Thin-slice laser based on topological structure dodging layer and preparation method of thin-slice laser

Abstract

The invention discloses a slice laser based on a topological structure dodging layer. The slice laser comprises a pumping system, a pumping light injection module and a composite dodging waveguide structure, pumping light generated by the pumping system enters the composite dodging waveguide structure through the pumping light injection module; the front end face of the composite dodging waveguide structure is plated with a pumping light wavelength high-reflective film and a laser wavelength antireflection film, and the rear end face of the composite dodging waveguide structure is plated with a pumping source wavelength and laser wavelength high-reflective film; the composite dodging waveguide structure comprises a slice gain medium, a topological structure dodging layer and a middle refractive index layer which are sequentially arranged from the front end face to the rear end face. The topological structure dodging layer is composed of a low-refractive-index material layer and a high-refractive-index material topological graph arranged on the low-refractive-index material layer; and the pump light injection module is fixed above the high refractive index material of the middle refractive index layer or the topological structure dodging layer. Pumping uniformity is improved fundamentally, high-order mode suppression and efficient fundamental mode extraction are facilitated, and output power and light beam quality are improved at the same time.

Description

A thin-film laser based on a topological homogenizing layer and its fabrication method Technical Field

[0001] This invention relates to the field of laser technology, and specifically to a thin-film laser based on a topological homogenizing layer and its fabrication method. Background Technology

[0002] All-solid-state lasers are widely used in military, medical, and industrial fields due to their advantages such as small size, compact structure, long lifespan, high conversion efficiency, and strong anti-interference ability. However, when these lasers operate at high power, the heat generated in the gain medium is difficult to dissipate effectively, which can easily lead to nonlinear phenomena such as thermal lensing and thermal birefringence, thus limiting further improvements in output power and beam quality.

[0003] To improve thermal management, the use of thin-film gain media has become an important technical approach. Thin-film lasers significantly increase the heat dissipation area by tightly bonding the reflective surface of the gain medium to the heat sink, and align the temperature gradient direction with the laser propagation direction, thereby effectively suppressing thermally induced wavefront distortion and maintaining high beam quality while outputting high-power lasers. Furthermore, the thin-film structure possesses good scaling and amplification potential; the average output power can be increased by increasing the aperture of the gain medium. However, the performance of thin-film lasers is largely limited by their pumping method. While the commonly used multi-pass pumping structure can improve absorption efficiency and pump uniformity by passing through the gain medium multiple times, it relies on the precise layout and adjustment of numerous spatially discrete optical components, resulting in a complex system that is extremely sensitive to assembly and adjustment errors. This makes the realization of large-aperture thin-film gain media a significant challenge.

[0004] Therefore, providing a thin-film laser that offers significant improvements in pump efficiency, output power, beam quality, and system stability, while being compact and easy to implement, remains a major technical hurdle to overcome in this field. Summary of the Invention

[0005] To address the shortcomings of the above-mentioned problems, the present invention provides a thin-film laser based on a topological homogenizing layer.

[0006] This invention discloses a thin-film laser based on a topological homogenizing layer, comprising: a pumping system, a pump light injection module, and a composite homogenizing waveguide structure; the pump light generated by the pumping system is incident into the composite homogenizing waveguide structure via the pump light injection module; the front end face of the composite homogenizing waveguide structure is coated with a pump light wavelength high-reflection film and a laser wavelength antireflection film, and the rear end face is coated with a pump source wavelength and a laser wavelength high-reflection film; the composite homogenizing waveguide structure includes a thin-film gain medium, a topological homogenizing layer, and an intermediate refractive index layer sequentially arranged from the front end face to the rear end face; the topological homogenizing layer is composed of a low refractive index material layer and a high refractive index material topological pattern disposed thereon, the high refractive index material topological pattern being determined according to the target light field distribution; the pump light injection module is fixed above the high refractive index material of the intermediate refractive index layer or the topological homogenizing layer; the... The refractive indices of the materials in the topological homogenizing layer satisfy the following order: high refractive index material > intermediate refractive index layer material > low refractive index material. The pump light emitted by the pump system is directly introduced into the intermediate refractive index layer by the pump light injection module, or first introduced into the high refractive index material of the topological homogenizing layer and then transmitted into the intermediate refractive index layer. Due to the refractive index difference between the intermediate refractive index layer material and the low refractive index material, the pump light undergoes total internal reflection at their interface, forming a waveguide for transmission. When the pump light is transmitted from the intermediate refractive index layer to the interface between the high refractive index material and the intermediate refractive index layer, part or all of it is transmitted into the thin-film gain medium via the high refractive index material, and the pump light propagates in a zigzag path. By controlling the topological pattern and spatial distribution of the high refractive index material on the low refractive index material, the homogenization of the pump light field and the optimization of mode matching are achieved.

