JP2008258341A - Semiconductor laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser element capable of emitting out a plurality of laser beams having different wavelengths and capable of suppressing the deterioration of polarization characteristic at least in the semiconductor laser element unit of one side. <P>SOLUTION: In a structure wherein a first semiconductor laser element unit 10 comprising a first waveguide 16c and a second semiconductor laser element unit 20 comprising a second waveguide 26c are formed on an n-type GaAs (gallium arsenide) substrate 1, this semiconductor laser element is formed so that the first waveguide 16c and the second waveguide 26c are respectively formed in plan view at positions so that the ratio of a distance (a), from the center 40 of the direction of short side (arrow sign X direction) of the n-type GaAs substrate 1 to the first waveguide 16c and the second waveguide 26c, to a distance (b), from the first wave guide 16c and the second wave guide 26c to one side end face 1a of the n-type GaAs substrate 1 and the other side end face 1b of the n-type GaAs substrate 1, or the ratio (a:b) becomes within the range from 0.43:0.57 to 0.57:0.43. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser element, and more particularly to a semiconductor laser element used as a light source for an optical pickup or the like.

  CD-R (Compact Disk Recordable) and DVD-R (Digital Versatile Disk Recordable) capable of reading / writing are widely used as optical disc media, and both CD-R and DVD-R can be read / written conventionally. Possible optical disk systems are known. In such an optical disk system, a monolithic semiconductor laser element that emits laser beams of different wavelengths from one chip is used as a light source of an optical pickup. Conventionally, as such a monolithic type semiconductor laser element, an element unit that emits an infrared laser beam for CD-R (wavelength to 780 nm) and a red laser beam for DVD-R (wavelength to 650 nm) are used. 2. Description of the Related Art A semiconductor laser element (two-wavelength semiconductor laser element) in which an emitting element portion is integrated on the same substrate is known (see, for example, Patent Document 1).

  FIG. 11 is a simplified cross-sectional view of the conventional semiconductor laser device described in Patent Document 1 described above. Referring to FIG. 11, the conventional semiconductor laser element includes a first semiconductor laser element portion 110 having an AlGaAs-based semiconductor layer and a second semiconductor laser element portion 120 having an AlGaInP-based semiconductor layer. The first semiconductor laser element unit 110 has a function of emitting infrared laser light in the 780 nm band, and the second semiconductor laser element unit 120 has a function of emitting red laser light in the 650 nm band. . The first semiconductor laser element unit 110 and the second semiconductor laser element unit 120 are formed on the same n-type GaAs substrate 130. The first semiconductor laser element unit 110 and the second semiconductor laser element unit 120 are respectively formed with a first waveguide 110a and a second waveguide 120a for emitting laser light. In addition, p-side electrodes 111 and 121 are formed in the first semiconductor laser element unit 110 and the second semiconductor laser element unit 120, respectively.

  Further, in such a conventional semiconductor laser element, the chip width W10 is generally formed to be about 300 μm. Further, the conventional semiconductor laser element generally has a first waveguide 110a on the upper surface of the submount 140 made of AlN in order to dissipate heat generated in the first waveguide 110a and the second waveguide 120a. And it attaches by the junction down system which turned the 2nd waveguide 120a to the downward side. Specifically, the p-side electrode 111 of the first semiconductor laser element unit 110 and the p-side electrode 121 of the second semiconductor laser element unit 120 are respectively connected to the submount 140 via solder layers 141 and 142 made of AuSn or the like. Are fused to electrodes 143 and 144 formed on the upper surface. In this manner, the semiconductor laser device is mounted on the can package or the frame package, and a semiconductor device is configured. The semiconductor device configured as described above is used as a light source of an optical pickup by being mounted in the optical pickup device.

Here, when a monolithic semiconductor laser element (two-wavelength semiconductor laser element) provided with a plurality of semiconductor laser element units that emit laser beams of different wavelengths on one substrate is used as a light source of an optical pickup, Since laser beams with different wavelengths pass through a common optical system, the polarization characteristics (polarization angle) of the laser beams with different wavelengths are important. On the other hand, when a monolithic semiconductor laser element (two-wavelength semiconductor laser element) that emits infrared laser light and red laser light is used as a light source of an optical pickup, generally, a second laser that emits red laser light is used. The optical design of the optical pickup is performed around the semiconductor laser element portion. At this time, since the optical design is made so as to correct the polarization angle of the red laser light on the optical pickup side, the deviation of the polarization angle of the red laser light emitted from the second semiconductor laser element portion does not matter so much. Therefore, when the monolithic semiconductor laser element as described above is used as the light source of the optical pickup, at least the polarization characteristics of the first semiconductor laser element portion that emits infrared laser light are important.
JP 2006-351784 A

  However, as a result of intensive studies by the present inventors, in the configuration of the conventional semiconductor laser device shown in FIG. 11, when the semiconductor laser device is fixed on the submount 140 by the junction down method, at least infrared laser light is used. It has been found that there is a problem in that the polarization characteristics deteriorate in the first semiconductor laser element portion that emits light.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to emit a plurality of laser beams having different wavelengths and at least one of the semiconductor laser element portions. It is an object of the present invention to provide a semiconductor laser device capable of suppressing a decrease in polarization characteristics.

