JP2017011174A - Surface emitting laser array, laser device, ignition device, and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light emitting laser array that can suppress an increase in temperature of a light emitting part.SOLUTION: A surface light emitting laser array 201 comprises: a surface light emitting laser array chip 230; sub mount 232; heat dissipation member 234; Peltier element 235; first metal layer 236; and second metal layer 237. The first metal layer 236 is formed on a surface of the sub mount 232 on which the surface light emitting laser array chip 230 is held and has a larger thermal conductivity than that of the sub mount 232. The surface light emitting laser array chip 230 is joined to the first metal layer 236 with a joint material 231.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a surface emitting laser array, a laser device, an ignition device, and an internal combustion engine. More specifically, the present invention relates to a surface emitting laser array having a plurality of light emitting units, a laser device and an ignition device having the surface emitting laser array, and The present invention relates to an internal combustion engine including the ignition device.

  A vertical cavity surface emitting laser (VCSEL) emits light in a direction perpendicular to a substrate, and is an edge emitting semiconductor laser that emits light in a direction parallel to the substrate. Are also attracting attention because of their low price, low power consumption, small size, suitable for two-dimensional devices, and high performance.

  A surface-emitting laser array in which a plurality of surface-emitting lasers are integrated can emit laser light with high output, and various uses are being studied.

  For example, Patent Document 1 discloses a semiconductor laser light source having an array element in which surface emitting laser elements (VCSEL) are two-dimensionally arranged, and a pulse for fuel ignition excited by the semiconductor laser light emitted from the semiconductor laser light source. An in-vehicle ignition device including a solid-state laser medium that emits laser light is disclosed.

  However, the semiconductor laser light source array element disclosed in Patent Document 1 has the disadvantage that the temperature of the surface emitting laser element rises.

  The present invention includes an array chip having a plurality of light emitting units and a holding member that holds the array chip, and the holding member includes an insulating member and a surface of the insulating member on the side where the array chip is held. And a first metal layer having a thermal conductivity higher than that of the insulating member.

  According to the surface emitting laser array of the present invention, the temperature rise of the light emitting part can be suppressed.

It is a figure for demonstrating the outline of the engine 300 which concerns on one Embodiment of this invention. It is a figure for demonstrating the ignition device. 6 is a diagram for explaining a laser resonator 206. FIG. 4 is a diagram for explaining a configuration of a surface emitting laser array 201. FIG. 5 is a diagram for explaining a surface emitting laser array chip 230. FIG. 5 is a diagram for explaining one light emitting unit in the surface emitting laser array chip 230. FIG. FIGS. 7A and 7B are diagrams for explaining the substrate of the surface emitting laser array 201, respectively. FIG. 6 is a view for explaining a first metal layer 236 formed on a submount 232. It is a figure for demonstrating vapor deposition of the joining material. It is a figure for demonstrating an insulation groove | channel. It is AA sectional drawing of FIG. FIGS. 12A and 12B are diagrams for explaining the relationship between the thickness of the lower metal layer 236a and the spectrum of light emitted from the surface emitting laser array 201, respectively. FIG. 11 is a diagram for explaining a case where a second metal layer 237 is not formed on the −Z side surface of the submount 232. FIG. 14A and FIG. 14B are diagrams for explaining a schematic configuration of a laser annealing apparatus, respectively. It is a figure for demonstrating schematic structure of a laser beam machine.

"Overview"
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a main part of an engine 300 as an internal combustion engine according to an embodiment.

  The engine 300 includes an ignition device 301, a fuel ejection mechanism 302, an exhaust mechanism 303, a combustion chamber 304, a piston 305, and the like.

The operation of engine 300 will be briefly described.
(1) The fuel ejection mechanism 302 ejects a combustible mixture of fuel and air into the combustion chamber 304 (intake).
(2) The piston 305 rises and compresses the combustible air-fuel mixture (compression).
(3) The ignition device 301 emits laser light into the combustion chamber 304. Thereby, the fuel is ignited (ignition).
(4) Combustion gas is generated and the piston 305 descends (combustion).
(5) The exhaust mechanism 303 exhausts the combustion gas to the outside of the combustion chamber 304 (exhaust).

  Thus, a series of processes consisting of intake, compression, ignition, combustion, and exhaust are repeated. Then, the piston 305 moves in response to a change in the volume of the gas in the combustion chamber 304 to generate kinetic energy. For example, natural gas or gasoline is used as the fuel.

  Engine 300 performs the above operation based on an instruction of an engine control device that is provided outside engine 300 and is electrically connected to engine 300.

  As shown in FIG. 2 as an example, the ignition device 301 includes a laser device 200, an emission optical system 210, a protection member 212, and the like.

