JP2013084791A - Multiwavelength semiconductor laser device and optical pickup device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an S/N ratio of outgoing light while achieving miniaturization of a multiwavelength semiconductor laser device and miniaturization and cost reduction of an optical pickup device.SOLUTION: A multiwavelength semiconductor laser device 1 has: a mounting substrate 2; a first semiconductor laser element 10 having a first substrate 11, a first semiconductor laser element part 20, and a second semiconductor laser element part 30 adjacent to the first semiconductor laser element part 20 in an X direction; and a second semiconductor laser element 40 adjacent to the second semiconductor laser element part 30 in the X direction. The first semiconductor laser element part 20 has a first semiconductor layer 22 including a first light-emission part A. The second semiconductor laser element part 30 has a second semiconductor layer 32 including a second light-emission part B. The second semiconductor laser element 40 has a second substrate 41 and a third semiconductor layer 42 including a third light-emission part C. The second light-emission part B is located on a central part C2 in the X direction of the mounting substrate 2.

Description

  The present invention relates to a multiwavelength semiconductor laser device and an optical pickup device including the multiwavelength semiconductor laser device.

  Currently, a two-wavelength semiconductor laser element used for recording and reproduction of CD (Compact Disc) and DVD (Digital Versatile Disc) and emitting infrared light and red light, and recording and reproduction of BD (Blu-ray Disc) 2. Description of the Related Art An optical pickup device is widely produced in general, in which a semiconductor laser element that is used in a semiconductor laser and emits blue-violet light is mounted in different packages, and a two-wavelength semiconductor laser element and a semiconductor laser element are incorporated as a light source. .

  However, the optical pickup device as described above has the following problems. A two-wavelength semiconductor laser element that emits infrared light and red light and a semiconductor laser element that emits blue-violet light are mounted in different packages. For this reason, a total of two optical systems, that is, an optical system including a lens and the like to which the emitted infrared light and red light are incident and an optical system including a lens and the like to which the emitted blue-violet light is incident are necessary. There arises a problem that the optical pickup device is enlarged. Furthermore, an optical component corresponding to each of the two optical systems is required, resulting in a problem that the cost of the optical pickup device increases.

  In order to solve these problems, a semiconductor laser device described in Patent Document 1 has been proposed. A conventional semiconductor laser device will be described with reference to FIG.

  As shown in FIG. 10, a conventional semiconductor laser device 1 includes a two-wavelength semiconductor laser element 10 having an infrared semiconductor laser element section 20 and a red semiconductor laser element section 30, a blue-violet semiconductor laser element 40, and two on the upper surface. A submount 2 on which the wavelength semiconductor laser element 10 and the blue-violet semiconductor laser element 40 are mounted and a package (not shown) to which the lower surface of the submount 2 is fixed are provided.

  In the conventional semiconductor laser device 1, the side surfaces 11 a and 11 b of the substrate 11 of the two-wavelength semiconductor laser element 10 are inclined so that the distance from the blue-violet semiconductor laser element 40 increases as the distance from the submount 2 increases. Thereby, the light emitting part C of the blue-violet semiconductor laser element 40 can be arranged close to the light emitting parts A and B of the two-wavelength semiconductor laser element 10. For this reason, it can suppress that the distance of the light emission part C and the light emission parts A and B becomes large. As a result, the optical system of the optical pickup device can be made one.

JP 2011-49293 A

  However, the conventional semiconductor laser device has the following problems.

  In the conventional semiconductor laser device 1, the side surfaces 11 a and 11 b of the substrate 11 of the two-wavelength semiconductor laser element 10 are inclined so that the distance from the blue-violet semiconductor laser element 40 increases as the distance from the submount 2 increases. Therefore, of the two light emitting portions A and B of the two-wavelength semiconductor laser element 10, the light emitting portion B adjacent to the blue-violet semiconductor laser element 40, that is, the light emitting portion B of the red semiconductor laser element portion 30 is Located far from the center C11. For this reason, there is a problem that the polarization direction of the emitted light from the light emitting portion B changes due to the stress caused by the difference in thermal expansion coefficient between the submount 2 and the substrate 11.

  In general, a polarizing element such as a wave plate is used in an optical pickup device. For this reason, only the outgoing light having a polarization component in a specific direction among the outgoing light from the light emitting part contributes as a substantial light output. Therefore, when the polarization direction of the emitted light changes, the substantial light output is reduced, and the S / N ratio (Signal to Noise ratio) of the emitted light is lowered.

  By the way, as the optical axis of the emitted light from the light emitting unit is separated from the optical axis (center axis) of the optical system, the light capturing efficiency of the emitted light may decrease.