  In order to achieve the above object, the inventors of the present application have conducted intensive studies. As a result, the first waveguide and the second waveguide are divided into a central portion in the width direction of the first semiconductor laser element portion and a second semiconductor laser element portion, respectively. It has been found that, when the semiconductor laser device is mounted on the submount by the junction down method, at least one of the semiconductor laser device portions is prevented from degrading the polarization characteristics by being arranged at the center in the width direction of It was.

  That is, a semiconductor laser device according to an aspect of the present invention includes a first semiconductor laser including a long substrate, a first waveguide formed on the substrate, and a light emitting layer containing Ga and As. An element portion and a second semiconductor laser element portion formed on the substrate and including the second waveguide are provided. The first waveguide and the second waveguide extend in parallel with each other along the longitudinal direction of the substrate, and when viewed in plan, the first waveguide and the second waveguide from the center in the short direction of the substrate. And the ratio of the distance from the first waveguide and the second waveguide to the one end surface of the substrate and the other end surface of the substrate is within the range of 0.43: 0.57 to 0.57: 043, respectively. It is formed at each position.

  In the semiconductor laser device according to this aspect, as described above, the first semiconductor laser device portion including the first waveguide and the light emitting layer containing Ga and As and the second waveguide are formed on the substrate. In the structure in which the second semiconductor laser element portion is formed, the first waveguide and the second waveguide are respectively viewed from the center in the short direction of the substrate when viewed in plan. The ratio of the distance to the waveguide and the distance from the first waveguide and the second waveguide to the one end face of the substrate and the other end face of the substrate is in the range of 0.43: 0.57 to 0.57: 043, respectively. When the semiconductor laser device is mounted on the submount by the junction down method, at least one of the semiconductor laser device portions can suppress a decrease in polarization characteristics. That.

  That is, in the semiconductor laser device according to one aspect, the first waveguide and the second waveguide are respectively arranged in the width direction of the first semiconductor laser element portion (short direction of the substrate) by configuring as described above. Since the semiconductor laser device can be disposed in the vicinity of the center portion and in the vicinity of the center portion in the width direction (short direction of the substrate) of the second semiconductor laser element portion, when mounting the semiconductor laser device on the submount by the junction down method, The stress applied to the waveguide and the second waveguide can be made substantially uniform. For this reason, it can suppress that a nonuniform mounting stress is added to a 1st waveguide and a 2nd waveguide. On the other hand, in the first semiconductor laser element portion including the light emitting layer containing Ga and As, the amount of heat generated during driving is relatively small, and therefore the first semiconductor laser is caused by the difference in the thermal expansion coefficient between the substrate and the submount. Thermal stress applied to the element portion is relatively small. For this reason, since the thermal stress applied to the first waveguide is also reduced, non-uniform mounting stress is applied to the first waveguide and the second waveguide when the semiconductor laser element is mounted on the submount by the junction down method. By suppressing the stress, the stress applied to the first waveguide can be reduced. Thereby, it is considered that at least in the first semiconductor laser element part including the light emitting layer containing Ga and As, it is possible to suppress a decrease in polarization characteristics due to the stress applied to the first waveguide.

  In the semiconductor laser device according to the aforementioned aspect, the second semiconductor laser device portion can be configured to include a light emitting layer containing at least Ga, In, and P.

  In the semiconductor laser device according to the aforementioned aspect, the substrate preferably has a length of 250 μm in the short direction. If comprised in this way, when the space | interval of a 1st waveguide and a 2nd waveguide is set to 110 micrometers, a 1st semiconductor laser can be easily made into a 1st waveguide and a 2nd waveguide, respectively. Since it can be disposed in the vicinity of the central portion in the width direction of the element portion (short direction of the substrate) and in the vicinity of the central portion in the width direction of the second semiconductor laser element portion (short direction of the substrate), at least easily In the first semiconductor laser element portion including the light emitting layer containing Ga and As, it is possible to suppress a decrease in polarization characteristics. Also, with this configuration, the plane area of the semiconductor laser element can be reduced, so that more semiconductor laser elements can be manufactured from one semiconductor wafer. As a result, the manufacturing efficiency can be improved and the cost can be reduced while suppressing the deterioration of the polarization characteristic in the first semiconductor laser element portion.

  In this case, the substrate preferably has a length of 200 μm in the short direction. If comprised in this way, while being able to suppress the fall of a polarization characteristic more easily in the 1st semiconductor laser element part containing the light emitting layer containing Ga and As more easily, it improves manufacturing efficiency easily. And can be used for cost reduction.

