JP2004047651A - Laser apparatus and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a light-emitting point of each semiconductor laser and the center of a collimator lens to be accurately aligned, in a state in which a focal position of the lens is located at the point of the lens and the lines for connecting the points to the center of the lenses are in parallel with each other at the point of the laser, in a method for manufacturing a laser apparatus in which a plurality of the semiconductor lasers are arranged, in a state in which the points are aligned in one direction. <P>SOLUTION: A smooth reference surface S, perpendicular to light-emitting axes O of the semiconductor lasers LD1-LD7, is formed at a forward side from a section for fixing the lasers LD1-LD of a block 10. The plurality of the lasers LD1-LD7 are fixed to the block 10, by position-regulating the emitting axis direction based on focal distance measuring information of the corresponding lenses 11-17, and thereafter the plurality of the collimator lenses 11-17 are position-regulated to copy the reference surface S. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser device, and more particularly to a laser device that converts laser beams emitted from a plurality of semiconductor lasers into parallel light by collimator lenses.
[0002]
The present invention also relates to a method of manufacturing the laser device as described above.
[0003]
[Prior art]
Conventionally, wavelength conversion lasers, excimer lasers, and Ar lasers that convert infrared light emitted from semiconductor laser-excited solid-state lasers into third harmonics in the ultraviolet region have been put to practical use as devices that generate ultraviolet laser beams. It is provided.
[0004]
Furthermore, recently, for example, Jpn. Appl. phys. Lett. , Vol. 37. p. As shown in L1020, a GaN-based semiconductor laser (laser diode) that emits a laser beam having a wavelength near 400 nm is also provided.
[0005]
A light source that emits a laser beam having such a wavelength is used as an exposure light source in an exposure apparatus that exposes a photosensitive material having sensitivity in a predetermined wavelength region (hereinafter referred to as “ultraviolet region”) including an ultraviolet region of 350 to 420 nm. It is also considered to apply. In this case, the light source for exposure is naturally required to have a sufficient output for exposing the photosensitive material.
[0006]
[Problems to be solved by the invention]
However, the excimer laser has a problem that the apparatus is large, and the cost and maintenance cost are high.
[0007]
In addition, a wavelength conversion laser that converts infrared light into the third harmonic in the ultraviolet region has extremely low wavelength conversion efficiency, so that it is extremely difficult to obtain a high output. At present, a solid laser medium is excited with a 30 W semiconductor laser to oscillate a 10 W fundamental wave (wavelength 1064 nm), which is converted into a 3 W second harmonic (wavelength 532 nm), and the sum frequency of both of them. The current practical level is to obtain a third harmonic of 1 W (wavelength 355 nm). In this case, the electro-optical efficiency of the semiconductor laser is about 50%, and the conversion efficiency to ultraviolet light is very low, about 1.7%. Such a wavelength conversion laser is considerably expensive because it uses an expensive optical wavelength conversion element.
[0008]
In addition, the Ar laser has a problem that the electro-optical efficiency is very low as 0.005% and the lifetime is as short as about 1000 hours.
[0009]
On the other hand, since a low dislocation GaN crystal substrate cannot be obtained for a GaN-based semiconductor laser, a low dislocation region of about 5 μm is created by a growth method called ELOG, and a laser region is formed thereon to increase the output. Attempts have been made to achieve high reliability. However, even in the GaN-based semiconductor laser manufactured in this way, it is difficult to obtain a substrate with a low dislocation over a large area, so that a high output of 500 mW to 1 W class has not yet been commercialized.
[0010]
As another attempt to increase the output power of a semiconductor laser, for example, it may be possible to obtain 10 W output by forming 100 cavities that output 100 mW light by one. It can be said that creating a large number of cavities at a high yield is almost unrealistic. This is especially true for GaN-based semiconductor lasers where it is difficult to achieve a high yield of 99% or more even in the case of a single cavity.
[0011]
In view of the above circumstances, the present applicant has previously proposed a laser apparatus capable of obtaining particularly high output in Japanese Patent Application Nos. 2000-2734949 and 273870.
[0012]
Japanese Patent Application No. 2000-2733849 discloses a laser device that collects a plurality of semiconductor lasers, one multimode optical fiber, and a laser beam emitted from each of the plurality of semiconductor lasers, and then combines them with the multimode optical fiber. And an optical optical system. In a preferred embodiment of the laser apparatus, the plurality of semiconductor lasers are arranged in a state where the respective light emitting points are aligned in one direction. On the other hand, the laser device of Japanese Patent Application No. 2000-273870 is formed by arranging a plurality of multi-cavity semiconductor laser chips having a plurality of light emitting points.
[0013]
As described above, in a laser device in which a plurality of semiconductor lasers are arranged in a state where each light emitting point is aligned in one direction, the plurality of semiconductor lasers are usually fixed and held on a block such as a heat dissipation block made of Cu or Cu alloy. Is done.
