Semiconductor laser end-pumped laser gain module and method of making same

Abstract

The application discloses a semiconductor laser end face pumped laser gain module and a manufacturing method thereof, and relates to the technical field of all-solid-state lasers. The semiconductor laser end face pumped laser gain module comprises a composite laser gain crystal; the composite laser gain crystal comprises a front non-doped optical crystal and a rear doped laser gain crystal; the front non-doped optical crystal is in the shape of a truncated cone, and a conical surface of the front non-doped optical crystal is used for refracting and converging incident pump light into the rear doped laser gain crystal; the composite laser gain crystal is immersed in cooling liquid, and the refractive index of the cooling liquid is smaller than the refractive index of the optical crystal. The technical scheme provided by the application can prolong the effective converging area of pump light, so that a longer laser gain crystal can be sufficiently pumped and excited, and thus the gain efficiency of the laser is improved.

Description

TECHNICAL FIELD

[0001] The present application 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

[0002] The laser gain medium is an important component in 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 pumping volume. Among various pumping methods, end-pumping has become the main technical solution for pumping laser gain media because it can provide higher pumping power density and better beam quality.

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

[0004] However, since the pumping light emitted by the semiconductor laser has poor beam quality, the high-power density area formed by the lens focusing is relatively short. This results in the pumping light being unable to maintain effective power density over a long distance, so that crystals exceeding a certain length cannot be fully pumped and excited, thereby limiting the gain efficiency and output power of the solid-state laser. SUMMARY

[0005] The present application provides a semiconductor laser end-pumped laser gain module and a manufacturing method thereof, which can prolong the effective convergence area of the pumping light, so that a longer laser gain crystal can be fully pumped and excited, thereby improving the gain efficiency of the solid-state laser.

[0006] In a first aspect of the present application, a semiconductor laser end-pumped laser gain module is provided, comprising a composite laser gain crystal;

[0007] The composite laser gain crystal comprises a front non-doped optical crystal and a rear doped laser gain crystal;

[0008] The front non-doped optical crystal is in the shape of a truncated cone, and the conical surface of the front non-doped optical crystal is used to refract and converge the incident pumping light into the rear doped laser gain crystal;

[0009] The composite laser gain crystal is immersed in a cooling liquid, and the refractive index of the cooling liquid is less than the refractive index of the optical crystal.

[0010] In some embodiments, the front non-doped optical crystal and the rear doped laser gain crystal use the same substrate material and are connected by bonding or fusion.

[0011] In some embodiments, the difference between the refractive index of the cooling liquid and the refractive index of the host material is less than 0.2.

[0012] In some embodiments, further comprising a cooling clamping mechanical structure, a sealed space is formed between the cooling clamping mechanical structure and the composite laser gain crystal, and the cooling liquid is filled in the sealed space.

[0013] In some embodiments, the cooling clamping mechanical structure is provided with a cooling liquid inlet and a cooling liquid outlet to make the cooling liquid flow in the sealed space.

[0014] In some embodiments, further comprising a pump light reflecting mirror arranged at the exit end of the rear section doped laser gain crystal for reflecting the pump light not absorbed.

[0015] In some embodiments, the first bottom surface of the front section undoped optical crystal is coated with a film system for transmitting pump light and laser light;

[0016] In some embodiments, the first bottom surface is one of the two bottom surfaces of the front section undoped optical crystal with a larger cross-sectional area, and the second bottom surface is the other bottom surface of the front section undoped optical crystal with a smaller cross-sectional area.

[0017] In some embodiments, further comprising a dichroic mirror arranged on the incident light path of the composite laser gain crystal, and the dichroic mirror is coated with a film system for transmitting pump light and highly reflecting laser light.

[0018] In some embodiments, further comprising a semiconductor laser and a collimating lens;

[0019] The semiconductor laser is used to emit pump light;

[0020] The collimating lens is arranged between the semiconductor laser and the composite laser gain crystal to collimate the pump light.