  As described above, according to the present invention, it is possible to easily provide a semiconductor laser element that can emit a plurality of laser beams having different wavelengths and can suppress a decrease in polarization characteristics in at least one semiconductor laser element unit. Can get to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view showing the structure of a semiconductor laser device according to an embodiment of the present invention. FIG. 2 is a plan view of the semiconductor laser device according to the embodiment of the present invention shown in FIG. 3 to 5 are views for explaining the structure of the semiconductor laser device according to the embodiment of the present invention shown in FIG. First, the structure of a semiconductor laser device according to an embodiment will be described with reference to FIGS.

  In the semiconductor laser device according to the embodiment, as shown in FIGS. 1 and 2, the first semiconductor laser element unit 10 that emits infrared laser light in the 780 nm band and the second semiconductor that emits red laser light in the 650 nm band. The laser element unit 20 is formed on the same n-type GaAs substrate 1. As shown in FIG. 2, the n-type GaAs substrate 1 has a length L of 1520 μm in the arrow Y direction (longitudinal direction) and 193 μm in the arrow X direction (short direction) orthogonal to the arrow Y direction. It is formed in a long shape having a width W of ˜255.8 μm. The n-type GaAs substrate 1 is an example of the “substrate” in the present invention.

  As shown in FIGS. 1 and 2, the first semiconductor laser element portion 10 and the second semiconductor laser element portion 20 are formed with ridge portions 16a and 26a, respectively. The first semiconductor laser element portion 10 and the second semiconductor laser element portion 20 are each n-type so that the ridge portions 16a and 26a extend along the longitudinal direction (arrow Y direction) of the n-type GaAs substrate 1, respectively. It is formed on the GaAs substrate 1. Thereby, in the semiconductor laser device according to the embodiment, as shown in FIG. 2, the length L is 1520 μm in the arrow Y direction (longitudinal direction), and the arrow X direction (short direction) is orthogonal to the arrow Y direction. ) To have a width W of 193 μm to 255.8 μm.

  As shown in FIG. 1, the first semiconductor laser element unit 10 and the second semiconductor laser element unit 20 are electrically connected between the first semiconductor laser element unit 10 and the second semiconductor laser element unit 20. A separation groove 30 is provided for separation. The separation groove 30 includes an inclined sidewall and has a width W1 of about 25 μm. The distance from one end face 1a of the n-type GaAs substrate 1 to the first semiconductor laser element portion 10 and the distance from the other end face 1b of the n-type GaAs substrate 1 to the second semiconductor laser element portion 20 are respectively About 12.5 μm.

  Further, the specific structure of the first semiconductor laser element portion 10 that emits infrared laser light in the 780 nm band is made of n-type GaInP having a thickness of about 0.4 μm on the upper surface of the n-type GaAs substrate 1. A buffer layer 11 is formed. An n-type cladding layer 12 made of n-type AlGaInP having a thickness of about 3.3 μm is formed on the buffer layer 11. A light emitting layer 13 is formed on the n-type cladding layer 12.

  As shown in FIG. 3, the light emitting layer 13 is formed by alternately laminating two well layers 13a made of GaAs having a thickness of about 3.7 nm and one barrier layer 13b made of AlGaAs having a thickness of about 8 nm. The first MQW active layer 13c formed is included. Further, an n-side light guide layer 13d and a p-side light guide layer 13e made of undoped AlGaAs having a thickness of about 9 nm are provided so as to sandwich the first MQW active layer 13c. The first MQW active layer 13c, the n-side light guide layer 13d, and the p-side light guide layer 13e constitute the light emitting layer 13.

  As shown in FIG. 1, a p-type first cladding layer 14 made of p-type AlGaInP having a thickness of about 0.2 μm is formed on the light emitting layer 13. An etching stop layer 15 made of p-type GaInP having a thickness of about 0.02 μm is formed on the p-type first cladding layer 14.

  A p-type second cladding layer 16 made of p-type AlGaInP having a thickness of about 1.6 μm is formed in a predetermined region on the etching stop layer 15, and the p-type second cladding layer 16 forms a ridge portion 16 a. Is configured. The ridge portion 16a has a width W2 of about 3 μm and is formed in a mesa shape (trapezoidal shape). A first waveguide 16 c is formed in the region corresponding to the ridge portion 16 a in the vicinity of the light emitting layer 13 so as to extend along the longitudinal direction (arrow Y direction) of the n-type GaAs substrate 1.

  A pair of support portions 16b for protecting the ridge portion 16a is formed on both sides of the ridge portion 16a so as to sandwich the ridge portion 16a. The support portion 16b is composed of the p-type second cladding layer 16, and is formed in a predetermined region on the etching stop layer 15 that is separated from the ridge portion 16a by a predetermined distance (about 10 μm).

