Carbon-based optically pumped semiconductor high-energy laser and laser device

Abstract

The present invention discloses a carbon-based optically pumped semiconductor high-energy laser, comprising: a carbon-based material substrate, one side of the carbon-based material substrate is a working surface, and the other side is a heat-conducting surface; an optically pumped semiconductor laser chip, the optically pumped semiconductor laser chip is arranged on the working surface of the carbon-based material substrate, a gain region is provided on the optically pumped semiconductor laser chip, and the energy gain provided by the gain region accounts for at least 95% of the energy gain provided by the optically pumped semiconductor laser chip; a cooling fluid supply device, the cooling fluid supply device is arranged on the heat-conducting surface of the carbon-based material substrate to provide a high-speed impact cooling fluid to conduct heat and cool the carbon-based material substrate. By expanding the working area of ​​the laser chip, the output power of the laser is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of optical equipment, and in particular to a carbon-based optically pumped semiconductor high-energy laser and a laser device. Background Art

[0002] High-energy lasers have a wide range of uses. Carbon-based materials have the characteristics of high thermal conductivity, high strength, and high hardness. Optically pumped semiconductor lasers (OPSL) have the characteristics of high gain, high absorption, wide laser wavelength range, and thin chip thickness.

[0003] The main problem facing the development of high-energy lasers is the treatment of waste heat. In order to dissipate heat better, a larger heat dissipation area is required. The gain material is usually made into a thin layer. High-power slab lasers and disk lasers are typical representatives. However, slab lasers and disk lasers generally use traditional doped crystals as gain regions, which have low gain coefficients and low absorption coefficients for pump light. Thicker crystals have to be used as gain regions. At the same time, the thermal conductivity of crystals is usually not high. Thicker gain regions mean higher thermal resistance and lower laser emission power. Therefore, the laser emission power of traditional slab lasers and disk lasers is limited. If the laser output power is to be further increased, the thickness of the gain region needs to be made thinner.

[0004] Semiconductor lasers have high gain and high absorption characteristics due to their materials, and the thickness of laser chips is usually in the micron range. Traditional edge-emitting semiconductor lasers are usually only used as pump light sources due to their poor beam quality. Surface-emitting semiconductor lasers have circular light spots. At the same time, the chip thickness of optically pumped vertical external cavity surface emitting lasers (Optically Pumped Vertical External-Cavity Surface Emitting Lasers, OP-VECSEL) is only a few microns thick. In recent years, the membrane external cavity surface emitting lasers (Membrane External Cavity Surface-Emitting Laser, MECSEL) have been removed due to the removal of the Bragg reflector (DBR), and the chip thickness is usually less than 1 micron. OP-VECSEL or MECSEL are also collectively referred to as optically pumped semiconductor lasers (OPSL).

[0005] Several kW / cm 2 The threshold pump power density of the order of magnitude is the bottleneck for OPSL to reach high power. When OPSL is working, the equivalent laser emission power density (the ratio of laser emission power to the chip working area) is several 10kW / cm 2, and it is also accompanied by waste heat of the same order of magnitude power density. Waste heat will increase the temperature of the gain region. The characteristics of semiconductor materials are closely related to temperature. The wavelength of the laser will redshift at a rate of 0.3nm / K as the temperature rises. Excessive temperature will also increase the electron concentration in the semiconductor material, increase the movement speed, shorten the carrier lifetime, and increase the laser threshold. When the temperature exceeds 600°C, the semiconductor material is easily oxidized in the air. Usually, the temperature of the semiconductor laser chip cannot exceed 300°C when working. Therefore, the temperature difference between the laser chip working at room temperature and the ambient temperature cannot exceed 300K. The currently reported way for higher-power OPSL to deal with this waste heat is to first use a small-sized high-thermal conductivity material (diamond, SiC, copper, etc.) to diffuse the waste heat on the chip, and then use a water-cooling structure to take the waste heat away. This heat dissipation method of first diffusing and then taking away makes the waste heat generated in the center more difficult to diffuse as the working area (pump spot) becomes larger. The temperature at the center of the pump spot is too high, thus limiting the size of the working area. The highest power reported by OP-VECSEL is 106W, and its spot diameter is only about 1mm.

