A multi-pass homogeneously pumped laser device based on blackbody absorption

Abstract

The application discloses a multi-pass uniform pumping laser device based on blackbody absorption, which comprises a pumping light source, a waveguide and a solid laser medium arranged along an optical path, and a curved surface reflecting device which is arranged on the same side of the pumping light source relative to the solid laser medium and forms a blackbody structure with the solid laser medium, and is used for reflecting the pumping light emitted after being absorbed by the solid laser medium back to the solid laser medium, so that the solid laser medium absorbs the pumping light for multiple passes, and generates and laterally outputs a laser beam. The application utilizes the curved surface reflecting device and the solid laser medium to form a blackbody structure to absorb the pumping light for multiple passes, increases the absorption length of the solid laser medium, can realize uniform pumping, reduces the thermal gradient, reduces the laser threshold, and improves the laser efficiency.

Description

Technical Field

[0001] This invention relates to the field of solid-state lasers. More specifically, it relates to a multi-pass uniformly pumped laser device based on blackbody absorption. Background Technology

[0002] With the development of semiconductor laser diodes, semiconductor-pumped all-solid-state lasers have advantages such as compact structure, high efficiency and good beam quality, and have broad application prospects, making them a key research focus in the laser field.

[0003] In recent years, with the development and cost reduction of high-performance InGaAs semiconductor lasers, a surge of research has emerged on quasi-three-level solid-state laser media doped with Yb and Tm ions. Due to its high quantum efficiency, broad absorption and emission spectra, long fluorescence lifetime, and excellent optical, thermodynamic, and mechanical properties, it has become one of the most promising solid-state laser materials for developing high-efficiency, high-power solid-state lasers.

[0004] Traditional methods for achieving quasi-three-level solid-state laser output at room temperature rely on end-pumping to reach high pump power density. This involves single / double-pass absorption of the pump light, necessitating increased ion doping concentration. While theoretically higher doping concentrations in the crystal lead to more active ions and thus higher power output, concentration quenching occurs at certain concentrations, and self-absorption intensifies with increasing concentration, raising the laser oscillation threshold, reducing efficiency, and impacting output. Furthermore, end-pumping requires shaping the pump light into a narrow stripe and coupling it into the crystal, presenting significant challenges in shaping and coupling.

[0005] Another approach is to increase the thickness of the solid-state laser medium. However, as the medium thickness increases, the distribution of pump light energy within the medium becomes more dispersed, leading to varying absorption intensities at different depths. This exponential absorption non-uniformity results in an increased thermal gradient, affecting pump uniformity. This thermal gradient can cause problems such as thermal stress and thermal expansion within the medium, and may even lead to its cracking or failure. Summary of the Invention

[0006] The present invention provides a multi-pass uniform pumped laser device based on blackbody absorption to solve at least one of the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a multi-path uniformly pumped laser device based on blackbody absorption. The laser device includes a pump source, a waveguide, and a solid-state laser medium arranged along the optical path.

[0009] A curved reflector is provided, which is disposed on the same side of the pump light source with respect to the solid-state laser medium and forms a blackbody structure with the solid-state laser medium. It is used to reflect the pump light emitted after being absorbed by the solid-state laser medium back to the solid-state laser medium, so that the solid-state laser medium absorbs the pump light through multiple passes and generates and outputs a laser beam laterally.

[0010] Preferably, the curved reflective device includes a reflective cavity, the reflective cavity having a through-hole for incident pump light from the light source; or

[0011] The reflecting cavity is integrally formed with the waveguide.

[0012] Preferably, the curved reflective device includes a light-transmitting body, wherein an anti-reflection coating is provided on the side of the light-transmitting body near the solid-state laser medium; an anti-reflection coating is provided on the side of the light-transmitting body away from the solid-state laser medium at a position corresponding to the incident pump light source; and a reflective coating is provided on the remaining portion, constituting a reflective light-transmitting body; or

[0013] The curved reflective device includes a reflective cavity, and the light-transmitting body is housed in the reflective cavity.

[0014] Preferably, the reflective cavity is coated with a reflective film.

[0015] Preferably, the curved surface of the curved reflector is hemispherical, ellipsoidal, or bell-shaped.

[0016] Preferably, a transmission film is provided on the surface of the solid laser medium near the curved reflective device; and / or

[0017] A reflective film is provided on the surface of the solid laser medium on the side away from the curved reflective device.

