JP2012089584A - Semiconductor laser apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser apparatus which suppresses the deterioration of light emission characteristics.SOLUTION: A semiconductor laser apparatus of this invention is formed by laminating multiple semiconductor laser units 10. Each semiconductor laser unit 10 includes a liquid cooling type heat sink 1 having a plate shape and forming a fluid channel therein, a semiconductor laser module 2 which includes a semiconductor laser bar and is fixed to one side surface of the heat sink 1, and a molybdenum reinforcement body 3 fixed to a position on the other side surface of the heat sink 1, which faces the semiconductor laser module 2, and having a linear expansion coefficient smaller than that of the heat sink 1.

Description

  The present invention relates to a semiconductor laser device provided with a heat sink.

  Conventional semiconductor laser devices are described in, for example, Patent Document 1, Patent Document 2, and Patent Document 3.

  Patent Document 1 discloses a semiconductor laser module in which both sides of a semiconductor laser bar are sandwiched between metal submounts. As the material of the submount, Mo, W, Cu, Cu—W alloy, Cu—Mo alloy, SiC, or AlN can be used. The thickness of each submount is 50 to 200 μm. In this semiconductor laser device, the semiconductor laser module is attached to a liquid-cooled heat sink. Thereby, it is possible to correct the warp of the semiconductor laser bar.

  Patent Document 2 discloses a semiconductor laser device in which a semiconductor laser bar is attached on a heat sink and a reinforcing member made of a material having a small linear expansion coefficient is attached on the same surface as the attachment surface of the semiconductor laser bar in the heat sink. ing. The material of the reinforcing member includes any one of Cu, Al, Ni, W, Mo, Fe, Cr, Co, and Bi.

  Patent Document 3 discloses a semiconductor laser device in which a liquid-cooled heat sink is covered with a resin layer and a semiconductor laser bar is attached. This document discloses a structure capable of improving cooling efficiency and preventing corrosion and water leakage.

JP 2007-73549 A JP 2007-73549 A Japanese Patent No. 4002234

  However, when a semiconductor laser stack is configured by combining a semiconductor laser module and a high-quality liquid-cooled heat sink, the warpage of the semiconductor laser module itself should be suppressed by the submount, but the emission point position from the semiconductor laser module However, the deterioration of the light emission characteristics was observed in which the target light emission distribution could not be obtained because the target light emission distribution was not obtained.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a semiconductor laser device capable of suppressing deterioration in light emission characteristics.

  The inventors of the present application intensively studied the cause of the characteristic deterioration of the semiconductor laser device. Since a Cu-W alloy having a small linear expansion coefficient is adopted as a pair of submounts and the semiconductor laser bar should be sandwiched using these, the emission point position should not be changed in principle. However, recent high-quality liquid-cooled heat sinks have high cooling efficiency and are downsized. However, since the thickness is small, the liquid-cooled heat sink can bend in the thickness direction when it expands and contracts. In this case, due to the difference in linear expansion coefficient between the laser module that should originally be highly rigid and the high-quality heat sink, stress is generated between them, and the heat sink is bent and deformed in the thickness direction. The inventors of the present application have found that the deviation of the light emitting point position is caused by such a high performance heat sink.

  In order to solve the above-described problems, a semiconductor laser device according to the present invention is a semiconductor laser device in which a plurality of semiconductor laser units are stacked. Each semiconductor laser unit has a plate-like shape in which a fluid passage is formed. A liquid-cooled heat sink, including a semiconductor laser bar, a semiconductor laser module fixed on one side of the heat sink, and fixed at a position facing the semiconductor laser module on the other side of the heat sink, smaller than the heat sink A molybdenum reinforcement body having a linear expansion coefficient and a thickness of 0.1 to 0.5 mm, wherein one surface of the molybdenum reinforcement body in one semiconductor laser unit is fixed to the heat sink of its own semiconductor laser unit, and the other surface Is in the semiconductor laser module of another semiconductor laser unit Characterized in that it is a constant.