[0006] If you want to expand the working area of ​​a thin-layer gain material laser and increase the output power of the laser, you need to abandon the original heat dissipation method of diffusing first and then taking it away. Ideally, the waste heat can be taken away in a direction perpendicular to the plane of the thin-layer structure, that is, a one-dimensional heat dissipation method is used. A heat dissipation structure with one-dimensional heat dissipation capability will not have too much impact on the temperature at the center of the working area when the working area of ​​the laser chip is expanded (of course, if the diffusion of waste heat parallel to the plane is taken into account, the heat dissipation effect of the heat dissipation structure will be better). One-dimensional heat dissipation requires that the load heat flux density of the cooling component is consistent with the waste heat density generated in the laser working area.

[0007] There are three ways to transfer heat: thermal radiation, thermal conduction and thermal convection. Among these three heat transfer methods, liquid thermal convection has the strongest heat dissipation capacity. Efficient cooling methods usually use liquid convection heat transfer to transfer waste heat. According to literature reports, among efficient cooling methods, the maximum load heat flux density of microchannel cooling can reach 5kW / cm 2 The jet impact cooling capacity is large and the load heat density can reach 10kW / cm 2 This requires that the waste heat density generated by the laser during operation should not be greater than 10kW / cm 2 The existing OPSL laser threshold pump light power density is as high as several kW / cm 2 , 10kW / cm 2 The heat load capacity is only 2-5 times the threshold power density of the laser, so the efficiency of the existing OPSL working under one-dimensional heat dissipation conditions will be very low. To achieve one-dimensional heat dissipation of OPSL, the waste heat density of the laser needs to be reduced to 10kW / cm2 Below, the laser threshold power density is reduced to 1kW / cm 2 the following.

[0008] In our previously filed patent (application number: 202011263399.4), we optimized the chip structure of an optically pumped semiconductor laser (OPSL) and reduced its threshold power density to 100W / cm 2 The waste heat density can be controlled at 10kW / cm during operation. 2 The following is consistent with the maximum load heat density of the efficient jet impingement cooling method.

[0009] Jet impact cooling generally uses high-speed water flow to carry away waste heat. High-speed water flow has very strong impact force and very high pressure, and has high requirements on the strength and hardness of the impacted material. The brittle and thin semiconductor material chip obviously cannot withstand such high impact force and pressure. In recent years, the technology of artificially synthesizing carbon-based materials such as diamond and SiC using CVD (Chemical Vapor Deposition) has developed rapidly. CVD diamond with a diameter of more than ten millimeters has been commercially mass-produced, and the size of SiC single crystal can reach 6-8 inches. Carbon-based materials represented by diamond and SiC have high hardness and high strength, which can withstand the strong impact force and pressure of jet impact cooling. The thermal conductivity of diamond is as high as 2000W / m K, ranking first among all known substances, which is 5 times that of pure copper (400W / m K), the metal material with the highest thermal conductivity. The thermal conductivity of SiC is also 490W / m K, which is higher than pure copper. The high thermal conductivity of carbon-based materials can quickly conduct waste heat in the chip to the impact surface. Summary of the invention

[0010] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a carbon-based optically pumped semiconductor high-energy laser, which can improve the heat dissipation capacity of the laser, thereby increasing the output power of the laser.

[0011] The present invention also provides a laser device having the above-mentioned carbon-based optically pumped semiconductor high-energy laser.

[0012] The carbon-based optically pumped semiconductor high-energy laser according to the first aspect of the present invention comprises:

[0013] A carbon-based material substrate, wherein one side of the carbon-based material substrate is a working side and the other side is a heat-conducting side;

[0014] An optically pumped semiconductor laser chip, wherein the optically pumped semiconductor laser chip is arranged on the working surface of the carbon-based material substrate, and a gain region is provided on the optically pumped semiconductor laser chip, and the energy gain provided by the gain region accounts for at least 95% of the energy gain provided by the optically pumped semiconductor laser chip;

[0015] A cooling fluid supply device is provided on the heat-conducting surface of the carbon-based material substrate to provide high-speed impact cooling fluid to conduct heat and cool the carbon-based material substrate.