  As shown in FIG. 10, the three light emitting portions A, B, and C are separated from each other. For this reason, when the optical system of the optical pickup device provided with the conventional semiconductor laser device 1 is one, the optical axis of the light emitted from the light emitting units A, B, and C is separated from the optical axis of the optical system. There is a possibility that the light capturing efficiency of the emitted light is lowered.

  In particular, among infrared semiconductor laser elements, red semiconductor laser elements, and blue-violet semiconductor laser elements, red semiconductor laser elements have the poorest high-temperature operating characteristics. For this reason, if the optical axis of the emitted light from the light emitting part B of the red semiconductor laser element part 30 is separated from the optical axis of the optical system and the light capturing efficiency of the emitted light is lowered, the substantial light output is further reduced. For this reason, the S / N ratio of the emitted light further decreases.

  In view of the above, an object of the present invention is to improve the S / N ratio of emitted light while reducing the size of a multi-wavelength semiconductor laser device and reducing the size and cost of an optical pickup device.

  To achieve the above object, a multi-wavelength semiconductor laser device according to the present invention is mounted on a mounting substrate and an upper surface of the mounting substrate, and is formed on the first substrate and the first substrate. And a first semiconductor laser element having a second semiconductor laser element part formed on the first substrate so as to be adjacent to the first semiconductor laser element part in the first direction; And a second semiconductor laser element portion mounted on the upper surface of the mounting substrate so as to be adjacent to each other in the first direction. The first semiconductor laser element portion includes: A second semiconductor laser element portion is formed on the first substrate and includes a second light emitting portion. The second semiconductor laser element portion is formed on the first substrate and includes a second light emitting portion. A second semiconductor laser element having a semiconductor layer is formed on the second substrate and the second substrate. And a third semiconductor layer including a third light emitting portion. The first semiconductor laser element and the second semiconductor laser element include an upper surface, a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. It mounts on the upper surface of a mounting substrate so that a semiconductor layer may oppose, and the 2nd light emission part is located on the center part of the 1st direction of a mounting substrate.

  According to the multiwavelength semiconductor laser device of the present invention, the second light emitting unit is positioned on the central portion of the mounting substrate in the first direction. Thereby, after the mounting substrate is fixed to the support, the stress generated in the second light emitting unit can be reduced, and thus the polarization direction of the emitted light from the second light emitting unit is prevented from changing. Can do. Therefore, the S / N ratio of the emitted light from the second light emitting unit can be improved.

  Furthermore, the first semiconductor laser element and the second semiconductor laser element can be mounted on the same mounting substrate. For this reason, the multi-wavelength semiconductor laser device can be miniaturized. Furthermore, the optical system of the optical pickup device can be made one. For this reason, it is possible to reduce the size and cost of the optical pickup device.

  The multiwavelength semiconductor laser device according to the present invention further includes a support to which the lower surface of the mounting substrate is fixed, and the second light emitting unit is located on a central portion in the first direction of the support. Is preferred.

  In this way, since the stress generated in the second light emitting part can be further reduced after fixing, it is possible to further suppress the change in the polarization direction of the emitted light from the second light emitting part. Therefore, the S / N ratio of the emitted light from the second light emitting unit can be further improved.

  In the multiwavelength semiconductor laser device according to the present invention, the wavelength of the emitted light from the second light emitting unit may be not less than 655 nm and not more than 665 nm.

  In the multiwavelength semiconductor laser device according to the present invention, the wavelength of the emitted light from the first light emitting unit is not less than 775 nm and not more than 790 nm, and the first semiconductor layer is formed on the first substrate. A first conductivity type cladding layer; an active layer formed on the first conductivity type cladding layer; and a second conductivity type cladding layer formed on the active layer; The clad layer preferably contains indium (In) as a group III element and phosphorus (P) as a group V element.

  In this way, the energy difference ΔE at the lower end of the conduction band between the active layer and the first conductivity type cladding layer can be increased. For this reason, even at the time of high temperature operation, the occurrence of carrier overflow can be suppressed, and the decrease in light output can be made difficult to occur.

  In the multiwavelength semiconductor laser device according to the present invention, the wavelength of the emitted light from the third light emitting unit may be not less than 400 nm and not more than 410 nm.

  In order to achieve the above object, an optical pickup device according to the present invention includes the multi-wavelength semiconductor laser device according to the present invention and an optical system including an objective lens, and the second light emitting unit is a first of the mounting substrate. Located above the center of the direction.

