JP4885767B2 - Semiconductor waveguide device, semiconductor laser, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a wavelength tunable semiconductor laser used as an optical fiber communication light source and an optical measurement light source, and more particularly to an optical wavelength (frequency) multiplexing system light source in optical communication and an optical measurement light source covering a wide band wavelength band. It is.

  While research on optical wavelength (frequency) multiplex communication systems has been conducted in response to an increase in the amount of communication information, a wide range of wavelength adjustment functions are required as a light source for transmission and a tunable light source for synchronous detection. In the field of optical measurement, it is desired to realize a wavelength tunable light source that covers a wide wavelength band.

  Various variable wavelength light sources have been studied so far, and they can be broadly divided into those that change continuously in one oscillation mode and those that change discontinuously with mode jumping. Can be divided. In consideration of application to an actual system, it is preferable that the wavelength changes continuously from the viewpoint of controllability. As a means for controlling the wavelength of the wavelength tunable light source, the oscillation wavelength is controlled by using the refractive index change of the optical waveguide layer by temperature adjustment, and the oscillation wavelength by using the refractive index change of the optical waveguide layer by current injection. Two of them are mainly used. In terms of the wavelength change speed, it is preferable to use a change in refractive index due to current injection because faster wavelength switching is possible.

  As a wavelength tunable light source capable of continuously changing the oscillation wavelength by using the change in the refractive index of the optical waveguide layer by the current injection described above, a double waveguide laser (TTG laser) or a distributed reflection laser (DBR laser) is used. Semiconductor lasers such as those described above have been studied, and values of 7 nm for TTG lasers and 4.4 nm for DBR lasers have been reported as continuous wavelength variable widths. In recent years, so-called short resonator DRB lasers in which the active layer region is shortened in order to suppress the mode jump of the DBR laser have been studied.

  As the discontinuous wavelength variable width with mode jump, a value of 10 nm is obtained by the DBR laser. Moreover, as a semiconductor laser that is discontinuous but has a wide wavelength tunable width, a Y-branch laser, a super-periodic structure diffraction grating laser, and the like have been prototyped, and a wavelength tunable width of 50 to 100 nm is obtained.

  However, the conventional TTG laser and DBR laser as described above have the following problems.

In the TTG laser, a current is injected into an active waveguide layer that amplifies light to cause a laser oscillation operation, and a current is independently supplied to a wavelength control inactive waveguide layer formed in the immediate vicinity of the active waveguide layer. By injecting, the oscillation wavelength is changed. Here, if the period of the diffraction grating is Λ and the equivalent refractive index of the waveguide is n, the Bragg wavelength λb is expressed by the following equation (1).
λb = 2nΛ (1)

The laser oscillates in one resonant longitudinal mode near this Bragg wavelength. When current is injected into the inactive waveguide layer, the equivalent refractive index of the waveguide changes, and the Bragg wavelength also changes in proportion to the equation (1). Here, the change rate Δλb / λb of the Bragg wavelength is equal to the change rate Δn / n of the equivalent refractive index as shown in the following equation (2).
Δλb / λb = Δn / n (2)

In addition, the resonance longitudinal mode wavelength also changes as the equivalent refractive index changes due to current injection. In the case of a TTG laser, since the equivalent refractive index of the entire resonator changes uniformly, the change ratio Δλr / λr of the resonance longitudinal mode wavelength is expressed by the ratio Δn / of the change of the equivalent refractive index as shown in the equation (3). equal to n.
Δλr / λr = Δn / n (3)

  From the formulas (2) and (3), in the TTG laser, the change in the Bragg wavelength is equal to the change in the resonance longitudinal mode, so that the oscillation wavelength continuously changes while the first oscillation mode is maintained. Has characteristics.

  However, in order to perform a single transverse mode oscillation operation, the width of the double waveguide needs to be 1 to 2 μm, and the thickness of the n-type spacer layer formed between the active layer and the wavelength control layer Since it is necessary to reduce the thickness to 1 μm or less, a buried structure used in a normal semiconductor laser cannot be formed, and a structure for efficiently injecting current into each waveguide layer is manufactured. There was a problem that it was very difficult.

  In contrast, the DBR laser has a structure in which an active waveguide layer and an inactive waveguide layer for amplifying light are coupled in series, and therefore, a buried stripe structure for performing current confinement in the same manner as a normal semiconductor laser. Further, independent current injection into each waveguide layer can be easily realized by separating the electrodes formed above each waveguide layer.

The mechanism for changing the Bragg wavelength by changing the equivalent refractive index by injecting current into the inactive waveguide layer is the same as that of the TTG laser, but the region where the equivalent refractive index changes is limited to a part of the resonator. For this reason, the change amount of the Bragg wavelength does not match the change amount of the resonance longitudinal mode wavelength. The change rate Δλr / λr of the resonant longitudinal mode wavelength is the change rate Δn / n of the equivalent refractive index by the ratio of the effective length Le of the distributed reflector to the total resonator length L, as shown in the equation (4). Less than.
Δλr / λr = (Le / L) · (Δn / n) (4)

  Therefore, from the equations (2) and (4), the DBR laser has a drawback that the mode jump occurs because the Bragg wavelength and the resonance longitudinal mode wavelength are relatively separated as the wavelength control current is injected. It was. In order to prevent mode jumping, it is necessary to provide a phase adjustment region in which no diffraction grating is formed, and to match the amount of change in the resonant longitudinal mode and the amount of change in the Bragg wavelength by injecting current there.

  However, this method requires an external circuit for controlling the wavelength control current to the two electrodes, and there is a problem that the device structure and control become complicated. Another method that does not cause mode jumping is a short-cavity DBR laser that shortens the cavity length and widens the longitudinal mode interval. However, since the active layer needs to be shortened, a large output can be obtained. There was a problem that it was difficult.

  The continuous wavelength tunable width in the TTG laser and the DBR laser is limited to the amount of change in the refractive index of the wavelength control layer, and the value remains at about 4 to 7 nm. In order to further widen the wavelength variable width, it is necessary to use a means that allows mode jumping and that the wavelength change amount of the wavelength filter is larger than the refractive index change amount. Both the Y-branch laser and the super-periodic structure diffraction grating laser use a means for increasing the filter wavelength change amount more than the refractive index change amount. In these lasers, in order to change the filter wavelength greatly and to obtain sufficient wavelength selectivity, it is necessary to control the current flowing through the two electrodes, and also to provide an electrode for controlling the resonance longitudinal mode wavelength. Become. As a result, in order to adjust the oscillation wavelength, it is necessary to control the injection current to the three electrodes, and there is a problem that the control becomes very complicated.

  With respect to these problems, Patent Document 1, Non-Patent Document 1, and the like disclose a distributed active DFB laser (TDA-DFB-LD). The distributed active DFB laser can continuously change the oscillation wavelength by about 4 to 7 nm by controlling the injection current to one electrode, and can also efficiently inject current into the active waveguide layer and the inactive waveguide layer. Although the semiconductor laser is obtained and mode jump is involved, the oscillation wavelength can be changed over a range of about 50 to 100 nm by controlling the injection current to the two electrodes. According to such a structure, since the active layer volume can be sufficiently secured, it is possible to achieve high output.

  FIG. 11 shows the structure of a distributed active DFB laser disclosed in Non-Patent Document 1. FIG. 11A is a top view of the distributed active DFB laser, and FIG. 11B is a cross-sectional view taken along line xx ′ in FIG.

  As shown in FIG. 11, the distributed active DFB laser has an active waveguide layer 502 and an inactive waveguide layer (wavelength control region) 503 alternately on the lower clad 501 with constant lengths La and Lt, respectively. It has a structure that is periodically coupled in series. An upper cladding 504 is formed on the active waveguide layer 502 and the inactive waveguide layer 503, and unevenness, that is, a diffraction grating 505 is formed between the active waveguide layer 502 and the inactive waveguide layer 503 and the upper cladding 504. Is formed. Further, an active layer electrode 507 and a wavelength control electrode 508 are provided on the upper cladding 504 corresponding to the active waveguide layer 502 and the inactive waveguide layer 503, respectively. A common electrode 510 is provided below the lower clad 501.

  In the distributed active DFB laser shown in FIG. 11, gain is generated along with light emission by injection of the current Ia into the active waveguide layer 502, and the period of the diffraction grating 505 formed between the active waveguide layer 502 and the upper cladding 504. Only the wavelength according to the wavelength is selectively reflected to cause laser oscillation.

On the other hand, when the current It is injected into the inactive waveguide layer 503, the refractive index of the inactive waveguide layer 503 changes due to the plasma effect generated according to the carrier density. The optical period of the diffraction grating 505 formed between the upper cladding 504 and the upper cladding 504 changes. Then, the equivalent refractive index of the inactive waveguide layer 503 changes, and the resonant longitudinal mode wavelength is shifted to the short wavelength side by the ratio of the length of the wavelength control region to the length of one cycle. If the length of one cycle of the repetitive structure is L and the wavelength control region length is Lt, the rate of change of the resonance longitudinal mode wavelength is expressed by the following equation (5).
Δλr / λr = (Lt / L) · (Δn / n) (5)

On the other hand, each wavelength of the plurality of reflection peaks is also shifted to the short wavelength side as a result of the change in the equivalent refractive index due to the injection of the current It. Since the reflection peak wavelength is proportional to the average equivalent refractive index change within one cycle of the repetitive structure, the change ratio Δλs / λs of the reflection peak wavelength is expressed by the following equation (6).
Δλs / λs = (Lt / L) · (Δn / n) (6)

  From the equations (5) and (6), the reflection peak wavelength and the resonance longitudinal mode wavelength are shifted by the same amount. Therefore, in this laser, the wavelength continuously changes while maintaining the mode in which it oscillates first.