[0014]
In addition, since laser beams are emitted from a plurality of semiconductor lasers in a divergent light state, when the laser beams are focused at one point, the divergent light beam is passed through a collimator lens and collimated. Further, it is necessary to make the collimated laser beams travel in the same direction and enter the condenser lens. To do so, position each collimator lens in a state where the focal point of each collimator lens is at the emission point of the semiconductor laser and the lines connecting the emission point of each semiconductor laser and the center of the collimator lens are parallel to each other. Must be matched. If this alignment is incorrect, it is impossible to converge a plurality of laser beams to a sufficiently small spot diameter.
[0015]
In order to prevent this problem, it is necessary to align the collimator lens in the XYZ3 direction with a micron to submicron accuracy at a narrow pitch in accordance with the semiconductor laser. Naturally, when the pitch is narrowed, the distance between the lenses is narrowed, and for example, only a gap of 100 μm or less can be taken. There is known a method of adjusting and positioning by moving the lens one by one by shining the semiconductor laser with the active method, but there is not enough room to securely hold the lens, and the lens is moved with reference to the semiconductor laser. However, it is not easy to align and position in the three axis directions.
[0016]
For example, in order to align three axes, the collimator lens and laser block must be fixed via a holder member. Therefore, at least two fixing points are required, and seven semiconductor lasers are used for multiplexing. For all of the 14 positions, the alignment positioning must be fixed with micron to submicron accuracy. Since the yield in this case is effective at the 14th power of the individual yield, it is very difficult to secure the yield above a certain level if the number of adhesion points increases even if the fixing reliability is increased.
[0017]
In addition, matching the parallelism of the bonding surface of the holder, lens, and semiconductor laser block is an important factor for maintaining the fixing accuracy. There is a contradiction that is not always compatible with each other, and it is difficult to ensure accuracy. Therefore, the alignment yield deteriorates, the alignment time becomes long, and the cost of parts increases, leading to an increase in the cost of the laser device.
[0018]
The present invention has been made in view of the above circumstances, and in a method of manufacturing a laser device in which a plurality of semiconductor lasers are arranged in a state where each light emitting point is aligned in one direction, the focal position of each collimator lens Is located at the emission point of the semiconductor laser, and the lines connecting the emission point of each semiconductor laser and the center of the collimator lens are parallel to each other.
[0019]
Another object of the present invention is to provide a laser device in which the collimator lens and the semiconductor laser are accurately aligned as described above.
[0020]
[Means for Solving the Problems]
A method of manufacturing a laser device according to the present invention includes:
Multiple semiconductor lasers,
A block in which these semiconductor lasers are fixedly held in a state in which the respective emission points are aligned in one direction;
In a method of manufacturing a laser device comprising a plurality of collimator lenses for collimating laser beams emitted from the semiconductor laser,
Forming a smooth reference plane perpendicular to the emission axis of the semiconductor laser on the front side of the portion where the plurality of semiconductor lasers of the block are fixed,
Each of the plurality of semiconductor lasers is fixed to the block by adjusting the position in the emission axis direction based on the focal length measurement information of the corresponding collimator lens,
Thereafter, the positions of the plurality of collimator lenses are adjusted along the reference plane and then fixed to the reference plane.
[0021]
Moreover, the laser apparatus according to the present invention comprises:
Multiple semiconductor lasers,
A block in which these semiconductor lasers are fixedly held in a state in which the respective emission points are aligned in one direction;
In a laser apparatus comprising a plurality of collimator lenses that collimate each laser beam emitted from the semiconductor laser,
A smooth reference plane that is perpendicular to the emission axis of the semiconductor laser is formed on the front side of the portion where the plurality of semiconductor lasers of the block are fixed,
Each of the plurality of semiconductor lasers is fixed to the block in a state in which the position is adjusted in the emission axis direction based on each of the focal lengths of the corresponding collimator lenses,
The plurality of collimator lenses are fixed to the reference surface in a state where the position is adjusted following the reference surface.
[0022]
In the laser device according to the present invention having the above-described configuration, the semiconductor laser is mounted on the submount in a junction-down manner, and the submount to which the semiconductor laser is fixed is arranged so that the emission points of the semiconductor lasers are arranged in a line. It is desirable to be disposed on a heat block as a block.
[0023]
In such a case, it is desirable that the mounting is performed so that the feature point indicating the light emission position of the front end of the semiconductor laser can be recognized when viewed from the submount side.
[0024]
【The invention's effect】
According to the laser device manufacturing method of the present invention, a smooth reference plane perpendicular to the emission axis of the semiconductor laser is formed in front of a portion of the block where the plurality of semiconductor lasers are fixed. Is adjusted in the direction of the emission axis based on the focal length measurement information of the corresponding collimator lens and fixed to the block, so that the emission point of each semiconductor laser is accurately located at the focal position of each collimator lens. Both of them can be aligned with the position. After that, the position of the collimator lenses is adjusted to follow the reference plane and then fixed to the reference plane. Therefore, the lines connecting the emission points of the semiconductor lasers and the centers of the collimator lenses are mutually connected. You can create a parallel state.
