JP2009111230A - Laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize wavelength multiplexing (multi-wavelength) of oscillating wavelengths without changing the internal structure of a semiconductor laser, in a laser module equipped with a semiconductor laser array having a plurality of light emitting points. <P>SOLUTION: This laser module is equipped with the semiconductor laser array 1 having a plurality of the light emitting points 3, and a heat sink 2 mounting this semiconductor laser array 1. The heat sink 2 has different compositions of a heat sink material (CuW for instance) in the arranged direction of the light emitting points 3, and is structured so that different stresses are impressed on the semiconductor laser array 1 depending on the arrangement directional locations of the light emitting points 3, owing to the difference in the coefficients of linear expansions, accompanying the change of the compositions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser module configured using a semiconductor laser.

  The projection display has a feature that a large screen can be obtained with a relatively small device, and is an image display system which has been attracting attention in the recent trend of increasing the size of home televisions. Conventionally, ultra-high pressure mercury lamps have been used as light sources for projection displays, but due to their short lifetime and poor color rendering properties, LED (Light Emitting Diode) and lasers have recently been used as light sources. Yes.

  Although an LED can be manufactured at a low price, it has a large light emitting area and is not suitable for a small panel (light spatial modulation element). In this respect, a laser is a light source that has recently attracted attention because of its small emission point and sharp spectrum (good color rendering).

  However, when a laser is used as a light source, a problem that cannot be avoided is the glare of the screen called speckle noise. When coherent light such as a laser hits the screen, it is recognized as a glare with a sense of perspective due to the interference effect.

  As a countermeasure against speckle noise, a method of mechanically moving an optical element or a screen is known. As specific measures, various proposals have been made to reduce the coherency of the light source by mainly providing an optical path multiplexing mechanism in the light source or optical system.

  For example, Patent Documents 1 to 7 describe what modulates the laser light source itself.

JP 2001-189520 A JP 2004-102226 A JP 2004-94199 A JP 2004-94200 A JP 2004-157504 A JP 2004-70286 A JP 2004-157505 A

  Patent Documents 8 to 13 describe what divides an optical path of a light source with a fiber or the like.

Japanese Patent Laid-Open No. 11-101925 Japanese Patent Laid-Open No. 11-223795 Japanese Patent Application Laid-Open No. 11-326653 JP 2000-89160 A JP 2000-121836 A JP 2003-156698 A

  Patent Documents 14 to 19 describe what disturbs the optical path by inserting a diffusion plate (or one having a diffusion effect).

JP-A-11-218726 JP 2004-138669 A JP 2004-144936 A JP 2003-279889 A Special table 2004-534265 gazette Japanese Patent Laid-Open No. 2005-10772

  Patent Documents 20 and 21 describe what synthesizes the polarization direction.

JP 2003-156710 A Special table 2003-521740 gazette

  Patent Documents 22 to 24 describe what rotates and vibrates the diffusion plate.

Japanese Patent Laid-Open No. 6-208089 JP 2002-90881 A JP 2002-296514 A

  Patent Document 25 describes what vibrates the projection lens.

JP 2003-21806 A

  However, measures such as moving an optical element or a screen require a member for realizing it. For this reason, the configuration of the projection display becomes large. Further, when the optical element or the screen is moved as a measure against speckle noise, the image is blurred on the screen. Furthermore, since the movable part is indispensable for moving the optical element and the screen, there is a concern that reliability may be lowered due to a failure of the movable part.

  An object of the present invention is to realize multiplexing of oscillation wavelengths (multiple wavelengths) without changing the internal structure of a semiconductor laser in a laser module including a semiconductor laser array having a plurality of light emitting points.

  A laser module according to the present invention includes a semiconductor laser array having a plurality of light emitting points, and a mounting body for mounting the semiconductor laser array, and the mounting body is different from the semiconductor laser array in the arrangement direction of the light emitting points. It is characterized by applying stress.

  In the laser module according to the present invention, by using the mounting body on which the semiconductor laser array is mounted, by applying different stresses to the semiconductor laser array in the arrangement direction of the light emitting points, the oscillation wavelengths in the semiconductor laser array are respectively It changes according to the magnitude of the stress acting on the light emitting point portion.

  According to the present invention, by using the mounting body on which the semiconductor laser array is mounted, by applying different stresses to the semiconductor laser array in the arrangement direction of the light emitting points, the oscillation wavelength can be changed without changing the internal structure of the semiconductor laser. Multiplexing can be realized.

