JP2005259851A - Semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device that can prevent the degradation of output characteristic of a laser light even if a resonator becomes larger in length, and whose service life can last for a long time. <P>SOLUTION: The semiconductor laser device is provided with a semiconductor laser element 11; a submount 14 having a first main surface that has almost the same length as the size of the semiconductor laser element 11 in the extended lengthwise direction of a resonator and a width enough to mount the semiconductor laser element 11, a second main surface facing the first main surface, and a plurality of grooves 15 that are vertical in the lengthwise direction and parallel in the widthwise direction. Both ends in the widthwise direction are open and that are open on the second surface; and a heat block 17 having a mounting face to which the submount 14 is mounted. The direction of extended length of the resonator of the semiconductor laser element 11 is aligned with the lengthwise direction of the submount 14, and the semiconductor laser element 11 and the first main surface of the submount 14 are fixed by a bonding material. Then the second main surface of the submount 14 and the mounting face of the heat block 17 are fixed by a bonding material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device characterized by a submount on which a high-power semiconductor laser element is mounted.

  In recent years, a visible light semiconductor laser device has been used as a writing light source such as a DVD (Digital Versatile disc) or an MO (Magnetic-Optical) disc. In order to increase the writing speed, an improvement in light output is required. In order to achieve this high output, as a method of increasing gain and increasing the heat dissipation effect, the resonator length of the semiconductor laser element is often increased.

  Conventionally, a semiconductor laser device has a semiconductor laser element mounted on a submount and further comprises an assembly mounted on a heat block or stem having a heat sink function to obtain stable laser oscillation. (For example, refer to Patent Document 1).

  The submount or the heat block is required to be composed of a material having a thermal expansion coefficient equivalent to that of the semiconductor laser element and sufficient heat conduction characteristics to release heat generated by the semiconductor laser element. In many cases, it is difficult to obtain a material that satisfies these requirements at the same time and is easy to obtain or process. Therefore, the necessary characteristics are realized by devising appropriate combinations and shapes of materials.

  For example, FIG. 6 shows a schematic perspective view of only a portion (referred to as an assembly) that extends from the semiconductor laser element disclosed in Patent Document 1 to the heat block. As shown in FIG. 6, the assembly 50 has a submount 54 made of aluminum nitride (AlN) placed on a heat block 57 made of copper (Cu) or tungsten copper (Cu—W). The semiconductor laser element 51 is mounted in a so-called face-down manner in which the light emitting region 52 is disposed on the submount 54 side. Each contact portion is connected and fixed by gold (Au) / gold tin (AuSn) solder.

When the optical output of the semiconductor laser device is relatively small, the resonator length that contributes to laser oscillation, that is, the length of the semiconductor laser element can be made relatively short, so in the above configuration, the output characteristics of the laser beam do not deteriorate, Long-term stable oscillation was obtained.
JP 2000-11417 A (page 8, FIG. 6)

  However, in order to increase the output, when the cavity length of the semiconductor laser element, that is, the length of the semiconductor laser element is increased and assembled through a thermal process, the physical properties of the semiconductor laser element, the submount and the heat block, That is, the stress due to the difference in thermal expansion coefficient, elastic constant, etc. has a great influence on the semiconductor laser element, and the optical output characteristics of the semiconductor laser element are deteriorated or the life is shortened.

  Accordingly, an object of the present invention is to provide a semiconductor laser device capable of preventing deterioration of output characteristics of laser light and extending the life even when the resonator length is extended.

  In order to achieve the above object, a semiconductor laser device according to an aspect of the present invention includes a semiconductor laser element, a length that is approximately the same as a dimension of the semiconductor laser element in a cavity extension direction, and a width in which the semiconductor laser element can be mounted. A first main surface having a second main surface opposite to the first main surface, a vertical direction parallel to the length direction and parallel to the width direction, and both ends in the width direction being open and the second main surface A submount having a plurality of grooves open on the top, and a heat block having a mounting surface on which the submount is mounted, the resonator extending direction of the semiconductor laser element and the length direction of the submount being The semiconductor laser element and the first main surface of the submount are fixed via a bonding material, and the second main surface of the submount and the mounting surface of the heat block are fixed via a bonding material. ing And wherein the door.