  Further, on the upper surface of the support portion 16b, the side surface of the support portion 16b, the side surface of the ridge portion 16a, and the etching stop layer 15, an undoped layer having a thickness of about 0.4 μm in this order from the etching stop layer 15 side. A current blocking layer 17 composed of an AlInP layer 17a and an n-type GaAs layer 17b having a thickness of about 0.4 μm is formed. A p-type contact layer 18 made of p-type GaAs having a thickness of about 1.25 μm is formed on the current blocking layer 17 and the upper surface of the ridge portion 16a. A p-side electrode 19 having a thickness of about 4.2 μm is formed on the p-type contact layer 18. The p-side electrode 19 includes a Cr layer having a thickness of about 15 nm, an Au layer having a thickness of about 1 μm, and a Pt layer having a thickness of about 0.2 μm, which are sequentially formed from the p-type contact layer 18 side. , And an Au layer having a thickness of about 3 μm.

  In addition, as a specific structure of the second semiconductor laser element unit 20 that emits red laser light in the 650 nm band, a buffer made of n-type GaInP having a thickness of about 0.4 μm on the upper surface of the n-type GaAs substrate 1 is used. Layer 21 is formed. An n-type cladding layer 22 made of n-type AlGaInP having a thickness of about 3.4 μm is formed on the buffer layer 21. A light emitting layer 23 is formed on the n-type cladding layer 22.

  As shown in FIG. 4, the light emitting layer 23 includes three well layers 23a made of GaInP having a thickness of about 6.3 nm and two barrier layers 23b made of AlGaInP having a thickness of about 4 nm. The second MQW active layer 23c formed is included. Further, an n-side light guide layer 23d and a p-side light guide layer 23e made of undoped AlGaInP having a thickness of about 20 nm are provided so as to sandwich the second MQW active layer 23c. The second MQW active layer 23c, the n-side light guide layer 23d, and the p-side light guide layer 23e constitute the light emitting layer 23.

  As shown in FIG. 1, a p-type first cladding layer 24 made of p-type AlGaInP having a thickness of about 0.34 μm is formed on the light emitting layer 23. An etching stop layer 25 having a thickness of about 0.02 μm is formed on the p-type first cladding layer 24. The etching stop layer 25 is formed by alternately stacking three p-type GaInP layers (not shown) having a thickness of about 3.6 nm and two p-type AlGaInP layers (not shown) having a thickness of about 5 nm. It is configured by being.

  A p-type second cladding layer 26 made of p-type AlGaInP having a thickness of about 1.2 μm is formed in a predetermined region on the etching stop layer 25, and the p-type second cladding layer 26 allows the ridge portion 26a. Is configured. The ridge portion 26a has a width W3 of about 2 μm, and is formed so that the side surface (side wall) is substantially perpendicular to the upper surface of the ridge portion 26a. A second waveguide 26 c is formed in a region corresponding to the ridge portion 26 a in the vicinity of the light emitting layer 23. The second waveguide 26c is formed to extend along the longitudinal direction (arrow Y direction) of the n-type GaAs substrate 1 in parallel with the first waveguide 16c.

  A pair of support portions 26b for protecting the ridge portion 26a are formed on both sides of the ridge portion 26a so as to sandwich the ridge portion 26a. The support portion 26b is composed of the p-type second cladding layer 26 and is formed in a predetermined region on the etching stop layer 25 that is separated from the ridge portion 26a by a predetermined distance (about 10 μm). The p-type second cladding layer 26 is formed to have a thickness (about 1.2 μm) smaller than the thickness (about 1.6 μm) of the p-type second cladding layer 16 of the first semiconductor laser element portion 10.

  Further, on the upper surface of the support portion 26b, on the side surface of the support portion 26b, on the side surface of the ridge portion 26a, and on the etching stop layer 25, an undoped layer having a thickness of about 0.4 μm in this order from the etching stop layer 25 side. A current blocking layer 27 composed of an AlInP layer 27a and an n-type GaAs layer 27b having a thickness of about 0.4 μm is formed. A p-type contact layer 28 made of p-type GaAs having a thickness of about 1.25 μm is formed on the current blocking layer 27 and the upper surface of the ridge portion 26a. A p-side electrode 29 having the same configuration as the p-side electrode 19 formed in the first semiconductor laser element unit 10 is formed on the p-type contact layer 28. That is, on the p-type contact layer 28, in order from the p-type contact layer 28 side, a Cr layer having a thickness of about 15 nm, an Au layer having a thickness of about 1 μm, and a Pt layer having a thickness of about 0.2 μm. And a p-side electrode 29 composed of an Au layer having a thickness of about 3 μm.

  An n-side electrode 2 having a thickness of about 1 μm is formed on the back surface of the n-type GaAs substrate 1. The n-side electrode 2 includes an Au layer having a thickness of about 7 nm, a Ge layer having a thickness of about 20 nm, and an Au layer having a thickness of about 160 nm, which are sequentially formed from the back side of the n-type GaAs substrate 1. The Ni layer has a thickness of about 30 nm, and the Au layer has a thickness of about 800 nm.