[0016] The carbon-based optically pumped semiconductor high-energy laser according to the embodiment of the present invention has at least the following beneficial effects: utilizing the high gain, high absorption, small thickness and other characteristics of the optically pumped semiconductor laser, combining the high thermal conductivity, high hardness and high strength characteristics of the carbon-based material, and taking one-dimensional heat dissipation and convection heat transfer conditions as theoretical basis, the convection heat transfer capacity of the cooling fluid and the carbon-based material substrate is matched with the waste heat density generated in the gain region when the optically pumped semiconductor high-energy laser is working, and the output power of the laser is increased by expanding the working area of ​​the laser chip.

[0017] According to some embodiments of the present invention, the thickness of the gain region does not exceed 20 μm.

[0018] According to some embodiments of the present invention, the distance between the gain region and the carbon-based material substrate does not exceed 50 μm.

[0019] According to some embodiments of the present invention, the thickness of the carbon-based material substrate is greater than 100 μm and less than 2000 μm.

[0020] According to some embodiments of the present invention, the cooling fluid provided by the cooling fluid supply device is in direct contact with the heat-conducting surface of the carbon-based material substrate or the minimum distance therebetween does not exceed 100 μm.

[0021] According to some embodiments of the present invention, the cooling fluid supply device provides a high-speed fluid with a flow rate exceeding 100 m / s to impact the heat-conducting surface of the carbon-based material substrate to achieve heat dissipation.

[0022] According to some embodiments of the present invention, the heat-conducting surface of the carbon-based material substrate is provided with a microstructure to expand the heat exchange area between the carbon-based material substrate and the cooling fluid.

[0023] The laser device according to the second embodiment of the present invention includes a laser device body and the above-mentioned carbon-based optically pumped semiconductor high-energy laser.

[0024] The laser device according to the embodiment of the present invention has at least the following beneficial effects: the laser device using the above-mentioned carbon-based material combined with the optically pumped semiconductor laser chip makes the convection heat transfer capacity of the cooling fluid and the carbon-based material substrate match the waste heat density generated in the gain region when the optically pumped semiconductor high-energy laser is working, and the output power of the laser device is increased by expanding the working area of ​​the laser chip. According to some embodiments of the present invention, the laser device body provides an atmospheric pressure working environment exceeding 2atm for the carbon-based optically pumped semiconductor high-energy laser.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0027] Figure 1 This is a schematic diagram of the structure of a carbon-based optically pumped semiconductor high-energy laser according to an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of an embodiment of a carbon-based optically pumped semiconductor high-energy laser;

[0029] Figure 3 The figure is a schematic diagram of the structure of an embodiment of an optically pumped semiconductor laser chip.

[0030] Reference numerals:

[0031] Optically pumped semiconductor laser chip 1, gain region 11, Bragg reflector 12, chip window layer 13, chip surface reflective film 14, gain region barrier 112, quantum well 111;

[0032] Carbon-based material substrate 2, cooling fluid supply device 3, laser resonant cavity 4, resonant cavity laser standing wave 5, output coupling mirror 6, pump light 7, pump light source 8, collimation system 9. DETAILED DESCRIPTION

[0033] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0034] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0035] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0036] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0037] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0038] like Figure 1 As shown, the carbon-based optically pumped semiconductor high-energy laser according to an embodiment of the present invention comprises:

[0039] A carbon-based material substrate 2, wherein one side of the carbon-based material substrate 2 is a working side and the other side is a heat-conducting side;

[0040] An optically pumped semiconductor laser chip 1, wherein the optically pumped semiconductor laser chip 1 is arranged on a working surface of a carbon-based material substrate 2, and a gain region 11 is provided on the optically pumped semiconductor laser chip 1, wherein the energy gain provided by the gain region 11 accounts for at least 95% of the energy gain provided by the optically pumped semiconductor laser chip 1;

[0041] The cooling fluid supply device 3 is arranged on the heat-conducting surface of the carbon-based material substrate 2 to provide high-speed impact cooling fluid to conduct heat and cool the carbon-based material substrate 2.

[0042] refer to Figures 1 to 3As shown, by utilizing the high gain, high absorption, and small thickness characteristics of the optically pumped semiconductor laser chip 1, combined with the high thermal conductivity, high hardness, and high strength characteristics of the carbon-based material substrate 2, and taking one-dimensional heat dissipation and convection heat transfer conditions as theoretical basis, the convection heat transfer capacity of the cooling fluid and the carbon-based material substrate 2 is matched with the waste heat density generated by the gain region 11 when the optically pumped semiconductor laser chip 1 is working. Reduce the thickness of the waste heat passing through each layer of material, and reduce the thermal resistance between the gain region 11 and the carbon-based material substrate 2. Utilize the strength and high hardness characteristics of the carbon-based material substrate 2 to increase the velocity of the impact cooling fluid to obtain a higher convection heat transfer coefficient, thereby improving the heat dissipation capacity of the laser, and by expanding the working area of ​​the laser chip, increase the output power of the laser.