  As a result, for example, when a laser module is used as a light source for a projection display, speckle noise can be reduced due to a decrease in coherency associated with the increase in the number of wavelengths of the laser light source without mechanically moving an optical element or a screen. .

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

  First, as reported in the following references, the characteristics of semiconductor laser elements change the band gap of the semiconductor material due to lattice strain, and change in the direction in which the band gap expands when subjected to compressive strain. . Further, it is known that not only the stress due to the difference in the composition inside the semiconductor laser element but also the band structure is changed and the oscillation wavelength is changed by applying external stress to the semiconductor laser element.

<References>
`` Effect of mismatch strain on band gap in III-V semiconductors '', Journal of Applied Physics, USA, 1985, Vol. 57 p.5428-5432

  In the present invention, by applying different stresses to the plurality of semiconductor laser elements by utilizing the above properties, the oscillation wavelengths of the semiconductor laser array including the plurality of semiconductor laser elements are multiplexed.

  Here, in the experimental results by the applicant, there is a correlation between the speckle noise and the spectrum width of the oscillation wavelength, and in order to reduce the speckle noise, it is effective to increase the spectrum width. I know it. In addition, it has been clarified that when the oscillation wavelength is multiplexed, the half width of the spectrum is required to be 2 nm or more in order to obtain the effect of reducing speckle noise.

  For this reason, an oscillation wavelength difference of 2 nm or more in the entire semiconductor laser array is a necessary characteristic for reducing speckle noise. However, if the oscillation wavelength difference of the entire semiconductor laser array is expanded indefinitely, for example, when used as a light source for a projection display, there is a concern that some trouble (for example, narrowing of the color reproduction region) may occur due to the influence of the oscillation wavelength difference. Is done. For this reason, it is desirable to define the lower limit value of the oscillation wavelength difference at 2 nm or more, while defining the upper limit value of the oscillation wavelength difference at 30 nm or less, for example.

  Consider a case of an AlGaInP-based 640 nm band semiconductor laser array using GaInP (gallium indium, phosphorus) as an active layer. If the oscillation wavelength is 643 nm as a reference, 643 nm = 1.928 [eV] from the relational expression of light energy [eV] = 1240 / wavelength [nm]. If this is increased by 2 nm to 641 nm, 641 [nm] = 1.934 [eV] from the above relational expression. For this reason, the difference in light energy corresponding to the oscillation wavelength difference is 0.006 [eV] = 6 [meV].

  In GaInP as an active layer material, as the magnitude of the stress for expanding the energy of 6 [meV], a compressive strain of about 1000 ppm is required according to the report of the above reference.

  Here, with respect to a semiconductor laser array having a plurality of light emitting points, a structure in which different values of external stress are constantly applied to the end face region for each semiconductor laser element constituting the semiconductor laser array. In order to realize it simply, for example, the following phenomenon that occurs in the process of soldering a semiconductor laser array chip (hereinafter referred to as “laser array chip”) to a heat sink can be used.

In soldering, the laser array chip is first heated in a state of being superimposed on a heat sink via a solder material, and the temperature is raised to a temperature T higher than the melting point and freezing point temperature of the solder material. Here, the laser array chip and the heat sink expand independently with κ _L (T−T _R ) and κ _H (T−T _R ), which have different expansion amounts according to the respective linear expansion coefficients κ _L and κ _H. Here, T _R is the room temperature (normal temperature).

Subsequently, after the solder material has reached a sufficiently familiar thermal equilibrium in both the molten laser array chip heat sink, it lowered to room T _R. In this temperature-decreasing process, the solder material solidifies when it reaches the freezing point temperature T _S , but before the solidification (T _S <T), the laser array chip heat sink contracts independently, whereas after the solidification (T <T _{In S} ), the laser array chip is bonded to the heat sink, and thereafter both shrink together.

As a result, the laser array chip contracts in the form of κ _H (T _S −T _R ), which is the contraction amount of the heat sink material having a thickness several tens of times larger than itself, and finally the following formula at room temperature: The external stress of the amount represented by is constantly applied.

{Κ _L (T _S −T _R )} − {κ _H (T _S −T _R )} = (κ _L −κ _H ) (T _S −T _R )

Here, when the sign of the linear expansion coefficient difference κ _L −κ _H between the laser array chip and the heat sink is negative, it is a compressive stress, when it is positive, it is a tensile stress, and when it is zero, there is no stress.