  The structure of the distributed active DFB laser disclosed in Patent Document 1 is shown in FIG.

  Similarly to the distributed active DFB laser shown in FIG. 11, this distributed active DFB laser has an active waveguide layer 602 and an inactive waveguide layer 603 alternately formed on the lower cladding 601 with constant lengths La and Lt, respectively. The upper cladding 604 is formed on the active waveguide layer 602 and the non-active waveguide layer 603, and has an irregularity between the active waveguide layer 602 and the upper cladding 604. A diffraction grating 605 is formed. Further, an active layer electrode 607 and a wavelength control electrode 608 are provided on the upper cladding 604 corresponding to the active waveguide layer 602 and the inactive waveguide layer 603, respectively. A common electrode 610 is formed below the lower clad 601. In this distributed active DFB laser, the diffraction grating 605 is formed only in a part, but the wavelength continuously changes as in the distributed active DFB laser of FIG.

  Further, in Patent Document 1, as shown in FIG. 13, it has the same structure as the distributed active DFB laser shown in FIG. 12, and the repetition periods of the active waveguide layer 602 and the inactive waveguide layer 603 are L1, A structure in which two different lasers L2 are coupled in series is also disclosed. Note that members that are substantially the same as those shown in FIG. 12 are given the same reference numerals, and descriptions thereof are omitted.

Japanese Patent No. 3237733 Ishii et al., “A Tunable Distributed Amplification DFB Laser Diode (TDA-DFB-LD)”, IEEE Photonics Letters, vol.10, no.1, January 1998, p.30-32

  However, in the above-described structure of the distributed active DFB laser, the active region and the inactive region are alternately repeated with a short region length, so that the leakage current flowing from the electrode in the active region to the inactive region or vice versa The leakage current flowing from the region electrode to the active region cannot be ignored. Due to the mutual leakage current, wavelength control cannot be performed accurately and the wavelength control range becomes narrow.

  In general, as a method for increasing the electrode separation resistance, there is a method of widening the electrode interval We between the active region and the non-active region as shown in FIG. 14, but each region length is short in the above-mentioned distributed active DFB laser. In order to use this effectively, it is desirable that the electrode interval be as close as possible. On the other hand, there is a method of providing a separation groove 814 as shown in FIG. If the depth d of the separation groove 814 is deeper, the electrode separation resistance can be increased. However, if the depth d is too deep, reflected light increases due to the difference in refractive index between the semiconductor and the separation groove 814. Become. For this reason, a problem different from the leakage current occurs, such as an unexpected resonance mode.

  The present invention solves such a problem, and provides a semiconductor waveguide device and a semiconductor laser capable of suppressing an influence of a reflected wave by a separation groove and increasing an electrode separation resistance while maintaining an electrode interval. The purpose is to do.

A semiconductor waveguide device according to a first invention for solving the above-described problems includes a first semiconductor cladding layer, an optical waveguide layer having an optical refractive index larger than that of the first semiconductor cladding layer, and the optical waveguide. In a semiconductor waveguide device in which two or more optical waveguides each including at least one second semiconductor clad layer having a refractive index smaller than that of the layers are coupled in series in the direction of the optical waveguide, An electrode for supplying current, and an electrode separation groove provided in the second semiconductor clad layer located between the adjacent electrodes, and a normal line of a surface intersecting the waveguide direction of the electrode separation groove is guided. and against the waveguide direction inclined by an inclination angle theta, the inclination of the electrode separation grooves in the waveguide direction intersecting the waveguide direction of the electrode separation grooves adjacent to the inclined angle theta and the electrode separation groove surface intersecting plane Are the angles θ different from each other? When the inclination angle θ of the surface of the electrode separation groove intersecting the waveguide direction is equal to the inclination angle θ of the surface of the electrode separation groove adjacent to the electrode separation groove intersecting the waveguide direction, the electrode separation groove and the electrode The distance x between the electrode separation grooves adjacent to the separation grooves satisfies “x> 2d / sin (2θ)” .

  A semiconductor waveguide device according to a second invention for solving the above-described problems is the semiconductor waveguide element according to the first invention, wherein the normal line of the surface intersecting the waveguide direction of the electrode separation groove is 5 with respect to the waveguide direction. It is characterized in that it is tilted more than degrees.

  According to a third aspect of the present invention, there is provided a semiconductor waveguide device according to the first aspect, wherein the normal of the surface intersecting the waveguide direction of the electrode separation groove is 10 with respect to the waveguide direction. It is inclined at an angle of not less than 54 degrees and not more than 54 degrees.

  A semiconductor waveguide device according to a fourth invention for solving the above-described problems is the waveguide waveguide device according to any one of the first to third inventions, wherein the surfaces of all the electrode separation grooves intersecting the waveguide direction are waveguides. It has the same inclination angle with respect to the direction.

  A semiconductor waveguide device according to a fifth aspect of the present invention for solving the above-mentioned problems is that, in any one of the first to third aspects of the invention, every other electrode separation groove with respect to the plane intersecting the waveguide direction. The electrode separation grooves having equal inclination angles and adjacent along the waveguide direction are symmetric with respect to a plane perpendicular to the waveguide direction.

A semiconductor waveguide device according to a sixth invention for solving the above-mentioned problems is the semiconductor waveguide device according to any one of the first to fifth inventions, wherein the electrode separation groove is the second semiconductor cladding on the optical waveguide layer. The thickness of the layer is provided at a depth of 1500 nm or less.

A semiconductor waveguide device according to a seventh aspect of the present invention for solving the above-described problems is the hole formed in the insulating film provided on the upper surface of the second semiconductor cladding in any one of the first to sixth aspects of the invention. An end portion that intersects the waveguide direction of the electrode, an end portion that intersects the waveguide direction of the electrode, or both are formed in parallel to the corresponding electrode separation groove. And

A semiconductor waveguide device according to an eighth invention for solving the above-described problems is the semiconductor waveguide device according to any one of the first to seventh inventions, wherein the lead portions of the electrodes located at both ends of the device are directed toward the center of the device. The film is stretched.

A semiconductor waveguide device according to a ninth invention for solving the above-mentioned problems is any one of the first to eighth inventions, wherein the coupling surface of the waveguide layer has an inclination equal to that of the separation groove. It is characterized by.

Semiconductor waveguide device according to the invention of the first 0 for solving the aforementioned problem, in any of the first to ninth, and further comprising a semi-insulating current blocking layer doped with ruthenium To do.

The semiconductor laser according to the first aspect of the present invention for solving the above problems is characterized by comprising a semiconductor waveguide device according to any one of the first to 1 0.

A method for manufacturing a semiconductor waveguide device according to a twelfth aspect of the present invention for solving the above problems includes a first semiconductor cladding layer, an optical waveguide layer having an optical refractive index larger than that of the first semiconductor cladding layer, In the method of manufacturing a semiconductor waveguide device in which two or more optical waveguides each including one or more second semiconductor cladding layers having a refractive index smaller than that of the optical waveguide layer are coupled in series in the optical waveguide direction, Extends in a direction intersecting the waveguide direction and perpendicular to the waveguide direction to the second semiconductor clad layer positioned between the adjacent electrodes, each supplying current independently to the optical waveguide. comprising a step of forming an electrode separation grooves having inclined against the normal line of the plane intersecting the waveguide direction of the electrode separation grooves, so as to inclined at angle θ with respect to the waveguide direction, the electrode The inclination angle θ of the surface intersecting the waveguide direction of the separation groove and the inclination angle θ of the surface intersecting the waveguide direction of the electrode separation groove adjacent to the electrode separation groove are different from each other or the waveguide direction of the electrode separation groove And the electrode separation groove adjacent to the electrode separation groove when the inclination angle θ of the surface intersecting the waveguide direction of the electrode separation groove adjacent to the electrode separation groove is equal And the distance x satisfies “x> 2d / sin (2θ)” .

  According to the semiconductor laser of the present invention, it is possible to suppress the influence of the reflected wave by the separation groove and increase the electrode separation resistance while maintaining the electrode interval, so that the active region and the inactive region are alternately repeated. Even in a structure such as a distributed active DFB laser, it is possible to reduce the leakage current flowing between the mutual regions, expand the wavelength control range, and accurately perform the wavelength control.

  Embodiments of the present invention will be described in detail in the following examples.

  The first embodiment of the present invention will be described in detail with reference to FIGS.

  1A is a top view of the semiconductor laser according to the present embodiment, FIG. 1B is a cross-sectional view taken along line xx ′ shown in FIG. 1A, and FIG. 1C is a semiconductor laser according to the present embodiment. FIG. 1D is a top view of the semiconductor laser according to the present embodiment with the electrode and the insulating film removed, and FIG. 1E is the y-axis of FIG. 1A. FIG. 2 is a top view showing another example of the semiconductor laser according to the present embodiment, FIG. 3 is a graph showing the relationship between the thickness of the clad layer and the equivalent refractive index, and FIG. FIG. 5 is a graph showing the relationship between the band gap wavelength and the refractive index difference, and FIG. 6 is a graph showing the coupling ratio of the reflected wave with respect to the incident angle to the refractive index boundary. It is.

  As shown in FIG. 1, the semiconductor laser according to the present embodiment includes an optical waveguide layer 15 having an optical refractive index larger than that of the lower cladding 1 on the lower cladding (semiconductor substrate) 1 made of n-type InP, and the optical waveguide. Each layer includes at least one upper cladding 4 having a refractive index lower than that of the layer 15.