[0025]
Therefore, according to this method of manufacturing a laser device, it is possible to obtain a laser device that accurately collimates the laser beams emitted from the respective semiconductor lasers and advances the collimated laser beams in parallel with each other. . According to such a laser device, it becomes impossible to converge a plurality of laser beams to a sufficiently small spot diameter when used in combination with a condensing lens.
[0026]
In addition, with the adjustment by the conventional lens, the fixing position of the semiconductor laser and the collimator lens becomes twice the number of combined waves, and it is difficult to ensure reliability. In the present invention, by focusing on the semiconductor laser side, the number of fixing points can be reduced by half (the number of combined beams), and a simple alignment device configuration can be obtained. . Since the yield works as a power, the effect of halving the fixed part is great.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0028]
1 and 2 show a planar shape and a side shape of the laser device according to the first embodiment of the present invention, respectively. As shown in the figure, this combined laser light source is arranged as an array fixed on a horizontal laser fixing surface 10a of a heat block (heat sink) 10 made of copper. , LD2, LD3, LD4, LD5, LD6, and LD7, and collimator lenses 11, 12, 13, 14, provided for the GaN semiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6, and LD7, respectively. 15, 16 and 17.
[0029]
4, 5 and 6 show the side shape, planar shape, and front shape of an ultraviolet light high-intensity multiplexing fiber module using this laser device. This multiplexing fiber module will be described in detail later.
[0030]
In the present embodiment, the GaN-based semiconductor lasers LD1 to LD7 are respectively fixed on the submount M, and are fixed on the laser fixing surface 10a of the heat block 10 via the submount M. The attachment state of the GaN-based semiconductor lasers LD1 to LD7 to the heat block 10 is shown in FIG. Note that the GaN-based semiconductor lasers LD1 to LD7 may be directly fixed on the laser fixing surface 10a without using the submount M.
[0031]
Hereinafter, attachment of the GaN semiconductor lasers LD1 to LD7 and the collimator lenses 11 to 17 will be described in detail. The focal lengths of the collimator lenses 11 to 17 are previously measured with another measurement system. Assume that each measurement result is represented by errors Δf11 to Δf17 with respect to f1, with the collimator lens production reference plane being positive.
[0032]
When the GaN-based semiconductor lasers LD1 to LD7 mounted in advance on the submount M are sequentially arranged on the heat block 10 to form an array, one surface of the heat block 10 is used as a reference surface S, and the production standard for the collimator lenses 11 to 17 The surfaces are brought into contact with each other by being brought into contact with each other, and corrected by errors Δf11 to Δf17 with respect to the position of f1 = 3 mm from this surface, respectively, in the optical axis direction (focal length adjustment direction: left and right direction in FIGS. 1 and 2). Position. At this time, the position reference in the focal direction of the GaN-based semiconductor lasers LD1 to LD7 is the chip edge forming the emission end face.
[0033]
In the arrangement direction of the GaN-based semiconductor lasers LD1 to LD7, positioning is performed at a design dimension of 1.25 mm pitch. Positioning in this direction does not require strict accuracy because there is a step of lens adjustment later. Thereafter, GaN-based semiconductor lasers LD1 to LD7 mounted in advance on the submount M are mounted and fixed on the heat block 10 in an array at the adjusted position.
[0034]
In the present embodiment, one surface S of the heat block 10 is used as a reference surface. Although it is preferable to take a reference plane on the integrated heat block 10 in terms of component accuracy and cost, the reference plane may be formed of a separate member.
[0035]
Laser beams B1, B2, B3, B4, B5, B6 and B7 (see FIG. 5) emitted from the GaN-based semiconductor lasers LD1 to LD7 in a divergent state are respectively collimators attached to the reference plane S of the heat block 10. The lenses 11, 12, 13, 14, 15, 16 and 17 are collimated.
[0036]
This is because, for example, when the collimator lens 11 is brought into contact with the reference surface S, the distance between the collimator lens 11 and the GaN-based semiconductor laser LD1 is equal to f1 + Δf11, that is, the actually measured focal length. It is. Regarding the other GaN-based semiconductor lasers LD2 to LD7 and the collimator lenses 12 to 17, the distance between them is set to the actually measured focal lengths f1 + Δf12 to f1 + Δf17. Therefore, it is not necessary to adjust the collimator lenses 11 to 17 in the optical axis direction again, and a lens holder for fixing the optical axis is not required.
[0037]
Next, adjustment of the laser beams B1 to 7 emitted from the GaN-based semiconductor lasers LD1 to LD7 will be described. In the laser beams B1 to 7, the parallelism between the axes is important. These beams are parallel light, but the axes are not parallel to each other. Therefore, the collimator lenses 11 to 17 are abutted against the reference surface S of the heat block 10 orthogonal to the laser emission axis O, respectively. It is necessary to align the directions of the parallel beams by fixing the in-plane positions so that the focal length does not change with respect to the corresponding GaN-based semiconductor lasers LD1 to LD7.