  Therefore, the amount of strain applied to the material of the laser array chip can be controlled by adjusting the linear expansion coefficient of the heat sink or the freezing point of the solder material.

  In the present invention, the amount of strain generated in the semiconductor laser array is controlled by applying different stresses to the semiconductor laser array using the linear expansion coefficient of the mounting body on which the semiconductor laser array is mounted as a parameter.

  As a specific mounting form, when the semiconductor laser array is directly mounted on the heat sink, the heat sink becomes a mounting body, and when the semiconductor laser array is mounted on the heat sink via the submount, the submount and / or the heat sink is mounted. Become a body.

  The laser module according to the present invention is used, for example, as a light source for a projection display. However, the use of the laser module is not limited to this, and may be used for a laser processing light source, a medical laser light source, and the like.

<First Embodiment>
1A and 1B show a configuration of a laser module according to a first embodiment of the present invention. FIG. 1A is a top view of the laser module, and FIG. 1B is a front view of the laser module.

  The illustrated laser module includes a semiconductor laser array 1 and a heat sink 2. The X direction in the figure corresponds to the longitudinal direction of the semiconductor laser array 1, and the Y direction in the figure corresponds to the short direction of the semiconductor laser array 1. Further, the Z direction in the figure corresponds to the thickness direction of the semiconductor laser array 1 and the heat sink 2. These X direction, Y direction and Z direction are orthogonal to each other.

  The semiconductor laser array 1 is composed of a rod-shaped laser array chip that forms an integral structure. The semiconductor laser array 1 has a plurality (10 in the illustrated example) of light emitting points 3. The number of light emitting points 3 provided in one semiconductor laser array 1 is increased or decreased as necessary.

  The semiconductor laser array 1 is a semiconductor having a semiconductor layer including a GaInP active layer made of an AlGaInP (aluminum-gallium-indium-phosphorus) compound semiconductor on an n-type conductive substrate made of, for example, GaAs (gallium-arsenic). By providing a plurality of laser elements side by side in one laser array chip, a plurality of light emitting points 3 having a 1: 1 correspondence with the plurality of semiconductor laser elements are provided.

  Each light emitting point 3 is provided on the front end surface of the semiconductor laser array 1 in the short direction (Y direction). Further, the respective light emitting points 3 are arranged side by side at a predetermined interval in the longitudinal direction (X direction) of the semiconductor laser array 1.

  The semiconductor laser array 1 constitutes, for example, a red laser having an oscillation wavelength band of 640 nm, an infrared laser, or the like. The oscillation wavelengths of the semiconductor laser elements constituting the semiconductor laser array 1 are set equal at the stage of manufacturing the semiconductor laser array 1. For this reason, the oscillation characteristics of the semiconductor laser array 1 alone (in a state where no external stress is applied) are such that the spectral width of the entire oscillation wavelength of the laser array is within about 1 nm with respect to the reference oscillation wavelength. .

  The longitudinal dimension (laser array chip dimension in the X direction) of the semiconductor laser array 1 is set to about 10 mm, for example, and the resonator length of each semiconductor laser element in the short direction (Y direction) of the semiconductor laser array 1 is, for example, 700 μm. Is set to about. Further, the thickness dimension (laser array chip dimension in the Z direction) of the semiconductor laser array 1 is set to about 100 μm, for example.

  The semiconductor laser array 1 is mounted (bonded and fixed) on the upper surface of the heat sink 2 using, for example, an AuSn (gold-tin) solder material as a bonding material. On the upper surface of the heat sink 2, the end surface portion of the semiconductor laser array 1 in which a plurality of light emitting points 3 are arranged and the end surface portion of the heat sink 2 corresponding thereto are arranged on the same plane.

  The heat sink 2 is configured using, for example, a sintered body such as CuW (copper-tungsten) as a heat sink material having high thermal conductivity. The heat conductivity of the heat sink 2 is a characteristic necessary for efficiently releasing the heat generated in the semiconductor laser array 1 and maintaining the semiconductor laser array 1 at an appropriate temperature.

  The composition (component ratio) of CuW constituting the heat sink 2 differs in the X direction, which is the direction in which the light emitting points 3 are arranged. For example, in the mounting region of the semiconductor laser array 1 in the heat sink 2, the composition of CuW gradually changes from one end 1A in the longitudinal direction of the semiconductor laser array 1 toward the other end 1B.