[0018] Preferably, the waveguide is a plate waveguide, and the light-transmitting body is integrally formed with the plate waveguide; or

[0019] The plate waveguide is disposed within the through hole of the reflective cavity.

[0020] Preferably, the light-transmitting body is a plane or an arc surface convex to the solid-state laser medium on the side closest to the solid-state laser medium.

[0021] Preferably, the laser device further includes a first cooling module, comprising a cooling water flow channel disposed on the surface of the solid laser medium near the curved reflector; and a second cooling module, comprising a cooling heat sink welded to the surface of the solid laser medium away from the curved reflector.

[0022] Preferably, the laser device includes a first pump optical path and a second pump optical path respectively disposed on both sides of the solid-state laser medium.

[0023] The first pump optical path includes a first pump light source and a first curved surface reflector disposed on the same side.

[0024] The second pump optical path includes a second pump light source and a second curved surface reflector disposed on the same side, wherein the first curved surface reflector, the second curved surface reflector and the solid laser medium form a blackbody structure.

[0025] Preferably, the laser device includes multiple pump light source optical paths and a curved reflector. Each light source optical path includes a pump light source, a focusing lens and a waveguide arranged in sequence, and each waveguide incident the pump light from the corresponding light source onto the solid laser medium.

[0026] The beneficial effects of this invention are as follows:

[0027] This invention utilizes curved reflective devices to form a blackbody structure with a solid-state laser medium, enabling multi-path absorption of the pump light by the laser medium. This increases the effective absorption length of the solid-state laser medium, reduces the dopant ion concentration, and improves laser efficiency, achieving high-power, high-efficiency laser output. This solves the problems of high ion doping concentration, severe self-absorption, increased laser oscillation threshold, large thermal gradient, uneven pumping, and low efficiency in existing quasi-trilevel crystals at room temperature. Furthermore, this invention further improves beam quality, power, and stability by thermally managing both the upper and lower surfaces of the solid-state laser medium. Compared to existing room-temperature quasi-trilevel solid-state laser modules, the laser device of this invention reduces pump shaping difficulty, is simpler, and easier to use. Attached Figure Description

[0028] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0029] Figure 1 A schematic diagram of the structure of the laser device according to the first embodiment of the present invention is shown;

[0030] Figure 2 This diagram illustrates the optical path of the pump light within the blackbody structure according to a second embodiment of the present invention.

[0031] Figure 3 A schematic diagram showing the absorption pump power of a solid-state laser medium with different absorption lengths;

[0032] Figure 4 This diagram illustrates the structure of a multi-pass uniformly pumped slab laser device according to a third embodiment of the present invention.

[0033] Figure 5 This diagram shows a bell-shaped curved reflective device in the fourth embodiment of the present invention.

[0034] Figure 6A schematic diagram of the structure of the laser device according to the fifth embodiment of the present invention is shown. Detailed Implementation

[0035] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0036] One aspect of the present invention provides a multi-path uniformly pumped laser device based on blackbody absorption. The laser device includes a pump source, a waveguide, a solid-state laser medium, and a curved reflector arranged along the optical path. The curved reflector and the pump source are arranged on the same side of the solid-state laser medium and form a blackbody structure with the solid-state laser medium. This blackbody structure reflects the pump light emitted after absorption by the solid-state laser medium back to the solid-state laser medium, so that the solid-state laser medium performs multi-path absorption of the pump light to generate and laterally output a laser beam. As an example, the laser device of the present invention is a side-pumped slab laser device, utilizing the two large surfaces of the slab for pumping. The thickness direction of the slab is the absorption direction of the pump light, and the incident direction of the pump light is, for example, perpendicular to the light transmission direction of the gain medium. By utilizing a blackbody structure formed by a curved reflector and a solid-state laser medium, the pump light passes through a waveguide and the curved reflector. It is incident on the first large surface of the solid-state laser medium, absorbed, reflected by the second large surface, absorbed again, and exits from the first large surface. The light is then reflected back into the solid-state laser medium by the reflecting surface of the curved reflector, and is again incident on the first large surface and absorbed. This process of multi-path absorption is repeated multiple times until the pump light is almost completely absorbed. In this way, by forming a blackbody structure, the effective absorption length of the solid-state laser medium is increased, achieving high-power, high-efficiency laser output. This invention reduces the requirements for the performance of the solid-state laser medium and solves the problems of increased laser oscillation threshold, large thermal gradient, uneven pumping, and low efficiency in existing technologies.