[0038]
At this time, the collimator lenses 11 to 17 are pressed against the reference surface S. However, in order to maintain the reproducibility in the focal direction, the surface roughness of the lens surface and the reference surface S needs to be kept small in terms of component manufacture. This surface roughness is preferably 1 μm or less in terms of centerline average roughness Ra. In-plane position adjustment is usually performed by illuminating the GaN-based semiconductor lasers LD1 to LD7 and collimating the laser beams B1 to B7 through the condenser lens onto the NFP optical system so that the image is condensed at one point. To do. Thus, the collimator lenses 11 to 17 are adjusted in position in the reference plane with respect to the GaN semiconductor lasers LD1 to LD7, and are sequentially fixed. Since the collimator lenses 11 to 17 are fixed at only one place, and a simple alignment device configuration can be obtained, assembly with higher reliability can be expected with less man-hours.
[0039]
The focal lengths of the collimator lenses 11 to 17 are measured in a separate measurement system in the present embodiment, but the GaN-based semiconductor lasers LD1 to LD7 are emitted on-line while being fed with a prober or the like in a chip state. While moving in the focal direction with reference to the collimator lenses 11-17, the FFP optical system or the like is used to find the point where the spread angle of the laser beams B1-7 passing through the collimator lenses 11-17 is the smallest and focus here. It is also possible to adopt a method of mounting on the heat block 10 on the spot.
[0040]
Next, an ultraviolet light high-intensity multiplexing fiber module using the above laser device will be described in detail with reference to FIGS. These FIGS. 4, 5 and 6 show the side shape, planar shape and front shape of the fiber module, respectively.
[0041]
The GaN-based semiconductor lasers LD1 to LD7 have a common oscillation wavelength of 405 nm, for example, and a maximum output of 100 mW. Laser beams B1, B2, B3, B4, B5, B6, and B7 emitted in a divergent light state from these GaN-based semiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6, and LD7 are collimator lenses 11, 12 respectively. , 13, 14, 15, 16 and 17 are collimated.
[0042]
The parallel laser beams B1 to B7 are collected by the condenser lens 20 and converge on the incident end face of the core 30a of the multimode optical fiber 30. In this example, the collimating lenses 11 to 17 and the condensing lens 20 constitute a condensing optical system, and the multimode optical fiber 30 constitutes a multiplexing optical system. That is, the laser beams B1 to B7 condensed as described above by the condensing lens 20 are incident on the core 30a of the multimode optical fiber 30 and propagate there, and are combined into one laser beam B to be multiplexed. The light is emitted from the mode optical fiber 30. As the multimode optical fiber 30, a step index type, a graded index type, and a composite type thereof can all be applied.
[0043]
In this example, the optical elements constituting the module are accommodated in a box-shaped package 40 having an upper opening, and the opening of the package 40 is closed by the package lid 41, whereby the package 40 and the package lid 41 are defined. It is hermetically held in a closed space.
[0044]
A base plate 42 is fixed to the bottom surface of the package 40, the heat block 10 is attached to the top surface of the base plate 42, and a collimator lens holder 44 that holds the collimator lenses 11 to 17 is fixed to the heat block 10. Has been. Further, a condenser lens holder 45 that holds the condenser lens 20 and a fiber holder 46 that holds the incident end of the multimode optical fiber 30 are fixed to the upper surface of the base plate 42. Further, the wirings 47 for supplying a driving current to the GaN-based semiconductor lasers LD1 to LD7 are drawn out of the package through openings formed in the lateral wall surface of the package 40.
[0045]
In FIG. 4, in order to avoid complication of the drawing, only one GaN-based semiconductor laser LD 7 is numbered among the GaN-based semiconductor lasers LD 1 to 7, and similarly, one of the collimator lenses 11 to 17. Only the collimator lens 17 is numbered.
[0046]
FIG. 6 shows the front shape of the mounting portion of the collimator lenses 11-17. As shown here, each of the collimator lenses 11 to 17 has a shape obtained by cutting a region including the optical axis of an aspherical circular lens into an elongated shape, and is formed by molding a resin or optical glass, for example. The 7 (1) and (2) respectively show the enlarged side surface shape and front surface shape of one collimator lens 17 on behalf of them, including the dimensions (unit: mm) of the main part.
[0047]
As shown in FIGS. 6 and 7, the collimator lenses 11 to 17 have directions in which the aperture diameters in the direction in which the light emitting points of the GaN-based semiconductor lasers LD1 to LD7 are aligned (the left-right direction in FIG. 6) are perpendicular to the direction (FIG. 6). It is formed smaller than the opening diameter in the vertical direction) and is closely arranged in the direction in which the light emitting points are arranged.
[0048]
On the other hand, the GaN-based semiconductor lasers LD1 to LD7 emit laser beams B1 to B7 having an emission width of 2 μm and divergence angles in a direction parallel to and perpendicular to the active layer, respectively, as 10 ° and 30 °, for example. Things are used. These GaN-based semiconductor lasers LD1 to LD7 are arranged so that the light emitting points are arranged in a line in a direction parallel to the active layer.