  By changing the composition of CuW in this way, when the semiconductor laser array 1 is joined to the heat sink 2 with solder or the like, stress is applied to the semiconductor laser array 1 due to the difference in linear expansion coefficient between the semiconductor laser material and the heat sink material. . In this case, the magnitude of stress applied to the semiconductor laser array 1 varies depending on the composition of CuW. That is, since the linear expansion coefficient of Cu is larger than the linear expansion coefficient of W, a larger stress is applied to a portion where the composition (%) of Cu is higher in the longitudinal direction of the semiconductor laser array 1, and the amount of distortion increases accordingly.

  As a result, in the semiconductor laser array 1, the oscillation wavelength changes due to the stress applied to the semiconductor laser array 1 and the accompanying change in the band structure of each semiconductor laser element. Also, the oscillation wavelength difference of the entire semiconductor laser array 1 corresponds to the difference between the maximum value and the minimum value of stress applied to the semiconductor laser array 1.

  As an example, an AlGaInP-based semiconductor laser array 1 having a GaInP active layer formed on a GaAs substrate and having an oscillation wavelength band of 640 nm is used as a heat sink 2 made of CuW and AuSn solder having a melting point of 280 ° C. Consider the case of implementation in

  FIG. 2 shows the correlation between the Cu composition and the CuW linear expansion coefficient. The horizontal axis represents the Cu composition (component ratio) [%], and the vertical axis represents the CuW linear expansion coefficient [ppm / K]. . In FIG. 2, the linear expansion coefficient of CuW when Cu is 0% (W is 100%) is the same value as the linear expansion coefficient of W (4.5 ppm / K), and Cu is 100%. The linear expansion coefficient of CuW when (W is 0%) is the same value as the linear expansion coefficient of Cu (16.8 ppm / K).

  As the composition of CuW of the heat sink 2, for example, a portion corresponding to one end portion 1A in the longitudinal direction (X direction) of the semiconductor laser array 1 and containing 16% Cu and 84% W is used. The coefficient of linear expansion of the heat sink 2 is found to be 6.5 ppm / K from the equation representing the correlation shown in FIG.

  In this case, when the semiconductor laser array 1 and the heat sink 2 are soldered by heating, when the semiconductor laser array 1 is returned to room temperature (25 ° C.), the rate at which the semiconductor laser array 1 changes due to the stress received from the heat sink 2 is as follows. Since the linear expansion coefficient of the GaAs substrate, which is the main material, is 5.9 ppm / K, “−153 ppm” is obtained by the following calculation formula. As described above, a positive sign corresponds to a tensile stress, and a negative sign corresponds to a compressive stress.

  (5.9−6.5) × (280−25) = − 153 [ppm]

As described above, when GaInP is used for the active layer, assuming that the peak wavelength difference is 2 nm or more, the other end side in the longitudinal direction of the semiconductor laser array 1 is compressed corresponding to 1000 ppm from the report of the above reference. Distortion is required. Therefore, the linear expansion coefficient (κ _H ) of CuW necessary to generate a compressive strain of 1000 ppm at the portion corresponding to the other end portion 1B in the longitudinal direction of the semiconductor laser array 1 is obtained by the following calculation formula.

(5.9−κ _H ) × (280−25) ≦ −153−1000 [ppm]
κ _H ≧ 10.4 [ppm / K]

  The composition of CuW that satisfies the condition of the linear expansion coefficient is found to be 48% or more from the formula showing the correlation shown in FIG. Therefore, as the composition of CuW constituting the heat sink 2, for example, a portion corresponding to one end portion 1A in the longitudinal direction of the semiconductor laser array 1 containing 16% Cu and 84% W was used as described above. In this case, a portion corresponding to the other end portion 1B in the longitudinal direction of the semiconductor laser array 1 containing 48% Cu and 52% W is used, so that the semiconductor laser array 1 as a whole has an oscillation wavelength difference of 2 nm. be able to. Further, by using the portion corresponding to the other end portion 1B in the longitudinal direction of the semiconductor laser array 1 that contains 48% or more of Cu, the semiconductor laser array 1 as a whole can have an oscillation wavelength difference of 2 nm or more. .