[0021] In the second aspect of the present application, a manufacturing method of a semiconductor laser end-pumped laser gain module is provided, comprising:

[0022] The front section undoped optical crystal and the rear section doped laser gain crystal are connected by bonding or fusing to form a composite laser gain crystal, the front section undoped optical crystal is in the shape of a frustum, and the tapered surface of the front section undoped optical crystal is used to refract and converge the incident pump light into the rear section doped laser gain crystal;

[0023] The composite laser gain crystal is immersed in a cooling liquid with a refractive index less than that of the optical crystal.

[0024] To sum up, the one or more technical solutions provided in the present application have at least the following technical effects or advantages:

[0025] By adopting the composite laser gain crystal and immersing it in the cooling liquid with a refractive index less than that of the optical crystal, the conical surface of the front non-doped optical crystal can refract and converge the incident pump light, and the pump light after passing through the cooling liquid is incident into the rear doped laser gain crystal, thereby realizing effective convergence of the pump light in a long distance. Compared with the prior art which only relies on a lens group to focus the pump light, the present solution can prolong the effective convergence area of the pump light, so that the long laser gain crystal can be fully pumped and excited, thereby improving the gain efficiency of the laser. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0027] Figure 1 is a structure schematic diagram of a semiconductor laser end-pumped laser gain module provided by an embodiment of the present application.

[0028] Figure 2 is a three-dimensional structure schematic diagram of a composite laser gain crystal provided by an embodiment of the present application.

[0029] Figure 3 is an optical design schematic diagram of a composite laser gain crystal provided by an embodiment of the present application.

[0030] Figure 4 is a flowchart of a manufacturing method of a semiconductor laser end-pumped laser gain module provided by an embodiment of the present application.

[0031] Reference signs:

[0032] 1: semiconductor laser; 2: collimating lens; 3: dichroic mirror;

[0033] 4: composite laser gain crystal; 41: front non-doped optical crystal;

[0034] 42: rear doped laser gain crystal; 5: pump light reflecting mirror;

[0035] 6: cooling clamping mechanical structure; 7: cooling liquid. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0037] The semiconductor laser is a common pump source of the all-solid-state laser, and a lens set is usually used to collimate and focus the pump light output by the semiconductor laser to obtain high light power density. The semiconductor laser is used to end-pump the laser gain medium, and high-beam-quality laser output can be obtained. Since the beam quality of the pump light emitted by the semiconductor laser is poor, the length of the lens focusing area is short, the pump power density cannot be effectively focused in a very long area to reach a certain intensity, and therefore the semiconductor laser cannot effectively pump and excite a crystal with a length exceeding a certain length, thereby limiting the upper limit of the laser gain efficiency and the output power of the laser.

[0038] To solve the above problems, please refer to Figure 1 , Figure 1 is a structure diagram of a semiconductor laser end-pumped laser gain module provided by an embodiment of the present application. The semiconductor laser end-pumped laser gain module comprises a composite laser gain crystal 4.

[0039] The composite laser gain crystal 4 comprises a front non-doped optical crystal 41 and a rear doped laser gain crystal 42.

[0040] The front non-doped optical crystal 41 is in the shape of a truncated cone, and the conical surface of the front non-doped optical crystal 41 is used to refract and converge the incident pump light.

[0041] The composite laser gain crystal 4 is immersed in a cooling liquid 7, and the refractive index of the cooling liquid 7 is less than the refractive index of the matrix material.

[0042] Specifically, the composite laser gain crystal 4 is composed of the front non-doped optical crystal 41 and the rear doped laser gain crystal 42.

[0043] On the basis of Figure 1 , please refer to Figure 2 , Figure 2 is a three-dimensional structure diagram of the composite laser gain crystal 4 provided by the embodiment of the present application.

[0044] From Figure 2As shown, the front non-doped optical crystal 41 is frustum-shaped, which is composed of a cylindrical body and a circular truncated cone. The front non-doped optical crystal 41 has a tapered surface, a side surface and two bottom surfaces, wherein the first bottom surface is one of the two bottom surfaces with a larger cross-sectional area, and the second bottom surface is the other bottom surface with a smaller cross-sectional area. The light is incident from the first bottom surface of the front non-doped optical crystal 41, and the central part of the pump light is emitted from the second bottom surface of the front non-doped optical crystal 41, and the peripheral part of the pump light is refracted on the tapered surface of the front non-doped optical crystal 41.