  According to the semiconductor laser of the present invention, the liquid-cooled heat sink has high performance. However, as described above, when the thickness is small, the difference in linear expansion coefficient from the laser module (semiconductor laser bar + submount) There is a tendency to bend. However, it was found that the overall rigidity is remarkably improved by laminating the laser modules and fixing a molybdenum reinforcement having a small linear expansion coefficient on the opposite side of the laser modules. In particular, when all the semiconductor laser units are stacked and have an adhesive layer that is thermally melted between the elements, the adhesive layer is disposed between the elements, and heat is simultaneously applied to fix them. In this case, the overall rigidity is remarkably improved. Therefore, according to the semiconductor laser device of the present invention, the curvature of the heat sink is suppressed, the displacement of the light emitting point position is suppressed, and the deterioration of the light emission characteristics can be suppressed.

  The molybdenum reinforcing body is a reinforcing body containing molybdenum as a main component (weight percent 80% or more), but the same effect can be obtained even if some impurities are mixed.

  According to the semiconductor laser device of the present invention, it is possible to suppress the deterioration of the light emission characteristics.

It is a perspective view of a semiconductor laser device. It is the side view which looked at the semiconductor laser apparatus from the arrow II direction. It is the front view which looked at the semiconductor laser apparatus from the arrow III direction. It is a perspective view of a semiconductor laser unit. It is the side view which looked at the semiconductor laser unit from the arrow V direction. It is the front view which looked at the semiconductor laser unit from the arrow VI direction. It is a disassembled perspective view of a semiconductor laser unit. It is a perspective view of a semiconductor laser bar. It is an exploded perspective view of a liquid cooling type heat sink. It is a front view of the semiconductor laser apparatus which enlarged the width direction dimension of the heat sink. It is a front view of the semiconductor laser unit used as a comparative example.

  Hereinafter, the semiconductor laser device according to the embodiment will be described. Note that the same reference numerals are used for the same elements, and redundant description is omitted.

  1 is a perspective view of a semiconductor laser device in which a plurality of semiconductor laser units 10 are stacked, FIG. 2 is a side view of the semiconductor laser device viewed from the direction of arrow II, and FIG. 3 is a side view of the semiconductor laser device from the direction of arrow III. FIG.

  This semiconductor laser device is a so-called semiconductor laser stack, in which a plurality of semiconductor laser units 10 are stacked along the Z axis. In the figure, an example in which three semiconductor laser units 10 are stacked is shown, but two or four or more semiconductor laser units 10 may be stacked.

  The detailed structure of each semiconductor laser unit 10 is shown in FIG. 4 and subsequent figures, but includes a heat sink 1, a semiconductor laser module 2, and a reinforcing body 3 made of molybdenum. , And a spacer 4 having a fluid passage inside.

  The heat sink 1 is a plate-like liquid-cooled heat sink having a fluid passage formed therein, and has a rigidity capable of bending in the thickness direction as a single unit. The semiconductor laser module 2 includes a semiconductor laser bar 2 b at the center, and is fixed to the upper surface (one surface) side of the heat sink 1. The reinforcing body 3 is fixed at a position facing the semiconductor laser module 2 on the lower surface (other surface) side of the heat sink 1, but has a smaller linear expansion coefficient than the heat sink 1. The thickness of each reinforcing body 3 is 0.1 to 0.5 mm. Each unit 10 is reinforced with molybdenum and curving is suppressed, but the units 10 are stacked and pressurized. Note that the units 10 are not joined by solder but are in contact by pressing from above.

  Since the expansion / contraction amount according to the temperature of one heat sink 1 is limited by the reinforcing body 3 having a low linear expansion coefficient, there is an advantage that the heat sink 1 itself is not easily distorted. Therefore, bending of the semiconductor laser unit 2 due to the distortion of the heat sink 1 is suppressed. Of course, when paying attention to the semiconductor laser unit 10 (e.g., the central semiconductor laser unit) located at positions other than both ends in the vertical direction, the lower heat sink 1 in which expansion and contraction is suppressed, Since the upper reinforcing body 3 comes into contact, the curvature of the semiconductor laser module 2 itself is remarkably suppressed.