[0037] The curved reflective device can be a reflective cavity, which has a through-hole for incident pump light from the light source. The surface of the reflective cavity is preferably coated with a reflective film to improve reflection efficiency. As preferred examples, the reflective cavity is, for example, a hemispherical cavity, an ellipsoidal cavity, a bell-shaped cavity, etc. The waveguide can be, for example, a plate waveguide, and the through-hole of the reflective cavity provides support for the plate waveguide while providing the pump light path. The waveguide can be, for example, a waveguide cavity, and the reflective cavity can be integrally formed with the waveguide cavity from a metal component.

[0038] The curved reflective device can be a transparent body. The transparent body has an anti-reflection coating on the side near the solid-state laser medium and an anti-reflection coating on the side away from the solid-state laser medium corresponding to the incident pump light source. The remaining portion is coated with a reflective film, thus becoming a reflective transparent body. As a preferred example, the curved reflective device includes a reflective cavity and a transparent body. The transparent body is disposed in the reflective cavity, which provides support for the transparent body and provides specular reflection for the curved reflective device, improving the pump light reflection efficiency.

[0039] In a preferred embodiment, the waveguide is a plate waveguide, and the light-transmitting body and the plate waveguide can be separated or integrated. In an integrated structure, the light-transmitting body has an anti-reflection coating on the side near the solid-state laser medium and a reflective coating on the side away from the solid-state laser medium. This structure reduces the difficulty of forming the reflective coating on the light-transmitting body and improves the incident efficiency of the pump light from the light source.

[0040] The light-transmitting body is a plane or preferably an arc surface convex to the solid laser medium on the side closest to the laser medium. Increasing the area of ​​the light-transmitting body on the side closest to the laser medium can reduce the surface energy density, lower the temperature, and reduce energy loss.

[0041] In a preferred embodiment, the curved surface of the reflective device can be hemispherical, ellipsoidal, or bell-shaped. Utilizing the unique geometry of the curved surface, the reflective surface can better and more uniformly reflect the pump light back, thereby improving the uniformity of the pump light. Specifically, a bell-shaped reflective surface can generate more "diffuse reflection points" on the surface of the light source, allowing the light to be scattered and reflected more uniformly. Furthermore, the bell-shaped blackbody can reduce the deviations caused by secondary reflection and diffuse reflection, further improving the uniformity of the pump light.

[0042] As a specific example, the pump light is incident from one side of the laser medium. A transmission film is provided on the surface of the solid laser medium near the curved reflector, and a reflection film is provided on the surface away from the curved reflector, thereby improving transmittance and reducing energy loss.

[0043] In a preferred embodiment, the laser device further includes a first cooling module disposed on the surface of the solid laser medium near the curved reflector; and / or a second cooling module disposed on the surface of the solid laser medium away from the curved reflector. The cooling module can be a cooling water flow channel or a cooling heat sink welded to the surface of the solid laser medium.

[0044] In a second aspect, the provided laser device includes a solid-state laser medium and a first pump optical path and a second pump optical path respectively disposed on both sides of the solid-state laser medium. The first pump optical path includes a first pump light source, a first coupling focusing lens, a first waveguide, and a first curved surface reflector disposed on the same side. The second pump optical path includes a second pump light source, a second coupling focusing lens, a second waveguide, and a second curved surface reflector disposed on the same side. The first curved surface reflector and the second curved surface reflector form a blackbody structure with the solid-state laser medium. The first pump light passes through the first coupling focusing lens, the first waveguide, and the first curved surface reflector, is incident on the first large surface of the solid-state laser medium, and is absorbed by the medium. The second pump light passes through the second coupling focusing lens, the second waveguide, and the second curved surface reflector, is incident on the second large surface of the solid-state laser medium, and is absorbed by the medium. Pump light emitted from the first large surface is reflected back into the solid-state laser medium by the reflecting surface of the first curved reflector, and then incident on the first large surface of the solid-state laser medium again and is absorbed. Pump light emitted from the second large surface is reflected back into the solid-state laser medium by the reflecting surface of the second curved reflector, and then incident on the second large surface of the solid-state laser medium again and is absorbed. This multi-path absorption is repeated multiple times until a laser beam is formed and output from the side end face. In this way, by forming a blackbody structure, the absorption efficiency of the solid-state laser medium is further improved, and high-power, high-efficiency laser output can be achieved with a compact structure. As a specific example, the surfaces of the corresponding first and second pump light paths of the solid-state laser medium are coated with anti-reflection films.