[0045] The rear doped laser gain crystal 42 is doped with laser gain ions and is cylindrical, which includes an incident surface, an emission surface and a side surface. The size of the incident surface is the same as that of the second bottom surface of the front non-doped optical crystal 41.

[0046] The front non-doped optical crystal 41 uses the tapered surface to refract and converge the incident pump light, thereby overcoming the technical defect that the effective focusing area of the pump light is short in the conventional end-pumping mode.

[0047] Further, when the pump light is incident on the tapered surface of the front non-doped optical crystal 41, the pump light is gradually converged during the propagation due to the frustum-shaped structure of the front non-doped optical crystal 41. This convergence effect is different from the focusing mode of the conventional lens group, and a longer effective convergence distance can be achieved. After the pump light is refracted and converged by the tapered surface of the front non-doped optical crystal 41, the pump light enters the rear doped laser gain crystal 42, and a higher pump power density is maintained in a longer crystal region, thereby improving the laser gain efficiency.

[0048] In order to ensure the heat dissipation effect of the whole system, the composite laser gain crystal 4 is immersed in the cooling liquid 7. The refractive index of the cooling liquid 7 is smaller than that of the optical crystal, and this design is to ensure that the pump light can produce a suitable refraction effect at the interface between the crystal and the cooling liquid 7, so as to maintain the convergence effect of the pump light and reduce the interface reflection loss. The cooling liquid 7 not only plays a role in heat dissipation, but also participates in the optical path design of the pump light.

[0049] By adopting the above technical scheme, the end-pumped laser gain module provided by the embodiment of the present application can prolong the length of the effective pump region compared with the conventional end-pumping mode. Secondly, a higher pump power density is maintained in a longer crystal region. Finally, through the heat dissipation and optical refraction of the cooling liquid 7, the overall efficiency and stability of the system are improved.

[0050] Please refer to Figure 3 , Figure 3is a schematic diagram of an optical design of a composite laser gain crystal 4 provided by an embodiment of the present application. On the basis of the above embodiment, as an alternative embodiment, the front non-doped optical crystal 41 and the rear doped laser gain crystal 42 adopt the same substrate material and are connected by bonding or fusion.

[0051] 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 adopt the same substrate material and are connected by bonding or fusion. The same substrate material is used to ensure that the light beam does not produce additional optical loss and distortion when transmitting between the two crystals due to the difference in material refractive index.

[0052] In specific implementation, first, appropriate substrate materials are selected, such as calcium fluoride crystal, yttrium aluminum garnet crystal, and other commonly used optical crystal materials, which are respectively made into the front non-doped optical crystal 41 and the rear doped laser gain crystal 42. The front part remains non-doped to ensure good optical transmittance, and the rear part 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 contact surfaces of the two crystals to optical level flatness in a strictly controlled clean environment, and to realize molecular-level bonding under specific temperature and pressure conditions. High-temperature fusion is to realize the complete fusion of the two crystals by using the dispersion effect of the material in a high-temperature environment close to the melting point of the crystal.

[0053] By using the above technical solution, since the two crystals adopt the same substrate material, the refractive index mismatch at the interface is avoided, and the optical loss is minimized. Secondly, the bonding or fusion connection method makes the two crystals form an integral structure, which not only improves the mechanical strength, but also eliminates the possible interface scattering and reflection. Thirdly, the integral structure design simplifies the alignment process of the optical system and improves the reliability and stability of the system.

[0054] On the basis of the above embodiment, as an alternative 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.

[0055] Specifically, as shown in Figure 3 , the pump light needs to undergo multiple refraction processes when transmitting in the composite laser gain crystal 4. When the pump light is vertically incident on the first bottom surface of the front non-doped optical crystal 41 from the air (refractive index ), the optical path will exhibit different transmission characteristics: the central part of the pump light directly enters the rear doped laser gain crystal 42, and the peripheral part needs to be refracted through a tapered surface (taper angle ) into the cooling liquid 7. For the pump light refracted through the tapered surface, the incident angle of the pump light on the interface between the tapered surface and the cooling liquid 7 is less than the critical angle of total reflection, so the pump light can be refracted into the cooling liquid 7. There is a geometric relationship between the taper angle When the pump light is incident to the coolant 7 (refractive index ) from the crystal (refractive index ), according to the refraction law, we have , which determines the propagation direction of the pump light in the coolant 7.