  The optical waveguide layer 15 is configured by periodically coupling the active waveguide layer 2 and the inactive waveguide layer 3 in series along the light propagation direction. The active waveguide layer 2 has an optical gain with respect to light in the oscillation wavelength band, and is an active region having a length La made of GaInAsP. The inactive waveguide layer 3 is an inactive region having a length Lt made of GaInAsP having no optical gain and having a composition different from that of the active waveguide layer 2, and is a wavelength control region. In this example, the region lengths La and Lt were 29.5 μm, respectively, and the repetition period L (= La + Lt) of the active waveguide layer 2 and the inactive waveguide layer 3 was 59 μm.

  An upper clad 4 made of p-type InP is formed on the active waveguide layer 2 and the inactive waveguide layer 3, and a light propagation direction (hereinafter referred to as a light guide) is formed between the optical waveguide layer 15 and the upper clad 4. A diffraction grating 5 is formed in which concaves and convexes are formed at the same period over the entire length and the equivalent refractive index of the optical waveguide layer 15 is periodically modulated. In this example, the diffraction grating period was set to 243 nm in order to obtain an oscillation wavelength of 1.55 μm.

  On the upper cladding 4, a contact layer 6 having a multilayer structure of highly doped p-type InGaAsP and / or InGaAs is provided for ohmic contact between the active waveguide layer 2 and the inactive waveguide layer 3, and An active layer electrode 7 and a wavelength control electrode 8 are provided thereon so as to correspond to the active waveguide layer 2 and the inactive waveguide layer 3, respectively.

  Between the active region and the non-active region, an electrode separation groove (hereinafter simply referred to as “separation groove”) 11 having a depth d = 2 μm and a width We = 5 μm is formed in a part of the contact layer 6 and the upper cladding 4. It is formed (seven places in FIG. 1). The depth d of the separation groove 14 is a depth at which the upper clad 4 remains 0.5 μm on the optical waveguide layer 15 after the separation groove 14 is formed.

  The position of the isolation groove 14 can be efficiently prevented from leaking current between the mutual regions by providing the center of the boundary between the active region and the non-active region, but it is not necessarily centered on the boundary between the active region and the non-active region. The effect of the separation groove 14 can be obtained even if it is disposed at a position offset in either region. In the case of the distributed active DFB laser of this embodiment, a relatively large current is injected in the active region in order to generate a sufficient gain for obtaining a desired oscillation output, and in the wavelength control region (inactive region). The wavelength is controlled by a relatively small current.

  Therefore, the bias voltage of the inactive region is lower than that of the active region, and in many cases, leakage current flows from the active region to the inactive region. In this case, the effect of suppressing the leakage current can be enhanced by shifting the center of the isolation groove 14 to the active region side instead of disposing it at the connection portion between the active region and the inactive region.

  Note that all the active layer electrodes 7 and the wavelength control electrodes 8 are integrated with each other and short-circuited on each other. A common electrode 10 is formed at the bottom of the substrate, that is, below the lower cladding 1.

  When GaInAsP having a band gap wavelength of 1.55 μm is used for the active waveguide layer 2, a laser having a band gap wavelength shorter than that, for example, GaInAsP having a band gap wavelength of 1.4 μm, is used for the inactive waveguide layer 3. Since it does not contribute to the oscillation gain, the carrier density is not constant. Thereby, the refractive index can be changed greatly by current injection.

  The active waveguide layer 2 and the inactive waveguide layer 3 do not have to be a bulk material. For example, a quantum well structure, a multilayer quantum well structure in which quantum wells are stacked with a barrier layer interposed therebetween, a quantum wire, a quantum dot, or the like Further, it may have a low-dimensional quantum well structure. In order to enhance light confinement and carrier confinement in the active layer, a separate confinement heterostructure (SCH) that introduces a layer having an intermediate refractive index between the active layer and the cladding layer may be introduced.

  The semiconductor used for this element is not limited to the combination of InP and GaInAsP, and may be another semiconductor such as GaAs, GaInNAs, AlGaInAs, InAs, and GaInNAs. The active waveguide layer 2 and the inactive waveguide layer 3 The combination of the band gap wavelengths is not limited to the above.

  As shown in FIG. 1A, the active layer electrodes 7 and the wavelength control electrodes 8 are integrated with each other to form a comb shape. As shown in FIG. 1B, an insulating film 9 is formed under the active layer electrode 7 and the wavelength control electrode 8. A hole 9a as an electrode window as shown in FIG. 1C is formed in the insulating film 9 immediately above the waveguide and corresponding to the active region and the non-active region, and the contact layer 6 is exposed. It is supposed to be. In other words, the optical waveguide layer 15 formed along the waveguide direction is located below the hole 9a. Further, below the insulating film 9, as shown in FIGS. 1D and 1E, the contact layer 6 is provided along the waveguide direction so that the contact layer 6 is left only on the waveguide in each region. Both sides are etched. The depth of etching is d as in the separation groove 14.

  As shown in FIG. 1D, in this embodiment, the contact layer 6 is formed in a parallelogram. Thereby, a separation groove 14 having an inclination angle θ with respect to a direction orthogonal to the waveguide direction is formed between the regions. In order to increase the electrode separation resistance, a part of InP below the contact layer is also etched.

  Further, as shown in FIG. 1E, p-type semiconductors 11 and n-type semiconductors 12 each made of InP are alternately formed as current blocking layers 13 on both sides of the optical waveguide layer 15 having a width Ws, and buried heterostructures are formed. (BH). Thereby, current is efficiently injected into the active waveguide layer 2 or the inactive waveguide layer 3. In this embodiment, the waveguide width Ws is 1.5 μm.

  In this embodiment, the length of the separation groove 14 corresponds to the width Wa of the contact layer. The length Wa of the separation groove 14 needs to be set at least longer than the waveguide width Ws = 1.5 μm. Although there is no major problem caused by the length Wa of the separation groove 14 being longer than the waveguide width Ws, in this embodiment, there is a problem when the contact resistance or the electrode is routed to inject the current Ia or It into the waveguide layer 2. Considering the size that does not become, the separation groove width Wa was set to 5 μm.

  As shown in FIG. 1C, after the contact layer 6 and the upper clad 4 are covered with the insulating film 9, a hole 9a is formed only in the portion of the insulating film 9 corresponding to the current Ia or It injection portion (FIG. 1). Then 8 places). The shape of the hole 9a is usually a rectangle. Even if the shape is rectangular, the effect of the present invention can be obtained, but the manufacturing process can be facilitated by using the same parallelogram as the shape of the contact layer 6. That is, there is a step formed on the surface of the substrate in which the contact layer 6 is convex as shown in FIG. 1E, and a pattern for forming a hole in the insulating film 9 with a photoresist is formed here. Become. The resist thickness of the step portion is not necessarily uniform, and the thickness is often smoothly changed according to the distance from the step. By matching the shape of the contact layer 6 with the shape of the hole, the hole pattern has a constant distance from the step, and thus the pattern can be made uniformly.

  As shown in FIG. 1 (a), the electrode patterns of the active layer electrode 7 and the wavelength control electrode 9 also reflect the shapes of the contact layer 6 and the insulating film 9, and the plane intersecting the waveguide direction is in the waveguide direction. Wiring is performed so as to incline with respect to the orthogonal direction. Similarly to the hole 9a, the active layer electrode 7 and the wavelength control electrode 8 may be drawn out in a direction perpendicular to the waveguide direction, but the electrode pattern is also formed by lift-off using a photoresist or by wet etching. It is desirable to perform wiring so that the influence of the step is reduced as much as possible. Therefore, instead of the shape shown in FIG. 1A, the active layer electrode 17 and the wavelength control electrode 18 shown in FIG. 2 may be used.

  When the shape of the contact layer 6 is a parallelogram in top view as in this embodiment, the element area is affected depending on which side the active layer electrode 7 and the wavelength control electrode 8 are drawn out. For example, in this embodiment, when the wavelength control electrode 8 is integrated on the y side in FIG. 1A and the active layer electrode 7 is integrated on the y ′ side in FIG. Since it is necessary to increase the substrate area in the waveguide direction, that is, before and after the light propagation direction, it is necessary to couple extra waveguides. Accordingly, as shown in FIG. 1B, the electrode area can be reduced by extending the electrode positioned at the end with respect to the waveguide direction while inclining it toward the center of the element, as shown in FIG. .

  Next, an example of a manufacturing method of the distributed active DFB laser according to the present embodiment will be described.

First, an active waveguide layer 2 is formed on the lower cladding 1 made of n-type InP by metal organic vapor phase epitaxy. Next, a part of the active waveguide layer 2 is etched using SiO ₂ or SiN as a mask. Using the etching mask as it is, the inactive waveguide layer 3 is produced by a selective growth method. Thereafter, a diffraction grating pattern is formed on the applied resist by using an electron beam exposure method, and the semiconductor is etched using this as a mask to form the diffraction grating 5.

After re-growing a part of the upper clad 4 made of p-type InP by metal organic vapor phase epitaxial growth, in order to suppress the transverse mode, the waveguide is processed in a stripe shape having a width of 1.5 μm using SiO ₂ or SiN as a mask. To do. Using the etching mask as it is, an InP current blocking layer 13 made of the p-type semiconductor 11 / n-type semiconductor 12 is grown on both sides of the striped waveguide by a selective growth method.

