Semiconductor laser end face pumped laser gain module and manufacturing method thereof

Abstract

The invention discloses a laser gain module for end face pumping of a semiconductor laser and a manufacturing method thereof, and relates to the technical field of all-solid-state laser. The laser gain module of the semiconductor laser end face pump comprises a composite laser gain crystal. The composite laser gain crystal comprises a front-section non-doped optical crystal and a rear-section doped laser gain crystal; the front-section non-doped optical crystal is in a frustum shape, and the conical surface of the front-section non-doped optical crystal is used for refracting and converging incident pump light into the rear-section doped laser gain crystal; the composite laser gain crystal is immersed in the cooling liquid, and the refractive index of the cooling liquid is smaller than that of the optical crystal. By implementing the technical scheme provided by the invention, the effective convergence area of the pump light can be prolonged, so that the longer laser gain crystal can obtain sufficient pump excitation, thereby improving the gain efficiency of the laser.

Description

Technical Field

[0001] The present invention relates to the field of all-solid-state laser technology, and in particular to a semiconductor laser end-pumped laser gain module and a manufacturing method thereof. Background Art

[0002] Laser gain medium is an important component of all-solid-state lasers. In order to obtain high-power laser output, it is necessary to increase the length of the laser gain medium to expand the effective pump excitation volume. Among various pumping methods, end pumping has become the main technical solution for pumping laser gain medium because it can provide higher pump power density and good beam quality.

[0003] At present, the commonly used end-pumping scheme is to use a semiconductor laser as a pump source, collimate and focus the pump light output by the semiconductor laser through a lens group, and form a high-power density pump light field on the end face of the gain medium. This scheme enhances the laser gain effect by increasing the power density of the pump light.

[0004] However, since the pump light emitted by the semiconductor laser has poor beam quality, the high power density area formed by lens focusing is short, which makes it impossible for the pump light to maintain effective power density over a long distance, making it impossible for crystals over a certain length to obtain sufficient pump excitation, thus limiting the gain efficiency and output power of the solid-state laser. Summary of the invention

[0005] The present invention provides a semiconductor laser end-pumped laser gain module and a manufacturing method thereof, which can extend the effective focusing area of ​​pump light, so that a longer laser gain crystal can obtain sufficient pump excitation, thereby improving the gain efficiency of the solid laser.

[0006] In a first aspect of the present invention, there is provided a semiconductor laser end-pumped laser gain module, comprising a composite laser gain crystal; The composite laser gain crystal comprises a front-end non-doped optical crystal and a rear-end doped laser gain crystal; The front-end non-doped optical crystal is in the shape of a truncated cone, and the conical surface of the front-end non-doped optical crystal is used to refract and converge the incident pump light into the rear-end doped laser gain crystal; The composite laser gain crystal is immersed in a cooling liquid, and the refractive index of the cooling liquid is smaller than the refractive index of the optical crystal.

[0007] In some embodiments, the front-end non-doped optical crystal and the back-end doped laser gain crystal use the same matrix material and are connected by bonding or fusion.

[0008] In some embodiments, the difference between the refractive index of the cooling liquid and the refractive index of the matrix material is less than 0.2.

[0009] In some embodiments, a cooling and clamping mechanical structure is further included, wherein a sealed space is formed between the cooling and clamping mechanical structure and the composite laser gain crystal, and the cooling liquid is filled in the sealed space.

[0010] In some embodiments, the cooling clamping mechanical structure is provided with a cooling liquid input port and a cooling liquid output port so that the cooling liquid can flow in the sealed space.

[0011] In some embodiments, a pump light reflector is further included. The pump light reflector is disposed at the output end of the back-end doped laser gain crystal and is used to reflect unabsorbed pump light.

[0012] In some embodiments, the first bottom surface of the non-doped optical crystal in the front section is coated with a film system for enhancing the transmittance of pump light and laser light; Among them, the first bottom surface is the bottom surface with a larger cross-sectional area among the two bottom surfaces of the front-end non-doped optical crystal in a frustum shape, and the second bottom surface is the bottom surface with a smaller cross-sectional area among the two bottom surfaces of the front-end non-doped optical crystal in a frustum shape.

[0013] In some embodiments, a dichroic mirror is further included. The dichroic mirror is arranged on the incident light path of the composite laser gain crystal, and the dichroic mirror is coated with a film system that increases the transmittance of pump light and has high reflectivity for laser light.