[0056] Further, from the perspective of the refracted light path, the pump light needs to be incident to the rear doped laser gain crystal 42 from the side of the rear doped laser gain crystal 42 after propagating in the coolant 7. At this time, the incident angle and the previous refraction angle and the taper angle α satisfy the geometric relationship When the pump light is incident to the laser gain crystal from the coolant 7, the incident angle and the refraction angle satisfy the refraction law .

[0057] Through the above optical transmission process, the pump light located at the same circular ring radius will converge in the axial direction of the center of the laser gain crystal. It is worth noting that as the radius increases, the pump light power incident in the same width of the annular region gradually increases, which makes the pump light converge to obtain greater pump light power density in the same length of the laser gain crystal, especially in the rear end part of the gain crystal.

[0058] Based on the above optical path transmission analysis, when the refractive index difference satisfies , optimization can be achieved in two key aspects: first, this refractive index difference can ensure that the pump light produces sufficient refraction convergence effect at the taper 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 maximize the reduction of interface reflection loss, improving the energy utilization efficiency of the pump light. This refractive index matching design also takes into account the feasibility in practical engineering applications, because an excessively large refractive index difference can provide stronger convergence effect, but will cause serious reflection loss, while an excessively small refractive index difference cannot achieve effective beam shaping.

[0059] ​By adopting the technical scheme, not only efficient transmission and convergence of the pump light are realized, but also the spatial distribution of the pump light in the laser gain crystal is optimized through accurate parameter design. Specifically, by reasonably designing the conical 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: the pump power density gradually increases with the increase of the axial position, which compensates for the loss of the pump light in the transmission process, ensures that the laser gain crystal can maintain efficient laser gain effect 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 pumping efficiency of the edge region, realizes more uniform and efficient energy distribution, and finally achieves the purpose of improving the laser gain efficiency.

[0060] On the basis of the above-mentioned embodiment, as an optional embodiment, the semiconductor laser end-pumped laser gain module further comprises 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 the cooling liquid 7 is filled in the sealed space.

[0061] Specifically, in the working process of the laser gain module, the pump light is converted into heat after being absorbed by the composite laser gain crystal 4, which causes the temperature of the crystal to rise, causes thermal stress and thermal lens effect, and thus affects the laser output performance. In order to effectively solve the heat 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 cooling liquid 7. The cooling clamping mechanical structure 6 is provided with a rubber sealing ring at the contact position with the composite laser gain crystal 4, so as to ensure that the cooling liquid 7 does not leak, and at the same time, foreign matters in the outside are also prevented from entering the cooling system.

[0062] Further, the design of the sealed space fully considers the flow characteristics and heat exchange efficiency of the cooling liquid 7. The cooling liquid 7 is completely filled in the sealed space and directly contacts with the composite laser gain crystal 4 to form a high-efficiency heat exchange interface. Since the cooling liquid 7 has dual functions of optical refraction and heat exchange, the structure design of the sealed space not only needs to ensure the accuracy of the optical path, but also needs to ensure the cooling effect. By reasonably designing the shape and size of the sealed space, the cooling liquid 7 can uniformly surround the composite laser gain crystal 4, which not only provides the optical refraction function, but also fully takes away the heat generated by the crystal.

[0063] By adopting the technical scheme, multiple functions of mechanical support, optical refraction and heat management are realized. The cooling liquid 7 in the sealed space not only participates in the light path design of the pump light, but also effectively reduces the working 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 pollution of the cooling liquid 7, prolongs the service life of the system, and reduces the maintenance cost. The structure design makes the laser gain module be able to maintain good beam quality and output characteristics under high-power working state.

[0064] On the basis of the above-mentioned embodiment, as an optional embodiment, the cooling clamping mechanical structure 6 is provided with a cooling liquid 7 input port and a cooling liquid 7 output port, so that the cooling liquid 7 flows in the sealed space.