  In the semiconductor laser device according to the embodiment, as shown in FIG. 5, the interval W4 between the first waveguide 16c of the first semiconductor laser element unit 10 and the second waveguide 26c of the second semiconductor laser element unit 20 is 110 ± 1 μm, and the first waveguide 16c and the second waveguide 26c are symmetrical with respect to the center 40 in the short direction (arrow X direction) of the n-type GaAs substrate 1 (semiconductor laser element). Is arranged.

  Here, in the present embodiment, the width W of the n-type GaAs substrate 1 (the width W of the semiconductor laser element) is formed to be 193 μm to 255.8 μm, so that the first waveguide 16c of the first semiconductor laser element unit 10 is formed. In plan view, the distance a from the center 40 in the short direction (arrow X direction) of the n-type GaAs substrate 1 to the first waveguide 16c and one of the n-type GaAs substrate 1 from the first waveguide 16c. It is formed at a position where the ratio (a: b) to the distance b to the side end face 1a is within the range of 0.43: 0.57 to 0.57: 0.43. In addition, the second waveguide 26c of the second semiconductor laser element section 20 has a distance a from the center 40 in the short direction of the n-type GaAs substrate 1 to the second waveguide 26c in plan view, and the second waveguide 26c. Formed in a position where the ratio (a: b) to the distance b from the waveguide 26c to the other end face 1b of the n-type GaAs substrate 1 is within the range of 0.43: 0.57 to 0.57: 0.43. Has been.

  Specifically, when the width W of the n-type GaAs substrate 1 (the width W of the semiconductor laser element) is 255.8 μm, one side of the n-type GaAs substrate 1 from the center 40 in the short direction of the n-type GaAs substrate 1. The distance (1 / 2W) to the side end face 1a is 127.9 μm. Since the distance a from the center 40 in the short direction of the n-type GaAs substrate 1 to the first waveguide 16c is 55 μm, the distance b from the first waveguide 16c to the one end face 1a of the n-type GaAs substrate 1 is b. Becomes 72.9 μm (= 127.9 μm-55 μm). Thereby, the ratio of the distance a from the center 40 in the short direction of the n-type GaAs substrate 1 to the first waveguide 16c and the distance b from the first waveguide 16c to the one end face 1a of the n-type GaAs substrate 1 (A: b) is 55 μm: 72.9 μm, that is, 0.43: 0.57.

  Further, when the width W of the n-type GaAs substrate 1 (the width W of the semiconductor laser element) is 193 μm, from the center 40 in the short direction of the n-type GaAs substrate 1 to the one end face 1a of the n-type GaAs substrate 1. The distance (1/2 W) is 96.5 μm. Since the distance a from the center 40 in the short direction of the n-type GaAs substrate 1 to the first waveguide 16c is 55 μm, the distance b from the first waveguide 16c to the one end face 1a of the n-type GaAs substrate 1 is b. Is 41.5 μm (= 96.5 μm-55 μm). Thereby, the ratio of the distance a from the center 40 in the short direction of the n-type GaAs substrate 1 to the first waveguide 16c and the distance b from the first waveguide 16c to the one end face 1a of the n-type GaAs substrate 1 (A: b) is 55 μm: 41.5 μm, that is, 0.57: 0.43.

  The ratio of the distance a from the center 40 in the short direction of the n-type GaAs substrate 1 to the second waveguide 26c and the distance b from the second waveguide 26c to the other end face 1b of the n-type GaAs substrate 1 ( Regarding a: b), it can be considered as in the case of the first waveguide 16c described above.

  In addition, the semiconductor laser device according to the above-described embodiment is mounted on a semiconductor device by being attached to the submount 50, and thereby provided as a light source of an optical pickup. FIG. 6 is a cross-sectional view for explaining a method of mounting a semiconductor laser device according to an embodiment of the present invention on a submount. Next, a method for mounting the semiconductor laser device according to the embodiment on the submount 50 will be described with reference to FIG. First, as shown in FIG. 6, the submount 50 is placed on the heater stage 60, and a semiconductor laser element is placed on the submount 50 by a pickup collet 70. At this time, the semiconductor laser element is sub-aligned so that the p-side electrode 19 of the first semiconductor laser element unit 10 and the p-side electrode 29 of the second semiconductor laser element unit 20 are in contact with the solder layers 51 and 52 of the submount 50, respectively. Place on the mount 50.

  Next, the heater layers 60 are heated (heated) to a predetermined temperature at which the solder layers 51 and 52 of the submount 50 are melted to melt the solder layers 51 and 52. Then, the pickup collet 70 is held for a predetermined time (1 to 20 seconds) in a state where a weight of 10 to 100 g is applied. Thereafter, the molten solder layers 51 and 52 are solidified by cooling. In this manner, the semiconductor laser element is attached to the upper surface of the submount 50 by the junction down method.