[0014] In some embodiments, it further includes: a semiconductor laser and a collimating lens; The semiconductor laser is used to emit pump light; The collimating lens is arranged between the semiconductor laser and the composite laser gain crystal, and is used for collimating the pump light.

[0015] In a second aspect of the present invention, a method for manufacturing a laser gain module for end-pumping of a semiconductor laser is provided, comprising: The front-end non-doped optical crystal and the back-end doped laser gain crystal are connected by bonding or fusing to form a composite laser gain crystal, wherein the front-end non-doped optical crystal is in a frustum shape, and the conical surface of the front-end non-doped optical crystal is used to refract and converge the incident pump light into the back-end doped laser gain crystal; The composite laser gain crystal is immersed in a cooling liquid having a refractive index less than that of the optical crystal.

[0016] In summary, one or more technical solutions provided in the present invention have at least the following technical effects or advantages: By using a composite laser gain crystal and immersing it in a coolant with a refractive index lower than that of the optical crystal, the conical surface of the non-doped optical crystal at the front section can refract and converge the incident pump light, and the pump light is incident on the doped laser gain crystal at the rear section after passing through the coolant, thereby achieving effective convergence of the pump light over a longer distance. Compared with the prior art that relies solely on a lens group to focus the pump light, this solution can extend the effective convergence area of ​​the pump light, so that a longer laser gain crystal can obtain sufficient pump excitation, thereby improving the gain efficiency of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic structural diagram of a laser gain module for end-pumping of a semiconductor laser provided in an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the three-dimensional structure of a composite laser gain crystal provided in an embodiment of the present application.

[0020] Figure 3 It is a schematic diagram of the optical design of a composite laser gain crystal provided in an embodiment of the present invention.

[0021] Figure 4 It is a schematic flow chart of a method for manufacturing a laser gain module for end-pumping of a semiconductor laser provided in an embodiment of the present invention.

[0022] Reference numerals: 1: semiconductor laser; 2: collimating lens; 3: dichroic mirror; 4: composite laser gain crystal; 41: front-end non-doped optical crystal; 42: back-end doped laser gain crystal; 5: pump light reflector; 6: Cooling clamping mechanical structure; 7: Cooling liquid. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Semiconductor lasers are commonly used pump sources for all-solid-state lasers. A lens group is usually used to collimate and focus the pump light output by the semiconductor laser to obtain a high optical power density. By using this semiconductor laser to end-pump the laser gain medium, a laser output with high beam quality can be obtained. Since the beam quality of the pump light emitted by the semiconductor laser is poor and the lens focusing area is short, it cannot be effectively focused in a very long area to achieve a certain intensity of pump power density. Therefore, it is impossible to effectively pump and excite a crystal that exceeds a certain length, thereby limiting the laser gain efficiency and the upper limit of the laser output power.

[0025] To solve the above problems, please refer to Figure 1 , Figure 1 1 is a schematic diagram of the structure of a semiconductor laser end-pumped laser gain module provided by an embodiment of the present invention. The semiconductor laser end-pumped laser gain module includes a composite laser gain crystal 4; The composite laser gain crystal 4 includes a front-end non-doped optical crystal 41 and a rear-end doped laser gain crystal 42; The front non-doped optical crystal 41 is in a frustum shape, and the conical surface of the front non-doped optical crystal 41 is used to refract and converge the incident pump light; The composite laser gain crystal 4 is immersed in a cooling liquid 7, and the refractive index of the cooling liquid 7 is smaller than the refractive index of the matrix material.

[0026] Specifically, the composite laser gain crystal 4 is composed of a front-end non-doped optical crystal 41 and a rear-end doped laser gain crystal 42 .

[0027] exist Figure 1 Based on Figure 2 , Figure 2 It is a schematic diagram of the three-dimensional structure of the composite laser gain crystal 4 provided in an embodiment of the present application.

[0028] Depend on Figure 2As shown, the front non-doped optical crystal 41 is in the shape of a truncated cone, which is composed of an integrally formed cylinder and a truncated cone. The front non-doped optical crystal 41 has a conical surface, a side surface and two bottom surfaces, wherein the first bottom surface is the bottom surface with a larger cross-sectional area among the two bottom surfaces, and the second bottom surface is the bottom surface with a smaller cross-sectional area among the two bottom surfaces. Light is incident from the first bottom surface of the front non-doped optical crystal 41, the pump light of the central part is emitted from the second bottom surface of the front non-doped optical crystal 41, and the pump light of the peripheral part is refracted at the conical surface of the front non-doped optical crystal 41.