  According to the present invention, it is possible to provide a semiconductor laser device capable of preventing deterioration of output characteristics of laser light and extending the life even when the resonator length is extended.

  Embodiments of the present invention will be described below with reference to the drawings. In the figure shown below, the same code | symbol is attached | subjected to the same component.

  A semiconductor laser device according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a schematic perspective view in which a part of a semiconductor laser device is notched so that the inside can be seen. FIG. 2 is a semiconductor laser element, submount, and heat block placed inside the semiconductor laser device. FIG. 3 is a schematic perspective view of an assembly used for comparison with the assembly according to the present invention, and FIG. 4 is an assembly according to the present invention and for comparison. It is a graph which shows the displacement amount which generate | occur | produces in the resonator of the semiconductor laser element of this assembly.

  As shown in FIG. 1, the main part of the semiconductor laser device 1 for visible light includes an assembly 5 composed of a semiconductor laser element 11, a submount 14, and a heat block 17, and the assembly 5 and a laser beam for monitoring the laser light. The two lead pins 27 to which the monitor photodiode 32 is fixed are composed of a metal stem 21 that is electrically insulated and planted. The semiconductor laser element 11 is fixed perpendicularly to the stem 21 so as to extract the laser beam 31 on the opposite side of the stem 21. The monitor photodiode 32 is fixed to the stem 21 on one side of the semiconductor laser element 11. The semiconductor laser element 11 and the monitor photodiode 32 are electrically connected to the lead 27 by a wire or the like.

  A metal cap 23 is sealed to the stem 21 with the assembly 5, the monitor photodiode 32, and the like built therein. A window glass 25 for taking out the laser beam 31 is provided on the top of the cap 23, and the laser beam 31 from the semiconductor laser element 11 passes through the window glass 25 from one end face of the semiconductor laser element 11 to the outside of the cap 23. The laser light 31 emitted from the other end face is incident on a monitor photodiode 32 for controlling light emission.

  As shown in FIG. 2, the semiconductor laser element 11 has a substantially rectangular parallelepiped shape with a width of about 250 μm, a thickness of about 100 μm, and a dimension (length) in the cavity length direction of about 1100 μm. An InGaAlP system is formed on a GaAs substrate. The visible laser beam 31 with a wavelength of 650 nm is oscillated. The laser beam 31 is emitted from the light emitting region 12 which is the end of the resonator on the end surface perpendicular to the extending direction of the semiconductor laser element 11. Metal electrodes (not shown) mainly composed of Au are formed on both surfaces of the semiconductor laser element 11 facing in the thickness direction, that is, on the upper surface and the lower surface in the drawing.

  The submount 14 has a width of about 600 μm, a thickness of about 160 μm, a length of about 1100 μm, has an insulating property, a large thermal conductivity, and a thermal expansion coefficient close to the thermal expansion coefficient of the GaAs substrate. It is a sintered body mainly composed of AlN adjusted to 5.5E-6 / ° C. The first main surface of the submount 14 is a flat surface having a width of about 600 μm and a length of about 1100 μm, and the second main surface opposite to the first main surface is perpendicular to the length direction of the submount 14. Five grooves 15 extending parallel to the width direction are provided.

  The end face in the extending direction of the groove 15 is substantially rectangular, has a width of about 100 μm, a depth corresponding to the thickness direction of the submount 14, and a length of the groove 15 of about 600 μm corresponding to the width of the submount 14. When the submount 14 has a cross section perpendicular to the extending direction of the groove 15, the submount 14 has a comb shape opened on the second main surface side, and the shape in which the groove 15 is filled is substantially a rectangular parallelepiped shape. A metal electrode (not shown) whose main component is Au is formed on the first main surface and the second main surface of the submount 14. The metal electrode on the first main surface is assembled to the assembly 5. After that, a bondable region (not shown) that can be electrically connected to the outside is provided.