  According to the optical pickup device of the present invention, the second light emitting unit is positioned on the central portion in the first direction of the mounting substrate. Thereby, since stress generated in the second light-emitting portion can be reduced after fixing, it is possible to suppress a change in the polarization direction of the emitted light from the second light-emitting portion. Therefore, the S / N ratio of the emitted light from the second light emitting unit can be improved.

  Furthermore, the first semiconductor laser element and the second semiconductor laser element can be mounted on the same mounting substrate. For this reason, the multi-wavelength semiconductor laser device can be miniaturized. Furthermore, the optical system of the optical pickup device can be made one. For this reason, it is possible to reduce the size and cost of the optical pickup device.

  In the optical pickup device according to the present invention, it is preferable that the optical axis of the light emitted from the second light emitting unit coincides with the optical axis of the optical system.

  If it does in this way, the fall of the light taking-in efficiency of the emitted light from the 2nd light emission part can be suppressed. Therefore, the S / N ratio of the emitted light from the second light emitting unit can be further improved.

  In the optical pickup device according to the present invention, it is preferable that the optical pickup device further includes a support to which the lower surface of the mounting substrate is fixed, and the second light emitting unit is located on the central portion in the first direction of the support. .

  In this way, since the stress generated in the second light emitting part can be further reduced after fixing, it is possible to further suppress the change in the polarization direction of the emitted light from the second light emitting part. Therefore, the S / N ratio of the emitted light from the second light emitting unit can be further improved.

  According to the optical pickup device including the multi-wavelength semiconductor laser device according to the present invention, the multi-wavelength semiconductor laser device can be reduced in size, and the S / N of the emitted light can be reduced while reducing the size and cost of the optical pickup device. The ratio can be improved.

FIG. 1 is a cross-sectional view showing the structure of a multiwavelength semiconductor laser device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the relationship between the distance from the central portion of the submount to the light emitting portion and the polarization angle. FIG. 3 is a diagram showing the polarization angle-polarization ratio characteristics of the two-wavelength semiconductor laser element. FIG. 4 is a cross-sectional view showing the structure of a two-wavelength semiconductor laser device of a comparative example. FIG. 5 is a diagram showing the relationship between the distance from the central portion of the substrate to the light emitting portion and the stress generated in the active layer (light emitting portion) after mounting. FIG. 6 is a cross-sectional view showing the structure of the semiconductor laser device. FIGS. 7A to 7C are diagrams showing current-light output characteristics of each of the infrared semiconductor laser element portion, the red semiconductor laser element portion, and the blue-violet semiconductor laser element. FIG. 8 is a diagram showing a structure of an optical pickup device according to an embodiment of the present invention. FIG. 9 is a diagram showing an objective lens and infrared emission light, red emission light, and blue-violet emission light. FIG. 10 is a cross-sectional view showing the structure of a conventional semiconductor laser device.

(One embodiment)
The structure of the multiwavelength semiconductor laser device according to one embodiment of the present invention will be described below with reference to FIG.

  As shown in FIG. 1, the multiwavelength semiconductor laser device 1 according to the present embodiment includes a substrate 11, a two-wavelength semiconductor laser element 10 having an infrared semiconductor laser element section 20 and a red semiconductor laser element section 30, and a blue-violet semiconductor. A laser element 40, a submount (mounting substrate) 2 on which the two-wavelength semiconductor laser element 10 and the blue-violet semiconductor laser element 40 are mounted on the upper surface, and a package in which the lower surface of the submount 2 is fixed by an adhesive 3 ( Support) 4.

  The infrared semiconductor laser element portion 20 and the red semiconductor laser element portion 30 are formed on the substrate 11 so as to be adjacent to each other in the X direction (the first direction, the horizontal direction on the paper surface of FIG. 1). The blue-violet semiconductor laser element 40 is mounted on the submount 2 so as to be adjacent to the red semiconductor laser element portion 30 in the X direction.

  The infrared semiconductor laser element unit 20 emits laser light having a wavelength of 785 nm (775 nm or more and 790 nm or less), and is used for CD recording and reproduction, for example. The red semiconductor laser element section 30 emits laser light having a wavelength in the 660 nm band (655 nm or more and 665 nm or less), and is used for DVD recording and reproduction, for example. For example, the blue-violet semiconductor laser element 40 emits laser light having a wavelength of 405 nm (400 nm or more and 410 nm or less), and is used for recording and reproducing BD.

  The two-wavelength semiconductor laser element 10 is a monolithic two-wavelength semiconductor laser element, and includes a substrate 11, an infrared semiconductor laser element portion 20 formed on the substrate 11, and a red semiconductor formed on the substrate 11. And a laser element unit 30. The substrate 11 is made of, for example, GaAs having a thickness of about 100 μm.