[0029] The rear-stage doped laser gain crystal 42 is doped with laser gain ions, is cylindrical, and includes an incident surface, an exit surface, and a side surface, wherein the size of the incident surface is the same as the second bottom surface of the front-stage non-doped optical crystal 41 .

[0030] The front non-doped optical crystal 41 utilizes its conical surface to refract and converge the incident pump light, thereby overcoming the technical defect of a short effective focusing area of ​​the pump light in the traditional end-face pumping method.

[0031] Furthermore, when the pump light is incident on the conical surface of the front non-doped optical crystal 41, the pump light gradually converges during the propagation process due to the truncated cone structure of the front non-doped optical crystal 41. This convergence effect is different from the focusing method of the traditional lens group, and can achieve effective convergence over a longer distance. After the pump light is refracted and converged by the conical surface of the front non-doped optical crystal 41, it enters the rear doped laser gain crystal 42, maintaining a higher pump power density in a longer crystal area, thereby improving the laser gain efficiency.

[0032] In order to ensure the heat dissipation effect of the entire system, the composite laser gain crystal 4 is immersed in the coolant 7. The refractive index of the coolant 7 is smaller than the refractive index of the optical crystal. This design is to ensure that the pump light can produce a suitable refraction effect at the interface between the crystal and the coolant 7, which can not only maintain the convergence effect of the pump light, but also reduce the interface reflection loss. The coolant 7 not only plays a role in heat dissipation, but also participates in the optical path design of the pump light.

[0033] By adopting the above technical solution, an end-pumped laser gain module provided by an embodiment of the present invention extends the length of the effective pumping area compared with the traditional end-pumping method; secondly, a higher pumping power density is maintained in a longer crystal area; finally, the heat dissipation and optical refraction of the coolant 7 improve the overall efficiency and stability of the system.

[0034] Please refer to Figure 3 , Figure 3Schematic diagram of optical design of a composite laser gain crystal 4 provided in an embodiment of the present invention. Based on the above embodiment, as an optional embodiment, the front-end non-doped optical crystal 41 and the rear-end doped laser gain crystal 42 use the same matrix material and are connected by bonding or fusion.

[0035] Specifically, in order to further optimize the optical performance and structural stability of the composite laser gain crystal 4, the front non-doped optical crystal 41 and the rear doped laser gain crystal 42 use the same matrix material and are connected by bonding or fusion. The same matrix material is used to ensure that when the light beam is transmitted between the two crystals, no additional optical loss and distortion will be generated due to the difference in the refractive index of the material.

[0036] During the specific implementation, firstly, a suitable matrix material is selected, such as calcium fluoride crystal, yttrium aluminum garnet crystal and other commonly used optical crystal materials, and they are made into a front-end non-doped optical crystal 41 and a rear-end doped laser gain crystal 42. The front-end remains non-doped to ensure good optical transmittance, and the rear-end is doped with the required laser gain ions. In the process of connecting the crystals, optical bonding or high-temperature fusion can be selected. Optical bonding is to polish the contacting surfaces of the two crystals to optical-grade flatness under a strictly controlled clean environment, and to achieve molecular-level bonding under specific temperature and pressure conditions. High-temperature fusion is to use the diffusion effect of the material to achieve complete fusion of the two sections of the crystal in a high-temperature environment close to the melting point of the crystal.

[0037] By adopting the above technical solution, since the two sections of the crystal use the same matrix material, the refractive index mismatch at the interface is avoided and the optical loss is minimized to the greatest extent; secondly, the bonding or fusion connection method enables the two sections of the crystal to form an integral structure, which not only improves the mechanical strength but also eliminates possible interface scattering and reflection; thirdly, the integral structural design simplifies the assembly process of the optical system and improves the reliability and stability of the system.

[0038] Based on the above embodiment, as an optional embodiment, the difference between the refractive index of the cooling liquid 7 and the refractive index of the optical crystal is less than 0.2.