  The heat block 17 has a width of about 1000 μm, a thickness of about 800 μm, a length of about 1500 μm, is made of Fe or an alloy containing Fe as a main component, and has a rectangular parallelepiped shape with six surfaces forming a plane.

  As shown in FIG. 2, the assembly 5 has a configuration in which the heat block 17, the submount 14, and the semiconductor laser element 11 are stacked in the same thickness direction from the bottom to the top of the drawing. The semiconductor laser element 11 is in contact with the first main surface of the submount 14 in a so-called face-down manner, so that both ends of the semiconductor laser element 11 and the submount 14 in the length direction coincide with each other. For example, AuSn solder is supplied between the metal electrodes formed on the semiconductor laser element 11 and the submount 14 so as to be joined and fixed. The AuSn solder is melted at a temperature equal to or higher than the solidification point (about 280 ° C.), and then the temperature is lowered below the solidification point, whereby the semiconductor laser element 11 and the submount 14 can be fixed.

  After the semiconductor laser element 11 is mounted on the submount 14, the submount 14 has one end face in the length direction that coincides with one end face of the heat block 17 or is located inside the one end face of the heat block 17. For example, AuSn solder is supplied between the metal electrode formed on the second main surface of the submount 14 and the heat block 17 to be bonded and fixed to the heat block 17. The AuSn solder is melted at a temperature equal to or higher than the solidification point, and then lowered to a temperature equal to or lower than the solidification point, whereby the submount 14 and the heat block 17 can be fixed. As a result, the assembly 5 including the heat block 17, the submount 14, and the semiconductor laser device 11 in which the groove 15 portion of the submount 14 is a gap is completed.

  In the development of the semiconductor laser device 1, the present inventors have found that the deformation of the resonator of the semiconductor laser element 11 that occurs in the assembly that has undergone the process of joining with AuSn solder is related to the light output characteristics or lifetime of the semiconductor laser device 1. Considering the importance, the degree of deformation of the semiconductor laser element 11 due to the difference in the shape of the submount, that is, how much the displacement amount is examined. The examination was performed by a method of obtaining the stress generated in the assembly or the amount of displacement in the resonator of the semiconductor laser element 11 by simulation based on the finite element method.

  As shown in FIG. 3, the assembly 6 for comparison is mounted on a submount 16 that is a semiconductor laser element 11 similar to that of the present embodiment extended in the longitudinal direction, and further mounted on a heat block 17. It is a configuration. The assembly 6 is different from the submount 14 of the above embodiment in that no groove is formed in the submount 16, but the size, configuration, material, joining method, etc. of other components are also included. Is the same as the assembly 5 of the above embodiment.

  FIG. 4 shows a deformation estimation result after assembly of the assembly 5 according to the present invention and the assembly 6 for comparison. As shown in FIG. 4, the horizontal axis represents the resonator length, and the amount of vertical displacement generated in the resonator of the semiconductor laser device 11 at room temperature (25 ° C.) Is represented by minus, the opposite side is upward, and the displacement is plus on the vertical axis. The resonators of the assemblies 5 and 6 are curved upwardly, that is, curved in a convex shape toward the semiconductor laser element 11 in the assemblies 5 and 6.

  The reason why the amount of displacement is curved upward is that the thermal expansion coefficients of the semiconductor laser element 11 and the submounts 14 and 16 are approximate and relatively small, while the thermal expansion coefficient of the heat block 17 is the semiconductor laser element 11. This is a result of the heat block 17 contracting more greatly when the AuSn solder solidification temperature is lowered from about 280 ° C. to room temperature because it is much larger than the thermal expansion coefficient of the submounts 14 and 16.