  The infrared semiconductor laser element portion 20 includes a semiconductor layer 22 formed on the substrate 11 and including the light emitting portion A, and an electrode layer 23 formed on the semiconductor layer 22. The semiconductor layer 22 is formed on the active layer 22b, the p-type cladding layer 22c formed on the substrate 11, the active layer 22b formed on the p-type cladding layer 22c, and the electrode layer thereon. And an n-type clad layer 22a formed with 23. The p-type cladding layer 22c and the n-type cladding layer 22a are made of, for example, an AlGaInP system. The active layer 22b is made of, for example, AlGaAs. In the present specification, the “light emitting part” refers to a part from which emitted light having the maximum intensity is emitted.

  The red semiconductor laser element portion 30 includes a semiconductor layer 32 formed on the substrate 11 and including the light emitting portion B, and an electrode layer 33 formed on the semiconductor layer 32. The semiconductor layer 32 is made of, for example, an AlGaInP system. Although not shown in detail in FIG. 1, the semiconductor layer 32 is formed on the p-type cladding layer formed on the substrate 11, the active layer formed on the p-type cladding layer, and the active layer. And an n-type cladding layer on which the electrode layer 33 is formed. The p-type cladding layer, the active layer, and the n-type cladding layer are made of, for example, an AlGaInP system.

  The blue-violet semiconductor laser device 40 includes a substrate 41, a semiconductor layer 42 formed on the substrate 41 and including the light emitting part C, and an electrode layer 43 formed on the semiconductor layer 42. The substrate 41 is made of, for example, GaN having a thickness of about 100 μm. The semiconductor layer 42 is made of, for example, GaN. Although not shown in detail in FIG. 1, the semiconductor layer 42 is formed on the p-type cladding layer formed on the substrate 41, the active layer formed on the p-type cladding layer, and the active layer. And an n-type clad layer having an electrode layer 43 formed thereon. The p-type cladding layer, the active layer, and the n-type cladding layer are made of, for example, GaN.

  The submount 2 includes a wiring part 5a, a wiring part 5b, and a wiring part 5c formed on the upper surface. Electrode layers 23, 33 and 43 are joined to the wiring portions 5a, 5b and 5c via solder layers 6a, 6b and 6c. As described above, the two-wavelength semiconductor laser element 10 and the blue-violet semiconductor laser element 40 are electrically connected to the submount 2. The submount 2 is made of, for example, AlN. The solder layer 6a, the solder layer 6b, and the solder layer 6c are made of, for example, AuSn.

  The two-wavelength semiconductor laser element 10 and the blue-violet semiconductor laser element 40 are formed on the upper surface of the submount 2 so that the wiring portions 5a, 5b and 5c formed on the upper surface face the electrode layers 23, 33 and 43. Mounted on top. Thus, the two-wavelength semiconductor laser device 10 and the blue-violet semiconductor laser device 40 are mounted on the submount 2 in a junction-down manner. Here, “mounting at junction down” means mounting the electrode layers 23, 33 and 43 toward the submount 2 side.

  By mounting the two-wavelength semiconductor laser device 10 and the blue-violet semiconductor laser device 40 in a junction-down manner, the distance between the submount 2 that is a heat sink and the light emitting portions A, B, and C is set to, for example, several μm, and the submount 2 And the light emitting parts A, B and C can be brought close to each other. For this reason, the heat generated from the two-wavelength semiconductor laser element 10 and the blue-violet semiconductor laser element 40 can be efficiently conducted to the submount 2 and radiated.

  In the present embodiment, the light emitting part B is located on the center part C2 of the submount 2 in the X direction. Thereby, as shown in FIG. 2 described later, the polarization angle can be reduced. Furthermore, it is preferable that the light emitting part B is located on the central part C4 of the package 4 in the X direction.

  In this embodiment, as an example, the chip width W10 of the two-wavelength semiconductor laser element 10 is 190 μm, and the chip width W40 of the blue-violet semiconductor laser element 40 is 100 μm. The width W at which the two-wavelength semiconductor laser element 10 and the blue-violet semiconductor laser element 40 are separated needs to secure at least a margin width necessary for the mounting process. In this embodiment, as an example, the width W is 30 μm.

  The distance Wab between the light emitting part A and the light emitting part B is, for example, 90 μm. The distance Wbc between the light emitting part B and the light emitting part C is, for example, 90 μm. The distance Wb between the light emitting part B and the end of the substrate 11 adjacent to the substrate 41 is, for example, 30 μm. A distance Wc between the light emitting unit C and the end of the substrate 41 adjacent to the substrate 11 is, for example, 30 μm.