[0039] Specifically, Figure 3 As shown, the pump light needs to go through multiple refraction processes when it is transmitted in the composite laser gain crystal 4. ) is vertically incident on the first bottom surface of the front non-doped optical crystal 41, its optical path will present different transmission characteristics: the pump light in the center directly enters the rear doped laser gain crystal 42, while the peripheral part needs to pass through the cone surface (cone angle is ) is refracted into the coolant 7. For the pump light refracted by the cone, its incident angle is With cone angle There is a geometric relationship between When the pump light is emitted from the crystal (refractive index ) is incident on the coolant 7 (refractive index ), according to the law of refraction, we can get , which determines the propagation direction of the pump light in the coolant 7.

[0040] Further, from the perspective of the refraction light path, after propagating in the coolant 7, the pump light needs to be incident on the back-doped laser gain crystal 42 from the side of the back-doped laser gain crystal 42. At this time, the incident angle Compared with the previous refraction angle And the cone angle α satisfies the geometric relationship When the pump light enters the laser gain crystal from the cooling liquid 7, its incident angle is and refraction angle It also satisfies the law of refraction .

[0041] Through the above optical transmission process, the pump light at the same ring radius will converge toward the axial direction of the center of the laser gain crystal. It is worth noting that as the radius increases, the incident pump light power in the ring area of ​​the same width gradually increases, which enables the pump light to converge and obtain a larger pump light power density in the laser gain crystal of the same length, especially at the rear end of the gain crystal.

[0042] Based on the above optical path transmission analysis, when the refractive index difference satisfies When the refractive index difference is , optimization can be achieved in two key aspects: first, this refractive index difference can ensure that the pump light produces sufficient refractive convergence effect at the cone surface, so that the pump light can be effectively focused to the expected area of ​​the laser gain crystal; second, this moderate refractive index difference can minimize the interface reflection loss and improve the energy utilization efficiency of the pump light. This refractive index matching design also takes into account the feasibility in practical engineering applications, because although a too large refractive index difference can provide a stronger convergence effect, it will cause serious reflection loss, while a too small refractive index difference cannot achieve effective beam shaping.

[0043] By adopting the above technical solution, not only the efficient transmission and convergence of the pump light is achieved, but also the spatial distribution of the pump light in the laser gain crystal is optimized through precise parameter design. Specifically, by reasonably designing the cone angle of the front non-doped optical crystal 41, the length and aperture of the rear doped laser gain crystal 42 and other parameters, the pump light forms a unique power density distribution in the rear doped laser gain crystal 42: with the increase of the axial position, the pump power density gradually increases. This distribution characteristic compensates for the loss of the pump light during the transmission process and ensures that the laser gain crystal can maintain efficient laser gain in a longer area. At the same time, since the convergence effect of the pump light increases with the increase of the radius, this design also improves the pump efficiency in the edge area, realizes a more uniform and efficient energy distribution, and finally achieves the purpose of improving the laser gain efficiency.

[0044] On the basis of the above embodiment, as an optional embodiment, the laser gain module of the semiconductor laser end pumping further includes a cooling clamping mechanical structure 6, a sealed space is formed between the cooling clamping mechanical structure 6 and the composite laser gain crystal 4, and a coolant 7 is filled in the sealed space.

[0045] Specifically, during the operation of the laser gain module, the pump light is converted into heat after being absorbed by the composite laser gain crystal 4. This heat will cause the crystal temperature to rise, causing thermal stress and thermal lens effect, thereby affecting the laser output performance. In order to effectively solve the thermal management problem, a special cooling clamping mechanical structure 6 is designed in this embodiment. The cooling clamping mechanical structure 6 not only plays a mechanical fixing role, but more importantly, forms a sealed space with the composite laser gain crystal 4 to provide a closed flow channel for the coolant 7. A rubber sealing ring is provided at the contact point between the cooling clamping mechanical structure 6 and the composite laser gain crystal 4 to ensure that the coolant 7 will not leak, and at the same time, external impurities are prevented from entering the cooling system.

[0046] Furthermore, the design of the sealed space fully considers the flow characteristics and heat exchange efficiency of the coolant 7. The coolant 7 is completely filled in the sealed space and directly contacts the composite laser gain crystal 4 to form an efficient heat exchange interface. Since the coolant 7 has both optical refraction and heat exchange functions, the structural design of the sealed space must ensure both the accuracy of the optical path and the cooling effect. By reasonably designing the shape and size of the sealed space, the coolant 7 can evenly surround the composite laser gain crystal 4, providing optical refraction while fully taking away the heat generated by the crystal.