  Therefore, when a laser module having the semiconductor laser array 1 and the heat sink 2 is used as a light source for a projection display, speckle noise can be reduced due to a decrease in coherency accompanying the increase in the number of wavelengths of the semiconductor laser array 1.

  As a specific example, as shown in FIG. 3, in the mounting region of the semiconductor laser array 1, the linear expansion coefficient of the heat sink 2 gradually decreases from one end 1A in the longitudinal direction of the semiconductor laser array 1 toward the other end 1B. Thus, when the composition of CuW is continuously changed, when the semiconductor laser array 1 is mounted on the heat sink 2 by solder bonding, the magnitude of the stress acting on each light emitting point 3 portion is different. Become. Further, a relatively large compressive strain is generated in one end 1A of the semiconductor laser array 1 and relative to the other end 1B of the semiconductor laser array 1 in accordance with the magnitude of stress acting on each light emitting point 3 portion. Small compression distortion occurs.

  On the other hand, the oscillation wavelength of each semiconductor laser element included in the semiconductor laser array 1 becomes shorter as the compressive strain generated at the light emitting point 3 portion of the semiconductor laser element becomes larger. For this reason, the oscillation wavelength of the semiconductor laser element arranged at one end 1A of the semiconductor laser array 1 is relatively short, and the oscillation wavelength of the semiconductor laser element arranged at the other end 1B of the semiconductor laser array 1 is relatively It becomes long.

  Therefore, the composition of CuW in the portion corresponding to one end 1A of the semiconductor laser array 1 is Cu = 48%, W = 52%, and the composition of CuW in the portion corresponding to the other end 1B of the semiconductor laser array 1 is By adopting a configuration in which the composition of the heat sink material is gradually changed in the X direction with Cu = 16% and W = 84%, the oscillation wavelength is multiplexed using the difference in stress applied to the semiconductor laser array 1. The entire semiconductor laser array 1 can have an oscillation wavelength difference of 2 nm.

  The heat sink material applied to the heat sink 2 is not limited to CuW, but may be any material that has a difference in linear expansion coefficient and can change the stress applied to the semiconductor laser array 1. Specifically, Cu-Mo, Al-SiC, diamond, etc. can be considered as heat sink materials other than CuW. Also, a composite of these materials may be used.

  In the first embodiment, the semiconductor laser array 1 is directly mounted on the heat sink 2 as an example. However, the present invention is not limited to this. For example, as shown in FIG. When mounting the semiconductor laser array 1 via the (stress relaxation member) 4, a configuration in which the composition of the submount material is gradually changed in the X direction instead of the heat sink material or in combination with the heat sink material should be adopted. That's fine.

Second Embodiment
FIG. 5 shows a configuration of a laser module according to the second embodiment of the present invention, in which (A) is a top view of the laser module and (B) is a front view of the laser module. In the second embodiment, the same reference numerals are given to the portions corresponding to the constituent elements mentioned in the first embodiment.

  The illustrated laser module includes a semiconductor laser array 1, a submount 4, and a heat sink 2.

  The submount 4 is interposed between the semiconductor laser array 1 and the heat sink 2 as a stress relaxation member. The submount 4 is made of a submount material having a linear expansion coefficient smaller than that of the heat sink material, for example, a submount material such as SiC.

  The heat sink 2 is made of a heat sink material having high thermal conductivity, for example, a heat sink material such as Cu. A semiconductor laser array 1 is mounted on the heat sink 2 via a submount 4.

  In the mounting region of the semiconductor laser array 1, the thickness ratio (thickness ratio) between the heat sink 2 and the submount 4 gradually changes from one end 1A in the longitudinal direction of the semiconductor laser array 1 toward the other end 1B. Yes.

  Specifically, the thickness of the submount 4 is increased stepwise from one end 1A in the longitudinal direction of the semiconductor laser array 1 toward the other end 1B, whereas the thickness of the heat sink 2 is It is thin like a staircase. However, the total thickness of the submount 4 and the heat sink 2 is constant in the longitudinal direction of the semiconductor laser array 1.

  In this way, by changing the thickness ratio of the submount 4 and the heat sink 2 in the mounting region of the semiconductor laser array 1, when the semiconductor laser array 1 is joined to the heat sink 2 with solder or the like with the submount 4 interposed therebetween, The magnitude of the stress applied to the semiconductor laser array 1 varies depending on the thickness ratio between the submount 4 and the heat sink 2. That is, since the linear expansion coefficient of the heat sink 2 is larger than the linear expansion coefficient of the submount 4, a larger stress is applied to a portion where the thickness ratio of the heat sink 2 is higher in the longitudinal direction of the semiconductor laser array 1, and the amount of distortion is correspondingly increased. Become more.