[0045] In a third aspect, the provided laser device includes multiple pump source optical paths arranged on the same side of a solid-state laser medium and a curved reflector. Each source optical path includes a pump source, a coupling focusing lens, and a waveguide arranged sequentially. Each waveguide directs pump light from its corresponding source onto the solid-state laser medium. Similarly, this arrangement allows for a compact structure that improves the absorption efficiency of the solid-state laser medium, achieving high-power, high-efficiency laser output. As a specific example, the surface of the solid-state laser medium near the curved reflector is coated with an anti-reflection film, while the surface away from the curved reflector is coated with a reflective film.

[0046] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0047] The first embodiment of the present invention provides a multi-pass uniform pumped laser device based on blackbody absorption, see [link to documentation]. Figure 1 The laser device includes a first semiconductor pump source 11, a first pump light coupling focusing lens 12, a first waveguide 13, a first curved surface reflecting device, and a solid-state laser medium 2 arranged along the optical path, as well as a first cooling module 16 and a second cooling module 17.

[0048] The first semiconductor pump source 11 is used to emit the first pump light;

[0049] The first pump light coupling focusing lens 12 and the first semiconductor pump source 11 are spaced apart to focus and couple the first pump light into the first waveguide 13.

[0050] The first waveguide 13, whose top can be curved or flat, is used to increase the scattering of the pump light due to total internal reflection, so that the distribution of the pump light tends to be uniform. The first waveguide 13 homogenizes the incoming first pump light and outputs it to the solid laser medium 2. It is also used to increase the interaction between the pump light and the solid laser medium to improve the multi-pass absorption effect.

[0051] The first curved surface reflective device includes a first sub-curved surface reflective device and a second sub-curved surface reflective device, namely a first light-transmitting body 14 and a first metal reflective shell 15 providing a reflective cavity. The first curved surface reflective device and the solid laser medium 2 form a blackbody structure with a closed space. The first waveguide 13 and the first light-transmitting body 14 can be integrally arranged or separately arranged.

[0052] The first metallic reflective shell 15 is an opaque copper block. The surface of the first metallic reflective shell 15 near the solid-state laser medium 2 is recessed inward to form a first hemispherical cavity. A first pump light through-hole 151A is provided on the portion of the first metallic reflective shell 15 corresponding to the first waveguide 13. A metallic reflective layer 151B is plated on the inner surface of the first hemispherical cavity of the first metallic reflective shell 15, forming a mirror-like reflective shell. The first light-transmitting body 14 is housed within the recess on the surface of the first metallic reflective shell 15 near the solid-state laser medium 2. As another specific example (not shown), the first metallic reflective shell 15 can form a blackbody structure with the solid-state laser medium 2, creating a laser device with a simple structure.

[0053] The solid laser medium 2 is in the shape of a strip or a rod, and is used to perform multi-path absorption of the incident first pump light; the solid laser medium 2 has a bonded structure; and / or, the solid laser medium is made of a quasi-three-level solid laser medium doped with Yb ions, Tm ions, etc.

[0054] A film with high transmittance to pump light is deposited on the large surface of the solid laser medium 2 on the side close to the first curved reflector, thereby increasing the transmittance of pump light into the solid laser medium 2; a film with high reflectivity to pump light is deposited on the large surface of the solid laser medium 2 on the side away from the first curved reflector, thereby repeatedly reflecting pump light to achieve multi-path absorption of pump light.

[0055] The first cooling module 16 includes, for example, a cooling water flow channel, disposed on the surface of the solid laser medium 2 near the first reflective light-transmitting body 14, for cooling the solid laser medium 2.

[0056] The second cooling module 17, for example, is a cooling heat sink, welded to the surface of the solid laser medium 2 away from the first reflective light-transmitting body 14, and is used to cool the solid laser medium 2.

[0057] In a specific example, the solid-state laser medium 2 is shaped like a strip; the first waveguide 13 is plate-shaped with a curved top; the first light-transmitting body 14 is a solid, transparent hemisphere, with its surface near the solid-state laser medium 2 being an arc-shaped surface and its surface away from the solid-state laser medium 2 being a hemisphere. This hemisphere, along with the first metal reflective shell 15 which is also hemispherical, facilitates the specular reflection of the pump light. The top of the first waveguide 13 can also be made flat, and the shape of the first reflective light-transmitting body 14 can also be other shapes, as long as they meet the requirement of achieving specular reflection of the pump light.