  Subsequently, in order to confirm the effect of the semiconductor laser device of the present embodiment having the above structure, the inventors of the present application conducted the following experiment.

  First, by varying the width W of the semiconductor laser element, the distance a from the center 40 in the short direction of the n-type GaAs substrate 1 to the first waveguide 16c and the first waveguide 16c to the n-type GaAs substrate 1 are changed. Three types of semiconductor laser elements having different ratios (a: b) to the distance to the one side end face 1a were prepared. That is, the semiconductor laser elements according to Examples 1 and 2 included in the semiconductor laser element according to the present embodiment and the semiconductor laser element according to the comparative example were manufactured. FIGS. 7 and 8 are cross-sectional views showing simplified structures of the semiconductor laser device according to the first embodiment and the semiconductor laser device according to the second embodiment, respectively. FIG. 9 shows the structure of the semiconductor laser device according to the comparative example. It is sectional drawing simplified and shown. Specifically, as shown in FIG. 7, in the semiconductor laser element according to the first embodiment, the semiconductor laser element according to the first embodiment is configured such that the width W (see FIG. 1) of the semiconductor laser element is 200 μm. Thereby, in Example 1, it was comprised so that a: b might be set to 0.55: 0.45. Further, as shown in FIG. 8, in the semiconductor laser element according to the second embodiment, the semiconductor laser element according to the present embodiment is configured such that the width W of the semiconductor laser element (see FIG. 1) is 250 μm. Thereby, in Example 2, it was comprised so that a: b might be set to 0.44: 0.56. On the other hand, as shown in FIG. 9, in the semiconductor laser device according to the comparative example, the width W of the semiconductor laser device (see FIG. 1) is set to 300 μm so as to have the same width as that of the conventional semiconductor laser device. Thereby, in the comparative example, it was comprised so that a: b might be set to 0.37: 0.63. The configurations other than the width of the semiconductor laser device were the same as those of the semiconductor laser device according to the present embodiment described above in all of Example 1, Example 2, and Comparative Example.

  Next, the semiconductor laser devices according to Example 1, Example 2, and the comparative example were each mounted on the submount 50 to produce a semiconductor device. The mounting on the submount 50 was performed by the same method as the method for mounting the semiconductor laser device according to the present embodiment on the submount 50 described above. The mounting conditions were the same in Example 1, Example 2, and Comparative Example. Further, three semiconductor devices each having the semiconductor laser elements according to Example 1, Example 2, and Comparative Example attached thereto were manufactured and used for experiments.

  Using the semiconductor device manufactured as described above, the polarization angle of infrared laser light was measured. Here, the polarization angle will be described. When laser light is passed through the polarizing prism while rotating the polarizing prism, the light intensity of the laser light that has passed through the polarizing prism changes depending on the rotation angle of the polarizing prism. At this time, the rotation angle of the polarizing prism when the light intensity of the laser beam becomes maximum is the polarization angle. The smaller the absolute value of the polarization angle, the better the polarization characteristics. The polarization angle is measured by converting the laser light emitted from the semiconductor device into parallel light by a collimator lens, and then passing the laser light through the polarizing prism while rotating the polarizing prism so that the light intensity of the laser light is maximized. This was done by measuring the rotation angle of the polarizing prism. The results are shown in Table 1 and FIG.

測定結果としては、半導体レーザ素子の幅Ｗが小さくなるに従って、偏光角が小さくなっている。すなわち、比較例＞実施例２＞実施例１の順に、偏光角が小さくなっている。具体的には、半導体レーザ素子の幅Ｗが３００μｍである比較例では、偏光角は、それぞれ、１１．２°、１３．３°および１４．１°であったのに対して、半導体レーザ素子の幅Ｗが２５０μｍである実施例２では、偏光角は、それぞれ、４．１°、３．８°および２．５°であり、半導体レーザ素子の幅Ｗが２００μｍである実施例１では、偏光角は、それぞれ、−１．８°、−２．６°および０．２°であった。

As a measurement result, the polarization angle decreases as the width W of the semiconductor laser element decreases. That is, the polarization angle becomes smaller in the order of Comparative Example> Example 2> Example 1. Specifically, in the comparative example in which the width W of the semiconductor laser element is 300 μm, the polarization angles were 11.2 °, 13.3 °, and 14.1 °, respectively, whereas the semiconductor laser element In Example 2 where the width W of the laser beam is 250 μm, the polarization angles are 4.1 °, 3.8 ° and 2.5 °, respectively, and in Example 1 where the width W of the semiconductor laser element is 200 μm, The polarization angles were -1.8 °, -2.6 °, and 0.2 °, respectively.

  Here, when the reference of the polarization angle at which the polarization characteristics are good is within ± 5 °, in the comparative example, the result is much higher than the reference, whereas in the example 1 and the example 2, , You can see that it is within the standards.