[0007] As a further improvement of the present invention, the pumping system includes a pump source module and a pump light coupling module arranged in sequence, wherein the pump light generated by the pump source module is incident on the pump light injection module after passing through the pump light coupling module.

[0008] As a further improvement of the present invention, the central axes of the thin-film gain medium, the topological homogenizing layer, and the intermediate refractive index layer coincide; the material of the thin-film gain medium is a light-transmitting material, including one of YAG, YLF, YVO4, Al2O3, and SiO2; wherein, the light-transmitting material is doped with one or more of lanthanide metal ions and transition metal ions as gain ions, and the lanthanide metal ions include Yb 3+ 、Nd 3+ and Er 3+ The transition metal ions include Cr 3+ Fe 3+ and Ti 3+The low refractive index material is selected from alkaline earth metal fluorides, such as CaF2 and MgF2; the high refractive index material is selected from nitride semiconductor materials, such as Si3N4, AlN, BN, and GaN; and the intermediate refractive index layer material is selected from silicon-based oxides, such as SiO2.

[0009] As a further improvement of the present invention, it also includes: a heat sink; the heat sink is attached to the thin gain medium on the front end face or to the intermediate refractive index layer on the rear end face, and the heat sink is copper, diamond, copper-tungsten alloy or other types of materials.

[0010] As a further improvement of the present invention, the topological homogenizing layer is directly deposited on a thin-film gain medium or connected by bonding.

[0011] As a further improvement of the present invention, the pump light injection module is selected from a right-angle prism or a square prism, and the surface of the pump light injection module that is perpendicular to the end face of the thin-film gain medium and located outside the system is the pump surface; wherein, the pump light injection module can be fabricated with microstructures to shape the pump light; the propagation of the pump light in the waveguide and its subsequent spatial distribution can be optimized by optimizing the size parameters of the prism in the pump light injection module.

[0012] As a further improvement of the present invention, the pump source module is a semiconductor laser or a fiber laser. The pump light generated by the pump source module is collimated or decollimated by the pump light coupling module in the form of fiber coupling or spatial optical coupling and is perpendicularly incident on the pump surface of the pump light injection module. Each pump surface of the pump light injection module is incident with pump light. The wavelength of the pump light generated by the pump source module matches the center of the absorption spectrum of the gain medium. The number of pump source modules is odd to prevent the pump source from being damaged by pump light that is not completely absorbed.

[0013] As a further improvement of the present invention, the pump source module is configured such that the incident angle of its emitted light is adjustable, so as to change the initial position of the pump light injected into the intermediate refractive index layer, thereby regulating the distribution of the pump light and thus regulating its distribution in the thin-film gain medium.

[0014] As a further improvement of the present invention, the topological pattern of the high refractive index material can be designed according to the target pump light absorption distribution to actively control the spatial distribution of the pump light in the gain medium; the width of the topological pattern of the high refractive index material increases in a gradient along the direction pointing to the thin-film gain medium to optimize the spatial distribution of the pump light.

[0015] This invention also discloses a method for fabricating a thin-film laser based on a topological homogenizing layer, comprising the following steps: Step 1, obtaining a thin-film gain medium through conventional grinding and polishing; Step 2, fabricating a low-refractive-index material layer on the rear face of the thin-film gain medium using physical vapor deposition (PVD); Step 3, forming a preset topological pattern structure on the low-refractive-index material layer through shadow mask deposition or photolithography and etching processes, or achieving a topological pattern structure with a gradient increase along the direction pointing towards the thin-film gain medium through multiple etching processes; Step 4, depositing a high-refractive-index material in the topological pattern structure using chemical vapor deposition (CVD), filling the pattern and forming an embedded structure to complete the topological homogenizing layer. The fabrication process is as follows: Step 5: Deposit an intermediate refractive index layer on the rear face of the topological homogenizing layer using PVD or CVD methods to complete the fabrication of the composite homogenizing waveguide structure; Step 6: Deposit a pump source wavelength high reflectivity film and a laser wavelength antireflection film on the front face of the thin-film gain medium, and deposit a pump source wavelength and laser wavelength high reflectivity film on the rear face of the intermediate refractive index layer; Step 7: Fix the pump light injection module to the edge of the topological homogenizing layer using UV adhesive or mechanical fixation; Step 8: Connect the front face of the thin-film gain medium or the rear face of the intermediate refractive index layer to the heat sink using adhesive or welding; Step 9: Inject the pump light emitted by the pump system into the composite homogenizing waveguide structure through the pump light injection module.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By designing the topological pattern, the present invention can actively and flexibly shape the three-dimensional absorption distribution of the pump light in the gain medium, fundamentally improving the pump uniformity, which is conducive to achieving high-order mode suppression and efficient extraction of the fundamental mode, thereby simultaneously improving the output power and beam quality.