[0058] See Figure 1 The first semiconductor pump source 11 and the first pump light coupling focusing lens 12 are arranged at intervals. The first semiconductor pump source 11 is a bar array with a fast axis collimating lens. The fast axis collimating lens (FAC) collimates the emitted first pump light. The first semiconductor pump source 11 directs the collimated first pump light into the first pump light coupling focusing lens 12.

[0059] The first pump light coupling focusing lens 12 is spaced apart from the first waveguide 13. The first pump light, after being focused by the first pump light coupling focusing lens 12, is coupled into the curved surface at the top of the first waveguide 13. The first waveguide 13 homogenizes the incident pump light and outputs it to the solid-state laser medium 2. Specifically, the pump light incident into the first waveguide 13 undergoes multiple total internal reflections on the curved surface, resulting in increased beam divergence. The light is scattered or diffused at a larger angle and range, which in turn allows the originally unevenly distributed light to mix better, making the light distribution more uniform.

[0060] In this example, the first waveguide 13 and the first light-transmitting body 14 are separately disposed. The surface of the first light-transmitting body 14 near the solid laser medium 2 is an arc-shaped curved surface, and the surface away from the solid laser medium 2 is a hemispherical surface. The first light-transmitting body is coated with an anti-reflection film.

[0061] The first metal reflective housing 15 is a reflective device. Its surface near the solid-state laser medium 2 is recessed inward to form a first hemispherical cavity. The hemispherical surface facilitates specular reflection of the pump light. A first pump light through-hole 151A is provided on the portion of the first metal reflective housing 15 corresponding to the first waveguide 13. A metal reflective layer 151B is deposited on the inner surface of the first hemispherical cavity of the first metal reflective housing 15 to reflect the first pump light towards the solid-state laser medium 2. The first waveguide 13 is disposed within the first pump light through-hole 151A. The first metal reflective housing 15 is made of copper. Compared to traditional diffuse reflective bodies, specular reflection in this embodiment has high reflectivity and low loss. The first curved reflective device can be made in different shapes to prevent light escape, improve light uniformity, and enhance beam quality.

[0062] A first cooling module 16 is disposed between the surface of the solid-state laser medium 2 near the first light-transmitting body 14 and the first light-transmitting body 14. The first cooling module 16 includes a cooling water flow channel to provide cooling for the solid-state laser medium 2. A second cooling module 17 is welded to the surface of the solid-state laser medium 2 away from the first light-transmitting body 14. The second cooling module 17 is a cooling heat sink to provide cooling for the solid-state laser medium 2.

[0063] In this embodiment, the solid-state laser medium 2 is made of one of the quasi-three-level solid-state laser media doped with Yb ions or Tm ions. The solid-state laser medium 2 is primarily designed as a quasi-three-level gain medium at room temperature. Specifically, the solid-state laser medium 2 is selected from materials exhibiting severe self-absorption at room temperature, such as Yb:YAG crystal, Yb:YAG ceramic, or Tm:YAG crystal. These laser crystals possess advantages such as high quantum efficiency, broad absorption and emission spectra, long fluorescence lifetime, and excellent optical, thermodynamic, and mechanical properties, making it possible to achieve high-power laser output, realizing high-power, high-efficiency laser output, and expanding the application scope of lasers.

[0064] A high-transmittance film for pump light is deposited on the surface of the solid-state laser medium 2 near the curved reflector to increase the transmittance of pump light into the solid-state laser medium 2. A high-reflectance film for pump light is deposited on the surface of the solid-state laser medium 2 away from the curved reflector to achieve multi-path absorption of the pump light. In this embodiment, the transmittance of the high-transmittance film is above 90%, and the reflectance of the high-reflectance film is above 90%. For example, when the solid-state laser medium 2 is a Yb:YAG crystal, and the wavelength of the pump light is 940 nm, the upper surface of the solid-state laser medium 2 near the curved reflector is deposited with a film having a transmittance of 99.8% for 940 nm pump light, and the lower surface of the solid-state laser medium 2 away from the curved reflector is deposited with a film having a reflectance of 99.9% for 940 nm pump light.