  The emission optical system 210 condenses the light emitted from the laser device 200. Thereby, a high energy density can be obtained at the condensing point.

  The protection member 212 is a transparent window provided facing the combustion chamber 304. Here, as an example, sapphire glass is used as the material of the protection member 212.

  The laser device 200 includes a surface emitting laser array 201, a first condensing optical system 203, an optical fiber 204, a second condensing optical system 205, and a laser resonator 206. In the present specification, description will be made using the XYZ three-dimensional orthogonal coordinate system and assuming that the light emission direction from the surface emitting laser array 201 is the + Z direction.

  The surface emitting laser array 201 is an excitation light source and has a plurality of light emitting units. Each of the light emitting units is a vertical cavity surface emitting laser (VCSEL: Vertical Cavity Surface Emitting Laser). The wavelength of light emitted from the surface emitting laser array 201 is 808 nm.

  The surface-emitting laser array is a light source that is advantageous for exciting a Q-switched laser whose characteristics change greatly due to a shift in excitation wavelength because the wavelength shift of emitted light due to temperature is very small. Therefore, when a surface emitting laser array is used as an excitation light source, there is an advantage that environmental temperature control can be simplified.

  The first condensing optical system 203 condenses the light emitted from the surface emitting laser array 201.

  The optical fiber 204 is arranged so that the center of the end face on the −Z side of the core is located at a position where the light is collected by the first condensing optical system 203. Here, an optical fiber (manufactured by Thorlabs, model number: FT1500UMT) having a core diameter of 1.5 mm and an NA of 0.39 is used as the optical fiber 204.

  By providing the optical fiber 204, the surface emitting laser array 201 can be placed at a position away from the laser resonator 206. Thereby, the freedom degree of arrangement design can be increased. Further, when the laser device 200 is used as an ignition device, the surface emitting laser array 201 can be moved away from the heat source, so that the range of methods for cooling the engine 300 can be increased.

  The light incident on the optical fiber 204 propagates through the core and is emitted from the + Z side end face of the core.

  The second condensing optical system 205 is disposed on the optical path of the light emitted from the optical fiber 204 and condenses the light. The light condensed by the second condensing optical system 205 enters the laser resonator 206.

  The laser resonator 206 is a Q-switched laser and includes a laser medium 206a and a saturable absorber 206b as shown in FIG. 3 as an example.

  The laser medium 206a is a rectangular parallelepiped Nd: YAG crystal of 3 mm × 3 mm × 8 mm, and Nd is doped by 1.1%. The saturable absorber 206b is a cuboidal Cr: YAG crystal of 3 mm × 3 mm × 2 mm, and has an initial transmittance of 30%.

  Here, the Nd: YAG crystal and the Cr: YAG crystal are joined to form a so-called composite crystal. Both the Nd: YAG crystal and the Cr: YAG crystal are ceramics.

  The light from the second condensing optical system 205 is incident on the laser medium 206a. That is, the laser medium 206a is excited by the light from the second condensing optical system 205. The wavelength of the light emitted from the surface emitting laser array 201 is the wavelength with the highest absorption efficiency in the YAG crystal. The saturable absorber 206b operates as a Q switch.

  The surface on the incident side (−Z side) of the laser medium 206a and the surface on the exit side (+ Z side) of the saturable absorber 206b are subjected to an optical polishing process and serve as a mirror. Hereinafter, for convenience, the incident-side surface of the laser medium 206a is also referred to as a “first surface”, and the exit-side surface of the saturable absorber 206b is also referred to as a “second surface” (see FIG. 3).

  The first surface and the second surface are coated with a dielectric film corresponding to the wavelength of light emitted from the surface emitting laser array 201 and the wavelength of light emitted from the laser resonator 206. .

  Specifically, the first surface has a high transmittance of 99.5% for light with a wavelength of 808 nm and a high reflectance of 99.5% for light with a wavelength of 1064 nm. Has been made. In addition, the second surface is coated with a reflectivity of 50% for light having a wavelength of 1064 nm.

  As a result, the light resonates and is amplified in the laser resonator 206. Here, the resonator length of the laser resonator 206 is 10 (= 8 + 2) mm.

  Returning to FIG. 2, the driving device 220 drives the surface emitting laser array 201 based on an instruction from the engine control device 222. That is, drive device 220 drives surface emitting laser array 201 so that light is emitted from ignition device 301 at the timing of ignition in the operation of engine 300. The plurality of light emitting units in the surface emitting laser array 201 are turned on and off simultaneously.

  In the above embodiment, when it is not necessary to place the surface emitting laser array 201 at a position away from the laser resonator 206, the optical fiber 204 may not be provided.