[0065] Specifically, in order to further improve the cooling efficiency, the cooling liquid 7 input port and the cooling liquid 7 output port are designed on the cooling clamping mechanical structure 6 to form a forced convection cooling system. When the composite laser gain crystal 4 works continuously under the irradiation of high-power pump light, a large amount of heat will be generated. Only relying on the static cooling liquid 7 for heat exchange may not be able to timely take away the heat generated by the crystal, resulting in local overheating. By setting the input port and the output port on the cooling clamping mechanical structure 6, the cooling liquid 7 forms a continuous flow in the sealed space, which significantly enhances the heat exchange efficiency. The new low-temperature cooling liquid 7 is continuously injected from the input port, and the cooling liquid 7 carrying heat flows out from the output port, forming a closed-loop cooling circulation system.

[0066] Further, the positions of the cooling liquid 7 input port and the output port are optimized to make the cooling liquid 7 form a reasonable flow field distribution in the sealed space. The input port is usually arranged near the pump light incident end, so that the area with high heat load can be cooled preferentially; and the output port is arranged away from the incident end to ensure that the cooling liquid 7 can fully contact the entire composite laser gain crystal 4. By adjusting the flow rate and flow of the cooling liquid 7, the cooling effect can be optimized according to the actual working conditions. At the same time, the flowing cooling liquid 7 can also maintain the uniformity of the refractive index, avoiding optical distortion caused by temperature gradient.

[0067] By adopting the above technical scheme, not only the heat exchange efficiency is improved, but also the uniform distribution of temperature field is realized. The flowing cooling liquid 7 can more effectively take away the heat generated by the crystal, reducing the influence of thermal stress and thermal lens effect on the laser performance. In addition, since the cooling liquid 7 can be cooled by an external heat exchanger before being recycled, the system can work stably at a high power level for a long time.

[0068] On the basis of the above-mentioned embodiments, as an optional embodiment, the semiconductor laser end-pumped laser gain module further comprises a pump light reflecting mirror 5 arranged at the exit end of the rear doped laser gain crystal 42 for reflecting the unabsorbed pump light.

[0069] Specifically, during the operation of the laser gain module, part of the pump light can not be completely absorbed after passing through the rear doped laser gain crystal 42. In order to improve the pumping efficiency and make full use of the pump light energy, the embodiment arranges a pump light reflecting mirror 5 at the exit end of the rear doped laser gain crystal 42. The reflecting mirror can reflect the unabsorbed pump light that has passed through the crystal back to the rear doped laser gain crystal 42, realizing secondary pumping. When the unabsorbed pump light is reflected back to the crystal, it will interact with the doped gain ions again, forming additional population inversion, thereby improving the overall pumping efficiency.

[0070] Further, the reflecting surface of the pump light reflecting mirror 5 can be designed as a conical surface structure. This structure design can better match the transmission path of the pump light. Since the pump light presents a specific spatial distribution after passing through the refractive convergence of the composite laser gain crystal 4, the conical surface structure of the reflecting mirror 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 reflecting mirror 5 are also precisely designed to ensure that the reflected pump light can fully overlap with the gain region in the crystal, maximizing the effect of secondary pumping.

[0071] By adopting the above technical solution, the utilization efficiency of the pump light is improved. The reflected pump light provides a second energy excitation opportunity for the crystal, increases the effective pumping volume, and improves the degree of population inversion. Not only does it improve the laser gain coefficient, but it also improves the spatial distribution uniformity of the gain. At the same time, since more pump light is absorbed by the crystal, the invalid loss of the pump light is reduced, and the overall energy conversion efficiency of the system is improved.

[0072] On the basis of the above-mentioned embodiments, as an optional embodiment, the first bottom surface of the front undoped optical crystal 41 is coated with a film system that transmits pump light and laser.

[0073] Specifically, in order to reduce the energy loss at the optical interface and improve the optical transmission efficiency of the system, the embodiment designs a special film system for the first bottom surface of the front undoped optical crystal 41.

[0074] The first bottom surface of the undoped optical crystal 41 serves as the incident surface for both the pump light and the laser beam, requiring the simultaneous processing of two different wavelengths of light. Therefore, a dual-wavelength anti-reflection film system, which has anti-reflection properties for both the pump light and the laser beam, is deposited on the first bottom surface of the doped laser gain crystal 42. This dual-wavelength anti-reflection film system can significantly reduce the reflection loss of the pump light during incident light while ensuring the low-loss characteristics of the laser beam during transmission.