[0065] Figure 2 This is a schematic diagram of the optical path of the pump light within the blackbody structure according to the second embodiment of the present invention. In this embodiment, the curved reflective device is a reflective transparent body 214. The reflective transparent body 214 is a transparent solid quartz hemisphere. The surface of the reflective transparent body near the solid laser medium is an arc-shaped curved surface, and the surface away from the solid laser medium is a hemisphere. An antireflective film is coated at the portion 214A of the hemisphere corresponding to the first waveguide 13, and a reflective film 214B is coated at the remaining positions of the hemisphere. The shape of the reflective transparent body 214 includes, but is not limited to, a hemisphere, an ellipsoid, and a bell shape. After being absorbed by the solid laser medium, the pump light emitted is reflected by the mirror surface of the reflective transparent body 214 coated with the reflective film and then re-enters the solid laser medium 2, allowing the pump light to enter the solid laser medium multiple times. This enhances the interaction between the pump light and the matter, increases the absorption length, and improves the efficiency of light energy absorption.

[0066] like Figure 2 As shown, the first pump light emitted from the first semiconductor pump source 11 is coupled and focused by the first pump light coupling and focusing lens 12 and then coupled into the top curved surface of the first waveguide 13. The first waveguide 13 homogenizes the coupled first pump light and emits it, which is then directly injected into the solid-state laser medium 2 through the first reflective light-transmitting body 214, pumping the upper surface of the solid-state laser medium 2. The upper surface of the solid-state laser medium 2 refers to the large surface area of ​​the solid-state laser medium 2 near the first reflective light-transmitting body 214, and the lower surface of the solid-state laser medium 2 refers to the large surface area of ​​the solid-state laser medium 2 away from the first reflective light-transmitting body 214. After being irradiated by the first pump light, the solid-state laser medium 2 absorbs the energy of the first pump light once and converts it into a population inversion distribution; subsequently, the solid-state laser medium 2 further absorbs the pump light, generating laser oscillation, completing one absorption of the pump light. Specifically, as... Figure 2 As shown, when the first pump light emitted from the first waveguide 13 passes through the transparent portion 214A of the reflective transparent body 214 and enters the solid laser medium 2 through the upper surface of the solid laser medium 2, it first undergoes refraction and then undergoes exponential absorption through the upper surface of the solid laser medium 2 (see...). Figure 2 The pump light (①) is then emitted to the lower surface of the solid-state laser medium 2. After reaching the lower surface of the solid-state laser medium 2, it is reflected back to the upper surface of the solid-state laser medium 2 (see [reference]). Figure 2 (②), after exponential absorption again, the pump light is refracted back to the first reflective light-transmitting body 14, and then reflected back to the upper surface of the solid laser medium 2 through the reflective wall 214B of the first reflective light-transmitting body 214 for exponential absorption (see ②). Figure 2 (③) The pump light is emitted to the lower surface of the solid-state laser medium 2. After reaching the lower surface of the solid-state laser medium 2, it is reflected back to the upper surface of the solid-state laser medium 2 (see...). Figure 2 (④) The upper surface of the solid-state laser medium 2 is pumped, and the light is reflected back into the solid-state laser medium 2 by the reflector 214 (see ④). Figure 2 (⑤) This cycle repeats, and the pump light undergoes multi-stage absorption.

[0067] When a medium is subjected to a thermal gradient, temperature differences will occur in different parts, leading to thermal stress and thermal expansion within the material or on its surface. Thermal stress is the stress induced by deformation and pressure during temperature changes within the medium or on its surface; under the action of a thermal gradient, this stress will eventually reach equilibrium within the medium. Thermal expansion is the phenomenon of a material expanding in volume when heated. When a medium is affected by thermal stress or thermal expansion, the internal structure of the medium may undergo deformation or stress concentration areas may form, which may lead to the breakage or failure of the medium. Problems caused by thermal gradients are more likely to occur, especially when there are defects or stress concentration areas within the material.

[0068] In this embodiment, pumping is performed on the upper and lower surfaces of the solid laser medium 2 to increase the incident area and the degree of surface absorption; a low-doped, thin solid laser medium is used to reduce the thermal gradient and improve pump uniformity.

[0069] Figure 3 This is a schematic diagram of the absorption pump power of the laser device in this embodiment.