  Since the chip width W10 is 190 μm (a half of the chip width W10 is 95 μm) and the distance Wb is 30 μm, the distance from the central portion C11 in the X direction of the substrate 11 to the light emitting portion B is 65 μm ( = 95 μm-30 μm). Since the distance is 65 μm and the distance Wab is 90 μm, the distance from the central portion C11 to the light emitting portion A is 25 μm (= 90 μm−65 μm). Thus, it is preferable that the light emission part A is located in the vicinity area | region of the center part C11. For example, as can be seen from FIG. 5 described later, the light emitting portion A is preferably located in a region from the central portion C11 to ± 30 μm.

  Hereinafter, the relationship between the distance from the central portion C2 in the X direction of the submount 2 to the light emitting portion B and the polarization angle will be described with reference to FIG.

  In FIG. 2, the position of the central portion C2 is set to 0 μm. In FIG. 2, “+ Δμm” means that the distance from the central portion C2 is Δμm in one of the X directions. On the other hand, “−Δμm” means that the center portion C2 is separated by a distance of Δμm in the other direction of the X direction.

  As shown in FIG. 2, in the vicinity region of the central portion C2, for example, in the region from the central portion C2 to ± 150 μm, the change in the polarization direction is small, and the polarization angle is in the vicinity of 0 °. On the other hand, at both ends in the X direction of the submount 2, the change in the polarization direction is large and the polarization angle is large.

  This is for the reason explained below.

  As shown in FIG. 1, when the submount 2 is fixed on the package 4 with the adhesive 3, the red semiconductor laser element portion 30 after fixing is caused by the difference in thermal expansion coefficient between the submount 2 and the adhesive 3. Stress is generated in the active layer.

  Both ends in the X direction of the submount 2 are boundary portions between a portion fixed by the adhesive 3 and a portion not fixed. For this reason, the submount 2 is easily deformed at the positions of both ends, and the red semiconductor laser element portion 30 is easily deformed. For this reason, the stress which arises in an active layer is large in both ends. On the other hand, in the region near the central portion C2, the stress generated in the active layer is small.

  When stress is generated in the active layer, anisotropy occurs in the refractive index of the semiconductor layer including the active layer, and rotation of the polarization direction occurs.

  Therefore, the change in the polarization direction is small in the region near the center C2. On the other hand, the change in polarization direction is large at both ends.

  Therefore, in the present embodiment, as shown in FIG. 1, the light emitting portion B is positioned on the center portion C <b> 2 in the X direction of the submount 2. Thereby, the stress which arises in the active layer (light emission part B) of the red semiconductor laser element part 30 after adhering can be made small, and the change of the polarization direction of the emitted light from the light emission part B can be made small.

  Furthermore, in this embodiment, as shown in FIG. 1, the light emitting part B is positioned on the center part C4 in the X direction of the package 4. Thereby, the stress generated in the active layer (light emitting part B) of the red semiconductor laser element part 30 after fixing can be further reduced, and the change in the polarization direction of the emitted light from the light emitting part B can be further reduced. .

  By the way, in this embodiment, in order to make small the change of the polarization direction of the emitted light from the light emission part A, it is preferable to position the light emission part A in the vicinity area | region of the center part C11 of the X direction of the board | substrate 11. This is for the reason explained below.

  Hereinafter, the polarization angle-polarization ratio characteristics of the two-wavelength semiconductor laser device 10 will be described with reference to FIGS. 3 and 4 while comparing the two-wavelength semiconductor laser device 10 of the present embodiment with the two-wavelength semiconductor laser device of the comparative example. This will be described with reference to FIGS.

  In the present embodiment, the two-wavelength semiconductor laser element 10 is mounted on the same submount 2 as the blue-violet semiconductor laser element 40 as shown in FIG. The distance from the central part C11 to the light emitting part A is 25 μm. The distance from the central part C11 to the light emitting part B is 65 μm.

  In the comparative example, the two-wavelength semiconductor laser device is mounted on a submount 2 different from the blue-violet semiconductor laser element, as shown in FIG. The distance from the central part C11 to the light emitting part A and the distance from the central part C11 to the light emitting part B are 55 μm.

  In the case of this embodiment, the distance from the central part C11 to the light emitting part A is 25 μm, and in the case of the comparative example, the distance from the central part C11 to the light emitting part A is 55 μm. As shown in FIG. 5 described later, as the distance from the central portion C11 increases, the stress generated in the active layer (light emitting portion A) increases. For this reason, the stress which arises in the light emission part A of this embodiment is smaller than the stress which arises in the light emission part A of a comparative example. Therefore, the change in the polarization direction of the present embodiment is smaller than the change in the polarization direction of the comparative example. As shown in FIG. 3, the polarization angle (about 1 °) of the present embodiment is It is near 0 ° than about -4 °.