Thereafter, the selective growth mask is removed, and the remaining InP upper cladding 4 and GaInAs contact layer 6 are grown. Next, the contact layer 6 and a part of the upper clad 4 are etched so as to be arranged in a parallelogram in a top view and intermittently along the waveguide direction, thereby forming the separation groove 14. Next, the SiO ₂ insulating film 9 is formed, and a hole is made in a portion corresponding to the current Ia or It injection portion of the insulating film 9 on the active waveguide layer 2 and the inactive waveguide layer 3. Then, an electrode pattern is formed by lift-off so that the active layer electrodes 7 and the non-active layer electrodes 8 are short-circuited on the element.

  The semiconductor growth method is not limited to the metal organic vapor phase epitaxial growth method, and a molecular beam epitaxial growth method or other means may be used. The method of forming the diffraction grating is not limited to the electron beam exposure method, and a two-bundle interference exposure method or other means may be used.

  Further, as a method of etching a part of the contact layer 6 and the upper cladding layer 4, the active waveguide layer 2 and the inactive waveguide layer 3 are short in length and short in repetition period. Although an etching method with a small amount of side etching such as dry etching is desirable, there is no problem even with a method using wet etching or the like.

  In the present embodiment, the structure in which the active waveguide layers 2 and the inactive waveguide layers 3 are alternately and periodically described has been described as an example. Therefore, the active waveguide layer is not limited to the combination of the active waveguide layer 2 and the inactive waveguide layer 3, and the active waveguide layer is divided into a plurality of regions, or a plurality of inactive waveguide layers are provided. The present invention can be applied even in the case where the electrodes are provided by being divided into the above regions.

  As described above, when there are a plurality of regions, the influence of the leakage current appears remarkably, but even when there are only two regions, the present invention suppresses the leakage current flowing between them and guides them. Useful for suppressing light.

  In this embodiment, since an example of application to a distributed active DFB laser has been shown, a structure in which an electrode on an active waveguide and an electrode on an inactive waveguide are short-circuited on each element has been described. Can be applied even if each electrode is independent. Further, even if it is not a distributed active laser, it can be applied to, for example, an electrode of a laser part and an electrode part of a modulator in a device in which a laser and a modulator are integrated. That is, it can be applied to separation between different waveguide elements connected in series.

  Subsequently, the operation of the present invention will be described.

  FIG. 3 is a diagram showing the relationship between the upper clad thickness and the equivalent refractive index in the case of a semiconductor substrate composed of eight active layers and SHC layers that emit light at 1.55 μm. By forming the separation groove between the regions as in the present embodiment, the thickness of the upper clad of the separation groove portion is reduced and the equivalent refractive index is lowered. Although depending on the field distribution of light propagating in the waveguide, it can be seen from FIG. 3 that in this example, the equivalent refractive index rapidly decreases when the thickness of the upper cladding of the separation groove is less than about 1000 nm.

  For example, if the upper cladding thickness of the separation groove is 2000 nm, the equivalent refractive index is 3.1978, but if the upper cladding thickness of the separation groove is 1500 nm, the equivalent refractive index is 3.1977, and the upper cladding thickness of the separation groove is Is 1000 nm, the equivalent refractive index is 3.1974, and the equivalent refractive index is reduced by 0.0004 compared to when the upper cladding thickness of the separation groove is 2000 nm. Further, when the upper cladding thickness of the separation groove is 500 nm, the equivalent refractive index is further reduced to 3.1941, and the equivalent refractive index is decreased by 0.0037 compared to the case where the upper cladding thickness of the separation groove is 2000 nm. .

At the interface between materials having different refractive indexes, light is reflected when light enters from one material to the other. For example, as shown in FIG. 5, assuming that light is incident on the coupling interface 19 between the material 20 having the refractive index N ₁ and the material 21 having the refractive index N ₂ from the material X side, the reflectance R of the light at the coupling interface. Is expressed by the following equation (7).
R = ((N ₁ −N ₂ ) / (N ₁ + N ₂ )) ² (7)

  From equation (7), since the reflectance R is a function of the difference in refractive index, the cladding thickness of the separation groove is 1500 nm or less at which the refractive index starts to decrease, particularly 1000 nm or less at which the equivalent refractive index rapidly decreases. The reflectance R will also increase rapidly. Therefore, when the separation groove shape is perpendicular to the waveguide, if the reflectivity is a problem, the clad layer remains 1000 nm or more even if the reflectivity is somewhat acceptable up to a depth where the clad thickness remains 1500 nm or more. If the groove is not deep enough, the device characteristics will be affected by mode instability. Here, considering the confinement of light in the waveguide, the cladding layer needs to have a minimum layer thickness of 50 nm and is preferably 100 nm or more.

  In the distributed active DFB laser according to the present embodiment, since the difference in refractive index between the waveguide portion and the separation groove portion is small, the absolute value of the reflectance R is very small from the equation (7). However, on the other hand, as shown in FIG. 1, a plurality of separation grooves 14 exist in one element (distributed active DFB laser in this embodiment). For this reason, there is a possibility that the influence of light reflection is increased to a level that cannot be ignored in one entire element. Therefore, in an element having a plurality of separation grooves 14, it is important to keep the reflectivity R as low as possible, or to prevent the reflected wave from being coupled to the waveguide even if reflection occurs.

When light is incident obliquely on the boundary surfaces of substances having different refractive indexes, the incident angle is θ ₁ , and the refraction angle is θ ₂ , which is expressed by the following formula (8) according to Snell's law. In addition, refraction occurs at the interface.
sin θ ₁ / sin θ ₂ = N ₂ / N ₁ (8)

Here, when the incident angle θ ₁ coincides with the Brewster angle θ _B , reflection of a component parallel to the incident surface can be eliminated. The Brewster angle θ _B can be expressed by the following equation (9).
θ _B = tan ⁻¹ (N ₂ / N ₁ ) (9)

FIG. 5 shows the relationship between the incident angle θ _{1 of} light incident on the boundary surface 19 shown in FIG. In the present embodiment, the incident angle θ ₁ is an inclination angle of the light propagation direction with respect to the normal line of the boundary surface 19. In the graph shown in FIG. 5, the refractive index of the incident-side material 20 is N ₁ = 3.20, and the refractive index difference Δn between the material 20 and the material 21 having the refractive index N ₂ is Δn = N ₁ −N ₂ = 0. In the example, 005, 0.01, 0.015, and 0.02 are shown.

In this embodiment, since the difference in refractive index between the waveguide portion and the separation groove portion is small, the Brewster angle θ _B is approximately 45 degrees from the equation (9). That is, when the inclination angle θ of the surface intersecting the waveguide direction of the separation groove 14 is approximately 45 degrees, the reflectance R becomes 0, and the reflectance R becomes very small near the inclination angle θ = 45 degrees.

Taking the case of the refractive index difference Δn = 0.01 as an example, the reflectance R can be reduced when the incident angle θ ₁ is 10 degrees or more and 54 degrees or less from FIG. In particular, in order to suppress the reflectance R to less than half when light is incident perpendicular to the boundary surface, that is, when the incident angle θ ₁ = 0, the incident angle θ _{1 is set} to about 28 to 52 degrees. A value between may be used. Further, in order to suppress the reflectance R to 1/3 or less of the reflectance R at the incident angle θ ₁ = 0, the incident angle θ ₁ may be set to a value between about 33 degrees and 51 degrees. As can be seen from FIG. 6, should the incident angle theta ₁ is a Brewster angle theta _B lower than about, the incident angle theta ₁ is compared is greater than the Brewster angle theta _B, reflection with respect to the incident angle theta ₁ The change in the rate R is moderate.

Note that it is not always necessary to suppress all reflections at the boundary surface, and if the reflected wave does not have to be coupled to the waveguide even if reflection occurs, the selection range of the incident angle θ ₁ can be expanded as follows. .

FIG. 6 shows the relationship between the incident angle on the boundary surface and the coupling ratio of the reflected wave to the waveguide when the optical mode field width is 1.5 μm. Note that the reflected wave coupling factor is a reflection when the incident angle θ ₁ = 0, that is, when the boundary surface is orthogonal to the waveguide direction, so that the difference in refractive index at the boundary surface may not be taken into consideration. The coupling rate of the wave to the waveguide is shown as 1.

From FIG. 6, if the incident angle θ ₁ is about 5 degrees or more, the reflected wave coupling ratio to the waveguide can be reduced to half, and the incident angle θ ₁ is about 7 to reduce the reflected wave coupling ratio to about 30% or less. It is sufficient that the incident angle θ ₁ should be about 9 degrees or more in order to reduce the reflected wave coupling ratio by one digit.

  From the above, in the distributed active DFB laser shown in FIG. 1, the reflected wave coupling ratio is, for example, half or less compared to the case where the plane intersecting the waveguide direction of the separation groove 14 is orthogonal to the waveguide direction. In order to suppress this, the inclination angle θ of the separation groove 14 needs to be 5 degrees or more and less than 90 degrees with respect to the waveguide direction. Further, in order to suppress the reflected wave coupling ratio to 30% or less as compared with the case where the plane intersecting the waveguide direction of the separation groove 14 is orthogonal to the waveguide direction, the separation groove 14 of the separation groove 14 with respect to the waveguide direction is suppressed. The inclination angle θ needs to be 7 degrees or more and less than 90 degrees. Further, in order to reduce the reflected wave coupling ratio by an order of magnitude compared with the case where the plane intersecting the waveguide direction of the separation groove 14 is orthogonal to the waveguide direction, the inclination of the separation groove 14 with respect to the waveguide direction is reduced. The angle θ needs to be 9 degrees or more and less than 90 degrees.