  As a result, in the semiconductor laser array 1, the oscillation wavelength changes due to the stress applied to the semiconductor laser array 1 and the accompanying change in the band structure of each semiconductor laser element. Also, the oscillation wavelength difference of the entire semiconductor laser array 1 corresponds to the difference between the maximum value and the minimum value of stress applied to the semiconductor laser array 1.

  As an example, an AlGaInP-based semiconductor laser array 1 having an oscillation wavelength of 640 nm band formed on a GaAs substrate and having a GaInP active layer is connected to a heat sink 2 made of Cu via a submount 4 made of SiC, with a melting point of 280 ° C. Consider the case of mounting in a room temperature environment using an AuSn solder.

  Further, immediately below the mounting region of the semiconductor laser array 1 having a longitudinal dimension of 10 mm, the thickness of the submount 4 is set every 2.5 mm from the one end 1A to the other end 1B of the semiconductor laser array 1. The thickness of the heat sink 2 is 0.5 mm from 1.0 mm → 1.5 mm → 2.0 mm → 2.5 mm, whereas the thickness of the heat sink 2 is from the one end 1 </ b> A of the semiconductor laser array 1 to the other end. Towards 1B, the thickness is decreased by 0.5 mm every 4.0 mm, such as 4.0 mm → 3.5 mm → 3.0 mm → 2.5 mm. In this case, the combined thickness of the submount 4 and the heat sink 2 is constant at 5.0 mm.

  In the above example, first, the stress applied to the semiconductor laser array 1 is calculated at a portion where the thickness of the submount 4 is 1.0 mm and the thickness of the heat sink 2 is 4.0 mm. Considering this part as a composite of SiC and Cu, the linear expansion coefficient of the composite is considered to be obtained by adding the wall expansion ratio to the linear expansion coefficient of each material. Therefore, the linear expansion coefficient of the composite is “14.04 ppm / K” according to the following calculation formula.

  3 × 1.0 / (1.0 + 4.0) + 16.8 × 4.0 / (1.0 + 4.0) = 14.04 [ppm / K]

  Therefore, the stress applied to the semiconductor laser array 1 at the portion corresponding to the composite of the submount 4 = 1.0 mm and the heat sink 2 = 4.0 mm is “−2076 ppm” from the following calculation formula.

  (5.9-14.04) x (280-25) = -2076 [ppm]

  On the other hand, when the stress applied to the semiconductor laser array 1 is calculated at a portion where the thickness of the submount 4 is 2.5 mm and the thickness of the heat sink 2 is 2.5 mm by the same method as described above, the line of the composite is calculated. The expansion coefficient is “9.9 ppm / K” according to the following calculation formula.

  3 × 2.5 / (2.5 + 2.5) + 16.8 × 2.5 / (2.5 + 2.5) = 9.9 [ppm / K]

  Therefore, the stress applied to the semiconductor laser array 1 at the portion corresponding to the composite of the submount 4 = 2.5 mm and the heat sink 2 = 2.5 mm is “−1020 ppm” from the following calculation formula.

  (5.9−9.9) × (280−25) = -1020 [ppm]

  As a result, for the semiconductor laser array 1 having the GaInP active layer, a stress (strain amount) difference of 1000 ppm or more is relatively generated between the one end 1A and the other end 1B, and the entire semiconductor laser array 1 oscillates at 2 nm. A wavelength difference can be given.

  In this case, the thickness of the submount 4 increases stepwise from the one end 1A of the semiconductor laser array 1 toward the other end 1B, and the thickness of the heat sink 2 decreases stepwise. As shown in FIG. 6, a relatively large compressive strain is generated at one end 1A of the semiconductor laser array 1, and a relatively small compressive strain is generated at the other end 1B of the semiconductor laser array 1. For this reason, the oscillation wavelength of the semiconductor laser element arranged at one end 1A of the semiconductor laser array 1 is relatively short, and the oscillation wavelength of the semiconductor laser element arranged at the other end 1B of the semiconductor laser array 1 is relatively It becomes long.