  Further, each of the first condensing optical system 203, the second condensing optical system 205, and the exit optical system 210 may be composed of a single lens or a plurality of lenses. good.

  Here, the case of an engine (piston engine) in which a piston is moved by combustion gas as an internal combustion engine has been described. However, the present invention is not limited to this. For example, a rotary engine, a gas turbine engine, or a jet engine may be used. In short, what is necessary is just to burn the fuel and generate the combustion gas.

  In addition, the ignition device 301 may be used for cogeneration, which is a system that uses exhaust heat to extract power, heat, and cold to improve energy efficiency comprehensively.

  Although the case where the ignition device 301 is used in an internal combustion engine has been described here, the present invention is not limited to this.

  Although the case where the laser device 200 is used in an ignition device has been described here, the present invention is not limited to this. For example, it can be used for a laser processing machine, a laser peening apparatus, a terahertz generator, and the like.

"Details"
Next, details of the surface emitting laser array 201 will be described. Here, as shown in FIG. 4 as an example, the surface emitting laser array 201 includes a surface emitting laser array chip 230, a submount 232, a heat dissipation member 234, a Peltier element 235, a first metal layer 236, and a second metal. A layer 237 and the like. A composite member composed of the submount 232, the first metal layer 236, and the second metal layer 237 is a holding member that holds the surface emitting laser array chip 230.

  As an example, the surface emitting laser array chip 230 includes a plurality of light emitting units arranged two-dimensionally as shown in FIG. Each light emitting unit is a surface emitting laser (VCSEL). And the YZ cross section of one light emission part is shown by FIG. Here, the surface emitting laser array chip 230 is a large-scale laser array having 10,000 light emitting units.

  Each light emitting unit includes a substrate 101, a buffer layer 102, a lower semiconductor DBR 103, a lower spacer layer 104, an active layer 105, an upper spacer layer 106, an upper semiconductor DBR 107, a contact layer 109, a protective film 111, an upper electrode 113, a lower electrode 114, and the like. have.

  7A, the normal direction of the substrate surface is 15 degrees toward the crystal orientation [1 1 1] A direction with respect to the crystal orientation [1 0 0] direction (as shown in FIG. 7A). (θ = 15 °) An n-GaAs single crystal substrate inclined. That is, the substrate 101 is a so-called inclined substrate. Here, as shown in FIG. 7B, the crystal orientation [0 −1 1] direction is the + X direction, and the crystal orientation [0 1 −1] direction is the −X direction. Therefore, the tilt axis of the tilted substrate is parallel to the X-axis direction. The −Y direction is also referred to as “inclination direction”.

  Returning to FIG. 6, the buffer layer 102 is laminated on the + Z side surface of the substrate 101 and is a layer made of n-GaAs.

The lower semiconductor DBR 103 is stacked on the + Z side surface of the buffer layer 102, and includes 37 pairs of a low refractive index layer made of n-AlAs and a high refractive index layer made of n-Al _0.3 Ga _0.7 As. .5 pairs.

  Between each refractive index layer, in order to reduce an electrical resistance, a composition gradient layer having a thickness of 20 nm in which the composition is gradually changed from one composition to the other composition is provided.

  From the substrate 101 up to about 34.5 pairs, each refractive index layer includes 1/2 of the adjacent composition gradient layer, and the optical thickness is λ / 4 when the oscillation wavelength is λ. In the three pairs close to the lower spacer layer 104, the optical thickness of the high refractive index layer is λ / 4 and the optical thickness of the low refractive index layer includes 1/2 of the adjacent composition gradient layer. Is set to 3λ / 4.

  When the optical thickness is λ / 4, the actual thickness D of the layer is D = λ / 4n (where n is the refractive index of the medium of the layer).

  The lower spacer layer 104 is stacked on the + Z side of the lower semiconductor DBR 103 and is a layer made of non-doped AlGaInP.

The active layer 105 is stacked on the + Z side of the lower spacer layer 104, and a triple quantum well (TQW) in which quantum well layers made of GaAs and barrier layers made of Al _0.3 Ga _0.7 As are alternately stacked. : Triple Quantum Well) active layer.

  The upper spacer layer 106 is stacked on the + Z side of the active layer 105 and is a layer made of non-doped AlGaInP.

  The portion composed of the lower spacer layer 104, the active layer 105, and the upper spacer layer 106 is also referred to as a resonator structure, and includes a half of the adjacent composition gradient layer, and has an optical thickness of one wavelength. It is set so as to be an appropriate thickness. The active layer 105 is provided at the center of the resonator structure at a position corresponding to the antinode in the standing wave distribution of the electric field so that a high stimulated emission probability can be obtained.