  In order to reduce the reflectance R at the boundary surface between the waveguide and the separation groove 14 to, for example, less than half compared to the case where the separation groove 14 is orthogonal to the waveguide direction, the inclination angle θ of the separation groove 14 is set to In order to make it about 28 to 52 degrees or less than one third, the inclination angle θ of the separation groove 14 is about 33 to 51 degrees, and the reflection is compared with the case where the separation groove 14 is orthogonal to the waveguide direction. In order to make the rate R substantially zero, the inclination angle θ of the separation groove 14 needs to be 45 degrees.

  It is obvious that the effect of suppressing the influence of the reflected wave as described above increases as the number of coupled waveguides increases.

  Therefore, in the case of the present embodiment, if the separation groove 14 is formed so that the refractive index boundary surface is inclined at the above angle with respect to the waveguide direction, the reflection caused by the difference in refractive index caused by providing the separation groove 14. The rate can be reduced and the coupling of the reflected wave to the waveguide can be reduced. Accordingly, the depth of the separation groove 14 is increased in order to increase the separation resistance, and the reflectance can be suppressed even if the difference in equivalent refractive index increases. For example, the reflectance can be sufficiently suppressed even when the upper cladding thickness is 1500 nm or less or 1000 nm or less.

  In addition, this embodiment can obtain an effect independently regardless of the shape of the butt joint when the active waveguide layer 2 and the inactive waveguide layer 3 are coupled. The butt joint can prevent reflection depending on the shape, but crystal regrowth is necessary, and there is an optimal connection surface angle depending on the growth conditions, so the optimal angle for reflection countermeasures is not always good. However, the angle of the separation groove 14 may be determined independently in consideration of region separation and reflection countermeasures.

  However, in terms of fabrication, since the crystal growth surface is not flat on the bonding surface of the butt joint, if the separation groove 14 is formed so as to intersect the bonding surface, the depth and width of the separation groove 14 may be nonuniform. There is. Therefore, the above-mentioned problem in the process can be solved by forming the separation groove 14 along the connecting surface of the butt joint.

  A second embodiment of the present invention will be described in detail based on FIG.

  7A is a top view of the semiconductor laser according to the present embodiment, FIG. 7B is a cross-sectional view taken along line xx ′ of FIG. 7A, and FIG. 7C is a semiconductor laser according to the present embodiment. FIG. 7D is a top view of the semiconductor laser according to the present embodiment with the electrode and the insulating film removed, and FIG. 7E is the y-axis of FIG. 7A. It is y 'sectional drawing.

  As shown in FIG. 7, the semiconductor laser according to the present example includes an optical waveguide layer 115 having an optical refractive index larger than that of the lower cladding 101 on the lower cladding (semiconductor substrate) 101 made of n-type InP, and the optical waveguide. Each layer includes at least one upper clad 104 having a refractive index lower than that of the layer 115.

  The optical waveguide layer 115 is configured by alternately and periodically coupling the active waveguide layer 102 and the inactive waveguide layer 103 in series along the light propagation direction. The active waveguide layer 102 has an optical gain with respect to light in the oscillation wavelength band, and is an active region having a length La made of GaInAsP. The inactive waveguide layer 103 is an inactive region having a length Lt made of GaInAsP having no optical gain and having a composition different from that of the active waveguide layer 102, and is a wavelength control region. In this example, the region lengths La and Lt were 48.7 μm and 24.3 μm, respectively, and the repetition period L (= La + Lt) of the active waveguide layer 102 and the inactive waveguide layer 103 was 73 μm.

  An upper clad 104 made of p-type InP is formed on the active waveguide layer 102 and the inactive waveguide layer 103, and a light propagation direction (hereinafter referred to as a light guide) is formed between the optical waveguide layer 115 and the upper clad 104. A diffraction grating 105 is formed in which irregularities are formed at the same period over the entire length and the equivalent refractive index of the optical waveguide layer 115 is periodically modulated. In this example, the diffraction grating period was set to 242 nm in order to obtain an oscillation wavelength of 1.55 μm.

  A contact layer 106 made of a highly doped p-type InGaAsP and / or InGaAs or a multilayer structure thereof is provided on the upper cladding 104 for ohmic contact between the active waveguide layer 102 and the inactive waveguide layer 103, and An active layer electrode 107 and a wavelength control electrode 108 are provided thereon so as to correspond to the active waveguide layer 102 and the inactive waveguide layer 103, respectively. A common electrode 110 is provided below the lower clad 101.

  Between the active region and the non-active region, an electrode separation groove (hereinafter simply referred to as “separation groove”) having a depth d = 1.5 μm and a width We = 10 μm is formed in a part of the contact layer 106 and the upper cladding 104. 114 are formed (seven locations in FIG. 7). The depth d of the separation groove 114 is a depth at which the upper cladding 104 remains 1.0 μm on the optical waveguide layer 115 after the separation groove 114 is formed.

  When GaInAsP having a band gap wavelength of 1.55 μm is used for the active waveguide layer 102, a laser having a band gap wavelength shorter than that, for example, GaInAsP having a band gap wavelength of 1.4 μm, is used for the inactive waveguide layer 103. Since it does not contribute to the oscillation gain, the carrier density is not constant. Thereby, the refractive index can be changed greatly by current injection.

  The active waveguide layer and the inactive waveguide layer may not be a bulk material, for example, a quantum well structure, or a multilayer quantum well structure in which quantum wells are stacked with a barrier layer sandwiched therebetween, a quantum wire, a quantum dot, etc. It may have a low-dimensional quantum well structure. In order to enhance light confinement and carrier confinement in the active layer, a separate confinement heterostructure (SCH) that introduces a layer having an intermediate refractive index between the active layer and the cladding layer may be introduced.

  The semiconductor used for this element is not limited to the combination of InP and GaInAsP, and may be another semiconductor such as GaAs, GaInNAs, AlGaInAs, InAs, and GaInNAs, and the band of the active waveguide layer and the inactive waveguide layer. The combination of gap wavelengths is not limited to the above.

  As shown in FIG. 7A, the active layer electrodes 107 and the wavelength control electrodes 108 are arranged independently of each other. For example, if the active layer electrodes 107 and the wavelength control electrodes 108 are short-circuited by wires or the like outside the device, the same operation as in the first embodiment can be obtained. As shown in FIG. 7B, an insulating film 109 is formed under the active layer electrode 107 and the wavelength control electrode 108. In the insulating film 109, holes 109a as electrode windows as shown in FIG. 7 (c) are formed immediately above the waveguide and corresponding to the active region and the non-active region (in FIG. 7, there are 8 holes 109a). ), The contact layer 106 is exposed. In other words, the optical waveguide layer 115 formed along the waveguide direction is positioned below the hole 109a. Further, below the insulating film 109, the contact layer 106 is provided only on the waveguide in each region and is sandwiched between the semi-insulators 113. Each region is separated by a separation groove 114.

  As shown in FIG. 7D, in this embodiment, the contact layer 106 is formed in a parallelogram. Thereby, a separation groove 114 having an inclination angle θ with respect to a direction orthogonal to the waveguide direction is formed between the regions. In order to increase the electrode separation resistance, part of the lower clad 101 of the contact layer 106 is also etched.

  Further, as shown in FIG. 7E, the semiconductor laser according to this example has a buried heterostructure (BH) in which a current blocking layer is formed by a semi-insulator 113 on both sides of the optical waveguide layer 115 having a width Ws. ing. As a result, current is efficiently injected into the active waveguide layer 102 or the inactive waveguide layer 103. In this embodiment, the width Ws of the waveguide is 1.8 μm.

  In this embodiment, the length of the separation groove 114 corresponds to the width Wa of the contact layer. The length Wa of the separation groove 114 needs to be set longer than at least the waveguide width Ws = 1.8 μm. Although there is no major problem caused by the length Wa of the separation groove 114 being longer than the waveguide width Ws, in this embodiment, there is a problem when the contact resistance or the electrode is routed to inject the current Ia or It into the waveguide layer 115. Considering the size that does not become, the separation groove width Wa was set to 10 μm.

  As shown in FIG. 7C, after the contact layer 106, the semi-insulator 113, and the isolation trench 114 are covered with the insulating film 109, the hole 9a is formed only in the portion of the insulating film 109 corresponding to the current Ia or It injection portion. Form. The shape of the hole 9a is usually a rectangle. Even if the shape is rectangular, the effect of the present invention can be obtained, but the manufacturing process can be facilitated by using the same parallelogram as the shape of the contact layer 106. That is, as shown in FIG. 7 (e), a step is formed on the surface of the substrate in which the contact layer 106 is convex, and a pattern for forming a hole in the insulating film 109 with a photoresist is formed here. Become. The resist thickness of the step portion is not necessarily uniform, and the thickness is often smoothly changed according to the distance from the step. By matching the shape of the contact layer 106 with the shape of the hole, the hole pattern has a constant distance from the step, so that the pattern can be formed uniformly.

  As shown in FIG. 7A, the electrode patterns of the active layer electrode 107 and the wavelength control electrode 108 also reflect the shapes of the contact layer 106 and the insulating film 109, and a part of the surface intersecting the waveguide direction, specifically Are wired so that the portion located immediately above the optical waveguide 114 is inclined with respect to the direction orthogonal to the waveguide direction. Since the electrode pattern is also lifted off using a photoresist or formed by wet etching, it is desirable to perform wiring so that the influence of the step is reduced as much as possible.

  Next, an example of a manufacturing method of the distributed active DFB laser according to the present embodiment will be described.