[0047] By adopting the above technical solution, multiple functions of mechanical support, optical refraction and heat management are realized. The coolant 7 in the sealed space not only participates in the optical path design of the pump light, but also effectively reduces the operating temperature of the composite laser gain crystal 4, reduces the influence of thermal stress on the crystal, and improves the stability and reliability of the laser. At the same time, the closed cooling system also avoids the evaporation and contamination of the coolant 7, prolongs the service life of the system, and reduces the maintenance cost. This structural design enables the laser gain module to maintain good beam quality and output characteristics under high-power working conditions.

[0048] On the basis of the above embodiment, as an optional embodiment, the cooling and clamping mechanical structure 6 is provided with a coolant 7 input port and a coolant 7 output port, so that the coolant 7 flows in the sealed space.

[0049] Specifically, in order to further improve the cooling efficiency, the present embodiment designs a coolant 7 input port and a coolant 7 output port on the cooling clamping mechanical structure 6 to form a forced convection cooling system. When the composite laser gain crystal 4 continues to work under the irradiation of high-power pump light, a large amount of heat will be generated. Relying solely on the stationary coolant 7 for heat exchange may not be able to take away the heat generated by the crystal in time, resulting in local overheating. By setting an input port and an output port on the cooling clamping mechanical structure 6, the coolant 7 forms a continuous flow in the sealed space, which significantly enhances the heat exchange efficiency. New low-temperature coolant 7 is continuously injected from the input port, and the coolant 7 carrying heat flows out from the output port, forming a closed-loop cooling circulation system.

[0050] Furthermore, the positions of the coolant 7 input port and output port are optimized so that the coolant 7 can form a reasonable flow field distribution in the sealed space. The input port is usually set at a position close to the incident end of the pump light, so that the area with a large heat load can be cooled preferentially; while the output port is set at a position far away from the incident end to ensure that the coolant 7 can fully contact the entire composite laser gain crystal 4. By adjusting the flow rate and flow rate of the coolant 7, the cooling effect can be optimized according to the actual working conditions. At the same time, the flowing coolant 7 can also maintain the uniformity of the refractive index and avoid optical distortion caused by temperature gradients.

[0051] By adopting the above technical solution, not only the heat exchange efficiency is improved, but also the uniform distribution of the temperature field is achieved. The flowing coolant 7 can more effectively take away the heat generated by the crystal, reducing the influence of thermal stress and thermal lens effect on laser performance. In addition, since the coolant 7 can be cooled by an external heat exchanger and then recycled, the system can work stably at a high power level for a long time.

[0052] Based on the above embodiment, as an optional embodiment, the laser gain module of the semiconductor laser end pumping further includes a pump light reflector 5, which is arranged at the output end of the rear-end doped laser gain crystal 42 to reflect the unabsorbed pump light.

[0053] Specifically, during the operation of the laser gain module, part of the pump light may not be completely absorbed after passing through the rear-stage doped laser gain crystal 42. In order to improve the pumping efficiency and make full use of the pumping light energy, a pump light reflector 5 is provided at the output end of the rear-stage doped laser gain crystal 42 in this embodiment. The reflector can reflect the unabsorbed pump light that passes through the crystal back to the rear-stage doped laser gain crystal 42 to achieve secondary pumping. When the unabsorbed pump light is reflected back to the crystal, it will interact with the doped gain ions again to form an additional population inversion, thereby improving the overall pumping efficiency.

[0054] Furthermore, the reflective surface of the pump light reflector 5 can be designed as a conical structure, and this structural design can better match the transmission path of the pump light. Since the pump light presents a specific spatial distribution after the refraction and convergence of the composite laser gain crystal 4, the reflector with a conical structure can more accurately reflect the unabsorbed pump light back to the appropriate position, so that the reflected pump light can be more effectively absorbed by the crystal. At the same time, the position and angle of the pump light reflector 5 are also precisely designed to ensure that the reflected pump light can fully overlap with the gain area in the crystal, maximizing the effect of secondary pumping.

[0055] By adopting the above technical solution, the utilization efficiency of pump light is improved. The reflected pump light provides a second energy excitation opportunity for the crystal, increases the effective pump volume, and improves the degree of population inversion. Not only the laser gain coefficient is improved, but also the spatial distribution uniformity of the gain is improved. At the same time, since more pump light is absorbed by the crystal, the ineffective loss of pump light is reduced, and the overall energy conversion efficiency of the system is improved.

[0056] Based on the above embodiment, as an optional embodiment, the first bottom surface of the front-end non-doped optical crystal 41 is coated with a film system for enhancing the transmittance of pump light and laser.