The upper semiconductor DBR 107 is laminated on the + Z side of the upper spacer layer 106, and has a low refractive index layer made of p-Al _0.9 Ga _0.1 As and a high refractive index made of p-Al _0.3 Ga _0.7 As. It has 24 pairs of layers.

  A composition gradient layer is provided between the refractive index layers. Each refractive index layer is set to have an optical thickness of λ / 4 including 1/2 of the adjacent composition gradient layer.

  In one of the low refractive index layers in the upper semiconductor DBR 107, a selectively oxidized layer 108 made of p-AlAs is inserted with a thickness of 30 nm. The insertion position of the selectively oxidized layer 108 is a position optically separated from the upper spacer layer 106 by a distance of λ / 4, and is in the low refractive index layer.

  The contact layer 109 is stacked on the + z side of the upper semiconductor DBR 107 and is a layer made of p-GaAs.

The protective film 111 is a film made of SiO ₂ or SiN.

  The upper electrode 113 is electrically connected to the electrode pad.

  Here, a method for producing the surface emitting laser array chip 230 will be described.

(1) A buffer layer 102, a lower semiconductor DBR 103, a lower spacer layer 104, an active layer 105, and an upper portion are formed on a substrate 101 by crystal growth by metal organic vapor phase epitaxy (MOCVD) or molecular beam epitaxy (MBE). A spacer layer 106, an upper semiconductor DBR 107, a selective oxidation layer 108, and a contact layer 109 are formed. Note that a structure in which a plurality of semiconductor layers are stacked on the substrate 101 is also referred to as a “stacked body” for convenience in the following.

Trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as Group III materials, and phosphine (PH ₃ ) and arsine (AsH ₃ ) are used as Group V materials. Further, carbon tetrabromide (CBr ₄ ) and dimethyl zinc (DMZn) are used as the raw material for the p-type dopant, and hydrogen selenide (H ₂ Se) is used as the raw material for the n-type dopant.

(2) A resist pattern corresponding to the mesa shape is formed on the surface of the laminate. Specifically, a photoresist is applied on the contact layer 109, and exposure and development are performed by an exposure apparatus to form a resist pattern corresponding to the mesa shape. Here, the cross section of the mesa is a square with sides of 20 μm to 25 μm. Note that a positive resist is used as a resist applied on the contact layer 109, and exposure is performed by contact exposure.

(3) A square columnar mesa is formed by dry etching such as reactive ion etching (RIE). Here, the bottom of the etching is positioned in the lower spacer layer 104. Note that the inclination angle of the side surface of the mesa can be adjusted by adjusting the dry etching conditions. Here, the dry etching conditions are adjusted so that the inclination angle of the side surface of the mesa is 70 ° to 80 ° with respect to the surface of the substrate 101. In this case, disconnection of the wiring member can be suppressed.

(4) The resist pattern is removed.

(5) The laminated body is heat-treated in water vapor. Here, Al in the selective oxidation layer 108 is selectively oxidized from the outer periphery of the mesa. Then, an unoxidized region 108b surrounded by the Al oxide layer 108a is left in the center of the mesa. As a result, an oxidized constriction structure that restricts the drive current path of the light-emitting portion to only the central portion of the mesa is created. The non-oxidized region 108b is a current passage region (current injection region). Here, the current passing region 108b has a substantially square shape with a side length of about 5 μm.

(6) A protective film 111 made of SiN is formed using a plasma CVD method. The thickness of the protective film 111 may be 150 nm to 200 nm.

(7) Create a resist pattern for forming contact holes on the top surface of the mesa.

(8) The protective film 111 at the opening of the resist pattern is removed by wet etching using BHF (buffered hydrofluoric acid).

(9) The resist pattern is removed.

(10) A resist pattern for masking the injection region is created.

(11) The material of the upper electrode 113 is deposited. Here, a metal film made of Cr / AuZn / Au is sequentially laminated by EB (electron beam) evaporation.

(12) The metal film on the region where the resist pattern is formed is removed by lift-off. Thereby, the upper electrode 113 is formed.

(13) After the back side of the substrate 101 is polished until the thickness of the substrate 101 becomes 200 μm, a metal film made of Cr / AuGe / Au is sequentially laminated by EB (electron beam) vapor deposition to form the lower electrode 114. . Au is set to have a thickness of 1 μm. Note that all of the substrate 101 may be removed.

(14) Annealing is performed at 400 ° C. for 5 minutes to establish ohmic conduction between the upper electrode 113 and the lower electrode 114. Thereby, the mesa becomes a light emitting part.

(15) Divide each chip.