[0070] Figure 3 The figure shows the pump power absorbed by the pump light in a 3mm slab laser medium. The horizontal axis represents the depth along the 3mm thickness of the slab, and the vertical axis represents the normalized absorbed pump power. As shown, different curves represent the absorbed pump power at absorption lengths of 1, 2, and 5 passes. Based on the results of the pump light absorbed by the pump power, it can be seen that the pump light uniformity is optimal when the absorption length is 5 passes. This means that increasing the absorption length of the solid-state laser medium using this device improves the pump light uniformity.

[0071] Figure 4 The diagram shows a schematic of the structure of a multi-pass uniformly pumped slab laser device according to the third embodiment. This embodiment is based on specific embodiment 1, but the second cooling module 17 is removed. A second semiconductor pump source 31, a second pump light coupling focusing lens 32, a second waveguide 33, a second curved surface reflector, and a third cooling module 37 are added to the surface of the solid laser medium 2 away from the first reflective light transmittance body 14. The solid laser medium 2 has a transmission film deposited on both the first and second large-area surfaces of the incident pump light.

[0072] The second semiconductor pump source 31 is used to emit the second pump light. The second semiconductor pump source 31 and the first semiconductor pump source 11 are respectively disposed on opposite sides of the solid-state laser medium 2. The second semiconductor pump source 31 is a bar array with a fast-axis collimating lens (FAC) to collimate the light emitted by the semiconductor laser.

[0073] The second semiconductor pump source 31 is used to focus and couple the collimated second pump light into the second waveguide 33. The second pump light coupling focusing lens 32 and the first pump light coupling focusing lens 12 are respectively disposed on opposite sides of the solid laser medium 2. The second pump light coupling focusing lens 32 and the second semiconductor pump source 31 are spaced apart.

[0074] The first and second curved surface reflectors form a closed blackbody structure with the solid-state laser medium 2. This structure reflects the pump light emitted after absorption by the solid-state laser medium 2 back to the solid-state laser medium 2, allowing the solid-state laser medium 2 to perform multi-path absorption of the first and second pump lights, generating and outputting a laser beam. The second curved surface reflector includes a third sub-curved surface reflector and / or a fourth sub-curved surface reflector. The third sub-curved surface reflector is a second light-transmitting body 34, which is a transparent solid quartz hemisphere. The surface near the solid-state laser medium 2 is an arc-shaped curved surface, and the surface away from the solid-state laser medium 2 is a hemispherical surface. An anti-reflection coating is deposited on the hemispherical surface corresponding to the second waveguide 33. The fourth sub-curved surface reflector is a second metal reflective shell 35, which is an opaque arc-shaped copper block. The surface of the second metal reflective shell 35 near the solid laser medium 2 is recessed inward to form a hemispherical cavity. A second pump light through hole 351A is provided at the position of the second waveguide 33 on the second metal reflective shell 35. The second waveguide 33 is located in the second pump light through hole 351A. A reflective metal layer 351B is plated on the inner surface of the second hemispherical cavity of the second metal reflective shell 35.

[0075] The second waveguide 33 is plate-shaped with a curved top. It is separate from the second light-transmitting body 34. The second waveguide 33 homogenizes the incident second pump light, which then enters the solid-state laser medium 2. The second light-transmitting body 34 is solid and made of quartz. The second light-transmitting body 34 and the first light-transmitting body 14 are located on opposite sides of the solid-state laser medium 2.

[0076] The second reflector 351B is constructed as an arc-shaped structure such as a hemisphere or ellipsoid, that is, its cross-section is an arc-shaped structure, which facilitates the specular reflection of the pump light. In this embodiment, the second reflector 351B is hemispherical, but other shapes can also be used, as long as they can satisfy the requirement of specular reflection of the pump light.

[0077] In this embodiment, the first light-transmitting body 14 and the second light-transmitting body 34 are made of the same material and have the same structure. Of course, the first light-transmitting body 14 and the second light-transmitting body 34 can also be made of different materials and have different structures.

[0078] High-transmittance films are deposited on both the surface of the solid-state laser medium 2 near the first curved reflector and the surface near the second curved reflector. This means that the pump light emitted by the first semiconductor pump source 11 and the second semiconductor pump source 31 undergoes multi-path absorption between the first and second curved reflectors through the same solid-state laser medium 2. The high-transmittance films have a transmittance of over 90%.