[0049]
Therefore, the laser beams B1 to B7 emitted from the respective light emitting points coincide with the direction of the large aperture diameter in the direction of the maximum divergence angle with respect to the respective collimator lenses 11 to 17 having the elongated shape as described above. The incident light is incident in a state where the direction with the smallest divergence angle coincides with the direction in which the aperture diameter is small. That is, each of the collimator lenses 11 to 17 having a long and narrow shape is used with the ineffective portion as small as possible corresponding to the elliptical cross-sectional shape of the incident laser beams B1 to B7. Specifically, in this embodiment, the aperture diameters of the collimator lenses 11 to 17 are 1.1 mm and 4.6 mm in the horizontal direction and the vertical direction, respectively, and the horizontal and vertical directions of the laser beams B1 to 7 incident thereon. The direction beam diameters are 0.9 mm and 2.6 mm, respectively. Further, the focal lengths f of the collimator lenses 11 to 17 ₁ = 3 mm, NA = 0.6, and lens arrangement pitch = 1.25 mm.
[0050]
Further, (1) and (2) in FIG. 8 respectively show the enlarged side surface shape and front surface shape of the condenser lens 20 including the dimensions (unit: mm) of the main part. As shown here, the condensing lens 20 also has a shape in which the region including the optical axis of the aspherical circular lens is cut into an elongated shape and is long in the alignment direction of the collimator lenses 11 to 17, that is, in the horizontal direction, and short in the direction perpendicular thereto. Has been. The focal length f of the condenser lens 20 ₂ = 12.5 mm, NA = 0.3. The condensing lens 20 is also formed by molding resin or optical glass, for example.
[0051]
On the other hand, the multimode optical fiber 30 is based on a graded index type optical fiber manufactured by Mitsubishi Cable Industries, Ltd., the core center portion is a graded index and the outer peripheral portion is a step index. Core diameter = 25 μm, NA = 0. 3. The transmittance of the end coat is 99.5% or more. In the case of this example, the value of the core diameter × NA described above is 7.5 μm.
[0052]
In the configuration of the present embodiment, the coupling efficiency of the laser beams B1 to B7 to the multimode optical fiber 30 is 0.9. Therefore, when each output of the GaN-based semiconductor lasers LD1 to LD7 is 100 mW, a combined laser beam B having an output of 630 mW (= 100 mW × 0.9 × 7) is obtained.
[0053]
Next, a combined laser light source according to the second embodiment of the present invention will be described with reference to FIGS. In FIG. 9, the same elements as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted unless necessary (the same applies hereinafter).
[0054]
Compared with the laser apparatus shown in FIGS. 1 and 2, the laser apparatus according to the second embodiment has seven lens elements 51 and 52 instead of the seven collimator lenses 11 to 17 formed individually. , 53, 54, 55, 56, and 57 are basically different in that a collimator lens array 50 is used.
[0055]
In the assembly when the collimator lens array is used, the optical axes of the collimated light cannot be finally adjusted by adjusting the individual collimator lenses as in the first embodiment. For this reason, in general, the collimator lens array and the semiconductor laser array are mounted with the same size design and passively combined. This method is the least expensive, requires less man-hours, and is simple as an assembly process.
[0056]
However, in order to perform passive mounting, it is necessary to process a reference surface and a positioning mark for assembling both with high accuracy, and it is not easy to actually implement. Therefore, it is conceivable to assemble the collimator lens array and the semiconductor laser array after adjusting the relationship between the lens elements and the semiconductor laser with high accuracy and then adjusting and fixing the arrays. If the relationship between the individual elements is determined, it is possible to combine and average 7 together to collect and multiplex them. In the adjustment between the arrays, alignment of 3 axes + 4 axes of rotation around the optical axis is performed. However, when adjustment in the optical axis direction is included, a lens holder is separately required, and the alignment process becomes complicated.
[0057]
On the other hand, a concern when using a glass-molded collimator lens array is a variation in optical performance among the seven lens elements. In the height direction and pitch direction, it is easy to drive with the mold and the performance is close to tolerance, but the variation in the focal direction is a deviation from a considerably large design value when the focal length is 1 to 3%, such as weight variation of the preform and shrinkage with time. Occur. If the focal length varies individually in one array, all seven cannot be optimally adjusted even if the lens array is combined with the semiconductor laser array mounted as designed.
[0058]
On the other hand, in the present invention, the focal length of each lens element constituting the collimator lens array is measured in advance, and the semiconductor laser array is formed by correcting the focal length, so that the variation of the array lens is absorbed. In addition, the arrays can be focused on each other. In addition, since focusing is performed at the position of the semiconductor laser, not only a lens holder is not required when aligning with the lens, but also the alignment is changed to adjustment in the same plane with 2 axes + rotation around the axis, so the device configuration is simple This can reduce man-hours.
[0059]
Hereinafter, the second embodiment will be described in detail. The focal lengths of the lens elements 51 to 57 of the collimator lens array 50 are previously measured by another measurement system. Assume that each measurement result is represented by errors Δf51 to Δf57 with respect to f1, with the collimator lens production reference plane being positive. The semiconductor laser chip is pre-junction mounted on the submount M. When the submounts M with the semiconductor laser are sequentially arranged on the heat block 10 to form an array, one surface of the heat block 10 is used as a reference surface S, and a collimator The manufacturing reference planes of the lens array 50 are brought into contact with each other, and the semiconductor laser is attached in the optical axis direction (focal length adjustment direction) by correcting errors Δf51 to Δf57 with reference to the position of f1 = 3 mm from this plane. The submount M is positioned.