  When attention is paid to the semiconductor laser units 10 at both ends, the own heat sink 1 has stress caused by the difference in thermal expansion coefficient with the lower reinforcing body 3 and stress caused by the difference in thermal expansion coefficient with the upper laser module 2. Since it takes the same direction and the same size, the structure as a whole cancels out stress. Therefore, also in the semiconductor laser modules 10 at both ends, the bending due to the bending of the heat sink 1 is suppressed.

  In the case where the semiconductor laser units 10 are stacked, a conductive adhesive layer may be interposed between the reinforcing member 3 of the semiconductor laser unit 10 and the submount 2c positioned below the reinforcing body 3, but in this example, Are in contact. The material of such an adhesive layer is the same as the material of other adhesive layers t1 and the like. The elements located on both sides of the adhesive layer are preferably fixed by applying heat simultaneously after laminating them from the viewpoint of reducing distortion during cooling. Of course, after the units 10 are fixed and completed using the adhesive layers t1, t2, t3, and t5, the units 10 can be bonded to each other via the adhesive layer.

  The spacer 4 is interposed between the semiconductor laser units 10 and is made of a metal or an insulator. When made of a metal such as Cu, a short circuit between the semiconductor laser units 10 can be prevented by using an insulating material for the adhesive layer with the heat sink 1, but when made of an insulator such as glass or ceramic, the bonding is possible. There is no limit to the material of the layer. In this example, the spacer 4 is made of silicone resin (rubber), and no adhesive layer is interposed between the spacer 4 and the heat sink.

  When the semiconductor laser stack is driven, a drive current may be supplied between the submount 2c that is the upper electrode and the submount 2a that is the lower electrode. Since each submount is electrically connected via the reinforcing body 3, in principle, a drive voltage is applied between the uppermost submount 2c and the lowermost submount 2a in the entire stack. For example, a current is supplied to all of the semiconductor laser bars 2b positioned between them, and a plurality of laser beams are emitted in the −X direction from the two-dimensional light emission points in the semiconductor laser bars 2b.

  Each heat sink 1 has two through holes 1c2 and 1c3 extending in the thickness direction, which communicate with the through holes 42 and 43 of the spacer 4, respectively. The cooling medium introduced along the arrow W1 from the lowermost through hole 1c3 (see FIG. 2) passes through the fluid passage in the heat sink 1 and the through hole 43 of the spacer 4 as shown by the arrows W2 and W1. It can escape into the upper heat sink 1 and the through hole 1c3, and can pass through the fluid passage inside the heat sink 1 into the through hole 1c2. Most of the cooling medium introduced from the uppermost through-hole 1c2 along the arrow W3 can pass through the group of through-holes communicating therewith to the lowermost through-hole 1c2.

  If necessary, O-rings R2 and R3 are disposed on the upper and lower surfaces of the heat sink 1 and the upper surface of the spacer 4 so as to surround the through holes 1c2, 1c3, 42, and 43 (see FIG. 2). It is preferable to improve the sealing performance between the contacting members.

  Next, the structure of each semiconductor laser unit 10 will be described.

  4 is a perspective view of the semiconductor laser unit, FIG. 5 is a side view of the semiconductor laser unit viewed from the direction of arrow V, and FIG. 6 is a front view of the semiconductor laser unit viewed from the direction of arrow VI.

  The semiconductor laser unit is disposed on the heat sink 1, the laser module 2 fixed to the heat sink 1, the reinforcing body 3 fixed to the heat sink 1 at a position facing the laser module 2, and the upper surface of the heat sink 1. And a spacer 4 fixed so as not to move with the pressure of. The spacer 4 also has a function as a sealing material when a cooling medium such as water is introduced therein, and an O-ring or the like is disposed around the openings 42 and 43 provided in the member 4 as necessary. .

  The heat sink 1 is a plate-like liquid-cooled heat sink in which a fluid passage is formed. Further, since the thickness Z1 of the heat sink 1 is 3 mm or less, the heat sink 1 is allowed to bend in the thickness direction alone. The detailed structure of the heat sink 1 is shown in FIG.