[0043] In some embodiments of the present invention, the thickness of the gain region 11 does not exceed 20 μm.

[0044] Specifically, refer to Figures 1 to 3 As shown, the gain region 11 is the core of the optically pumped semiconductor laser chip 1 , providing gain for the laser in the laser resonant cavity 4 when the laser is working. Most of the waste heat generated when the laser chip is working also comes from the gain region 11 .

[0045] In the optically pumped semiconductor laser chip 1, the thickness of the gain region 11 is relatively thin. When the laser output is designed to be large enough, the diameter of the working area is much larger than the thickness of the gain region 11. At this time, the conduction and diffusion of waste heat on the side of the optically pumped semiconductor laser chip 1 is negligible relative to the thin layer plane, and the direction of heat flow is the normal direction of the thin layer plane. At this time, the heat conduction can be regarded as one-dimensional heat conduction.

[0046] In the heat dissipation structure of the present invention, the direction of the gain region 11 plane pointing to the carbon-based material substrate 2 and the cooling fluid of the cooling fluid supply device 3 is the heat conduction direction, and this direction is set as the z-axis direction of the coordinate system. Assume that the boundaries of the gain region 11 along the z-axis direction are z0 and z1 respectively. 11 The position of z0 <z 11 <z1,z 11 The waste heat load conducted per unit time at position z0 to z 11 Total waste heat power generated at

[0047]

[0048] Where g(z) is the heat generated in the volume of the micro-unit of the gain region 11, and ΔS is the area of ​​the calculated micro-unit perpendicular to the z-axis.

[0049] Since ΔS is independent of z, it can be mentioned before the integral sign as a constant

[0050]

[0051] z 11 The heat flux density at can be expressed as

[0052]

[0053] If the waste heat generated in the gain region 11 is uniformly distributed in the z-axis direction, then g(z) = g.

[0054]

[0055] According to Fourier's law

[0056]

[0057] Where k is the thermal conductivity of the material. Calculate z 11 Temperature gradient along the axis

[0058]

[0059] where k gain represents the thermal conductivity of the material in the gain region 11. The temperature difference between z0 and z1 in the gain region is

[0060]

[0061] The thickness of the gain region 11 is

[0062] d gian =(z1-z0).

[0063] Heat flux density at the interface z1 of gain region 11

[0064]

[0065] The temperature difference between the gain zone z0 and z1, i.e. the internal temperature rise of the gain zone, can also be expressed as

[0066]

[0067] It can be seen that under the same heat load density condition, the temperature difference between the upper and lower surfaces of the gain region 11 is proportional to the thickness of the gain region 11. The thinner the gain region 11 is designed, the smaller the temperature difference between the inside and outside of the gain region 11. gain =10kW / cm 2 Under the condition of heat load density, if the thermal conductivity k of the material in the gain region 11 is gain =50W / mK, gain region 11 thickness d gian = 20μm, the temperature rise inside the gain region 11 is 20K, which is acceptable. gian=200μm, the internal temperature rises to 200K, which is obviously unacceptable. Therefore, the thickness of the gain region 11 is set to no more than 20μm. In contrast, the thermal conductivity of the YAG crystal commonly used in traditional doped crystal lasers is only k YAG =14W / mK, taking 10at.% Yb-YAG crystal as an example, its absorption coefficient for pump light is 11cm -1 To obtain 90% absorption efficiency of pump light, the crystal thickness needs to reach 4.2 mm. Even if the pump light is allowed to pass through the crystal 10 times (the optical path will be more complicated in this case), the thickness needs to reach d YAG =210μm, even at 1kW / cm 2 Under the heat load density, the temperature inside the gain region 11 rises to 75K. Meanwhile, a lower heat load density also means a lower laser output power. Therefore, semiconductor materials with high gain, high absorption and only micrometer-level thickness are ideal choices for gain materials.