[0060]
In the direction in which the GaN-based semiconductor lasers LD1 to LD7 are arranged, they are positioned with a design dimension of 1.1 mm pitch. Unlike the individual lens adjustment, the positioning in this direction cannot be individually adjusted later, and there is only an adjustment process for the entire array, so that strict mounting accuracy is required. Thereafter, the submount M with a semiconductor laser is mounted and fixed on the heat block 10 at the adjusted position to form a semiconductor laser array.
[0061]
In the present embodiment, one surface of the heat block 10 is used as the reference surface S. Although it is preferable to take a reference plane on the integrated heat block 10 in terms of component accuracy and cost, the reference plane may be formed of a separate member.
[0062]
Laser beams B1, B2, B3, B4, B5, B6 and B7 (see FIG. 5) emitted from the GaN-based semiconductor lasers LD1 to LD7 in a divergent light state are respectively collimators attached to the reference plane S of the heat block 10. The light is collimated by lens elements 51, 52, 53, 54, 55, 56 and 57 of the lens array 50.
[0063]
This is because, after the collimator lens array 50 is brought into contact with the reference plane S, the rotation between the LD1 and the lens element 51 becomes equal to f1 + Δf51, that is, the actually measured focal length by adjusting the rotation around the axis. . Also for the other LD2 to LD7 and the lens elements 52 to 57, the mutual distance is set to the actually measured focal lengths f1 + Δf51 to f1 + Δf57 (see FIG. 9).
[0064]
Therefore, there is no need to adjust the lens in the optical axis direction again, and the lens holder for fixing the optical axis is not required.
[0065]
Next, adjustment of the laser beams B1-7 emitted from the arrayed GaN semiconductor lasers LD1-7 described above will be described. For the laser beams B1 to 7, the parallelism between the axes becomes important. Although these laser beams B1 to B7 are parallel lights, the optical axes are not parallel to each other, so that a plurality of collimator lens elements 51 to 57 are projected to the reference plane S of the heat block 10. It is necessary to adjust the directions of the parallel beams by adjusting and fixing the in-plane positions of the GaN-based semiconductor lasers LD1 to LD7 so that the focal length does not change.
[0066]
At this time, the collimator lens array 50 is pressed against the reference surface S. However, in order to maintain the reproducibility in the focal direction, the surface roughness of the lens array surface and the reference surface S must be kept small in the production of components. is there. Preferably, the center line average roughness Ra is 1 μm or less. Further, since the collimator lens array 50 is longer than an individual lens, it suppresses the generation of stress due to the difference in thermal expansion from the heat block 10, and the inclination of the lens due to the unevenness of the adhesive surface and the positional deviation in the focal direction. The adhesive area is preferably small, and the design is made within a range where sufficient adhesive strength can be obtained. The collimator lens array 50 is fixed to the GaN-based semiconductor lasers LD1 to LD7 when the position in the heat block reference plane is adjusted and the seven elements 51 to 57 are aligned on average. Since the GaN-based semiconductor lasers LD1 to LD7 and the collimator lens array 50 are fixed only at this one position, a simple alignment device configuration can be obtained, and therefore, the assembly can be expected with less man-hours.
[0067]
The alignment of the collimator lens array 50 and the GaN-based semiconductor lasers LD1 to LD7 in the height direction is passively performed because adjustment is not effective in this configuration. Accordingly, both the collimator lens array 50 and the GaN semiconductor lasers LD1 to LD7 in the height direction need to be suppressed within an allowable error range. In order to match the height direction with a semiconductor laser array, it is usually recommended to perform junction down mounting.
[0068]
However, when the GaN-based semiconductor lasers LD1 to LD7 are directly mounted on the heat block 10 in a junction-down manner, the heat block is not necessarily caused by the positional deviation in the optical axis direction of the individual GaN-based semiconductor lasers LD1 to LD7 by adjusting the variation in the focal direction. Since the GaN-based semiconductor lasers LD1 to LD7 are not mounted on the end face, vignetting of the laser beam occurs in the heat block 10. Once the submount is mounted junction-down with reference to the end face, even if the mounting position varies in the focal direction depending on the thickness of the submount, the submount thickness is sufficiently larger than the focus variation value. No worries about beam vignetting.
[0069]
However, since the variation in the height of the light emitting points of the GaN-based semiconductor lasers LD1 to LD7 is suppressed by suppressing the variation in the thickness of the submount, the variation in the thickness of the submount needs to be suppressed beyond the required accuracy in the height direction. There is.
[0070]
As described above, by using a semiconductor laser array with a submount, it is possible to suppress variations in the height direction of the array by junction down mounting that suppresses variations in the thickness of the submount while eliminating vignetting of the laser beam due to focus variation adjustment. Both are possible.