[0017] 2. This invention eliminates the need for complex multi-pass spatial folding optical paths, relying primarily on integrated planar waveguide structures, significantly reducing the number of discrete optical components and the dependence on precision fitting. The system has a compact structure, good robustness, and is easy to modularize.

[0018] 3. This invention maintains the inherent excellent heat dissipation characteristics of thin-film lasers. By increasing the aperture of the gain medium and the area of ​​the homogenizing layer, the power density and thermal load in the gain medium can be effectively reduced without significantly increasing the system complexity. This is beneficial to giving full play to the scaling and amplification potential of the thin-film medium and achieving higher power output.

[0019] 4. The thin film deposition, photolithography, etching and other processes involved in this invention are all mature micro-nano processing technologies with good compatibility with semiconductor processes, which is conducive to realizing the miniaturization, integration and mass production of devices. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the pump structure of the thin-film laser based on the square prism-type topological homogenizing layer disclosed in this invention; Figure 2 is a schematic diagram of the topological homogenizing layer in Figure 1; Figure 3 is a schematic diagram of the pump light incident on the square prism in the thin-film laser based on the square prism-type topological homogenizing layer disclosed in this invention; Figure 4 is a schematic diagram of the folded-back transmission optical path of the pump light in the composite homogenizing waveguide structure in the thin-film laser based on the square prism-type topological homogenizing layer disclosed in this invention; Figure 5 is a schematic diagram of the pump structure of the thin-film laser based on the right-angle prism-type topological homogenizing layer disclosed in this invention; Figure 6 is a schematic diagram of the pump light incident on the right-angle prism in the thin-film laser based on the right-angle prism-type topological homogenizing layer disclosed in this invention; Figure 7 is a schematic diagram of the folded-back transmission optical path of the pump light in the composite homogenizing waveguide structure in the thin-film laser based on the right-angle prism-type topological homogenizing layer disclosed in this invention.

[0021] Symbol explanation: 1. Pump source module; 2. Pump optical coupling module; 3. Pump optical injection module; 4. Thin-film gain medium; 5. Low refractive index material layer; 6. High refractive index material; 7. Heat sink; 8. Topological homogenizing layer; 9. Intermediate refractive index layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1:

[0024] As shown in Figures 1-4, the present invention provides a thin-film laser based on a square prism-type topological homogenizing layer, comprising: a pumping system, a pump light injection module 3, a composite homogenizing waveguide structure, and a heat sink 5; wherein, the pumping system of the present invention comprises a pump source module 1 and a pump light coupling module 2 arranged sequentially, the pump light generated by the pump source module 1 is incident on the pump light injection module 3 after passing through the pump light coupling module 2, and then incident on the composite homogenizing waveguide structure through the pump light injection module 3. Furthermore, the pump source module 1 is a semiconductor laser or a fiber laser. The pump light generated by the pump source module 1 is coupled through the pump light coupling module 2 via fiber coupling or spatial optical coupling to form a collimated or decollimated pump beam that is perpendicularly incident on the pump surface of the pump light injection module 3, and each pump surface of the pump light injection module 3 receives pump light. The wavelength of the pump light generated by the pump source module 1 matches the center of the absorption spectral line of the gain medium. The number of pump source modules is odd to prevent the pump source from being damaged by incompletely absorbed pump light. Furthermore, the pump light injection module 3 uses a square prism, and the surface of the pump light injection module 3 perpendicular to the end face of the thin-film gain medium and located on the outside of the system is the pump surface. Furthermore, the pump light injection module 3 can be fabricated with microstructures to shape the pump light. The propagation of the pump light in the waveguide and its subsequent spatial distribution can be optimized by optimizing the size parameters of the prism in the pump light injection module. Furthermore, the pump source module 1 is configured to have an adjustable incident angle for its emitted light, thereby changing the initial position of the pump light injected into the intermediate refractive index layer, regulating the distribution of the pump light, and thus regulating its distribution within the thin-film gain medium.