  Returning to FIG. 4, the submount 232 is made of an insulating material. Here, aluminum nitride (AlN) having a thickness of 0.3 mm is used as the submount 232.

  On the surface on the + Z side of the submount 232, nickel (Ni) having a thickness of 1 μm is deposited as a base, and a first metal layer 236 is formed thereon by plating (+ Z side). Further, nickel (Ni) having a thickness of 1 μm is deposited as a base on the −Z side surface of the submount 232, and a second metal layer 237 is formed thereon by plating (−Z side). Has been. The first metal layer 236 and the second metal layer 237 are made of a material having a higher thermal conductivity than the submount 232.

  As shown in FIG. 8 as an example, the first metal layer 236 includes a lower metal layer 236a and an upper metal layer 236b that covers the lower metal layer 236a. The upper metal layer 236b prevents the lower metal layer 236a from being oxidized.

  Here, a copper (Cu) thin film with a thickness of 30 μm is used as the lower metal layer 236a, and a gold (Au) thin film with a thickness of 1 μm is used as the upper metal layer 236b.

  As shown in FIG. 8 as an example, the second metal layer 237 includes a lower metal layer 237a and an upper metal layer 237b that covers the lower metal layer 237a. The upper metal layer 237b prevents the lower metal layer 237a from being oxidized.

  Here, a copper (Cu) thin film with a thickness of 30 μm is used as the lower metal layer 237a, and a gold (Au) thin film with a thickness of 1 μm is used as the upper metal layer 237b. That is, the second metal layer 237 is the same metal layer as the first metal layer 236.

  The surface emitting laser array chip 230 is bonded to the upper metal layer 236b of the first metal layer 236 by a bonding material 231. As the bonding material 231, a gold tin (AuSn) alloy containing 70 wt% of gold (Au) is used.

  The bonding material 231 is deposited to a thickness of 3 μm on the upper metal layer 236b of the first metal layer 236 (see FIG. 9), and the surface emitting laser array chip 230 is placed thereon. Then, the surface emitting laser array chip 230 is heated to 300 ° C. with a heater while applying a load, and then cooled to room temperature, whereby the surface emitting laser array chip 230 and the upper metal layer 236b of the first metal layer 236 are formed. Be joined. That is, the surface emitting laser array chip 230 is held by the holding member.

  The thermal conductivity of aluminum nitride (AlN) is 170 (W / mK), the thermal conductivity of copper (Cu) is 400 (W / mK), and the thermal conductivity of gold (Au) is 318 (W / mK). mK), and the thermal conductivity of nickel (Ni) is 91 (W / mK).

  By the way, as shown in FIGS. 10 and 11 as an example, an insulating groove is formed in the first metal layer 236. 11 is a cross-sectional view taken along line AA in FIG. In this case, the first metal layer 236 on the + X side of the insulating groove can be electrically connected to the lower electrode 114. Further, the upper electrode 113 of each light emitting portion and the first metal layer 236 on the −X side of the insulating groove can be electrically connected by a wiring member.

  The heat dissipation member 234 is made of a material having a smaller thermal expansion coefficient than the second metal layer 237 and a larger thermal expansion coefficient than the submount 232. Here, a copper tungsten (CuW) plate having a thickness of 2 mm is used as the heat dissipation member 234.

  The heat dissipation member 234 is bonded to the upper metal layer 237b of the second metal layer 237 by the bonding material 233. As the bonding material 233, paste solder is used.

The thermal expansion coefficient of copper (Cu) is 16.6 × 10 ^{−6 to} 17 × 10 ⁻⁶ / K, and the thermal expansion coefficient of copper tungsten (CuW) is 6 × 10 ^{−6 to} 9 × 10 ⁻⁶ / K. The thermal expansion coefficient of GaAs is 5.7 × 10 ^{−6 to} 6.8 × 10 ⁻⁶ / K. Moreover, the thermal expansion coefficient of aluminum nitride (AlN) is 4.5 × 10 ^{−6 to} 4.7 × 10 ⁻⁶ / K. However, the thermal expansion coefficient of the material differs somewhat depending on the manufacturing method.

  Further, a Peltier element 235 is attached to the heat radiating member 234.

  By the way, when the surface emitting laser array chip is driven at a high output, a lot of heat is generated in the surface emitting laser array chip. Since the output of a surface emitting laser saturates as the temperature rises, it is necessary to quickly dissipate the generated heat, and it is necessary to mount it on a submount having a high thermal conductivity.

  As disclosed in Patent Document 1, a method of joining a surface emitting laser array chip to a silicon carbide (SiC) submount and further joining the submount to a copper (Cu) heat sink has been devised. In this case, among the plurality of light emitting units, the temperature of the light emitting unit located at the center of the array is particularly high, and the wavelength of light emitted from the light emitting unit may shift.