  In the laser module 2, a semiconductor laser bar 2b is sandwiched between a first submount 2a and a second submount 2c. The first submount 2a is fixed to the upper surface of the heat sink 1 via the adhesive layer t1, and is fixed to the semiconductor laser bar 2b via the adhesive layer t2. The semiconductor laser bar 2 is fixed to the second submount 2c via the adhesive layer t3. That is, the first submount 2a is fixed to one surface of the semiconductor laser bar 2b, and the second submount 2c is fixed to the other surface of the semiconductor laser bar 2b. In addition, the linear expansion coefficient (thermal expansion coefficient) of the material which comprises each submount 2b and 2c is smaller than the linear expansion coefficient of the heat sink 1, or a shape is plate shape (cuboid).

  As the constituent material of the submounts 2a and 2c, Mo, W, Cu, Cu—W alloy, Cu—Mo alloy, SiC, or AlN can be used, and the thickness of each submount may be 50 to 200 μm. it can.

  The reinforcing body 3 is made of plate-like molybdenum (Mo), and is located on the surface opposite to the mounting surface of the first submount in the heat sink 1 at a position facing the first submount 2a via an adhesive layer t5. It has been fixed. The constituent material of the reinforcing body 3 has a linear expansion coefficient smaller than that of the heat sink 1, and, unlike the submount, has a thickness in the range of 0.1 to 0.5 mm. The molybdenum reinforcing body 3 is a reinforcing body containing molybdenum as a main component (weight percent of 80% or more), but the same effect can be obtained even if some impurities are mixed.

  Here, it is preferable to use a Cu—W alloy for the submount, and it is preferable to use the reinforcing body 3 molybdenum. One reason is that the stress applied to the heat sink 1 at the time of expansion and contraction is offset, but the following effects are also obtained. That is, the Cu—W alloy has good heat conduction and is close in expansion coefficient to the semiconductor laser bar, so that it is convenient as a submount of the semiconductor laser bar. In addition, since the submount also requires an element as an electrode, it is made of a metal material for electrical conduction.

Suppose that an XYZ three-dimensional orthogonal coordinate system is set, the alignment direction of the light emitting points is the Y axis (the longitudinal direction of the laser bar), the thickness direction of the laser bar 2b is the Z axis, and the laser beam emission direction is parallel to the X axis. The exemplary dimensions (preferable ranges) of each component are as follows.
(1) Dimensions of heat sink 1 in the X direction length X1: 30 mm (10 mm to 30 mm)
Y direction length Y1 (= Y3 in this example): 12 mm (10 mm to 12 mm)
Z-direction length Z1: 1.1 mm (1 mm to 3 mm)
(2) Dimension X direction length X2 of the semiconductor laser module 2: 2 mm (1 mm to 5 mm)
Y direction length Y2 (= Y3 in this example): 10 mm (5 mm to 12 mm)
Z-direction length Z2: 450 μm (300 μm to 600 μm)
Submount 2a thickness Z3a: 150 μm (100 μm to 300 μm)
X-direction length of submount 2a = X2
Y-direction length of the submount 2a = Y2 (= Y3)
Submount 2c thickness Z3c: 150 μm (100 μm to 300 μm)
X-direction length of submount 2c = X2
Y-direction length of the submount 2c = Y2 (= Y3)
Thickness Z3c of semiconductor laser bar 2b: 140 μm (100 μm to 150 μm)
X-direction length X2b of the semiconductor laser bar 2b: 2 mm (1 mm to 5 mm)

In this example, X2b <X2. This is to secure an area for attaching the power supply line to the submount.
Y-direction length Y2b = Y2 (= Y3) of the semiconductor laser bar 2b
(3) Size X direction length X3 of the reinforcing body 3: 2 mm (1 mm to 5 mm)
Y direction length Y3: 10 mm (5 mm to 12 mm)
Z direction length Z3: 150 μm (100 μm to 500 μm)

  The adhesive layers t1, t2, t3, and t5 are all made of a solder material and each have a thickness Zt. SnAgCu or AuSn can be used as the adhesive layer, but AuSn can be used at t2 and t3, and SnAgCu can be used at t1 and t5. An exemplary dimension of the thickness Zt is 10 μm, and when the spacer 4 is made of an insulator such as ceramic, the resin layer can have an adhesive layer such as a solder material interposed between the heat sink. Then, as the spacer 4, a silicone resin (rubber) is used, and it has a function of insulation and a sealing material. The preferred range is 3-20 μm. The effect of the above numerical range will be described. When the numerical range is 3 to 20 μm, there is an effect that the solder does not protrude and can be uniformly bonded.