[0068] In some embodiments of the present invention, the distance between the gain region 11 and the carbon-based material substrate 2 is no more than 50 μm.

[0069] For details, refer to 2 and Figure 3 As shown, the waste heat generated by the laser operation is conducted from the gain region 11 and then conducted along the z-axis toward the carbon-based material substrate 2 and the cooling fluid supply device 3. It also needs to pass through various functional layer materials, such as the Bragg reflector (DBR) as the laser resonant cavity mirror, the solder layer formed by welding the optically pumped semiconductor laser chip 1 and the carbon-based material substrate 2, etc. These functional layers may be part of the optically pumped semiconductor laser chip 1 (such as DBR), or they may exist independently (such as solder layer). Under the one-dimensional heat dissipation approximation, it is assumed that the waste heat is conducted through n layers of different materials to the cooling fluid, and the thickness and thermal conductivity of the i-th layer of material are d i and k i , the temperature difference ΔT between the front and back surfaces of each layer of material can be obtained by Fourier's law i Satisfy the formula

[0070]

[0071] R i =d i / k iDefined as the thermal resistance of this layer of material, the thermal resistance is proportional to the thickness d of the material and inversely proportional to the thermal conductivity k of the material. Due to the conservation of energy in the heat conduction process (under the assumption of one-dimensional heat dissipation, the diffusion of waste heat parallel to the plane is ignored), if the thermal resistance of the two layers of medium is the same, then the temperature difference between the front and back contact surfaces of the medium is also the same, and the thermal conductivity of the two can be regarded as the same. The temperature difference between the two contact surfaces of each layer of the structure is the product of the heat density and the thermal resistance. To reduce the temperature rise of the gain region 11 when the laser is working, it is necessary to reduce the thermal resistance of the material. From the continuity of temperature, it can be obtained that the temperature difference between the interface z1 of the gain region 11 and the back surface of the nth layer of material

[0072]

[0073] The total thermal resistance R is the sum of the thermal resistances of the materials in each layer. To reduce the temperature rise of the gain region 11, it is only necessary to reduce the total thermal resistance of the material. One is to select a material with high thermal conductivity, and the other is to reduce the thickness of the material. In the functional layer, the choice of materials is very limited, so the material needs to be as thin as possible. Therefore, the present invention sets the characteristic that the distance between the gain region 11 and the flat carbon-based material is set to no more than 50μm, so as to reduce the thermal resistance between the gain region 11 and the carbon-based material substrate 2.

[0074] In some embodiments of the present invention, the thickness of the carbon-based material substrate 2 is greater than 100 μm and less than 2000 μm.

[0075] Specifically, the carbon-based material substrate 2, as a core component for heat dissipation, plays a very critical role in the present invention. High-energy power lasers have very high waste heat density and require jet impact cooling. High-speed water flow is generally used for heat dissipation. High-speed water flow has very strong impact force and very high pressure. Carbon-based materials have the characteristics of high hardness. Diamond and SiC are ranked first and second in hardness among known materials. High-hardness carbon-based materials will not be cut by the "water knife" formed by high-speed water flow.

[0076] Jet impact will generate very high pressure. The compressive strength of thin layer materials is proportional to the square of their thickness. Too thin carbon-based material substrate 2 is not enough to withstand the impact force caused by jet impact. The present invention sets the thickness characteristic of carbon-based material substrate 2 to be greater than 100μm. The carbon-based material substrate 2 has a very high thermal conductivity. The thermal conductivity of diamond can reach 2000W / (m K), which is 5 times that of pure copper, the metal with the best thermal conductivity. Under the same thermal resistance setting, the thickness of diamond can be designed to be 5 times that of pure copper. At the same time, the mechanical properties of diamond are much better than those of pure copper. Therefore, the impact resistance of the carbon-based material substrate 2 is nearly 2 orders of magnitude higher than that of metallic copper.

[0077] An overly thick carbon-based material substrate 2 will produce excessive thermal resistance. According to the one-dimensional heat dissipation theory, the thermal resistance of the carbon-based material substrate 2 is 10 kW / cm2 Under the condition of heat load density, even the temperature difference of diamond with the highest thermal conductivity on both sides of the 1000μm thick plate is 21K. Considering that the heat load density may be less than 10KW / cm 2 , the present invention sets the thickness of the carbon-based material to be less than 2000 μm.