  In the surface emitting laser array, if the wavelength of the light emitted from the light emitting section is shifted, the laser medium may be insufficiently excited or unstable.

  Here, the thickness of the lower metal layer 236a of the first metal layer 236 in the surface emitting laser array 201 is varied, and the relationship between the spectrum of light emitted from the surface emitting laser array 201 and the thickness of the lower metal layer 236a. I investigated. Here, a surface emitting laser array chip having about 15000 light emitting portions and a light emitting portion interval of about 50 μm was used.

  FIG. 12A shows a spectrum of light emitted from the surface emitting laser array 201 when the thickness of the lower metal layer 236a is 25 μm. FIG. 12B shows a spectrum of light emitted from the surface emitting laser array 201 when the thickness of the lower metal layer 236a is 70 μm. FIGS. 12A and 12B show the results at 200 A (ampere), QCW drive (500 μs, 20 Hz), and room temperature (17 ° C.).

  By the way, in the use of laser light, a single wavelength is often required. In particular, when used as an excitation light source for a solid-state laser, it is desirable that the peak wavelength of the excitation light coincides with the absorption peak wavelength of the solid-state laser (laser medium) and that the spectrum width be narrow (full width at half maximum is 2 nm or less). . According to the experiments by the inventors, the full width at half maximum when the thickness of the lower metal layer 236a is 25 μm is about 1.8 nm, and the full width at half maximum when the thickness of the lower metal layer 236a is 70 μm is about 1.2 nm. there were.

  That is, the surface emitting laser array 201 of the present embodiment can emit light having a narrow spectral width. In the case where there was no first metal layer 236, the full width at half maximum exceeded 2 nm. This is because heat transfer from the surface emitting laser array chip 230 to the submount 232 is promoted by the first metal layer 236, and the temperature rise of the light emitting portion in the surface emitting laser array chip 230 is suppressed. Show.

  Thus, in the surface emitting laser array 201 of this embodiment, the temperature rise of a light emission part can be suppressed. As a result, the laser medium 206a can be stably excited with high power.

  In the surface emitting laser array 201, the surface emitting laser array chip 230 is repeatedly turned on and off. By repeating this, the surface emitting laser array chip 230 is repeatedly heated and cooled. That is, a temperature change occurs in the surface emitting laser array 201.

  In the present embodiment, a first metal layer 236 is provided between the surface emitting laser array chip 230 and the submount 232. In this case, since the first metal layer 236 has higher ductility than the surface emitting laser array chip 230 and the submount 232, the difference in thermal expansion coefficient between the surface emitting laser array chip 230 and the submount 232 is different. Even if it is large, the first metal layer 236 is deformed, so that the thermal stress generated between the surface emitting laser array chip 230 and the submount 232 due to the temperature change can be relaxed. As a result, the bonding quality between the surface emitting laser array chip 230 and the submount 232 can be improved.

  Further, it was found that if the thermal expansion coefficient of the heat radiating member 234 is large, a large thermal stress is generated at the joint portion between the submount 232 and the heat radiating member 234 due to temperature fluctuation, and the joint quality is deteriorated. For example, in such a configuration, it was confirmed that a gap grows at a joint portion between the submount 232 and the heat dissipation member 234 in a temperature cycle test at −55 ° C. to 150 ° C.

  In this embodiment, when the linear expansion coefficient of the surface emitting laser array chip 230 is αLD, the linear expansion coefficient of the feeder line is αp, the linear expansion coefficient of the submount 232 is αs, and the linear expansion coefficient of the heat dissipation member 234 is αh, There is a relationship of αs <αLD <αp ≠ αh and αs <αh <αp. In this case, thermal stress applied to the joint between the submount 232 and the heat dissipation member 234 can be relaxed.

  As is clear from the above description, in the surface emitting laser array 201 according to this embodiment, the surface emitting laser array chip 230 constitutes an array chip in the surface emitting laser array of the present invention, and the submount 232 has an insulating member. It is configured. The submount 232, the first metal layer 236, and the second metal layer 237 constitute a holding member.

  As described above, the surface emitting laser array 201 according to this embodiment includes the surface emitting laser array chip 230, the submount 232, the heat radiating member 234, the Peltier element 235, the first metal layer 236, and the second metal layer 237. Etc.

  The first metal layer 236 is formed on the surface of the submount 232 on the side where the surface emitting laser array chip 230 is held, and has a higher thermal conductivity than the submount 232. The surface emitting laser array chip 230 is bonded to the first metal layer 236 by the bonding material 221.