First, an active waveguide layer 102 is formed on the lower clad 101 made of n-type InP by metal organic vapor phase epitaxy. Next, a part of the active waveguide layer 102 is etched using SiO ₂ or SiN as a mask. The inactive waveguide layer 103 is produced by a selective growth method using the etching mask as it is. Thereafter, a diffraction grating pattern is formed on the applied resist by using an electron beam exposure method, and the semiconductor is etched using this as a mask to form the diffraction grating 105.

After re-growing a part of the upper clad 104 made of p-type InP by metal organic vapor phase epitaxial growth, in order to suppress the transverse mode, the waveguide is processed in a stripe shape having a width of 1.5 μm using SiO ₂ or SiN as a mask. To do. Using the etching mask as it is, a semi-insulator current blocking layer 113 made of a semiconductor doped with Ru (or Fe) is grown on both sides of the striped waveguide by a selective growth method.

Thereafter, the selective growth mask is removed, and the remaining InP upper clad 104 and GaInAs contact layer 106 are grown. Next, in order to separate the active region and the non-active region, the contact layer 106 and a part of the upper cladding 104 are etched so as to have an inclination angle with respect to the direction orthogonal to the waveguide direction, thereby forming the separation groove 114. Form. Next, a SiO ₂ insulating film 109 is formed, and holes are formed in portions of the insulating film 109 on the active waveguide layer 102 and the inactive waveguide layer 103 corresponding to the current Ia or It injection portion. Then, an electrode pattern is formed by lift-off.

  The semiconductor growth method is not limited to the metal organic vapor phase epitaxial growth method, and a molecular beam epitaxial growth method or other means may be used. The method of forming the diffraction grating is not limited to the electron beam exposure method, and a two-bundle interference exposure method or other means may be used.

  In addition, as a method of etching part of the contact layer 106 and the upper cladding layer 104, the active waveguide layer 102 and the inactive waveguide layer 103 are short in length and short in repetition period. Although an etching method with a small amount of side etching such as dry etching is desirable, there is no problem even with a method using wet etching or the like.

  Note that Fe is often used as a doping material for the semi-insulator 113, but using Ru can suppress mutual diffusion with Zu, which is a p-type InP dopant. it can. Further, by using Ru, the capacitance is reduced as compared with the current blocking layer made of p-type and n-type semiconductors, so that the modulation characteristics can be improved. In addition, the modulation characteristic can be improved to 10 GHz or more by suppressing the leakage current between the active region and the non-active region by the current separation groove 1146.

  In the present embodiment, the structure in which the active waveguide layer 102 and the inactive waveguide layer 103 are alternately arranged in series has been described, but the present invention suppresses leakage currents flowing between a plurality of regions, for example, Since the reflection of the guided light is suppressed, the active waveguide layer is not limited to the combination of the active waveguide layer 102 and the inactive waveguide layer 103 shown in FIG. The present invention can be applied even when an electrode is provided in each region, or when an inactive waveguide layer is divided into a plurality of regions and an electrode is provided in each region.

  As described in the present embodiment, when one element has a plurality of regions, the influence of leakage current appears remarkably, but even if there are two regions, the leakage current flowing between them is suppressed, and The present embodiment that can suppress reflection of light to be guided is useful.

  In this embodiment, the distributed active DFB laser has been described as an example. However, the present invention is not limited to this. For example, the present invention can be applied to a laser unit and an electrode unit of an electrode modulator in a device in which a laser and a modulator are integrated. It is. That is, the present invention can be applied when separation between different waveguide elements connected in series is required.

  Note that the operation and effect of the present embodiment are substantially the same as those of the first embodiment described above, and redundant description is omitted.

  A third embodiment of the present invention will be described in detail based on FIG.

  8A is a top view of the semiconductor laser according to the present embodiment, FIG. 8B is a cross-sectional view taken along line xx ′ of FIG. 8A, and FIG. 8C is the semiconductor laser according to the present embodiment. FIG. 8D is a top view of the semiconductor laser according to this embodiment with the electrode and the insulating film removed, and FIG. 8E is the y-axis of FIG. 8A. It is y 'sectional drawing.

  As shown in FIG. 8, the semiconductor laser according to the present example includes an optical waveguide layer 215 having an optical refractive index larger than that of the lower cladding 201 on the lower cladding (semiconductor substrate) 201 made of n-type InP, and the optical waveguide. Each layer includes at least one upper clad 204 having a refractive index smaller than that of the layer 215.

  The optical waveguide layer 215 includes an active waveguide layer 202 and an inactive waveguide layer 203 that are alternately and periodically coupled in series along the light propagation direction. The active waveguide layer 202 has an optical gain with respect to light in the oscillation wavelength band, and is an active region having a length La made of GaInAsP. The inactive waveguide layer 203 is an inactive region having a length Lt made of GaInAsP having no optical gain and having a composition different from that of the active waveguide layer 202, and is a wavelength control region. In this example, the region lengths La and Lt were 22.3 μm and 44.7 μm, respectively, and the repetition period L (= La + Lt) of the active waveguide layer 202 and the inactive waveguide layer 203 was 67 μm.

  An upper clad 204 made of p-type InP is formed on the active waveguide layer 202 and the non-active waveguide layer 203, and a light propagation direction (hereinafter referred to as a light guide) is formed between the optical waveguide layer 215 and the upper clad 204. A diffraction grating 205 is formed in which concaves and convexes are formed at the same period over the entire length and the equivalent refractive index of the optical waveguide layer 215 is periodically modulated. In this example, the diffraction grating period was 241 nm in order to obtain an oscillation wavelength of 1.55 μm.

  On the upper clad 204, a contact layer 206 having a highly doped p-type InGaAsP and / or InGaAs multilayer structure for ohmic contact between the active waveguide layer 202 and the non-active waveguide layer 203 is provided. An active layer electrode 207 and a wavelength control electrode 208 are provided thereon so as to correspond to the active waveguide layer 202 and the inactive waveguide layer 203, respectively. A common electrode 210 is provided below the lower clad 201.

  Between the active region and the non-active region, an electrode separation groove (hereinafter simply referred to as “separation groove”) 214 having a depth d = 1 μm and a width We = 15 μm is formed in a part of the contact layer 206 and the upper cladding 204. It is formed (seven places in FIG. 8). The depth d of the separation groove 214 is a depth at which the upper cladding 204 remains on the optical waveguide layer 215 by 1.5 μm after the separation groove 214 is formed.

  When GaInAsP having a band gap wavelength of 1.55 μm is used for the active waveguide layer 202, a laser having a band gap wavelength shorter than that, for example, GaInAsP having a band gap wavelength of 1.4 μm, is used for the inactive waveguide layer 203. Since it does not contribute to the oscillation gain, the carrier density is not constant. Thereby, the refractive index can be changed greatly by current injection.

  The active waveguide layer and the inactive waveguide layer may not be a bulk material, for example, a quantum well structure, or a multilayer quantum well structure in which quantum wells are stacked with a barrier layer sandwiched therebetween, a quantum wire, a quantum dot, etc. It may have a low-dimensional quantum well structure. In order to enhance light confinement and carrier confinement in the active layer, a separate confinement heterostructure (SCH) that introduces a layer having an intermediate refractive index between the active layer and the cladding layer may be introduced.

  The semiconductor used for this element is not limited to the combination of InP and GaInAsP, and may be another semiconductor such as GaAs, GaInNAs, AlGaInAs, InAs, and GaInNAs, and the band of the active waveguide layer and the inactive waveguide layer. The combination of gap wavelengths is not limited to the above.

  As shown in FIG. 8A, the active layer electrodes 207 and the wavelength control electrodes 208 are arranged independently of each other. For example, if the active layer electrodes 207 and the wavelength control electrodes 208 are short-circuited by wires or the like outside the device, the same operation as in the first embodiment can be obtained. As shown in FIG. 8B, an insulating film 209 is formed under the active layer electrode 207 and the wavelength control electrode 208. In the insulating film 209, holes 209a are formed as electrode windows as shown in FIG. 8C in portions corresponding to the active region and inactive region immediately above the waveguide (in FIG. ), The contact layer 206 is exposed. In other words, the optical waveguide layer 215 formed along the waveguide direction is located under the hole 209a. Below the insulating film 209, the contact layer 206 is provided only on the waveguide in each region, and is sandwiched between the dielectrics 213. Each region is separated by a separation groove 214.

  As shown in FIG. 8D, in this embodiment, the contact layer 206 is formed in a parallelogram. Thus, a separation groove 214 having an inclination angle θ with respect to a direction orthogonal to the waveguide direction is formed between the regions. In order to increase the electrode separation resistance, part of the lower clad 201 of the contact layer 206 is also etched.

  Further, as shown in FIG. 8E, the semiconductor laser according to the present example has a ridge structure in which polyimide is embedded on both sides of the optical waveguide layer 215 having a width Ws. In this embodiment, the width Ws of the waveguide is 2.5 μm. In this embodiment, the width Wa of the separation groove 214 in the direction orthogonal to the waveguide direction is the same as the waveguide width and is 2.5 μm.

  As shown in FIG. 8C, after covering the contact layer 206, the semi-insulator 113, and the isolation trench 214 with the insulating film 209, the hole 9a is formed only in the insulating film 209 corresponding to the current Ia or It injection portion. Form. The shape of the hole 9a is usually a rectangle. Even if the shape is rectangular, the effect of the present invention can be obtained, but the manufacturing process can be facilitated by using the same parallelogram as the shape of the contact layer 206. In other words, as shown in FIG. 8E, a step is formed on the surface of the substrate where the contact layer 206 is convex, and a pattern for forming a hole in the insulating film 209 using a photoresist is formed here. Become. The resist thickness of the step portion is not necessarily uniform, and the thickness is often smoothly changed according to the distance from the step. By matching the shape of the contact layer 206 with the shape of the hole, the hole pattern has a constant distance from the step, so that the pattern can be formed uniformly.