[0057] Specifically, in order to reduce energy loss at the optical interface and improve the optical transmission efficiency of the system, this embodiment performs a special film design on the first bottom surface of the front-stage non-doped optical crystal 41.

[0058] The first bottom surface of the front non-doped optical crystal 41 is used as the incident surface for pump light and laser, and needs to process two different wavelengths of light at the same time. Therefore, a dual-wavelength film system with anti-reflection properties for both pump light and laser is plated on the first bottom surface of the back-doped laser gain crystal 42. This dual-wavelength anti-reflection film system can significantly reduce the reflection loss of pump light at the time of incidence, while ensuring the low loss characteristics of the laser during transmission.

[0059] Furthermore, the design of the film system needs to consider the optimization of multiple technical parameters. The dual-wavelength anti-reflection film system of the first bottom surface of the front non-doped optical crystal 41 usually adopts a multi-layer dielectric thin film structure, and achieves high transmittance at the wavelength position of the pump light and the laser by precisely controlling the material and thickness of each layer of the film. This film system design must not only consider the transmission characteristics at two wavelengths, but also ensure that it has a good anti-reflection effect within a certain range of incident angles to adapt to the divergence angle characteristics of the pump light.

[0060] By adopting the above technical solution, the transmission efficiency of the optical system is improved. The dual-wavelength anti-reflection film system on the first bottom surface of the front non-doped optical crystal 41 ensures that the pump light can enter the crystal efficiently, improving the utilization rate of the pump energy; at the same time, it also ensures the low loss characteristics of the laser during the transmission process.

[0061] On the basis of the above embodiments, as an optional embodiment, the laser gain module of the semiconductor laser end pumping further includes a dichroic mirror 3, which is arranged on the incident light path of the composite laser gain crystal 4, and is coated with a film system that increases the transmittance of the pump light and has high reflectivity to the laser.

[0062] Specifically, the dichroic mirror 3 is a plane mirror, which is disposed on the incident light path of the composite laser gain crystal 4 , and is coated with a film system that increases the transmittance of the pump light and has high reflectivity for the laser.

[0063] like Figure 1 As shown, the laser is irradiated onto the dichroic mirror 3 at an incident angle of 45°, reflected by the dichroic mirror 3 at a reflection angle of 45°, vertically incident on the composite laser gain crystal 4, transmitted along the central axis direction of the composite laser gain crystal 4, passed through the front-end non-doped optical crystal 41, and entered the rear-end doped laser gain crystal 42.

[0064] By adopting the above technical solution, the pump light and the laser light can enter the composite laser gain crystal 4 as completely as possible, thereby avoiding light loss.

[0065] Based on the above embodiment, as an optional embodiment, the laser gain module of the semiconductor laser end-pumping further includes: a semiconductor laser 1 and a collimating lens 2; The semiconductor laser 1 is used for emitting pump light; The collimating lens 2 is disposed between the semiconductor laser 1 and the composite laser gain crystal 4 and is used to collimate the pump light.

[0066] Specifically, the pump light source is a semiconductor laser 1 (eg, a laser diode (LD)) with fiber-coupled output, whose emission wavelength precisely matches the absorption peak of the composite laser gain crystal 4 to achieve efficient energy conversion.

[0067] The power and beam parameters of the semiconductor laser 1 need to match the characteristics of the composite laser gain crystal 4. The pump light output by fiber coupling has good spatial beam characteristics, which is beneficial to subsequent collimation and focusing.

[0068] Since the pump light output by the semiconductor laser 1 has a large divergence angle, directly using it for pumping will result in low energy utilization efficiency. Therefore, a collimating lens 2 needs to be set between the semiconductor laser 1 and the composite laser gain crystal 4 to collimate the pump light and convert the divergent pump light into a parallel beam.

[0069] The collimating lens 2 has good transmittance and chromatic aberration correction capabilities, and can achieve excellent imaging quality at the pump light wavelength. By adjusting the distance between the collimating lens 2 and the semiconductor laser 1, the collimation and beam diameter of the outgoing light beam can be accurately controlled to match the incident area of ​​the composite laser gain crystal 4.

[0070] The lens group of the collimating lens 2 may include multiple lenses. By optimizing the material, curvature and spacing of the lenses, effective collimation of the pump light is achieved, while compensating for optical aberrations such as chromatic aberration and spherical aberration, ensuring that the pump light can be efficiently incident on the composite laser gain crystal 4.