  Here, the physical quantities of the liquid-cooled heat sink 1, the first submount 2a, the semiconductor laser bar 2b, the second submount 2c, and the molybdenum reinforcing body 3 are adjusted so that the curvature of the semiconductor laser bar is substantially eliminated.

  FIG. 7 is an exploded perspective view of the semiconductor laser unit.

  The heat sink 1 has openings (through holes) 1 c 2 and 1 c 3 for introducing a cooling medium, which communicate with the openings (through holes) 42 and 43 of the spacer 4. The spacer 4 is provided as necessary and has a sealing function for the cooling medium. In the case of a semiconductor laser stack, the spacer 4 is provided on the laser unit at the top, and this is provided as an external device. It can also function as a spacer for incorporation.

  After the laser module 2 is disposed on the upper surface side of the heat sink 1 via an adhesive layer and the reinforcing body 3 is disposed on the rear surface side via an adhesive layer, heat and pressure along the Z-axis direction are simultaneously applied thereto. Apply and then fix them by cooling to room temperature. The temperature may be such that the adhesive layer melts. If necessary, the spacer 4 is disposed on the upper surface of the heat sink 1 through an adhesive layer, and is fixed by applying the same heat and pressure thereto. This fixing can be performed simultaneously after all the constituent elements of the semiconductor laser unit 10 are stacked. In this case, since all stresses are simultaneously applied to each element in the fixing step, there is an advantage that distortion of each element is reduced. That is, when an adhesive layer is disposed between the elements 3, 1, 2a, 2b, 2c, and 4 and is fixed by applying heat at the same time, the overall rigidity is remarkably improved. Of course, it is possible to fix each unit 10 without using an adhesive simply by performing bonding, interposing the spacer 4 between the completed units 10 and applying pressure to them. When the curved unit 10 is stacked, a gap is created, and water leakage and poor conduction are likely to occur. However, with the unit 10 in which bending is suppressed, stacking is easy and the above-described defects are unlikely to occur. There is an advantage.

  FIG. 8 is a perspective view of the semiconductor laser bar.

  The laser bar 2b has a plurality of light emitting points 2b2 arranged along a straight line on the Y axis. The laser bar 2b is composed of the compound semiconductor substrate 2b1, and an active layer is present at the position of the light emitting point 2b2, and a clad layer is located on both sides thereof. Known compound semiconductor materials include GaN, AlGaAs, GaN, AlGaN, and mixed crystals containing In. In this example, it is assumed that the laser bar 2b contains GaAs as a main component, the active layer further contains In, and the clad layers located on both sides thereof further contain Al. Since GaAs and Cu—W alloy have close thermal expansion coefficients, the stress between the submount and the laser bar is small.

  Here, the high-performance liquid-cooled heat sink 1 will be described.

  FIG. 9 is an exploded perspective view of a liquid-cooled heat sink.

  The heat sink 1 is formed by laminating and fixing three metal (Cu in this example) plate-like members 1a1, 1b1, and 1c1.

  The lowermost plate-like member 1a1 has two openings (through holes) 1a2 and 1a3 and a recess 1a4 that forms a fluid flow path together with the lower surface of the upper plate-like member 1b1. The recess 1a4 is continuous with the opening 1a3.

  The central plate-like member 1b1 has two openings (through holes) 1b2 and 1b3 and a plurality of through holes 1b4 constituting a fluid flow path. The through hole 1b4 is located at a position facing the recess 1a4.

  The upper plate-like member 1c1 has two openings (through holes) 1c2, 1c3 and a recess 1c4 that forms a fluid flow path with the upper surface of the lower plate-like member 1b1. The recess 1c4 is continuous with the opening 1c2, and is not continuous with the opening 1c3.