  Therefore, it is preferable to locate the light emitting part A in the vicinity of the central part C11.

  As shown in FIG. 5, the stress generated in the active layer increases as the distance from the central portion C11 increases. This is for the reason explained below.

  As shown in FIG. 1, when the two-wavelength semiconductor laser element 10 including the substrate 11 made of GaAs is mounted on the submount 2 made of AlN, the difference in thermal expansion coefficient between the submount 2 and the substrate 11 is large. . For this reason, stress is generated in the active layer of the two-wavelength semiconductor laser device 10 after mounting due to a temperature difference between the high temperature state during mounting and the room temperature state after mounting.

  The relationship between the stress generated in the active layer (light emitting part A) after mounting and the distance from the central part C11 to the light emitting part A is as shown in FIG. The relationship shown in FIG. 5 was obtained by calculating the stress generated in the active layer when the chip width W10 of the semiconductor laser element was 150 μm, 200 μm, and 250 μm. The temperature at the time of mounting was set to 350 ° C. FIG. 6 shows the structure of the semiconductor laser device used in the calculation of FIG. In FIG. 5, the position of the central portion C11 is 0 μm.

  As shown in FIG. 5, when the chip width W10 is 150 μm, 200 μm, or 250 μm, the stress is small in the region from the central portion C11 to ± 30 μm. On the other hand, the stress is greatest at both ends of the substrate 11 in the X direction. Both ends in the X direction of the substrate 11 are boundary portions between a portion fixed by the solder layer 6a and a portion not fixed. For this reason, the semiconductor laser element is easily deformed at both end positions, and the stress generated in the active layer is the largest.

  Therefore, the stress generated in the active layer increases as the distance from both ends increases, that is, as the distance from the central portion C11 increases.

  Since the distance from the central portion C11 of the comparative example to the light emitting portion B is, for example, 55 μm, the distance from the central portion C11 to the light emitting portion B of the present embodiment (for example, 65 μm) is the light emission from the central portion C11 of the comparative example. It is larger than the distance to the part B, and the polarization angle (about 10 °) of the present embodiment is larger than the polarization angle (about 4 °) of the comparative example. However, as described above, in the present embodiment, the light emitting portion B is positioned on the center portion C2 of the submount 2 in the X direction. Thereby, the stress which arises in the light emission part B after adhering can be made small, and the change of the polarization direction of the emitted light from the light emission part B can be made small.

  In the present embodiment, the infrared semiconductor laser device section 20 can suppress the occurrence of carrier overflow and can make it difficult for the optical output to decrease, compared to the red semiconductor laser device section 30. This is for the reason explained below. “Carrier overflow” is a phenomenon in which carriers injected into the active layer are excited by heat and leak into the cladding layer.

  The carrier overflow is dominated by the overflow of electrons having a lighter effective mass than holes to the p-type cladding layer. In order to suppress the occurrence of overflow of electrons into the p-type cladding layer, it is effective to increase the energy difference ΔEc at the lower end of the conduction band between the active layer and the p-type cladding layer.

  In the present embodiment, the p-type cladding layer 22c of the infrared semiconductor laser device section 20 and the p-type cladding layer of the red semiconductor laser device section 30 are made of AlGaInP. The active layer 22b of the infrared semiconductor laser element section 20 is made of AlGaAs, and the active layer of the red semiconductor laser element section 30 is made of AlGaInP. For this reason, ΔEc of the infrared semiconductor laser element unit 20 is larger by several hundred meV than ΔEc of the red semiconductor laser element unit 30.

  Therefore, compared with the red semiconductor laser element unit 30, the infrared semiconductor laser element unit 20 can suppress the occurrence of carrier overflow and can make it difficult for the optical output to decrease. For this reason, as shown in FIGS. 7A and 7B described later, the infrared semiconductor laser device section 20 is superior in high-temperature operating characteristics as compared to the red semiconductor laser device section 30.

  By the way, the change of the polarization direction of the emitted light from the light emission part C of the blue-violet semiconductor laser element 40 is small. This is for the reason described below. As shown in FIG. 1, when the blue-violet semiconductor laser device 40 including the substrate 41 made of GaN is mounted on the submount 2 made of AlN, the difference in thermal expansion coefficient between the submount 2 and the substrate 41 is small. . For this reason, the stress which generate | occur | produces in the active layer of the blue-violet semiconductor laser element 40 after mounting is small. Therefore, the change in the polarization direction of the light emitted from the light emitting unit C is small.