  As shown in FIG. 8A, the electrode patterns of the active layer electrode 207 and the wavelength control electrode 208 also reflect the shapes of the contact layer 206 and the insulating film 209, and the plane intersecting the waveguide direction is orthogonal to the waveguide direction. It is wired so as to be inclined with respect to the direction in which it is performed. Since the electrode pattern is also lifted off using a photoresist or formed by wet etching, it is desirable to perform wiring so that the influence of the step is reduced as much as possible.

  In this embodiment, the element area is affected depending on which side the active layer electrode 207 and the wavelength control electrode 208 are drawn to. For example, in this embodiment, when the wavelength control electrode 208 is integrated on the y side in FIG. 8A and the active layer electrode 207 is integrated on the y ′ side in FIG. Since it is necessary to increase the substrate area in the waveguide direction, that is, before and after the light propagation direction, it is necessary to couple extra waveguides. Therefore, as shown in FIG. 8B, the electrode area can be reduced by extracting the electrode located at the end with respect to the waveguide direction while inclining the electrode toward the center of the element, as shown in FIG. .

  Next, an example of a manufacturing method of the distributed active DFB laser according to the present embodiment will be described.

First, an active waveguide layer 202 is formed on the lower clad 201 made of n-type InP by metal organic vapor phase epitaxy. Next, a part of the active waveguide layer 202 is etched using SiO ₂ or SiN as a mask. The inactive waveguide layer 203 is produced by a selective growth method using the etching mask as it is. Thereafter, a diffraction grating pattern is formed on the applied resist by using an electron beam exposure method, and the semiconductor is etched using this as a mask to form a diffraction grating 205.

After the upper clad 204 made of p-type InP and the GaInAs contact layer 206 are regrown by metal organic vapor phase epitaxial growth, the waveguide is formed in a stripe shape having a width of 2.5 μm using SiO ₂ or SiN as a mask in order to suppress the transverse mode. Is processed. In this embodiment, the ridge is formed by wet etching using a sold resist as a mask. However, the ridge may be formed by dry etching using SiO ₂ or SiN as a mask. Thereafter, a SiO ₂ or SiN film is formed, and a pattern of the separation groove 214 is formed only on the ridge using a thick resist. Next, part of the contact layer 206 and the upper clad layer 204 is etched to form a separation groove 214 for separation between the regions. Subsequently, polyimide is embedded in the side of the ridge and in the separation groove 214 and solidified in an oven at 350 ° C., and then an SiO ₂ insulating film is formed to insulate the active waveguide layer 202 and the inactive waveguide layer 203. A hole is made in the membrane 209. An electrode pattern is formed by lift-off so that the active layer electrodes 102 and the non-active layer electrodes 103 are short-circuited on the element.

  The semiconductor growth method is not limited to the metal organic vapor phase epitaxial growth method, and a molecular beam epitaxial growth method or other means may be used. The method of forming the diffraction grating is not limited to the electron beam exposure method, and a two-bundle interference exposure method or other means may be used.

  In addition, as a method of etching part of the contact layer 206 and the upper cladding layer 104, the active waveguide layer 202 and the inactive waveguide layer 203 are short in length and short in repetition period. Although an etching method with a small amount of side etching such as dry etching is desirable, there is no problem even with a method using wet etching or the like.

  In this embodiment, the dielectric 213 is used to reduce the capacitance and protect the ridge structure, but both sides may be air. Moreover, although polyimide which is an organic material is used as the dielectric 213, other materials such as BCB may be used. By using the dielectric 213, the capacitance is reduced as compared with the current blocking layer, so that the modulation characteristics can be improved. In addition, the modulation characteristic can be improved to 10 GHz or more by suppressing the leakage current between the active region and the inactive region by the separation groove 214.

  In the present embodiment, the active waveguide layer 202 and the non-active waveguide layer 203 are alternately arranged in series, but the present invention suppresses leakage currents flowing between a plurality of regions, for example, Since the reflection of guided light is suppressed, the active waveguide layer is not limited to the combination of the active waveguide layer 202 and the inactive waveguide layer 203 shown in FIG. The present invention can be applied even when an electrode is provided in each region, or when an inactive waveguide layer is divided into a plurality of regions and an electrode is provided in each region.

  As described in the present embodiment, when one element has a plurality of regions, the influence of leakage current appears remarkably, but even if there are two regions, the leakage current flowing between them is suppressed, and The present embodiment that can suppress reflection of light to be guided is useful.

  In this embodiment, the distributed active DFB laser has been described as an example. However, the present invention is not limited to this. For example, the present invention can be applied to a laser unit and an electrode unit of an electrode modulator in a device in which a laser and a modulator are integrated. It is. That is, the present invention can be applied when separation between different waveguide elements connected in series is required.

  Note that the operation and effect of the present embodiment are substantially the same as those of the first embodiment described above, and redundant description is omitted.

  A fourth embodiment of the present invention will be described in detail based on FIG.

  9A is a top view of the semiconductor laser according to the present embodiment, FIG. 9B is a top view of the semiconductor laser according to the present embodiment with the electrodes removed, and FIG. 9C is the present embodiment. It is a top view of the state which removed the electrode and insulating film of the semiconductor laser which concerns.

  In the present embodiment, for example, the shapes of the active layer electrode 7, the wavelength control electrode 8, the hole 9 a formed in the insulating film 9, and the separation groove 14 described in the first embodiment are changed. is there. Other configurations are generally the same, and redundant description is omitted. In FIG. 9, 304 is an upper clad, 306 is a contact layer, 307 is an active layer electrode, 308 is a wavelength control electrode, 309 is an insulating film, 309a is a hole formed in the insulating film 309, and 314 is a separation groove.

  In the first to third embodiments described above, in order to suppress the reflection of light at the refractive index boundary surface, the separation groove is arranged in the waveguide direction for the purpose of inclining the refractive index boundary surface with respect to the waveguide direction. It provided so that it might incline with respect to. However, if all the separation grooves are inclined at the same angle with respect to the waveguide direction, resonance may occur.

  Therefore, in this embodiment, as shown in FIG. 9C, the adjacent separation grooves 314 are configured to have different inclinations. Thereby, even when reflection occurs in the separation groove 314, resonance can be suppressed.

  In FIG. 9, the separation groove 314 is formed so that the inclination angle with respect to the waveguide direction is symmetric with respect to the plane orthogonal to the waveguide direction so that the inclination angles are alternately equal. In order to suppress it, it is most preferable that the inclination angles of the separation grooves are all different angles. However, as long as the separation grooves 314 are located at some distance from each other, there is no problem even if they have the same inclination angle.

In the simplest case, the separation groove 314 having the same inclination angle may be intermittently disposed. Therefore, the width of the separation groove 314 in the direction orthogonal to the waveguide direction is d, and the separation groove 314 has a width in the waveguide direction. When the angle is θ, resonance can be suppressed by making the distance x between the separation grooves 314 having the same inclination angle satisfy the relationship of the following expression (10).
x> 2d / sin (2θ) (10)

  Further, as in this embodiment, the electrodes 307 and 308 are integrated in order to integrate the active layer electrodes 307 and the wavelength control electrodes 308 by alternately reversing the inclination angle of the separation groove 314. When pulling out, as shown in FIG. 9A, the widths of the leading portions 307a and 308a can be formed wider than those in the first to third embodiments, and pattern formation can be facilitated. .

  A fifth embodiment of the present invention will be described in detail based on FIG.

  10A is a top view of the semiconductor laser according to the present embodiment, FIG. 10B is a cross-sectional view taken along line xx ′ shown in FIG. 10A, and FIG. 10C is the semiconductor laser according to the present embodiment. FIG. 10D is a top view of the semiconductor laser according to the present embodiment with the electrode and the insulating film removed, and FIG. 10E is the y-axis of FIG. 10A. It is y 'sectional drawing.

  In the present embodiment, for example, the shapes of the active layer electrode 7, the wavelength control electrode 8, the hole 9 a formed in the insulating film 9, and the separation groove 14 are different from those in the first embodiment. Other configurations are generally the same, and redundant description is omitted. In FIG. 10, 401 is a lower clad, 402 is an active waveguide layer, 403 is an inactive waveguide layer, 404 is an upper clad, 405 is a diffraction grating, 406 is a contact layer, 407 is an active layer electrode, and 408 is a wavelength control electrode. , 409 is an insulating film, 409a is a hole formed in the insulating film 409, 410 is a common electrode, 413 is a current blocking layer, and 414 is a separation groove.

  In the first to third embodiments described above, in order to suppress the reflection of light at the refractive index boundary surface, the separation groove is arranged in the waveguide direction for the purpose of inclining the refractive index boundary surface with respect to the waveguide direction. It provided so that it might incline with respect to. However, if all the separation grooves are inclined at the same angle with respect to the waveguide direction, resonance may occur. Therefore, in the fourth embodiment, the inclination angle of the adjacent separation groove 314 is configured to be symmetric with respect to the plane orthogonal to the waveguide direction. As a result, even when reflection occurs in the separation groove 314, resonance can be suppressed. On the other hand, in this embodiment, in FIG. 10, the inclination angles of the separation grooves 414 with respect to the waveguide direction are all different.