[0071] By adopting the above technical solution, the collimated pump beam has a smaller divergence angle and uniform energy distribution, which improves the utilization efficiency of the pump energy; secondly, the collimated beam has good optical matching with the composite laser gain crystal 4, which reduces interface loss and improves the overall efficiency of the system.

[0072] Please refer to Figure 4 , Figure 4 A method for manufacturing a laser gain module for end-pumping of a semiconductor laser is provided in an embodiment of the present invention, and specifically may include the following steps: S101, connect the front-end non-doped optical crystal 41 and the rear-end doped laser gain crystal 42 by bonding or fusing to form a composite laser gain crystal 4, wherein the front-end non-doped optical crystal 41 is in a frustum shape, and the conical surface of the front-end non-doped optical crystal 41 is used to refract and converge the incident pump light into the rear-end doped laser gain crystal 42.

[0073] S102 , immersing the composite laser gain crystal 4 in a cooling liquid 7 whose refractive index is smaller than that of the optical crystal.

[0074] For the detailed process of the above steps, please refer to the relevant description of the above embodiments, and no further details will be given here.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A semiconductor laser end-pumped laser gain module, characterized in that: including a composite laser gain crystal; The composite laser gain crystal comprises a front-end non-doped optical crystal and a rear-end doped laser gain crystal; The front-end non-doped optical crystal is in the shape of a truncated cone, and the conical surface of the front-end non-doped optical crystal is used to refract and converge the incident pump light into the rear-end doped laser gain crystal; The composite laser gain crystal is immersed in a cooling liquid, and the refractive index of the cooling liquid is smaller than the refractive index of the optical crystal.

2. The semiconductor laser end-pumped laser gain module according to claim 1, characterized in that: The non-doped optical crystal at the front section and the doped laser gain crystal at the back section are made of the same matrix material and are connected by bonding or fusion.

3. The semiconductor laser end-pumped laser gain module according to claim 1, characterized in that: The difference between the refractive index of the cooling liquid and the refractive index of the optical crystal is less than 0.

2.

4. The semiconductor laser end-pumped laser gain module according to claim 1, characterized in that: It also includes a cooling and clamping mechanical structure, a sealed space is formed between the cooling and clamping mechanical structure and the composite laser gain crystal, and the cooling liquid is filled in the sealed space.

5. The semiconductor laser end-pumped laser gain module according to claim 4, characterized in that: The cooling clamping mechanical structure is provided with a cooling liquid input port and a cooling liquid output port so that the cooling liquid can flow in the sealed space.

6. The semiconductor laser end-pumped laser gain module according to claim 1, characterized in that: It also includes a pump light reflector, which is arranged at the output end of the rear-stage doped laser gain crystal and is used to reflect the pump light that is not absorbed.

7. The semiconductor laser end-pumped laser gain module according to claim 1, characterized in that: The first bottom surface of the non-doped optical crystal in the front section is coated with a film system for enhancing the transmittance of pump light and laser light; Among them, the first bottom surface is the bottom surface with a larger cross-sectional area among the two bottom surfaces of the front-end non-doped optical crystal in a frustum shape, and the second bottom surface is the bottom surface with a smaller cross-sectional area among the two bottom surfaces of the front-end non-doped optical crystal in a frustum shape.

8. The semiconductor laser end-pumped laser gain module according to claim 1, characterized in that: It also includes a dichroic mirror, which is arranged on the incident light path of the composite laser gain crystal and is coated with a film system that increases the transmittance of pump light and has high reflection of laser light.

9. The semiconductor laser end-pumped laser gain module according to claim 1, characterized in that: Also includes: Semiconductor laser and collimating lens; The semiconductor laser is used to emit pump light; The collimating lens is arranged between the semiconductor laser and the composite laser gain crystal, and is used for collimating the pump light.

10. A method for manufacturing a laser gain module for end-pumping of a semiconductor laser, characterized in that: include: The front-end non-doped optical crystal and the back-end doped laser gain crystal are connected by bonding or fusing to form a composite laser gain crystal, wherein the front-end non-doped optical crystal is in a frustum shape, and the conical surface of the front-end non-doped optical crystal is used to refract and converge the incident pump light into the back-end doped laser gain crystal; The composite laser gain crystal is immersed in a cooling liquid having a refractive index less than that of the optical crystal.

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