[0025] The composite homogenizing waveguide structure of the present invention has a front end coated with a pump wavelength high-reflection film and a laser wavelength antireflection film, and a rear end coated with a pump source wavelength and a laser wavelength high-reflection film, and is bonded to a heat sink 7. The composite homogenizing waveguide structure includes a thin-film gain medium 4, a topological homogenizing layer 8 and an intermediate refractive index layer 9 arranged sequentially from the front end to the rear end. The topological homogenizing layer 8 is composed of a low refractive index material layer 5 and a high refractive index material topological pattern disposed thereon, and the high refractive index material topological pattern is determined according to the target light field distribution. The pump light injection module 3 (square prism) is fixed above the high refractive index material 6 of the topological homogenizing layer. The refractive indices of each material in the topological homogenizing layer 8 satisfy the following order: high refractive index material > intermediate refractive index layer material > low refractive index material. Furthermore, the central axes of the thin-film gain medium 4, the topological homogenizing layer 8, and the intermediate refractive index layer 9 coincide. The material of the thin-film gain medium 4 is a light-transmitting material, including one of YAG, YLF, YVO4, Al2O3, and SiO2. The light-transmitting material is doped with one or more lanthanide metal ions and transition metal ions as gain ions, and the lanthanide metal ions include Yb. 3+ 、Nd 3+and Er 3+ The transition metal ions include Cr 3+ Fe 3+ and Ti 3+ The low-refractive-index material layer 5 is selected from alkaline earth metal fluorides, such as CaF2 and MgF2; the high-refractive-index material 6 is selected from nitride semiconductor materials, such as Si3N4, AlN, BN, and GaN. Further, the intermediate refractive-index layer 9 is selected from silicon-based oxides, such as SiO2. Further, the heat sink 7 is copper, diamond, copper-tungsten alloy, or other types of materials. Further, the topological homogenizing layer 8 is directly deposited on the thin-film gain medium 4 or connected by bonding. Further, the topological pattern of the high-refractive-index material 6 can be designed according to the target pump light absorption distribution to actively control the spatial distribution of the pump light within the gain medium; the width of the high-refractive-index material topological pattern increases gradually along the direction pointing to the thin-film gain medium to optimize the spatial distribution of the pump light.

[0026] The pump light generated by the pump source module 1 of the present invention is collimated or non-collimated by the pump light coupling module 2 through fiber coupling or spatial optical coupling and is perpendicularly incident on the pump surface of the pump light injection module 3. The pump light injection module 3 first guides the high refractive index material 6 of the topological homogenizing layer 8 and then transmits it into the intermediate refractive index layer 9. Due to the refractive index difference between the intermediate refractive index layer material and the low refractive index material, the pump light undergoes total internal reflection at the interface between the two, forming a waveguide transmission. When the pump light is transmitted from the intermediate refractive index layer 9 to the interface between the high refractive index material and the intermediate refractive index layer, part or all of it is transmitted through the high refractive index material into the thin-film gain medium 4. The pump light propagates in a zigzag path. By controlling the topological pattern and spatial distribution of the high refractive index material on the low refractive index material, the homogenization of the pump light field and the optimization of mode matching are achieved.

[0027] This invention provides a method for fabricating a thin-film laser based on a square prism-type topological homogenizing layer, comprising the following steps: S1, obtaining a thin-film gain medium 4 through conventional grinding and polishing; S2, fabricating a low-refractive-index material layer 5 on the rear end face of the thin-film gain medium 4 using physical vapor deposition (PVD); S3, forming a preset topological pattern structure on the low-refractive-index material layer 5 through shadow mask deposition or photolithography and etching processes, or achieving a topological pattern structure with a gradient increase along the direction pointing to the thin-film gain medium 4 through multiple etching processes; S4, depositing a high-refractive-index material 6 in the topological pattern structure using chemical vapor deposition (CVD), filling the pattern and forming an embedded structure to complete the process. Fabrication of the topological homogenizing layer 8; S5, Depositing an intermediate refractive index layer 9 on the rear end face of the topological homogenizing layer using PVD or CVD methods to complete the fabrication of the composite homogenizing waveguide structure; S6, Depositing a pump source wavelength high-reflection film and a laser wavelength antireflection film on the front end face of the thin-film gain medium 4, and depositing a pump source wavelength and laser wavelength high-reflection film on the rear end face of the intermediate refractive index layer 9; S7, Fixing the pump light injection module at the edge of the topological homogenizing layer 8 using UV adhesive or mechanical fixation; S8, Connecting the rear end face of the intermediate refractive index layer 9 to the heat sink 7 using adhesive or welding; S9, Injecting the pump light emitted by the pump system into the composite homogenizing waveguide structure through the pump light injection module 3. Example 2:

[0028] As shown in Figures 5-7, the present invention provides a thin-film laser based on a right-angle prism topology homogenizing layer. The difference from Embodiment 1 is that the pump light injection module 3 is a right-angle prism, and the pump light injection module 3 (right-angle prism) is fixed above the intermediate refractive index layer 9; the surface of the pump light injection module that is perpendicular to the end face of the thin-film gain medium and located outside the system is the pump surface.

[0029] The pump light generated by the pump source module 1 of the present invention is collimated or non-collimated by the pump light coupling module 2 in the form of optical fiber coupling or spatial optical coupling and is perpendicularly incident on the pump surface of the pump light injection module (right angle prism) 3, and is directly introduced into the intermediate refractive index layer 9 by the pump light injection module 3.

[0030] The advantages of this invention are: 1. By designing the topology, this invention can actively and flexibly shape the three-dimensional absorption distribution of the pump light in the gain medium, fundamentally improving the pump uniformity and facilitating the suppression of higher-order modes and efficient extraction of the fundamental mode, thereby simultaneously improving the output power and beam quality.

[0031] 2. This invention eliminates the need for complex multi-pass spatial folding optical paths, relying primarily on integrated planar waveguide structures, significantly reducing the number of discrete optical components and the dependence on precision fitting. The system has a compact structure, good robustness, and is easy to modularize.

[0032] 3. This invention maintains the inherent excellent heat dissipation characteristics of thin-film lasers. By increasing the aperture of the gain medium and the area of ​​the homogenizing layer, the power density and thermal load in the gain medium can be effectively reduced without significantly increasing the system complexity. This is beneficial to giving full play to the scaling and amplification potential of the thin-film medium and achieving higher power output.

[0033] 4. The thin film deposition, photolithography, etching and other processes involved in this invention are all mature micro-nano processing technologies with good compatibility with semiconductor processes, which is conducive to realizing the miniaturization, integration and mass production of devices.

[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A thin-film laser based on a topological homogenizing layer, characterized in that, include: The system comprises a pumping system, a pump light injection module, and a composite homogenizing waveguide structure. The pump light generated by the pumping system is incident into the composite homogenizing waveguide structure via the pump light injection module. The front end of the composite homogenizing waveguide structure is coated with a high-reflection film for the pump light wavelength and an anti-reflection film for the laser wavelength, and the rear end is coated with a high-reflection film for the pump source wavelength and the laser wavelength. The composite homogenizing waveguide structure includes a thin-film gain medium, a topological homogenizing layer, and an intermediate refractive index layer, sequentially arranged from the front end to the rear end. The topological homogenizing layer is composed of a low-refractive-index material layer and a high-refractive-index material topological pattern disposed thereon, the high-refractive-index material topological pattern being determined according to the target light field distribution. The pump light injection module is fixed above the high-refractive-index material of the intermediate refractive index layer or the topological homogenizing layer. Each element in the topological homogenizing layer... The refractive indices of the materials satisfy the following order: high refractive index material > intermediate refractive index layer material > low refractive index material. The pump light emitted by the pump system is directly introduced into the intermediate refractive index layer by the pump light injection module, or first introduced into the high refractive index material of the topological homogenizing layer and then transmitted into the intermediate refractive index layer. Due to the refractive index difference between the intermediate refractive index layer material and the low refractive index material, the pump light undergoes total internal reflection at their interface, forming a waveguide for transmission. When the pump light is transmitted from the intermediate refractive index layer to the interface between the high refractive index material and the intermediate refractive index layer, part or all of it is transmitted through the high refractive index material into the thin-film gain medium, and the pump light propagates in a zigzag path. By controlling the topological pattern and spatial distribution of the high refractive index material on the low refractive index material, the homogenization of the pump light field and the optimization of mode matching are achieved.