  Incidentally, as a final form when the semiconductor laser array 1 is joined to the heat sink 2 using a solder material or the like via the submount 4, as shown in FIG. It is preferable to adjust the thickness so that the surface on which the laser array 1 is mounted and the bottom surface of the heat sink 2 are parallel to each other.

  FIG. 7 is a front view showing a first modification of the laser module according to the second embodiment of the present invention. In the illustrated laser module, the thickness ratio of the submount 4 and the heat sink 2 changes in a slope shape in the longitudinal direction (X direction) of the semiconductor laser array 1.

  Specifically, the thickness of the submount 4 increases in a slope shape from the longitudinal center of the semiconductor laser array 1 toward both ends 1A and 1B, whereas the thickness of the heat sink 2 increases. It is thin like a slope. However, the total thickness of the submount 4 and the heat sink 2 is constant in the longitudinal direction of the semiconductor laser array 1.

  When such a configuration is adopted, in the mounting region of the semiconductor laser array 1, the thickness of the submount 4 is continuously increased from one end 1A in the longitudinal direction of the semiconductor laser array 1 to the other end 1B. Since the thickness of the heat sink 2 is continuously reduced, when the semiconductor laser array 1 is joined to the heat sink 2 with solder or the like with the submount 4 interposed therebetween, one end 1A of the semiconductor laser array 1 is A relatively large compressive strain is generated, and a relatively small compressive strain is generated in the other end portion 1B of the semiconductor laser array 1.

  For this reason, the oscillation wavelength of the semiconductor laser element arranged at one end 1A of the semiconductor laser array 1 is relatively short, and the oscillation wavelength of the semiconductor laser element arranged at the other end 1B of the semiconductor laser array 1 is relatively It becomes long. Therefore, by changing the thickness ratio between the submount 4 and the heat sink 2 so that a difference in stress (strain amount) of 1000 ppm or more is relatively generated between the one end 1A and the other end 1B of the semiconductor laser array 1, a semiconductor laser is obtained. The entire array 1 can have an oscillation wavelength difference of 2 nm or more.

  FIG. 8 is a front view showing a second modification of the laser module according to the second embodiment of the present invention. In the illustrated laser module, the wall thickness ratio of the submount 4 and the heat sink 2 gradually becomes symmetrical from the center in the longitudinal direction (X direction) of the semiconductor laser array 1 toward both ends 1A and 1B. It has changed.

  Specifically, the thickness of the submount 4 is increased stepwise from the longitudinal center of the semiconductor laser array 1 toward both ends 1A and 1B, whereas the thickness of the heat sink 2 is It is thin like a staircase. However, the total thickness of the submount 4 and the heat sink 2 is constant in the longitudinal direction of the semiconductor laser array 1.

  When such a configuration is adopted, the thickness of the heat sink 2 is gradually reduced from the longitudinal center of the semiconductor laser array 1 toward both ends 1A and 1B. When the semiconductor laser array 1 is bonded to the heat sink 2 with solder or the like, relatively large compressive strain is generated in the central portion of the semiconductor laser array 1 in the longitudinal direction. In 1B, a relatively small compressive strain occurs.

  For this reason, the oscillation wavelength of the semiconductor laser element arranged at the center in the longitudinal direction of the semiconductor laser array 1 becomes relatively short, and the oscillation wavelength of the semiconductor laser elements arranged at both ends 1A and 1B of the semiconductor laser array 1 Is relatively long. Therefore, by changing the thickness ratio between the submount 4 and the heat sink 2 so that a stress (strain amount) difference of 1000 ppm or more is relatively generated between the central portion of the semiconductor laser array 1 and the both end portions 1A and 1B, the semiconductor laser is changed. The entire array 1 can have an oscillation wavelength difference of 2 nm or more.

  FIG. 9 is a front view showing a third modification of the laser module according to the second embodiment of the present invention. In the illustrated laser module, the thickness ratio of the submount 4 and the heat sink 2 gradually changes from one end 1A in the longitudinal direction (X direction) of the semiconductor laser array 1 toward the other end 1B.

  Specifically, the thickness of the submount 4 is increased stepwise from one end 1A in the longitudinal direction of the semiconductor laser array 1 toward the other end 1B, whereas the thickness of the heat sink 2 is It is thin like a staircase. However, the total thickness of the submount 4 and the heat sink 2 is constant in the longitudinal direction of the semiconductor laser array 1.