[0078] The carbon-based material substrate 2 in the present invention also plays the role of heat storage and heat uniformity. The use of a thicker carbon-based material substrate 2 can store more thermal energy, so that the gain region 11 heats up more slowly, which can effectively prevent the instantaneous waste heat density from being too high (such as when the laser is suddenly detuned) and causing the laser chip to be damaged by high temperature. The waste heat density in the gain region 11 may be unevenly distributed, and the carbon-based material substrate 2 with high thermal conductivity will diffuse the local high-density heat to the surroundings, making the heat distribution in the gain region 11 more uniform. This effect will be more obvious when the material of the gain region 11 is a quantum dot or quantum wire structure.

[0079] In some embodiments of the present invention, the cooling fluid provided by the cooling fluid supply device 3 is in direct contact with the heat-conducting surface of the carbon-based material substrate 2 or the minimum distance therebetween does not exceed 100 μm.

[0080] The cooling fluid provided by the cooling fluid supply device 3 is in direct contact with the heat-conducting surface of the carbon-based material substrate 2. If other expansion layers are added to the heat-conducting surface of the carbon-based material substrate 2, such as adding a microstructure to expand the contact area, the thickness of the expansion layer does not exceed 100 μm. Because the thermal conductivity of the material is not too high, between 50-500 W / (m K), the thermal conductivity of the material under one-dimensional heat conduction conditions determines that this interval cannot exceed 100 μm.

[0081] In some embodiments of the present invention, the cooling fluid supply device 3 provides a high-speed fluid with a flow rate exceeding 100 m / s to impact the heat-conducting surface of the carbon-based material substrate 2 to achieve heat dissipation.

[0082] The carbon-based material substrate 2 and the cooling fluid exchange heat by means of convection heat transfer. The Newtonian cooling law describes the magnitude of the convection heat transfer or the heat transfer rate, and its expression is:

[0083] Q=hAΔT c

[0084] Where Q is the heat transfer power, h is the heat transfer coefficient, A is the heat exchange area, ΔT c is the convective heat transfer temperature difference.

[0085] If the contact surface of the carbon-based material substrate 2 with the cooling fluid is a plane, then A = S, where S is the normal plane section area in the heat conduction direction in the calculation area. Load heat density

[0086]

[0087] To obtain a higher load heat density, the heat transfer coefficient h value of the heat dissipation structure can be increased when it is working.

[0088] The heat transfer coefficient h is a physical quantity that is positively correlated with the flow rate of the cooling fluid. Existing high-pressure water guns can spray high-speed water flows of up to 1000m / s. When such high-speed water flows impact the surface of carbon-based materials, the heat transfer coefficient h will also become quite high.

[0089] In some embodiments of the present invention, the heat-conducting surface of the carbon-based material substrate 2 is provided with a microstructure to expand the heat exchange area between the carbon-based material substrate 2 and the cooling fluid.

[0090] According to Newton's cooling law, A is the heat exchange area. By designing or adding microstructures on the heat-conducting surface of the carbon-based material substrate 2, the heat exchange area can be increased so that A / S>1, thereby improving the heat dissipation capacity of the heat dissipation structure.

[0091] The present invention also discloses a laser device made of the carbon-based optically pumped semiconductor high-energy laser, comprising a laser device body and the carbon-based optically pumped semiconductor high-energy laser.

[0092] By adopting the laser device made of the above-mentioned carbon-based optically pumped semiconductor high-energy laser, the heat dissipation capacity of the laser device is improved, thereby being able to increase the upper limit of the output power of the laser device.

[0093] In some embodiments of the present invention, the laser device body provides a working environment of an atmospheric pressure exceeding 2 atm for a carbon-based optically pumped semiconductor high-energy laser.

[0094] Under standard atmospheric pressure, the freezing point of pure water is 0°C and the boiling point is 100°C, so ΔT < 100K. However, under high pressure, the boiling point of water increases. For example, under 2atm pressure, the boiling point of water reaches 119°C, and under 10atm pressure, the boiling point of water reaches 179°C. Therefore, when carbon-based optically pumped semiconductor high-energy lasers work under high pressure, the ΔT value can be increased to obtain a higher load heat density.