[0071]
FIG. 11 explains the vignetting described above. FIGS. 4A and 4B show the case where the semiconductor laser LD is directly fixed to the heat block 10, and FIGS. 4C and 4D are diagrams where the laser diode LD is fixed to the heat block 10 through the submount M. Shows the case. In the cases of (a) and (b), when the position of the semiconductor laser LD is adjusted by the focal position alignment, vignetting may or may not occur depending on the position. On the other hand, in the cases of (c) and (d), when the position of the semiconductor laser LD is adjusted by the focal position alignment, no vignetting occurs even if the position changes greatly.
[0072]
In general, a semiconductor laser can see a characteristic point (for example, a ridge) indicating a light emitting point from the top in the case of junction-up mounting, but has no characteristic indicating a light emitting point from the top in the case of a junction down mounting, so the chip is With an inverted optical system, the position is recognized by looking from the bottom and looking at the junction-up surface.
[0073]
However, when the semiconductor laser mounted junction-down on the submount is viewed from above, the semiconductor laser has no feature point indicating the beam emission point, and since it is mounted on the submount from below, the laser is junction-up. I can't see it in the state. Therefore, there is a problem that positioning information for mounting cannot be obtained by recognition from above and below.
[0074]
Therefore, as shown in FIGS. 12A, 12B, and 12C from the top, side, and bottom, the semiconductor laser chip LD is mounted with the semiconductor laser chip LD protruding from the submount M. A feature point H such as a ridge indicating a light emitting point when viewed from the above can be recognized. As a result, even when the junction is mounted on the submount M, the position can be easily recognized from below.
[0075]
FIGS. 13 and 14 show another configuration for recognizing the position when the junction down is mounted. Here again, (a), (b), and (c) show states viewed from above, from the side, and from below, respectively. The thing of FIG. 13 comprises the submount M by the transparent member or Si etc. which permeate | transmits infrared rays. Thereby, when viewed from below, the feature point H such as a ridge indicating a light emitting point can be recognized. In FIG. 14, the submount M is provided with an opening G such as a notch or a hole. Thereby, when viewed from below, the feature point H such as a ridge indicating a light emitting point can be recognized. The opening G may have any shape such as a rectangle or a circle, and is preferably formed as close to the light emitting portion as possible.
[0076]
Note that when the pitch information is measured in advance by measuring not only the focal length of the collimator lens but also between the pitches of the lens elements and set as pitch errors Δp51 to Δp57 with respect to the design dimension of 1.1 mm, this error Δp51. Positioning is performed in the pitch direction (semiconductor laser array arrangement direction) by correcting for ~ Δp57. Thus, even when the array lens cannot be designed according to the design direction with respect to the focal direction and the pitch direction, correction can be performed in the process of mounting the semiconductor laser array based on the previous measurement data, and the arrays can be adjusted.
[0077]
Next, a combined laser light source according to a third embodiment of the present invention will be described with reference to FIGS. Compared with the laser device shown in FIGS. 9 and 10, the laser device of the third embodiment is replaced with seven light emitting portions C1, instead of the seven individually formed GaN-based semiconductor lasers LD1-7. Basically, the multi-cavity diode MCD having C2, C3, C4, C5, C6 and C7 is used.
[0078]
In the assembly using the collimator lens array 50 and the multi-cavity diode 70, the optical axes of the collimated light cannot be finally adjusted by adjusting individual collimator lenses as in the first embodiment. Therefore, in general, the collimator lens array 50 and the multi-cavity diode 70 are mounted with the same size design in a passive manner. This method is the least expensive, requires less man-hours, and is simple as an assembly process.
[0079]
However, in order to perform passive mounting, it is necessary to process a reference surface and a positioning mark for assembling both with high accuracy, which is difficult in practice. Therefore, it is conceivable to assemble the collimator lens array 50 and the multi-cavity diode 70 by making the relationship between the lens element and the semiconductor laser element accurately and then adjusting and fixing the arrays to each other. If the relationship between the individual elements is determined, it is possible to combine and average the seven and collect and combine them. In the adjustment between the arrays, alignment of 3 axes + 4 axes of rotation around the optical axis is performed. However, when adjustment in the optical axis direction is included, a lens holder is separately required, and the alignment process becomes complicated.
[0080]
On the other hand, a concern when using a glass-molded collimator lens array is a variation in optical performance among the seven lens elements. The height direction and pitch direction are easy to follow with the mold, and the performance is close to tolerance, but the variation in the focal direction is 1 to 3% of the focal length, such as the weight variation of the preform and shrinkage with time, and a deviation from a considerably large design value Occur. If the focal length varies individually in one array, all seven can be optimally adjusted even if the lens array is aligned with a multi-cavity diode that is produced with lithographic accuracy almost as designed. Can not. Therefore, the minimum requirement is to produce a small variation between elements. In addition, the variation in focus between individual lenses can be corrected in the same way as in the first and second embodiments.