  Further, the submount 4 is a laminate in which thin film layers 4A made of a first submount material and thin film layers 4B made of a second submount material having a linear expansion coefficient different from that of the first submount material are alternately laminated. It is composed by the body.

  The thin film layer 4A is formed using, for example, SiC as the first submount material. The thin film layer 4B is formed using, for example, AlN as the second submount material. The thin film layers 4A and 4B are laminated with the same thickness.

  The maximum number of layers of the submount 4 is seven (four thin films 4A + three thin films 4B). Further, immediately below the mounting region of the semiconductor laser array 1 having a longitudinal dimension of 10 mm, the number of layers of the submount 4 is 1.25 mm from the one end 1A in the longitudinal direction of the semiconductor laser array 1 toward the other end 1B. In addition, 0 layer → 1 layer → 2 layer → 3 layer → 4 layer → 5 layer → 6 layer → 7 layer.

  Corresponding to the laminated structure of the submounts 4, the upper surface of the submount 4 decreases stepwise from one end 1 </ b> A to the other end 1 </ b> B of the semiconductor laser array 1 (the thickness of the submount 4 is thin). It is formed as follows. In addition, one end of each thin film layer 4 </ b> A, 4 </ b> B is arranged in alignment with one end of the heat sink 2 in the longitudinal direction of the semiconductor laser array 1.

  When such a configuration is adopted, in the mounting region of the semiconductor laser array 1, the thickness dimension of the submount 4 is gradually increased from one end 1A in the longitudinal direction of the semiconductor laser array 1 to the other end 1B. Since the thickness of the heat sink 2 is gradually reduced, when the semiconductor laser array 1 is joined to the heat sink 2 with solder or the like with the submount 4 interposed therebetween, A relatively large compressive strain is generated, and a relatively small compressive strain is generated in the other end portion 1B of the semiconductor laser array 1.

  For this reason, the oscillation wavelength of the semiconductor laser element arranged at one end 1A of the semiconductor laser array 1 is relatively short, and the oscillation wavelength of the semiconductor laser element arranged at the other end 1B of the semiconductor laser array 1 is relatively It becomes long. Therefore, by changing the thickness ratio between the submount 4 and the heat sink 2 so that a difference in stress (strain amount) of 1000 ppm or more is relatively generated between the one end 1A and the other end 1B of the semiconductor laser array 1, a semiconductor laser is obtained. The entire array 1 can have an oscillation wavelength difference of 2 nm or more.

  In each of the above embodiments, as an example of the configuration of the semiconductor laser array 1, an integrated type in which a plurality of semiconductor laser elements are arranged in parallel in one laser array chip (laser bar) is illustrated. Not limited to this, a plurality of semiconductor laser elements that are independent (separated) from each other may be arranged in a one-dimensional array in the X direction.

The structure of the laser module which concerns on 1st Embodiment of this invention is shown, (A) is a top view of a laser module, (B) is a front view of a laser module. It is a figure which shows the correlation of Cu composition and a CuW linear expansion coefficient. It is a figure explaining the characteristic of the laser module concerning a 1st embodiment of the present invention. It is a figure explaining the modification of a laser module in 1st Embodiment of this invention. The structure of the laser module which concerns on 2nd Embodiment of this invention is shown, (A) is a top view of a laser module, (B) is a front view of a laser module. It is a figure explaining the characteristic of the laser module which concerns on 2nd Embodiment of this invention. It is a front view which shows the 1st modification of the laser module which concerns on 2nd Embodiment of this invention. It is a front view which shows the 2nd modification of the laser module which concerns on 2nd Embodiment of this invention. It is a front view which shows the 3rd modification of the laser module which concerns on 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser array, 2 ... Heat sink, 3 ... Light emission point, 4 ... Submount

Claims (4)

A semiconductor laser array having a plurality of emission points;
A mounting body for mounting the semiconductor laser array;
The mounting body is formed by applying different stresses to the semiconductor laser array in the arrangement direction of the light emitting points. The laser module according to claim 1, wherein a linear expansion coefficient of the mounting body is different depending on an arrangement direction of the light emitting points. The laser module according to claim 1, wherein a composition of the mounting body is different in an arrangement direction of the light emitting points. The mounting body includes a first mounting body and a second mounting body having different linear expansion coefficients,
2. The laser module according to claim 1, wherein a thickness ratio of the first mounting body and the second mounting body is different in an arrangement direction of the light emitting points.

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