  The reason why such a measurement result is obtained is considered as follows. That is, in Example 1 and Example 2, compared with the comparative example, the first waveguide 16c and the second waveguide 26c are in the width direction of the first semiconductor laser element unit 10 and the second semiconductor laser element unit 20, respectively. Arranged in the vicinity of the center of the n-type GaAs substrate 1 in the short direction. For this reason, when the semiconductor laser element is mounted on the submount 50 by the junction down method, the stress applied to the first waveguide 16c and the second waveguide 26c can be made substantially uniform. It is possible to suppress the non-uniform mounting stress from being applied to 16c and the second waveguide 26c. On the other hand, the first semiconductor laser element unit 10 that emits infrared laser light generates a relatively small amount of heat during driving as compared with the second semiconductor laser element unit 20 that emits red laser light. The thermal stress applied to the first semiconductor laser element portion 10 due to the difference in thermal expansion coefficient between the first and submounts 50 becomes relatively small. For this reason, the thermal stress applied to the first waveguide 16c is also reduced. Therefore, when the semiconductor laser device is mounted on the submount 50 by the junction down method, the first waveguide 16c and the second waveguide 26c are mounted non-uniformly. By suppressing the stress, the stress applied to the first waveguide 16c of the first semiconductor laser element portion 10 can be reduced. Thereby, at least in the first semiconductor laser element unit 10 that emits infrared laser light, the polarization angle is considered to be small.

  As shown in FIG. 10, when the measurement result of the polarization angle is subjected to a quadratic curve regression by the least square method, the following equation (1) is obtained.

θ = 0.0009W ² −0.31W + 24.4 (1)
Here, θ is the polarization angle (°), and W is the width (μm) of the semiconductor laser element.

  Using this equation (1), in the semiconductor laser device of this embodiment described above, when the width W of the semiconductor laser device is the minimum width (193 μm) (a: b = 0.57: 0.43), When the width W of the laser element is the maximum width (255.8 μm) (a: b = 0.43: 0.57), the polarization angle θ (°) was calculated. As a result, the polarization angle when the width W of the semiconductor laser element was 193 μm was −1.9 °, and the polarization angle when the width W of the semiconductor laser element was 255.8 μm was 4 °. For this reason, when the width W of the semiconductor laser element is within the range of 193 μm to 255.8 μm, it is considered that the polarization angle falls within the standard of ± 5 ° that the polarization characteristics are good.

  As described above, the distance a from the center 40 in the short direction (arrow X direction) of the n-type GaAs substrate 1 to the first waveguide 16c and the second waveguide 26c in the plan view, and the first waveguide The ratio (a: b) of the distance b from the one end face 1a of the n-type GaAs substrate 1 to the other end face 1b of the n-type GaAs substrate 1 from the 16c and the second waveguide 26c is 0.43: 0. It has been confirmed that, by configuring so as to be within the range of 57 to 0.57: 043, at least in the first semiconductor laser element portion 10 that emits infrared laser light, a decrease in polarization characteristics is suppressed. .

  In the present embodiment, as described above, on the n-type GaAs substrate 1, the first waveguide 16c is included, the first semiconductor laser element portion 10 including the light emitting layer 13, and the second waveguide 26c including the second waveguide 26c. In the structure in which the semiconductor laser element portion 20 is formed, the first waveguide 16c and the second waveguide 26c are respectively centered in the short direction (arrow X direction) of the n-type GaAs substrate 1 when viewed in plan. The distance a from 40 to the first waveguide 16c and the second waveguide 26c, the one end face 1a of the n-type GaAs substrate 1 and the other of the n-type GaAs substrate 1 from the first waveguide 16c and the second waveguide 26c, respectively. The semiconductor laser device is formed in a junction-down manner by forming it at a position where the ratio (a: b) to the distance b to the side end face 1b is within the range of 0.43: 0.57 to 0.57: 043. When attached to Bumaunto 50 on at least the first semiconductor laser element 10 for emitting an infrared laser beam, it is possible to suppress the reduction of the polarization characteristics.

  In the present embodiment, the n-type GaAs substrate 1 (semiconductor laser element) is configured to have a length of 250 μm in the short direction (arrow X direction), so that the first waveguide 16c and The second waveguides 26c are disposed in the vicinity of the center portion in the width direction (arrow X direction) of the first semiconductor laser element portion 10 and in the vicinity of the center portion in the width direction (arrow X direction) of the second semiconductor laser element portion 20, respectively. Therefore, at least in the first semiconductor laser element portion 10 that emits infrared laser light, it is possible to easily suppress a decrease in polarization characteristics. Moreover, since the plane area of a semiconductor laser element can be made small by comprising as mentioned above, more semiconductor laser elements can be produced from one semiconductor wafer. As a result, manufacturing efficiency can be improved and cost reduction can be achieved while suppressing a decrease in polarization characteristics in the first semiconductor laser element unit 10 that emits infrared laser light.