[0095] The following is a specific example for explanation. Figure 2 and Figure 3 As shown:

[0096] Gain zone 11 sets a group of 4 consecutive In 0.17 Ga 0.83As material quantum well 111, well width Lw = 8nm, adjacent quantum wells are spaced 6nm apart, laser emission wavelength is 980nm; gain region barrier material is GaAs, gain region 11 total thickness is designed to be 25 half wavelengths (λ / 2n), thickness is 3.477μm, less than the 20μm described in the characteristic of the present invention. Optically pumped semiconductor laser chip 1 grows a Bragg reflector 12 behind gain region 11, with a reflectivity of up to 99.99% for 980nm emission laser wavelength, grown using 28.5 pairs of GaAs and AlAs semiconductor materials, with a thickness of 4.320 microns. The surface of the optically pumped semiconductor laser chip 1 is coated with a reflective film 14 as shown in Table 1. The reflectivity of the film layer to the 980nm wavelength laser that is incident into the air inside the optically pumped semiconductor laser chip 1 is 87%, so that the gain region 11 forms a Fabry-Perot cavity (FB cavity) between the reflective film 14 and the Bragg reflector 12. When the laser is working, the laser intensity in the cavity is 7.7 times the intensity of the external cavity.

[0097] Table 1 The arrangement order and refractive index of the six-layer dielectric film used in the chip surface reflective film 14

[0098] Serial number Material Thickness(nm) Refractive Index 1 Al2O3 151 1.621 2 TiO2 128 2.300 3 SiO2 169 1.451 4 TiO2 128 2.300 5 SiO2 169 1.451 6 TiO2 128 2.300

[0099] The quantum well material gain coefficient g0 is taken as 2000cm -1 , transparent carrier concentration N0 = 1.7 × 10 18 cm -3 , the single-molecule recombination coefficient of carriers in the quantum well is A = 1.0×10 7 s -1 , bimolecular recombination coefficient B = 1.0 × 10 - 10 cm 3 s -1 , Auger recombination coefficient C = 6.0 × 10 -30 cm 6 s -1 , the loss factor T of the laser in the external cavity loss =99%. Through simulation calculation, when the reflectivity R2 of the coupling output mirror 2 is 98.5%, the threshold power density is I th =407W / cm 2 ; If the reflectivity of the coupling output mirror 2 is R2 = 96%, the threshold power density is I th =554W / cm 2 The reflectivity of the reflective film 14 shown in Table 1 for the pump light of 808 nm incident from air at an incident angle of 30 degrees is only 0.5%. The absorption coefficient of the pump light in the chip is α = 13000 cm -1 The gain region with a thickness of 3.477 μm has an absorption rate of up to 99% for the incident pump light, and the total absorption rate of the pump light is ηabs =98.5%. The quantum efficiency of 808nm pump light output to excite 980nm pump light is η q =82.4%. Loss factor T loss The reflectivity of the output mirror is 96%, and the loss factor T loss =99%, Bragg reflector reflectivity R DBR = 99.99% laser coupling output efficiency η out =79%, the slope efficiency η of the laser can be calculated when the reflectivity of the coupling output mirror is 96% slop =0.645. Assume that all the energy of the pump light other than that converted into laser light is converted into waste heat in the gain region (the actual situation will be lower than this value). Then the equivalent laser output power density I on the chip when the laser is working laser and waste heat density q and pump power density I pump Satisfies the following expression:

[0100] I laser =(I punp -I th )η slop

[0101] q=I pump -I laser

[0102] Taking the output mirror reflectivity of 96% as an example, when the waste heat density q = 10kW / cm 2 In the case of pump =27kW / cm 2 , which is equivalent to the laser output power density I laser =17kW / cm 2 , the laser light conversion efficiency is about 63%. If the heat dissipation structure works under half load conditions, that is, q = 5000W / cm 2 , pump power density I pump =13kW / cm 2 , the laser output power is I laser =8kW / cm 2 , the light-to-light conversion efficiency is about 61%.