2. The thin-film laser as described in claim 1, characterized in that, The pumping system includes a pump source module and a pump light coupling module arranged in sequence. The pump light generated by the pump source module is incident on the pump light injection module after passing through the pump light coupling module.

3. The thin-film laser as described in claim 1, characterized in that, The central axes of the thin-film gain medium, the topological homogenizing layer, and the intermediate refractive index layer coincide; the material of the thin-film gain medium is a light-transmitting material, including one of YAG, YLF, YVO4, Al2O3, and SiO2; wherein, the light-transmitting material is doped with one or more lanthanide metal ions and transition metal ions as gain ions, and the lanthanide metal ions include Yb 3+ 、Nd 3+ and Er 3+ The transition metal ions include Cr 3+ Fe 3+ and Ti 3+ The low refractive index material is selected from alkaline earth metal fluorides, the high refractive index material is selected from nitride semiconductor materials, and the intermediate refractive index layer material is selected from silicon-based oxides.

4. The thin-film laser as described in claim 1, characterized in that, Also includes: Heat sink; the heat sink is attached to the thin gain medium on the front end face or to the intermediate refractive index layer on the rear end face.

5. The thin-film laser as described in claim 1, characterized in that, The topological homogenizing layer is directly deposited on a thin-film gain medium or connected by bonding.

6. The thin-film laser as described in claim 1, characterized in that, The pump light injection module uses a right-angle prism or a square prism. The surface of the pump light injection module that is perpendicular to the end face of the thin-film gain medium and located outside the system is the pump surface. The pump light injection module can be fabricated with microstructures to shape the pump light. The propagation of the pump light in the waveguide and its subsequent spatial distribution can be optimized by optimizing the size parameters of the prism in the pump light injection module.

7. The thin-film laser as described in claim 2, characterized in that, The pump source module is a semiconductor laser or a fiber laser. The pump light generated by the pump source module is collimated or decollimated by the pump light coupling module through fiber coupling or spatial optical coupling and is perpendicularly incident on the pump surface of the pump light injection module. Each pump surface of the pump light injection module is incident with pump light. The wavelength of the pump light generated by the pump source module matches the center of the absorption spectrum of the gain medium. The number of pump source modules is odd to prevent the pump source from being damaged by pump light that is not completely absorbed.

8. The thin-film laser as described in claim 1 or 2, characterized in that, The pump source module is configured to have an adjustable incident angle for its emitted light, thereby changing the initial position of the pump light injected into the intermediate refractive index layer, regulating the distribution of the pump light, and thus regulating its distribution within the thin-film gain medium.

9. The thin-film laser as claimed in claim 1, characterized in that, The topological pattern of the high refractive index material can be designed according to the target pump light absorption distribution to actively control the spatial distribution of the pump light in the gain medium; the width of the topological pattern of the high refractive index material increases in a gradient along the direction pointing to the thin-film gain medium to optimize the spatial distribution of the pump light.

10. A method for fabricating a thin-film laser as described in any one of claims 1 to 9, characterized in that, The process includes the following steps: Step 1: Prepare a thin-film gain medium; Step 2: Prepare a low-refractive-index material layer on the rear face of the thin-film gain medium using physical vapor deposition (PVD); Step 3: Form a pre-defined topological pattern on the low-refractive-index material layer using shadow mask deposition or photolithography and etching processes, or achieve a topological pattern with a gradient increasing along the direction pointing towards the thin-film gain medium through multiple etching steps; Step 4: Deposit a high-refractive-index material in the topological pattern using chemical vapor deposition (CVD) to fill the pattern and form an embedded structure, thus completing the fabrication of the topological homogenizing layer; Step 5: Apply P-coating to the rear face of the topological homogenizing layer. A middle refractive index layer is deposited using VD or CVD methods to complete the fabrication of the composite homogeneous waveguide structure; Step 6: A pump source wavelength high reflectivity film and a laser wavelength antireflection film are deposited on the front end face of the thin-film gain medium, and a pump source wavelength and laser wavelength high reflectivity film are deposited on the rear end face of the middle refractive index layer; Step 7: The pump light injection module is fixed to the edge of the topological homogeneous layer using UV adhesive or mechanical fixation; Step 8: The front end face of the thin-film gain medium or the rear end face of the middle refractive index layer is connected to the heat sink by adhesive bonding or welding; Step 9: The pump light emitted by the pump system is incident on the composite homogeneous waveguide structure through the pump light injection module.

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