  In this case, the heat transfer from the surface emitting laser array chip 230 to the submount 232 is promoted, and as a result, the temperature rise of the light emitting part in the surface emitting laser array chip 230 is suppressed, and the wavelength of light emitted from the light emitting part Shift can be suppressed. Therefore, the laser medium 206a can be stably excited with high power. Further, in this case, the temperature difference between the plurality of light emitting units can be made smaller than before.

  In addition, since the first metal layer 236 contains copper, the electric resistance value of the first metal layer 236 can be reduced. Therefore, a large current of 100 ampere can be passed through the surface emitting laser array chip 230.

  In the surface emitting laser array 201, the first metal layer 236 is formed on the + Z side surface of the submount 232, and the second metal layer 237 is formed on the −Z side surface. In this case, warpage of the submount 232 can be suppressed. When the surface emitting laser array chip 230 is bonded, the thickness of the bonding material 221 becomes uniform, and the thermal resistance value can be made uniform in the chip surface.

  Further, in the surface emitting laser array 201, the second metal layer 237 is formed on the −Z side surface of the submount 232, so that solder is used as the bonding material 223 when the heat dissipation member 234 is bonded to the submount 232. Can be used. Furthermore, since the warp of the submount 232 can be suppressed, the film thickness of the solder can be made uniform. Thereby, the thermal resistance value can be made uniform in the chip surface.

  Since the laser device 200 includes the surface emitting laser array 201, the laser device 200 can stably emit high-power laser light.

  Furthermore, since the ignition device 301 includes the laser device 200, stable ignition can be performed.

  Moreover, since the engine 300 includes the ignition device 301, the stability can be improved as a result.

  In the above embodiment, a water cooling device may be used instead of the Peltier element 235.

  In the above embodiment, when the amount of heat generated by the surface emitting laser array chip 230 is small, the Peltier element 235 may be omitted.

  Moreover, although the said embodiment demonstrated the case where aluminum nitride (AlN) was used as a material of the submount 232, it is not limited to this.

  Moreover, although the said embodiment demonstrated the case where the 1st metal layer 236 consists of a copper thin film and a gold thin film, it is not limited to this.

  Moreover, although the said embodiment demonstrated the case where the 1st metal layer 236 consists of two metal layers, it is not limited to this. For example, the first metal layer 236 may be composed of one metal layer.

  Moreover, the above embodiment is also an example for each bonding material, and the present invention is not limited to this.

  Further, in the above embodiment, when it is not necessary to consider the warpage of the submount 232, the second metal layer 237 may be omitted (see FIG. 13).

  Moreover, although the said embodiment demonstrated the case where copper tungsten (CuW) was used as a material of the thermal radiation member 234, it is not limited to this. For example, when the thermal stress generated at the joint between the submount 232 and the heat dissipation member 234 is not very large, copper (Cu) may be used as the heat dissipation member 234.

  In the above embodiment, the thickness of the first metal layer 236 and the thickness of the second metal layer 237 may be different.

  In the above embodiment, the material of the first metal layer 236 and the material of the second metal layer 237 may be different.

  Moreover, although the said embodiment demonstrated the case where the surface emitting laser array 201 was used for the laser apparatus 200 as a light source for excitation, it is not limited to this. The surface emitting laser array 201 may be used in a laser device as a light source that is not for excitation.

<Laser annealing equipment>
As an example, FIGS. 14A and 14B show a schematic configuration of a laser annealing apparatus 1000 as a laser apparatus. The laser annealing apparatus 1000 includes a light source 1010, an optical system 1020, a table device 1030, a control device (not shown), and the like.

  The light source 1010 has the surface emitting laser array 201 described in the above embodiment. The optical system 1020 guides the light emitted from the light source 1010 to the surface of the object P. The table device 1030 has a table on which the object P is placed. The table can move at least along the Y-axis direction.

  For example, when the object P is amorphous silicon (a-Si), when light from the light source 1010 is irradiated, the temperature of the amorphous silicon (a-Si) rises and then gradually cools. Crystallizes to become polysilicon (p-Si).

  In this case, the laser annealing apparatus 1000 can improve the processing efficiency because the light source 1010 has the surface emitting laser array 201.

<Laser processing machine>
As an example, FIG. 15 shows a schematic configuration of a laser processing machine 3000 as a laser apparatus. The laser processing machine 3000 includes a light source 3010, an optical system 3100, a table 3150 on which an object P is placed, a table driving device 3160, an operation panel 3180, a control device 3200, and the like.

  The light source 3010 has a surface emitting laser array 201 and emits light based on an instruction from the control device 3200. The optical system 3100 collects the light emitted from the light source 3010 in the vicinity of the surface of the object P. The table driving device 3160 moves the table 3150 in the X-axis direction, the Y-axis direction, and the Z-axis direction based on instructions from the control device 3200.