[0081]
That is, in the present embodiment, the focal length of each lens element constituting the collimator lens array 50 is measured in advance, and Δf is corrected if the error Δf between the average value of the focal lengths and the designed focal length f1 is obtained. If the multi-cavity diode 70 is mounted on the heat block 10 in such a manner that the deviation in the focal direction of the array lens is corrected, the lens array can be focused well by simply abutting the lens array against the reference plane. Will be able to. In addition, since the focusing is performed at the mounting position of the multi-cavity diode 70 on the heat block 10, not only the lens holder is unnecessary when aligning with the lens, but also the alignment is performed in the same plane as the rotation around the two axes + the axis. Since it changes to adjustment, the system configuration is simple and the number of man-hours can be reduced.
[0082]
Hereinafter, the adjustment work will be described in detail. The focal lengths of the lens elements 51 to 57 of the collimator lens array 50 are measured in advance by another measuring system. The average value of each measurement result is obtained, the collimator lens production reference plane is made positive, and the difference from the average value with respect to the focal length f1 is represented by an error Δf. The multi-cavity diode 70 is pre-junction mounted on the submount M, and when the submount M with multi-cavity diode is mounted on the heat block 10, the one surface S of the multi-cavity diode heat block 10 is used as a reference plane. The production reference surfaces of the collimator lens array 50 are brought into contact with each other, and the multicavity is corrected in the optical axis direction (focal length adjustment direction) by correcting an error Δf with reference to the position of f1 = 3 mm from this surface. Position the submount M with diode.
[0083]
In the pitch direction, a multi-cavity diode 70 in which light emitting points are arranged at a pitch of 1.1 mm, which is the design dimension, is used, and there is an adjustment process for the entire array. Therefore, positioning in the pitch direction is different from adjustment of a semiconductor laser array. There is no problem even if it is not mounted with such severe mounting accuracy. Thereafter, the submount M with a multi-cavity diode is mounted and fixed to the heat block 10 at the adjusted position.
[0084]
As described above, the embodiment in which the number of multiplexing is seven has been described, but the number of multiplexing when using the laser apparatus of the present invention is not limited to this seven, and any number of two or more is selected. May be.
[Brief description of the drawings]
FIG. 1 is a plan view showing a laser apparatus according to a first embodiment of the present invention.
FIG. 2 is a side view of the laser device of FIG.
3 is a perspective view showing a part of the laser device of FIG. 1;
FIG. 4 is a side view of an ultraviolet light high intensity multiplexing fiber module equipped with the laser device.
FIG. 5 is a plan view of the ultraviolet light high-intensity multiplexing fiber module.
FIG. 6 is a partial front view of the ultraviolet light high-intensity multiplexing fiber module.
FIG. 7 is a side view (1) and a front view (2) of a collimator lens used in the combined laser light source.
FIG. 8 is a side view (1) and a front view (2) of a condensing lens used in the combined laser light source.
FIG. 9 is a plan view showing a laser apparatus according to a second embodiment of the present invention.
10 is a side view of the laser device of FIG. 9;
FIG. 11 is a diagram for explaining vignetting of a laser beam by a laser element mounting structure;
FIG. 12 is a schematic view showing an example of a mounting structure of a laser element on a submount.
FIG. 13 is a schematic diagram showing an example of a mounting structure of a laser element on a submount.
FIG. 14 is a schematic view showing a mounting structure example of a laser element with respect to a submount.
FIG. 15 is a plan view showing a laser apparatus according to a third embodiment of the present invention.
16 is a side view of the laser device of FIG.
[Explanation of symbols]
10 Heat block
11-17 Collimator lens
20 Condensing lens
30 Multimode optical fiber
30a Multimode optical fiber core
50 Collimator lens array
70 Multicavity diode
LD1-7 GaN semiconductor laser
B1-7 Laser beam
B Combined laser beam
M submount
S Reference plane

Claims (2)

Multiple semiconductor lasers,
A block in which these semiconductor lasers are fixedly held in a state in which the respective emission points are aligned in one direction;
In a method of manufacturing a laser device comprising a plurality of collimator lenses for collimating laser beams emitted from the semiconductor laser,
Forming a smooth reference plane perpendicular to the emission axis of the semiconductor laser on the front side of the portion of the block where the plurality of semiconductor lasers are fixed,
Each of the plurality of semiconductor lasers is fixed to the block by adjusting the position in the emission axis direction based on the focal length measurement information of the corresponding collimator lens,
Thereafter, the position of the plurality of collimator lenses is adjusted along the reference plane, and then fixed to the reference plane. Multiple semiconductor lasers,
A block in which these semiconductor lasers are fixedly held in a state in which the respective emission points are aligned in one direction;
In a laser apparatus comprising a plurality of collimator lenses that collimate each laser beam emitted from the semiconductor laser,
On the front side of the portion of the block where the plurality of semiconductor lasers are fixed, a smooth reference plane that is perpendicular to the emission axis of the semiconductor laser is formed,
Each of the plurality of semiconductor lasers is fixed to the block in a state in which the position is adjusted in the light emitting axis direction based on the focal length of the corresponding collimator lens
The laser device, wherein the plurality of collimator lenses are fixed to the reference surface in a state of being adjusted in accordance with the reference surface.

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