  As described above, according to the present embodiment, as shown in FIG. 1, the light emitting part B is positioned on the center part C <b> 2 in the X direction of the submount 2. As a result, as shown in FIG. 2, since the stress generated in the active layer (light emitting part B) of the red semiconductor laser element part 30 after fixing can be reduced, the change in the polarization direction of the emitted light from the light emitting part B Can be reduced.

  Furthermore, as shown in FIG. 1, the light emitting part B is positioned on the center part C <b> 4 in the X direction of the package 4. Thereby, since the stress which arises in the active layer of the red semiconductor laser element part 30 after adhering can be made smaller, the change of the polarization direction of the emitted light from the light emission part B can be made smaller.

  Further, as shown in FIG. 1, the light emitting portion A is positioned in a region near the central portion C11 in the X direction of the substrate 11 (for example, a region from the central portion C11 to ± 30 μm). As a result, as shown in FIG. 5, since the stress generated in the active layer (light emitting part C) of the infrared semiconductor laser element part 20 after mounting can be reduced, the polarization direction of the emitted light from the light emitting part C can be reduced. Change can be reduced.

  The current-light output characteristics of each of the infrared semiconductor laser element unit 20, the red semiconductor laser element unit 30, and the blue-violet semiconductor laser element 40 during the pulse operation will be described below with reference to FIGS. While explaining.

  The conditions of the pulse operation of the infrared semiconductor laser element unit 20 are 85 ° C., a pulse width of 100 nsec, and a duty ratio of 50%. The conditions of the pulse operation of the red semiconductor laser element section 30 are 85 ° C., a pulse width of 50 nsec, and a duty ratio of 35%. The conditions of the pulse operation of the blue-violet semiconductor laser device 40 are 85 ° C., a pulse width of 30 nsec, and a duty ratio of 50%.

  As shown in FIG. 7 (b), in the case of the red semiconductor laser element section 30, thermal saturation occurs with a light output of about 400 mW. As shown in FIGS. 7A and 7C, in the case of the infrared semiconductor laser device section 20 and the blue-violet semiconductor laser device 40, thermal saturation occurs with a light output of 500 mW or more.

  As can be seen from FIGS. 7A to 7C, among the infrared semiconductor laser element portion 20, the red semiconductor laser element portion 30, and the blue-violet semiconductor laser element 40, the red semiconductor laser element 30 has the worst operating characteristics. .

  Therefore, when the multi-wavelength semiconductor laser device according to the present embodiment is incorporated in an optical pickup as a light source, it is possible to suppress a decrease in the light capturing efficiency of the emitted light from the light emitting part B of the red semiconductor laser element part 30 having the poorest high-temperature operating characteristics. It is important to.

  Hereinafter, an optical pickup device according to an embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 8, the optical pickup device 50 according to the present embodiment includes the multi-wavelength semiconductor laser device 1 according to the present embodiment and an optical system. The optical system includes a diffraction grating 51, a rising mirror 52, and an objective lens 53. Laser light is emitted from the optical pickup device 50 to the optical disk 54.

  As shown in FIGS. 8 and 9, in the light emitting unit B, the optical axis of the red emitted light L30 emitted from the light emitting unit B and incident on the objective lens 53 is the optical axis of the optical system (the optical axis of the objective lens 53). Arranged to match.

  In this way, the light emitting part B is arranged so that the optical axis of the red emitted light L30 coincides with the optical axis of the optical system. As a result, it is possible to suppress a decrease in the light capturing efficiency of the red emitted light L30 from the light emitting part B of the red semiconductor laser element part 30 having the inferior high-temperature operating characteristics.

  According to the present embodiment, the light emitting part B of the red semiconductor laser element part 30 is positioned on the center part C2 of the submount 2 in the X direction. Thereby, the change of the polarization direction of the red emitted light L30 from the light emission part B can be made small. Therefore, the S / N ratio of the red emitted light L30 can be improved.

  Further, the light emitting part B is arranged so that the optical axis of the red emitted light L30 coincides with the optical axis of the optical system. As a result, it is possible to suppress a decrease in the light capturing efficiency of the red emitted light L30 from the light emitting part B of the red semiconductor laser element part 30 having the inferior high-temperature operating characteristics. Therefore, the S / N ratio of the red emitted light L30 can be further improved.

  The light emitting unit A and the light emitting unit C are separated from the light emitting unit B by a distance Wab (for example, 90 μm) and a distance Wbc (for example, 90 μm), respectively. For this reason, there is a possibility that the infrared emission light L20 from the light emitting part A and the blue-violet emission light L40 from the light emission part C cannot fall within the light capturing range of the objective lens 53. For this reason, there is a possibility that the light capturing efficiency of the infrared emission light L20 and the blue-violet emission light L40 may be reduced.