  The amount of upward displacement of the assembly 5 according to the present invention is approximately 0.31 μm at the maximum when both ends of the resonator are set to zero, and roughly has small unevenness related to the position of the groove in the resonator length direction. Becomes a convex curve. The upward displacement of the resonator in the vicinity of the position where the horizontal axis is zero, that is, in the vicinity where the end surfaces of the semiconductor laser device 11, the submount 14, and the heat block 17 are fixed to be flush with each other, changes relatively abruptly. . On the other hand, the upward displacement amount in the vicinity of 1100 μm on the horizontal axis in the vicinity of the resonator end face on the opposite side is a relatively gradual change. This is presumably because the heat block 17 is continuously present on the right side even after the semiconductor laser element 11 and the submount 14 extended in the horizontal axis direction are interrupted in the vicinity of the horizontal axis of 1100 μm.

  Further, the upward displacement amount of the assembly 6 for comparison is about 0.40 μm at the maximum when both ends of the resonator length are set to zero, and there are no discontinuous portions in the assembly 6 in the resonator length direction. Therefore, it becomes a convex gentle curve. The maximum value is shifted to the left side from the center of the horizontal axis because the heat block 17 is continuously present on the right side even after the semiconductor laser element 11 and the submount 14 extended in the horizontal axis are disconnected. It is presumed that.

  Comparing these two curves, the upward maximum displacement amount of the assembly 5 according to the present invention is about 0.09 μm smaller than the upward maximum displacement amount of the resonator of the assembly 6 for comparison. That is, if the groove 15 is formed in the submount 14 and the semiconductor laser element 11 is mounted thereon, the amount of bending displacement can be reduced.

  Next, as shown in FIG. 1, the assembly 5 according to the present invention and the comparative assembly 6 are placed on a stem 21 and necessary electrical connections are made, and a laser output characteristic evaluation is performed as a semiconductor laser device. And a life test. The initial laser output is about 2.5 times that of the assembly 5 according to the present invention and the threshold current of the comparative assembly 6 is slightly higher than that of the semiconductor laser device having a short cavity length. A laser output of a certain degree could be obtained.

  Further, in the assembly 5 according to the present invention, the yield such as the polarization characteristics was inferior to that of the semiconductor laser device having a short resonator length, but in the assembly 6, the yield decreased. The life estimation is performed by an accelerated life test. The estimated life of the assembly 5 according to the present invention exceeds the standard equivalent to that of a semiconductor laser device having a short cavity length, while the accelerated life test of the comparative assembly 6 is performed. Then, the laser output drastically decreased in about half the time of the standard.

  The influence of the curvature of the resonator on the laser output characteristics and lifetime is estimated as follows. When the semiconductor laser element 11, the submount 14 and the heat block 17 that are stably fixed at a solidification point of AuSn solder of about 280 ° C. are lowered to room temperature 25 ° C., stress based on the respective thermal expansion coefficient, elastic constant, etc. is generated. The semiconductor laser element 11, that is, the resonator is curved in a convex shape upward. As this curvature increases, the laser light scattering in the resonator increases, which initially causes an increase in the threshold current of the laser output characteristics and deterioration of the polarization characteristics. As a result, more electric power is consumed to obtain an output, and the semiconductor laser device is rapidly deteriorated.

  As described above, the semiconductor laser device 1 in which the assembly 5 in which the semiconductor laser element 11 having an elongated resonator length is mounted on the submount 14 having the gap groove 15 is incorporated in the semiconductor laser device 1 at the initial target. The value could be improved. In addition, in the evaluation of the light output characteristics such as the polarization characteristics, there was no decrease in yield, the estimated lifetime exceeded the standard, and it was confirmed that a certain level of reliability was secured.

  According to the present invention, a groove is formed in the submount and mounted on the heat block, and the degree of curvature of the semiconductor laser element mounted on the submount is reduced, so that the semiconductor laser can be used for high output. Even if the resonator length of the element is increased, it is possible to provide a semiconductor laser device capable of preventing deterioration of output characteristics of laser light and extending the life.