[0075] Furthermore, the design of the film system requires optimization of multiple technical parameters. The dual-wavelength antireflection film system on the first bottom surface of the undoped optical crystal 41 typically employs a multilayer dielectric thin film structure. By precisely controlling the material and thickness of each layer, high transmittance can be achieved simultaneously at the wavelengths of the pump light and the laser. This film system design must not only consider the transmission characteristics at both wavelengths but also ensure good antireflection performance within a certain incident angle range to adapt to the divergence angle characteristics of the pump light.

[0076] By adopting the above technical solution, the transmission efficiency of the optical system is improved. The dual-wavelength antireflection film system on the first bottom surface of the undoped optical crystal 41 ensures that the pump light can enter the crystal efficiently, improving the utilization rate of pump energy; at the same time, it also ensures the low-loss characteristics of the laser during transmission.

[0077] Based on the above embodiments, as an optional embodiment, the laser gain module pumped by the end face of the semiconductor laser further includes a dichroic mirror 3. The dichroic mirror 3 is disposed in the incident light path of the composite laser gain crystal 4, and the dichroic mirror 3 is coated with a film system that enhances the transmission of pump light and has high reflectivity to laser light.

[0078] Specifically, the dichroic mirror 3 is a plane mirror, which is placed in the incident light path of the composite laser gain crystal 4. The dichroic mirror 3 is coated with a film that enhances the transmission of pump light and has high reflectivity to laser light.

[0079] like Figure 1 As shown, the laser beam is incident on the dichroic mirror 3 at an incident angle of 45°, and is reflected by the dichroic mirror 3 at a reflection angle of 45°. It is then incident perpendicularly on the composite laser gain crystal 4, propagated along the central axis of the composite laser gain crystal 4, and passes through the undoped optical crystal 41 in the front section before entering the doped laser gain crystal 42 in the back section.

[0080] By adopting the above technical solution, the pump light and laser light can enter the composite laser gain crystal 4 as much as possible, thus avoiding light loss.

[0081] Based on the above embodiments, as an optional embodiment, the end-pumped laser gain module of the semiconductor laser further includes: a semiconductor laser 1 and a collimating lens 2;

[0082] Semiconductor laser 1 is used to emit pump light;

[0083] A collimating lens 2 is arranged between the semiconductor laser 1 and the composite laser gain crystal 4, for collimating the pump light.

[0084] Specifically, the pump light source is selected as a fiber-coupled semiconductor laser 1 (for example, a laser diode (LD)), and the emission wavelength thereof is accurately matched with the absorption peak of the composite laser gain crystal 4, so as to realize efficient energy conversion.

[0085] The power and beam parameters of the semiconductor laser 1 need to be matched with the characteristics of the composite laser gain crystal 4. The pump light output through the fiber-coupled manner has good spatial beam characteristics, which is beneficial to subsequent collimation and focusing.

[0086] Since the pump light output by the semiconductor laser 1 has a large divergence angle, direct pumping will result in low energy utilization efficiency, and therefore, the collimating lens 2 needs to be arranged between the semiconductor laser 1 and the composite laser gain crystal 4 to collimate the pump light and convert the divergent pump light into parallel light beams.

[0087] The collimating lens 2 has good transmittance and chromatic aberration correction capability, and can realize excellent imaging quality at the pump light wavelength. By adjusting the distance between the collimating lens 2 and the semiconductor laser 1, the collimation degree and beam diameter of the outgoing light beam can be accurately controlled, so as to match the incident area of the composite laser gain crystal 4.

[0088] The lens group of the collimating lens 2 can include multiple lenses, and by optimizing the material, curvature and spacing of the lenses, effective collimation of the pump light can be realized, while compensating for optical aberrations such as chromatic aberration and spherical aberration, so as to ensure that the pump light can be efficiently incident to the composite laser gain crystal 4.

