laser device according to claim 7. A semiconductor laser device comprising: an edge-emitting semiconductor laser element; and a collimating lens that collimates a laser beam emitted from the semiconductor laser element,
The semiconductor laser element is
A lower cladding layer formed on the substrate;
An upper cladding layer;
An active layer interposed between the lower cladding layer and the upper cladding layer;
A photonic crystal layer interposed between the active layer and at least one of the upper and lower cladding layers;
A plurality of drive electrodes for supplying a drive current to a plurality of regions in the active layer that are parallel to the light emitting end face and aligned in the first direction in which the active layer extends;
A plurality of laser beams are emitted in different directions from each position corresponding to the plurality of regions on the light emitting end face,
In the collimating lens, the front surface and the rear surface have a curvature in a cross section including the first direction and the optical axis so that the optical path lengths from the respective positions corresponding to the plurality of regions on the light emitting end surface to the front main plane are equal. The collimating lens refracts and emits a plurality of laser beams emitted from the semiconductor laser element in a plane parallel to the thickness direction of the semiconductor laser element ,
The active layer includes a first region and a second region as the plurality of regions,
The plurality of drive electrodes include a first drive electrode for supplying a drive current to the first region, and a second drive electrode for supplying a drive current to the second region,
The longitudinal direction of the first drive electrode is inclined with respect to the normal of the light emitting end face when viewed from the thickness direction of the semiconductor laser element,
The region corresponding to the first region of the photonic crystal layer has first and second periodic structures in which arrangement periods of different refractive index portions having different refractive indexes from the surroundings are different from each other,
A predetermined angle with respect to the longitudinal direction of the first drive electrode when viewed from the thickness direction of the semiconductor laser element according to the difference between the reciprocals of the arrangement periods of the first and second periodic structures. 2 or more laser beams are generated inside the semiconductor laser element, and one of these laser beams toward the light emitting end face is set to have a refraction angle of less than 90 degrees with respect to the light emitting end face. And at least one further toward the light exit end face is set to satisfy a total reflection critical angle condition with respect to the light exit end face,
The longitudinal direction of the second drive electrode is inclined with respect to the normal of the light emitting end face when viewed from the thickness direction of the semiconductor laser element,
The region corresponding to the second region of the photonic crystal layer has third and fourth periodic structures in which arrangement periods of different refractive index portions having different refractive indexes from the surroundings are different from each other,
A predetermined angle with respect to the longitudinal direction of the second drive electrode when viewed from the thickness direction of the semiconductor laser element according to the difference between the reciprocals of the arrangement periods in the third and fourth periodic structures. 2 or more laser beams are generated inside the semiconductor laser element, and one of these laser beams toward the light emitting end face is set to have a refraction angle of less than 90 degrees with respect to the light emitting end face. And at least one other toward the light exit end face is set so as to satisfy a total reflection critical angle condition with respect to the light exit end face,
The difference between the reciprocal numbers of the array periods in the first and second periodic structures is different from the difference between the reciprocal numbers of the array periods in the third and fourth periodic structures.
A semiconductor laser device. The collimating lens, the refractive index is n, the front radius of curvature as R _1, the rear-side radius of curvature when the R _2,
F (θ) = {(n−1) × (1 / R ₁ + 1 / R ₂ )} ⁻¹
The front curvature radius R ₁ and the rear curvature radius R ₂ are set so that the focal length F (θ) represented by the following formula is constant.
The semiconductor laser device according to claim 9 . In the collimating lens, the curvatures of the front surface and the rear surface in the cross section including the first direction and the optical axis are constant, respectively.
The optical path length from each position corresponding to the plurality of regions on the light emitting end surface to the front main plane and the focal length of the collimating lens are substantially the same.
11. The semiconductor laser device according to claim 9 , wherein the semiconductor laser device is a semiconductor laser device. The center of curvature of the front surface and the rear surface in the cross section including the first direction and the optical axis is located at the center in the first direction of the semiconductor laser element, and the center of curvature of the front surface and the rear surface is used as an origin. The coordinate axis parallel to one direction is the X axis, the coordinate axis perpendicular to the light emitting end face is the Y axis, the width of the semiconductor laser element in the X axis direction is W, and the laser beam is normal to the light emitting end face. Is 0 at the center of the semiconductor laser element in the first direction and increases toward the end of the semiconductor laser element in the X-axis direction, and the X-axis of the semiconductor laser element is increased. When the maximum value of the angle θ at the end in the direction is θ _max
The position y ₀ in the Y-axis direction of the light emitting end surface with respect to the center of curvature is
y ₀ <W / (2 × tan θ _max )
And the angle θ at position x along the X axis is
θ = atan (x / y ₀ )
Stipulated based on
The collimating lens has a focal length F (θ) with respect to an angle θ when the optical path length between the center of curvature of the front and rear surfaces and the front main plane is OP.
F (θ) = OP−y ₀ × (1 + tan ² θ) ^1/2
Stipulated based on
11. The semiconductor laser device according to claim 9 , wherein the semiconductor laser device is a semiconductor laser device. In the collimating lens, the front main plane is y ₀ × ((1 + tan ² θ) ^1/2 −1) in the radial direction of the curvature of the front and rear surfaces.
Only located away from the semiconductor laser element,
The semiconductor laser device according to claim 12 .

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