  A semiconductor laser device according to Example 2 of the present invention will be described with reference to FIG. FIG. 5 is a schematic perspective view of an assembly composed of a semiconductor laser element, a submount, and a heat block mounted inside the semiconductor laser device. The present embodiment is different from the first embodiment in that the groove of the submount is filled with a filler. In addition, the same code | symbol is attached | subjected to the same component as Example 1, and the description is abbreviate | omitted.

  As shown in FIG. 5, the assembly 7 has a structure in which a groove 19 of the submount 14 is filled with a filler 19. For example, AuSn solder can be used as the filler 19. As shown in the first embodiment, when the AuSn solder is supplied between the metal electrode (not shown) formed on the second main surface of the submount 14 and the heat block 17, the groove 15 includes the AuSn. Supply an amount that does not overflow the solder. A metal film similar to the metal electrode formed on the second main surface may be formed on the surface of the groove 15. Thereafter, similarly to the first embodiment, the second main surface of the submount 14 and the heat block 17 are joined and fixed through a thermal process. As a result, the assembly 7 in which the groove 15 is filled with the filler 19 made of AuSn solder is completed.

  With respect to this assembly 7, the stress generated or the amount of displacement in the resonator of the semiconductor laser element 11 was determined by simulation based on the finite element method. The displacement amount curve (not shown) of the assembly 7 is almost the same as the displacement amount curve of the assembly 5 of the first embodiment shown in FIG. 4 and is convex upward, that is, in the assembly 7 toward the semiconductor laser element 11. It was shown that the maximum amount of upward displacement was about 0.31 μm.

  Then, as in the case shown in FIG. 1, the assembly 7 was placed on the stem 21 and necessary electrical connections were made, and a laser output characteristic evaluation and a life test were performed as a semiconductor laser device. The initial laser output was approximately 2.5 times that of the semiconductor laser device having a short cavity length.

  Further, the threshold current at which laser oscillation can be obtained was reduced by several percent compared to the semiconductor laser device 1 of Example 1. This is presumed that the improvement of the heat release characteristics due to heat conduction through the filler 19 filled in the groove 15 was effective. In addition, the yield such as polarization characteristics is comparable to that of a semiconductor laser device with a short cavity length, and the estimated lifetime in the accelerated life test is the same as that of a semiconductor laser device with a short cavity length. It was over.

  According to the present embodiment, a groove is formed in the submount, and the groove is filled with a filler, thereby reducing the degree of curvature of the semiconductor laser element mounted thereon, so as to cope with high output. In addition, even if the resonator length of the semiconductor laser element is increased, it is possible to provide a semiconductor laser device that can prevent the output characteristics of the laser light from deteriorating and can extend the service life. Further, since heat generated in the semiconductor laser element can be efficiently released when the laser beam is output, stable oscillation for a longer time, that is, higher reliability is estimated compared to the semiconductor laser device of the first embodiment.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, It can implement in various deformation | transformation within the range which does not deviate from the summary of this invention.

  For example, in the example, the number of grooves in the submount is five and the cross-sectional shape is rectangular. Depending on the length or output of the semiconductor laser element, it is possible to change to a more suitable number or shape of grooves. In particular, when further improvement of the laser output is intended, it is expected that the resonator length needs to be further extended, and there is a possibility that more grooves are formed in the corresponding extension submount. is there.

  Although the submount is AlN, Mo, W-Cu, alumina, diamond, or a diamond composite material having a thermal expansion coefficient close to that of GaAs can be selected.

  Although the heat block is a rectangular parallelepiped, it may have a shape in which the cross-sectional area increases as it moves away from the submount, that is, as it goes downward. Fe or Fe-based alloy was used as the heat block material, but metals such as Cu, W-Cu, Mo, etc. with high thermal conductivity, ceramics, composite materials of ceramic and metal, etc. were used. It is possible.