  When the cooling medium is introduced into the heat sink 1 along the arrow W1 from the bottom to the top, it can pass through the open aperture groups 1a3, 1b3, 1c3 and escape to the top, as indicated by the arrow W2. As described above, the opening 1c2 can be reached through the fluid flow path defined by the recess 1a4, the through hole 1b4, and the recess 1c4. The cooling medium introduced into the heat sink 1 along the arrow W3 from the opening 1c2 can also escape downward through the open aperture groups 1c2, 1b2, 1a2. In addition, although a plate-shaped member consists of metals, such as Cu, the surface is coat | covered with the resin layer and corrosion is prevented.

  FIG. 10 is a front view of the semiconductor laser unit in which the dimension in the width direction of the heat sink is increased.

  In the above description, the Y-direction length Y1 of the heat sink 1 coincides with the Y-direction length Y3 of the reinforcing body 3, but this may be larger than Y3 as shown in FIG. Moreover, you may make the X direction length of the heat sink 1 larger than the thing of the said embodiment. Even in this case, there is an effect similar to the above embodiment.

  FIG. 11 is a front view of a semiconductor laser unit as a comparative example.

  In the comparative example, in the semiconductor laser unit of the embodiment shown in FIG. 6, the reinforcing body 3 is attached to both sides of the upper surface of the heat sink 1 to form the reinforcing body 3Z. Other structures in the comparative example are the same as those shown in FIG.

  A liquid-cooled heat sink such as the above-described water-cooled heat sink has high performance, but when it is thin, it tends to bend due to a difference in linear expansion coefficient with the laser module 2.

  In the case of the comparative example, when the heat sink 1 is cooled, a force that reduces in the direction of the arrow F1 works. However, the semiconductor laser module 2 has a smaller coefficient of linear expansion than the heat sink 1, and this acts as a force that reduces in the direction of the arrow F2. . That is, there is a tendency to be convex upward due to the difference in linear expansion coefficient. Of course, since the reinforcing body 3Z is fixed, expansion and contraction of the heat sink 1 is slightly relaxed, but overall deformation cannot be suppressed.

  On the other hand, as in the embodiment shown in FIG. 6, stress from the laser module 2 side is applied to the heat sink 1 by fixing the molybdenum reinforcement body 3 having a small linear expansion coefficient on the opposite side to the laser module 2. The force that tends to bend due to (the force indicated by the arrow F2) and the force that tends to bend due to the stress from the reinforcing body 3 side (the force indicated by the arrow F3) tend to cancel each other. Moreover, the rigidity of the entire body is improved by attaching the reinforcing body 3 to the heat sink 1, and by adopting a stack structure in which simultaneous bonding is performed, the stress applied to the semiconductor laser bar from both the upper and lower sides is reduced. Has been. Therefore, according to the semiconductor laser device in which the semiconductor laser units 10 of the embodiment are stacked, the curvature of the heat sink 1 is suppressed, the displacement of the light emitting point position is suppressed, and the deterioration of the light emission characteristics can be suppressed.

  Further, in the case of the above-described structure, since the deformation of the heat sink 1 is suppressed, water leakage from the heat sink 1 can be suppressed. Further, when a power supply line to the laser (power is supplied between the upper and lower submounts of the semiconductor laser bar during laser driving) is attached to the submount, it is possible to suppress the disconnection of the supply line. In addition, when the lens is arranged on the front surface of the semiconductor laser unit, the light emitting point position does not shift, so that a product with a high system can be manufactured.

DESCRIPTION OF SYMBOLS 10 ... Semiconductor laser unit, 1 ... Heat sink, 2 ... Semiconductor laser module, 3 ... Molybdenum reinforcement body.

Claims (1)

In a semiconductor laser device formed by laminating a plurality of semiconductor laser units,
Individual semiconductor laser units
A plate-like liquid-cooled heat sink with a fluid passage formed therein;
A semiconductor laser module including a semiconductor laser bar and fixed to one side of the heat sink;
A molybdenum reinforcing body having a thickness of 0.1 to 0.5 mm, which is fixed at a position facing the semiconductor laser module on the other surface side of the heat sink, and has a smaller linear expansion coefficient than the heat sink;
With
One surface of the molybdenum reinforcing body in one semiconductor laser unit is fixed to the heat sink of its own semiconductor laser unit, and the other surface is fixed to the semiconductor laser module of another semiconductor laser unit. A semiconductor laser device.

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