  However, as described above, the change in the polarization direction of the infrared outgoing light L30 and the blue-violet outgoing light L40 is small compared to the red outgoing light L30. Furthermore, compared with the red semiconductor laser element part 30, the infrared semiconductor laser element part 20 and the blue-violet semiconductor laser element 40 are excellent in high temperature operation characteristics. For this reason, even if the light capturing efficiency of the infrared emission light L20 and the blue-violet emission light L40 decreases, the S / N ratio of the infrared emission light L20 and the blue-violet emission light L40 decreases compared to the red emission light L30. There is no.

  The present invention can reduce the size of a multi-wavelength semiconductor laser device and improve the S / N ratio of emitted light while reducing the size and cost of an optical pickup device. It is useful for the optical pickup device provided.

DESCRIPTION OF SYMBOLS 1 Multiwavelength semiconductor laser apparatus 2 Submount 3 Adhesive 4 Package 5a, 5b, 5c Wiring part 6a, 6b, 6c Solder layer 10 Two wavelength semiconductor laser element 11 Substrate 20 Infrared semiconductor laser element part 22 Semiconductor layer 22a N-type clad Layer 22b Active layer 22c P-type clad layer 23 Electrode layer 30 Red semiconductor laser device part 32 Semiconductor layer 33 Electrode layer 40 Blue-violet semiconductor laser device 41 Substrate 42 Semiconductor layer 43 Electrode layer 50 Optical pickup device 51 Diffraction grating 52 Rising mirror 53 Objective lens 54 Optical disk L20 Infrared emission light L30 Red emission light L40 Blue-violet emission light C2, C4, C11 Central part W10, W40 Chip width W width Wab, Wbc, Wb, Wc Distance A, B, C Light emitting part

Claims (8)

A mounting substrate;
A first substrate mounted on an upper surface of the mounting substrate, a first semiconductor laser element section formed on the first substrate, and the first semiconductor laser on the first substrate. A first semiconductor laser element having a second semiconductor laser element part formed so as to be adjacent to the element part in the first direction;
A second semiconductor laser element mounted on the upper surface of the mounting substrate so as to be adjacent to the second semiconductor laser element unit in the first direction;
The first semiconductor laser element section includes a first semiconductor layer formed on the first substrate and including a first light emitting section,
The second semiconductor laser element portion has a second semiconductor layer formed on the first substrate and including a second light emitting portion,
The second semiconductor laser element includes a second substrate, and a third semiconductor layer formed on the second substrate and including a third light emitting unit,
The mounting substrate is arranged so that the upper surface and the first semiconductor layer, the second semiconductor layer, and the third semiconductor layer face each other in the first semiconductor laser element and the second semiconductor laser element. Mounted on the top surface of
The multi-wavelength semiconductor laser device, wherein the second light emitting unit is located on a central portion of the mounting substrate in the first direction. Further comprising a support to which the lower surface of the mounting substrate is fixed;
2. The multiwavelength semiconductor laser device according to claim 1, wherein the second light emitting unit is located on a central portion of the support in the first direction.   3. The multiwavelength semiconductor laser device according to claim 1, wherein a wavelength of light emitted from the second light emitting unit is not less than 655 nm and not more than 665 nm. The wavelength of the emitted light from the first light emitting unit is 775 nm or more and 790 nm or less,
The first semiconductor layer includes: a first conductivity type cladding layer formed on the first substrate; an active layer formed on the first conductivity type cladding layer; and A second conductivity type cladding layer formed thereon,
The said 1st conductivity type cladding layer contains indium (In) as a group III element, and contains phosphorus (P) as a group V element, The any one of Claims 1-3 characterized by the above-mentioned. Multi-wavelength semiconductor laser device.   5. The multi-wavelength semiconductor laser device according to claim 1, wherein the wavelength of the emitted light from the third light emitting unit is 400 nm or more and 410 nm or less. A multi-wavelength semiconductor laser device according to claim 1;
An optical system including an objective lens,
The optical pickup device, wherein the second light emitting unit is located on a central portion of the mounting substrate in the first direction.   The optical pickup device according to claim 6, wherein an optical axis of light emitted from the second light emitting unit coincides with an optical axis of the optical system. Further comprising a support to which the lower surface of the mounting substrate is fixed;
The optical pickup device according to claim 6, wherein the second light emitting unit is located on a central portion of the support body in the first direction.

Images