  In the present embodiment, the n-type GaAs substrate 1 (semiconductor laser element) is configured to have a length of 200 μm in the short direction (arrow X direction), so that at least an infrared laser can be obtained more easily. In the first semiconductor laser element section 10 that emits light, it is possible to suppress a decrease in polarization characteristics, and to easily improve manufacturing efficiency and reduce costs.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above embodiment, a semiconductor laser element in which a first semiconductor laser element portion that emits infrared laser light and a second semiconductor laser element portion that emits red laser light are monolithically integrated has been described. The present invention is not limited to this, and at least a semiconductor laser in which semiconductor laser element portions that emit laser beams of different wavelengths are monolithically integrated as long as the first semiconductor laser element portion that emits infrared laser light is provided. It may be an element.

  In the above embodiment, the distance between the first waveguide and the second waveguide is set to 110 μm, and the width of the semiconductor laser element is set to 193 μm to 255.8 μm. The distance from the center in the short direction of the substrate to the first waveguide and the second waveguide, and the distance from the first waveguide and the second waveguide to the one end face and the other end face of the n-type GaAs substrate, respectively. Although an example in which the ratio is configured to be 0.43: 0.57 to 0.57: 0.43 has been shown, the present invention is not limited to this, and the shortness of the n-type GaAs substrate in plan view. The ratio of the distance from the center of the direction to the first waveguide and the second waveguide to the distance from the first waveguide and the second waveguide to the one end face and the other end face of the n-type GaAs substrate is 0. 43: 0.57 to 0.57: 0.43 If configured urchin, the distance between the first waveguide and the second waveguide, and the width of the semiconductor laser element may be other configurations.

It is sectional drawing which showed the structure of the semiconductor laser element by one Embodiment of this invention. FIG. 2 is a plan view of the semiconductor laser device according to the embodiment of the present invention shown in FIG. 1. FIG. 2 is a cross-sectional view showing a structure of a light emitting layer of a first semiconductor laser element portion of the semiconductor laser element shown in FIG. 1 according to the embodiment of the present invention. FIG. 3 is a cross-sectional view showing a structure of a light emitting layer of a second semiconductor laser element portion of the semiconductor laser element according to the embodiment of the present invention shown in FIG. FIG. 2 is an enlarged plan view showing a part of the semiconductor laser device according to the embodiment of the present invention shown in FIG. 1. It is sectional drawing for demonstrating the method to attach the semiconductor laser element by one Embodiment of this invention on a submount. 1 is a cross-sectional view showing a simplified structure of a semiconductor laser device according to Example 1. FIG. FIG. 6 is a cross-sectional view showing a simplified structure of a semiconductor laser device according to Example 2. It is sectional drawing which simplified and showed the structure of the semiconductor laser element by a comparative example. It is the graph which showed the measurement result of the polarization angle of the infrared laser beam of a semiconductor laser element. It is sectional drawing which simplified and showed the conventional semiconductor laser element described in patent document 1. FIG.

Explanation of symbols

1 n-type GaAs substrate (substrate)
DESCRIPTION OF SYMBOLS 1a One side end surface 1b The other side end surface 2 N side electrode 10 1st semiconductor laser element part 11, 21 Buffer layer 12, 22 n-type cladding layer 13, 23 Light emitting layer 14, 24 p-type 1st cladding layer 15, 25 Etching stop Layer 16, 26 p-type second cladding layer 16a, 26a Ridge portion 16b, 26b Support portion 16c First waveguide 17, 27 Current blocking layer 18, 28 p-type contact layer 19, 29 p-side electrode 20 Second semiconductor laser element Part 26c second waveguide 30 separation groove 50 submount 60 heater stage 70 pickup collet

Claims (4)

A substrate having an elongated shape;
A first semiconductor laser element portion formed on the substrate and including a first waveguide and including a light emitting layer containing Ga and As;
A second semiconductor laser element portion formed on the substrate and including a second waveguide,
The first waveguide and the second waveguide extend in parallel with each other along the longitudinal direction of the substrate, and when viewed in plan, the first waveguide and the second waveguide from the center in the short direction of the substrate. The ratio between the distance to the second waveguide and the distance from the first waveguide and the second waveguide to the one end surface of the substrate and the other end surface of the substrate is 0.43: 0.57, respectively. A semiconductor laser element, wherein the semiconductor laser element is formed at a position within a range of 0.57: 043.   2. The semiconductor laser device according to claim 1, wherein the second semiconductor laser device portion includes a light emitting layer containing at least Ga, In, and P. 3.   The semiconductor laser device according to claim 1, wherein the substrate has a length of 250 μm in a short direction.   The semiconductor laser device according to claim 3, wherein the substrate has a length of 200 μm in a short direction.

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