  Note that there is no problem even if the separation grooves 414 located at some distance from each other have the same inclination angle. In the simplest case, since the separation grooves 314 having the same inclination angle only need to be intermittently arranged, the width of the separation groove 314 in the direction perpendicular to the waveguide direction is d, and the direction perpendicular to the waveguide direction is When the angle of the separation groove 314 is θ, resonance can be suppressed by making the distance x between the separation grooves 314 having the same inclination angle satisfy the relationship of the above-described expression (10).

  Furthermore, in the present embodiment, as shown in FIG. 10A, the active layer electrode 407 and the wavelength control electrode 408 are formed so that the surfaces intersecting the waveguide direction are orthogonal to the waveguide direction. Yes. Accordingly, when the electrodes 407 and 408 are pulled out, the electrodes 407 and 408 overlap with the separation groove 414, so that the manufacturing process may be somewhat complicated. However, in the case where the inclination angles of the separation grooves 414 are all different, when all the electrodes 407 and 408 are made to coincide with the inclination angles of the separation grooves 414, the resistance varies due to the different electrode widths, and the current injection is uneven. There is a risk of becoming. Accordingly, as shown in FIG. 10A, the surfaces of the electrodes 407 and 408 that intersect the waveguide direction are formed so as to be orthogonal to the waveguide direction, and the shapes of the electrodes 407 and 408 can be kept constant. Is preferable.

  The present invention relates to a wavelength tunable semiconductor laser used as a light source for optical fiber communication and a light source for optical measurement. For example, the present invention relates to a light source for optical wavelength (frequency) multiplexing system in optical communication and a light source for optical measurement that covers a wideband wavelength band. Applicable.

1A is a top view of the semiconductor laser according to the first embodiment of the present invention, FIG. 1B is a cross-sectional view taken along line xx ′ shown in FIG. 1A, and FIG. 1C is FIG. 1) is a top view with the electrode removed, FIG. 1D is a top view with the electrode and the insulating film in FIG. 1A removed, and FIG. 1E is the y-y in FIG. 1A. 'Is a cross-sectional view. It is a top view which shows the other example of the semiconductor laser which concerns on Example 1 of this invention. It is a graph which shows the relationship between an upper clad thickness and an equivalent refractive index. It is explanatory drawing which shows refraction of the light in the interface of the substance from which a refractive index mutually differs. It is a graph which shows the relationship between an incident angle and a reflectance. It is a graph which shows the coupling factor of the reflected wave with respect to the incident angle to a refractive index boundary. 7A is a top view of a semiconductor laser according to Example 2 of the present invention, FIG. 7B is a cross-sectional view taken along line xx ′ shown in FIG. 7A, and FIG. 7C is FIG. 7) is a top view with the electrode removed, FIG. 7D is a top view with the electrode and the insulating film in FIG. 7A removed, and FIG. 7E is the y-y in FIG. 7A. 'Is a cross-sectional view. 8A is a top view of a semiconductor laser according to Example 3 of the present invention, FIG. 8B is a cross-sectional view taken along line xx ′ shown in FIG. 8A, and FIG. 8C is FIG. 8) is a top view with the electrode removed, FIG. 8D is a top view with the electrode and the insulating film in FIG. 8A removed, and FIG. 8E is the y-y in FIG. 8A. 'Is a cross-sectional view. 9A is a top view of a semiconductor laser according to Example 4 of the present invention, FIG. 9B is a top view of the semiconductor laser with the electrodes of FIG. 9A removed, and FIG. 9C is FIG. It is a top view of the state which removed the electrode and insulating film of a). 10A is a top view of a semiconductor laser according to Example 5 of the present invention, FIG. 10B is a cross-sectional view taken along line xx ′ shown in FIG. 10A, and FIG. 10C is FIG. 10) is a top view with the electrode removed, FIG. 10D is a top view with the electrode and the insulating film in FIG. 10A removed, and FIG. 10E is the y-y in FIG. 10A. 'Is a cross-sectional view. FIG. 11A is a top view of a conventional distributed active DFB laser, and FIG. 11B is a cross-sectional view taken along line xx ′ in FIG. It is sectional drawing which shows the other conventional distributed active DFB laser. It is sectional drawing which shows the other conventional distributed active DFB laser. It is sectional drawing which shows the other conventional distributed active DFB laser. It is sectional drawing which shows the other conventional distributed active DFB laser.

Explanation of symbols

1, 101, 201, 301, 401 Lower cladding 2, 102, 202, 302, 402 Active waveguide layer 3, 103, 203, 303, 403 Inactive waveguide layer 4, 104, 204, 304, 404 Upper cladding 5 , 105, 205, 305, 405 Diffraction grating 6, 106, 206 Contact layer 7, 107, 207, 307, 407 Active layer electrode 8, 108, 208, 308, 408 Wavelength control electrode 9, 109, 209, 309, 409 Insulating film 9a, 109a, 209a, 309a, 409a Hole 10, 110, 210, 310, 410 Common electrode 13, 313, 413 Current blocking layer 14, 114, 214, 314, 414 Electrode isolation groove 15 Optical waveguide layer 113 Semi-insulating Body 213 Dielectric

Claims (12)

An optical waveguide including at least one first semiconductor cladding layer, an optical waveguide layer having an optical refractive index larger than that of the first semiconductor cladding layer, and a second semiconductor cladding layer having a refractive index lower than that of the optical waveguide layer. In a semiconductor waveguide device in which two or more waveguides are coupled in series in the direction of the optical waveguide,
An electrode for supplying current independently to each of the optical waveguides, and an electrode separation groove provided in the second semiconductor cladding layer located between the adjacent electrodes,
Normal of plane intersecting the waveguide direction of the electrode separation grooves, inclined by pairs inclined angle θ to the waveguide direction,
The inclination angle θ of the surface that intersects the waveguide direction of the electrode separation groove and the inclination angle θ of the surface that intersects the waveguide direction of the electrode separation groove adjacent to the electrode separation groove are different from each other or the guide angle of the electrode separation groove. When the inclination angle θ of the surface intersecting the waveguide direction and the inclination angle θ of the surface intersecting the waveguide direction of the electrode separation groove adjacent to the electrode separation groove are equal, the electrode separation groove and the electrode adjacent to the electrode separation groove A semiconductor waveguide device, wherein an interval x with the separation groove satisfies "x> 2d / sin (2 [theta])" . 2. The semiconductor waveguide device according to claim 1, wherein a normal line of a surface intersecting the waveguide direction of the electrode separation groove is inclined by 5 degrees or more with respect to the waveguide direction. 2. The semiconductor waveguide device according to claim 1, wherein the normal line of the surface intersecting the waveguide direction of the electrode separation groove is inclined at an angle of 10 degrees to 54 degrees with respect to the waveguide direction. .   4. The semiconductor waveguide device according to claim 1, wherein surfaces of all of the electrode separation grooves intersecting with the waveguide direction have an equal inclination angle with respect to the waveguide direction. 5. The electrode separation grooves have an equal inclination angle with respect to every other plane intersecting the waveguide direction, and the electrode separation grooves adjacent to each other along the waveguide direction are mutually opposite to the plane perpendicular to the waveguide direction. 4. The semiconductor waveguide device according to claim 1, wherein the semiconductor waveguide device is symmetric. Any the electrode separation grooves, of claims 1 to 5, characterized in that <br/> the thickness of the second semiconductor cladding layer on said optical waveguide layer is provided at a depth to be 1500nm or less A semiconductor waveguide device according to claim 1. The end of the hole formed in the insulating film provided on the upper surface of the second semiconductor clad intersects with the waveguide direction, or the end of the electrode intersects with the waveguide direction, or both, The semiconductor waveguide device according to any one of claims 1 to 6 , wherein the semiconductor waveguide device is formed in parallel to the corresponding electrode separation groove . The semiconductor waveguide device according to any one of claims 1 to 7 , wherein lead portions of the electrodes located at both ends of the device are extended toward the center of the device. The semiconductor waveguide device according to any one of claims 1 to 8 , wherein a coupling surface of the waveguide layer has an inclination equal to that of the separation groove . The semiconductor waveguide device according to any one of claims 1 to 9 , further comprising a semi-insulating current blocking layer doped with ruthenium . Semiconductors lasers you wherein <br/> that a semiconductor waveguide device according to any one of claims 1 to 11. An optical waveguide including at least one first semiconductor cladding layer, an optical waveguide layer having an optical refractive index larger than that of the first semiconductor cladding layer, and a second semiconductor cladding layer having a refractive index lower than that of the optical waveguide layer. In a method of fabricating a semiconductor waveguide device in which two or more waveguides are coupled in series in the direction of an optical waveguide,
A direction that extends in a direction intersecting the waveguide direction and perpendicular to the waveguide direction to the second semiconductor clad layer positioned between the mutually adjacent electrodes that supplies current independently to the optical waveguide. Forming an electrode separation groove having an inclination with respect to
The normal line of the surface intersecting the waveguide direction of the electrode separation groove is inclined by an inclination angle θ with respect to the waveguide direction,
The inclination angle θ of the surface that intersects the waveguide direction of the electrode separation groove and the inclination angle θ of the surface that intersects the waveguide direction of the electrode separation groove adjacent to the electrode separation groove are different from each other or the guide angle of the electrode separation groove. When the inclination angle θ of the surface intersecting the waveguide direction and the inclination angle θ of the surface intersecting the waveguide direction of the electrode separation groove adjacent to the electrode separation groove are equal, the electrode separation groove and the electrode adjacent to the electrode separation groove A method for manufacturing a semiconductor waveguide device, wherein an interval x with the separation groove satisfies "x> 2d / sin (2?)" .

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