[0089] By adopting the above technical scheme, the collimated pump light beam has a small divergence angle and uniform energy distribution, which improves the utilization efficiency of the pump energy. In addition, the collimated light beam has good optical matching with the composite laser gain crystal 4, reduces the interface loss, and improves the overall efficiency of the system.

[0090] Please refer to Figure 4 , Figure 4 is a manufacturing method of a semiconductor laser end-pumped laser gain module provided by an embodiment of the present application, and specifically can include the following steps:

[0091] S101, the front non-doped optical crystal 41 and the rear doped laser gain crystal 42 are connected by bonding or fusing to form a composite laser gain crystal 4, the front non-doped optical crystal 41 is in the form of a truncated cone, and the tapered surface of the front non-doped optical crystal 41 is used to refract and converge the incident pump light into the rear doped laser gain crystal 42.

[0092] S102, immerse the composite laser gain crystal 4 in the coolant 7 with a refractive index less than that of the optical crystal.

[0093] The detailed process of the above steps can refer to the related description of the above examples, which will not be described in detail here.

[0094] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A semiconductor laser end-pumped laser gain module, characterized by, The composite laser gain crystal comprises a front non-doped optical crystal and a rear doped laser gain crystal; The front non-doped optical crystal is in the shape of a truncated cone, and the tapered surface of the front non-doped optical crystal is used to refract and converge the incident pump light into the rear doped laser gain crystal; The composite laser gain crystal is immersed in a cooling liquid, the refractive index of the cooling liquid is less than the refractive index of the optical crystal, the peripheral part of the pump light is refracted into the cooling liquid through the tapered surface, and the pump light is incident into the rear doped laser gain crystal from the side surface of the rear doped laser gain crystal after propagating in the cooling liquid; The front non-doped optical crystal and the rear doped laser gain crystal are connected by bonding or fusion, and are made of the same substrate material. The difference between the refractive index of the cooling liquid and the refractive index of the optical crystal is less than 0.

2.

2. The semiconductor laser end-pumped laser gain module of claim 1, wherein, A cooling clamping mechanical structure is further provided, and a sealed space is formed between the cooling clamping mechanical structure and the composite laser gain crystal, and the cooling liquid is filled in the sealed space.

3. The semiconductor laser end-pumped laser gain module of claim 1, wherein, The cooling clamping mechanical structure is provided with a cooling liquid input port and a cooling liquid output port to make the cooling liquid flow in the sealed space.

4. The semiconductor laser end-pumped laser gain module of claim 3, wherein, A pump light reflecting mirror is further provided, which is arranged at the exit end of the rear doped laser gain crystal and is used to reflect the pump light that is not absorbed.

5. The semiconductor laser end-pumped laser gain module of claim 1, wherein, The first bottom surface of the front non-doped optical crystal is coated with a film system that is transparent to the pump light and the laser light; 6. The semiconductor laser end-pumped laser gain module of claim 1, wherein, The first bottom surface is one of the two bottom surfaces of the front non-doped optical crystal in the shape of a truncated cone, and the second bottom surface is the other bottom surface of the front non-doped optical crystal in the shape of a truncated cone. A dichroic mirror is further provided, which is arranged on the incident light path of the composite laser gain crystal, and is coated with a film system that is transparent to the pump light and highly reflective to the laser light.

7. The semiconductor laser end-pumped laser gain module of claim 1, wherein, Further comprising:

8. The semiconductor laser end-pumped laser gain block of claim 1, wherein, 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 to collimate the pump light. Further comprising:

9. A method for fabricating a semiconductor laser end-face pumped laser gain module, characterized in that, The front non-doped optical crystal and the rear doped laser gain crystal are connected by bonding or fusion to form a composite laser gain crystal, the front non-doped optical crystal is in the shape of a truncated cone, the tapered surface of the front non-doped optical crystal is used to refract and converge the incident pump light into the rear doped laser gain crystal, the peripheral part of the pump light is refracted into a cooling liquid through the tapered surface, the pump light is incident into the rear doped laser gain crystal from the side surface of the rear doped laser gain crystal after propagating in the cooling liquid, and the front non-doped optical crystal and the rear doped laser gain crystal are made of the same substrate material; The composite laser gain crystal is immersed in a cooling liquid with a refractive index less than that of the optical crystal. ​

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