  The operation panel 3180 has a plurality of keys for the operator to make various settings and a display for displaying various information. The control device 3200 controls the light source 3010 and the table driving device 3160 based on various setting information from the operation panel 3180.

  In this case, since the light source 3010 has the surface emitting laser array 201, the laser processing machine 3000 can improve the processing efficiency of processing (for example, cutting and welding).

  Note that the laser processing machine 3000 may include a plurality of light sources 3010.

  The surface-emitting laser array 201 is also suitable for an apparatus that uses laser light other than a laser annealing apparatus and a laser processing machine. For example, the surface emitting laser array 201 may be used as a light source of a display device.

  DESCRIPTION OF SYMBOLS 101 ... Substrate, 102 ... Buffer layer, 103 ... Lower semiconductor DBR, 104 ... Lower spacer layer, 105 ... Active layer, 106 ... Upper spacer layer, 107 ... Upper semiconductor DBR, 108 ... Selective oxidation layer, 109 ... Contact layer, DESCRIPTION OF SYMBOLS 111 ... Protective film, 113 ... Upper electrode, 114 ... Lower electrode, 200 ... Laser apparatus, 201 ... Surface emitting laser array, 203 ... 1st condensing optical system, 204 ... Optical fiber, 205 ... 2nd condensing optical system, 206 ... Laser resonator 206a ... Laser medium 206b ... Saturable absorber 207 ... Ejecting optical system (optical system for condensing light emitted from the laser device) 208 ... Protective member 220 ... Drive device 222 ... engine control device, 230 ... surface emitting laser array chip (array chip), 231 ... bonding material, 232 ... submount (insulating member), 233 ... Compound material, 234 ... heat dissipation member, 235 ... Peltier element, 236 ... first metal layer, 236a ... lower metal layer, 236b ... upper metal layer, 237 ... second metal layer, 237a ... lower metal layer, 237b ... upper part Metal layer, 300 ... engine (internal combustion engine), 301 ... ignition device, 302 ... fuel injection mechanism, 303 ... exhaust mechanism, 304 ... combustion chamber, 305 ... piston, 1000 ... laser annealing device (laser device), 1010 ... light source, DESCRIPTION OF SYMBOLS 1020 ... Optical system, 1030 ... Table apparatus, 3000 ... Laser processing machine (laser apparatus), 3010 ... Light source, 3100 ... Optical system, 3150 ... Table, 3160 ... Table drive apparatus, 3180 ... Operation panel, 3200 ... Control apparatus, P …Object.

JP 2014-192166 A

Claims (13)

An array chip having a plurality of light emitting portions;
A holding member for holding the array chip,
The holding member is a surface emitting laser array having an insulating member and a first metal layer formed on a surface of the insulating member on the side where the array chip is held and having a higher thermal conductivity than the insulating member.   2. The surface emitting laser array according to claim 1, wherein the insulating member is aluminum nitride (AlN).   The surface emitting laser array according to claim 1, wherein the first metal layer is made of a material containing at least copper. The array chip is held on the holding member by a bonding material,
The surface emitting laser array according to any one of claims 1 to 3, wherein a material of the bonding material is a gold tin (AuSn) alloy.   The said holding member further has the 2nd metal layer formed in the surface on the opposite side to the surface by which the said array chip is hold | maintained in the said insulating member, The any one of Claims 1-4 characterized by the above-mentioned. The surface emitting laser array according to one item. A heat dissipating member attached to the holding member;
The material of the heat radiating member is a material having a thermal expansion coefficient smaller than that of the second metal layer and a thermal expansion coefficient larger than that of the insulating member. The surface emitting laser array according to 1. A heat dissipating member attached to the holding member;
The surface emitting laser array according to any one of claims 1 to 5, wherein a material of the heat dissipation member is copper (Cu) or copper tungsten (CuW). A laser device for irradiating an object with laser light,
The surface emitting laser array according to any one of claims 1 to 7,
An optical system that guides laser light emitted from the surface-emitting laser array to the object. The surface emitting laser array according to any one of claims 1 to 7,
A laser device comprising: a laser resonator on which laser light from the surface emitting laser array is incident.   The laser device according to claim 9, wherein the laser resonator is a Q-switched laser.   The laser device according to claim 10, wherein the laser resonator includes a laser medium and a saturable absorber. The laser apparatus according to any one of claims 9 to 11,
And an optical system that collects the light emitted from the laser device. In an internal combustion engine that generates combustion gas by burning fuel,
An internal combustion engine comprising the ignition device according to claim 12 for igniting the fuel.

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