  The assembly order including the assembly order of the semiconductor laser elements, submounts, and heat blocks constituting the assembly, or the order from assembly of the assembly to the order of fixing to the stem is merely an example in the above embodiment. The order can be changed.

  In addition, an example of a semiconductor laser device in which an assembly including a semiconductor laser element, a submount, and a heat block is sealed with a stem and a cap is shown. However, the assembly is built in a package in which a lead frame is combined with plastic. It may be incorporated in another type of package such as a type. Furthermore, the semiconductor laser device does not have an independent package, and a submount having a groove on which a semiconductor laser element is mounted is mounted on a heat block that also serves as a pedestal or sheet sink on which other components are mounted. For example, an optical pickup optical unit or the like may be used.

  In Example 2, although the example which uses AuSn solder as a filler was shown, it is possible to use the filler of another material. After assembling the semiconductor laser device, the submount, and the heat block in the same manner as in the first embodiment, the groove is filled with a filler made of, for example, paste-like Sn solder, and the assembly is subjected to a thermal process. It can be completed.

  Further, in this embodiment, an example in which a semiconductor laser element in which an InGaAlP system is stacked on a GaAs substrate is mounted on a submount in which a groove is formed is shown. Replacing this semiconductor laser element with a semiconductor laser element in which an AlGaAs system is stacked on a GaAs substrate, a semiconductor laser element in which an InGaAsP system is stacked on an InP substrate, or a semiconductor laser element in which an InGaAlN system is stacked on a GaN substrate, etc. Is possible. In that case, it is needless to say that the material of the submount in which the groove is formed may be made of a material close to the thermal expansion coefficient of the InP substrate or the GaN substrate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view in which a notch is formed in a part of a semiconductor laser device according to a first embodiment of the present invention so that the inside can be seen. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view of an assembly that is inside a semiconductor laser device according to a first embodiment of the present invention and includes a semiconductor laser element, a submount, and a heat block. FIG. 2 is a schematic perspective view of an assembly according to Example 1 of the present invention and an assembly used for comparison. 6 is a graph showing the amount of displacement generated in the resonator of the semiconductor laser device of the assembly according to Example 1 of the present invention and the assembly for comparison. The typical perspective view of the assembly which consists of a semiconductor laser element concerning Example 2 of the present invention, a submount, and a heat block. The typical perspective view of the assembly which consists of the conventional semiconductor laser element, a submount, and a heat block.

Explanation of symbols

1 Semiconductor laser device 5, 6, 7, 50 Assembly 11, 51 Semiconductor laser element 12, 52 Light emitting region 14, 16, 54 Submount 15 Groove 17, 57 Heat block 19 Filler 21 Stem 23 Cap 25 Window glass 27 Lead pin 31 Laser light 32 Monitor photodiode

Claims (5)

A semiconductor laser element;
A first main surface having a length approximately equal to a dimension of the semiconductor laser element in a cavity extension direction; a width capable of mounting the semiconductor laser element; a second main surface opposite to the first main surface; A submount having a plurality of grooves perpendicular to the length direction and parallel to the width direction, open at both ends in the width direction and opened on the second main surface;
A heat block having a mounting surface on which the submount is mounted;
And the length direction of the submount of the semiconductor laser element is aligned with the length direction of the submount, and the semiconductor laser element and the first main surface of the submount are fixed via a bonding material. A semiconductor laser device, wherein the second main surface of the mount and the mounting surface of the heat block are fixed via a bonding material.   2. The semiconductor laser device according to claim 1, wherein the groove is a gap.   The semiconductor laser device according to claim 1, wherein at least a part of the groove is filled with a filler.   4. The semiconductor laser device according to claim 1, wherein the submount has a thermal expansion coefficient approximate to that of the semiconductor laser element. 5.   5. The semiconductor laser device according to claim 1, wherein the heat block is a metal or a ceramic or a composite material having a heat conduction characteristic equivalent to that of a metal. 6.

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