[0103] At waste heat density q = 10 kW / cm 2 In the case of , the thickness of the gain region 11 is 3.477 μm, and the main material of the gain region 11 is GaAs, and its thermal conductivity k gain =24W / mK, the internal temperature rise of the gain region 11 can be calculated to be ΔT0 = 7.24K, the DBR thickness is 4.320μm, and its thermal conductivity k DBR=61W / mK, it can be calculated that the DBR temperature rise ΔT1 = 7.08K, the optically pumped semiconductor laser chip 1 and the carbon-based material substrate 2 are bonded by indium soldering, the thickness of the indium soldering is 10μm, and the thermal conductivity k In =84W / mK, the temperature rise caused by indium soldering can be calculated to be ΔT2 = 11.9K. The carbon-based material substrate 2 uses a 0.5mm thick diamond sheet with a thermal conductivity k d = 2000 W / mK, it can be calculated that the temperature rise caused by the diamond is ΔT2 = 25 K. Then the temperature difference from the inside of the gain region 11 to the diamond water-cooled impact surface is ΔT = ΔT0 + ΔT1 + ΔT2 + ΔT3 = 51.2K.

[0104] If the temperature of the diamond water-cooled impact surface is 120° C. (approximately the boiling point of water at a pressure of 2 atm) during operation, the temperature of the gain region 11 is approximately 170° C. The optically pumped semiconductor laser chip 1 can operate normally at this temperature.

[0105] When using water close to the freezing point (0°C) for shock cooling, the convective heat transfer temperature difference ΔT c = 120K. When the water flow directly impacts the diamond surface, the heat exchange area A = S, q = 10kW / cm 2 The heat transfer coefficient h required for the heat load is 8.3×10 5 W / K m 2 , which can be obtained by increasing the velocity of the impact water flow. If a microstructure that increases the heat dissipation area is added so that A = 5S, the heat transfer coefficient h only needs to reach 1.6×10 5 W / K m 2 , this instruction is easy to achieve.

[0106] In the calculation of this embodiment, the heat conduction adopts a one-dimensional approximation. Under the one-dimensional approximation condition, the diffusion of heat in the plane direction of the flat plate structure is not considered. Therefore, when the laser working area is increased, that is, when the pump spot diameter is increased, the temperature rise of the gain region 11 will not exceed the simulated calculation value. By increasing the pump spot size, a higher energy laser output can be obtained. 3 W / cm 2 Under the laser output conditions, a spot with a diameter of 13mm can obtain a laser output of more than 10,000W.

[0107] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0108] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A carbon-based optically pumped semiconductor high-energy laser, characterized in that: include: A carbon-based material substrate, wherein one side of the carbon-based material substrate is a working side and the other side is a heat-conducting side; An optically pumped semiconductor laser chip, wherein the optically pumped semiconductor laser chip is arranged on the working surface of the carbon-based material substrate, a gain region is provided on the optically pumped semiconductor laser chip, the energy gain provided by the gain region accounts for at least 95% of the energy gain provided by the optically pumped semiconductor laser chip, the thickness of the gain region does not exceed 20 μm, and the distance between the gain region and the carbon-based material substrate does not exceed 50 μm; A cooling fluid supply device is provided on the heat-conducting surface of the carbon-based material substrate to provide high-speed impact cooling fluid to conduct heat and cool the carbon-based material substrate.

2. The carbon-based optically pumped semiconductor high-energy laser according to claim 1, characterized in that: The thickness of the carbon-based material substrate is greater than 100 μm and less than 2000 μm.

3. The carbon-based optically pumped semiconductor high-energy laser according to claim 1, characterized in that: The cooling fluid provided by the cooling fluid supply device is in direct contact with the heat-conducting surface of the carbon-based material substrate or the minimum distance is no more than 100 μm.

4. The carbon-based optically pumped semiconductor high-energy laser according to claim 3, characterized in that: The cooling fluid supply device provides a high-speed fluid with a flow rate exceeding 100 m / s to impact the heat-conducting surface of the carbon-based material substrate to implement heat dissipation.

5. The carbon-based optically pumped semiconductor high-energy laser according to claim 4, characterized in that: The heat-conducting surface of the carbon-based material substrate is provided with a microstructure to expand the heat exchange area between the carbon-based material substrate and the cooling fluid.

6. A laser device, characterized in that: The invention comprises a laser device body and the carbon-based optically pumped semiconductor high-energy laser according to any one of claims 1 to 5.

7. The laser device according to claim 6, characterized in that: The laser device body provides a working environment with an atmospheric pressure exceeding 2 atm for the carbon-based optically pumped semiconductor high-energy laser.

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