[0079] The pump light emitted by the first semiconductor pump source 11 and the second semiconductor pump source 31 has the same wavelength, so that the pump light emitted by the first semiconductor pump source 11 and the second semiconductor pump source 31 achieves multi-path absorption of the solid laser medium 2 through the first reflective light-transmitting body 14 and the second reflective light-transmitting body 34.

[0080] The third cooling module 37 includes a cooling water flow channel, which uses cooling water to dissipate heat from the lower surface of the solid laser medium 2.

[0081] In this embodiment, the pump light is reflected by setting the first curved surface reflector and the second curved surface reflector as symmetrical about the solid laser medium 2, which increases the pump light that provides excitation in the solid laser medium 2, increases the effective absorption length of the medium, and realizes multi-path absorption of the pump light.

[0082] As a fourth embodiment, based on the first embodiment, the first semiconductor pump source 11, the first pump light coupling focusing lens 12, the first waveguide 13, the solid-state laser medium 2, the first cooling module 16, and the second cooling module 17 remain unchanged. The shape of the curved surface of the curved reflective device is adjusted. Preferably, the shape of the reflective surface of the reflective cavity 45 and the light-transmitting body 44 is adjusted to a bell shape. Figure 5 This is a schematic diagram of a curved reflective device with a bell-shaped reflective surface.

[0083] Due to its unique geometry, the bell-shaped reflective surface generates more diffuse reflection points on the light source surface, resulting in more uniform scattering and reflection of light, thus improving the uniformity of the pump light. Furthermore, the bell-shaped reflective surface reduces deviations caused by secondary and diffuse reflections of the pump light, further enhancing its uniformity.

[0084] Those skilled in the art should understand that the shape of the reflective surface of a curved reflective device can also be selected in other shapes to achieve specular reflection of the pump light.

[0085] As a fifth embodiment, compared with the first embodiment, this embodiment increases the number of semiconductor pump sources, pump light coupling focusing lenses and waveguides on the same side of the curved reflector, and correspondingly increases the number of pump light through holes in the curved reflector, thereby improving the stability and reliability of the system. Figure 6This is a schematic diagram of a laser device including two pump light source optical paths in this embodiment.

[0086] Specifically, in this embodiment, those skilled in the art should understand that it is impossible to set multiple identical waveguides on the same solid-state laser medium. Therefore, it is preferable to set two identical pump sources to increase the absorption length. Specifically, two first semiconductor pump sources 11 and 51, two first pump light coupling focusing lenses 12 and 52, two first waveguides 13 and 53, and two first pump light through-holes 551A on the curved reflector are set on the same side of the solid-state laser medium 2 to realize two pump light paths. By increasing the number of pump light paths, the incident area and energy of the pump light are increased, allowing more pump light to enter the curved reflector. This can increase the multi-path absorption effect on the surface of the laser medium and improve the absorption efficiency. It can also make the light field more uniformly distributed in the curved reflector, avoiding the situation of excessive local light intensity or non-uniformity, thereby improving the uniformity of energy transmission.

[0087] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0088] It should also be noted that in the description of this invention, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0089] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A multi-pass uniformly pumped laser device based on blackbody absorption, characterized in that, The laser device includes a pump source, a waveguide, and a solid-state laser medium arranged along the optical path, as well as a curved reflector. The curved reflector is arranged on the same side as the pump source with respect to the solid-state laser medium and forms a blackbody structure with the solid-state laser medium. It is used to reflect the pump light emitted after being absorbed by the solid-state laser medium back to the solid-state laser medium, so that the solid-state laser medium absorbs the pump light in multiple passes and generates and outputs a laser beam laterally. The curved reflective device includes a reflective cavity. The waveguide is a plate waveguide, and the reflecting cavity is provided with a through-hole for incident pump light from the light source and for providing support for the plate waveguide; or The waveguide is a waveguide cavity, and the reflecting cavity is integrally formed with the waveguide; The curved reflective device includes a light-transmitting body disposed in the reflective cavity. The light-transmitting body has an anti-reflection coating on the side close to the solid-state laser medium, an anti-reflection coating on the side away from the solid-state laser medium corresponding to the incident pump light, and a reflective coating on the remaining part, thus forming a reflective light-transmitting body; or the curved reflective device includes a reflective cavity, and the light-transmitting body is housed in the reflective cavity. The translucent body is solid and made of quartz. The laser device includes a third cooling module, which includes a cooling water flow channel and uses cooling water to dissipate heat from the lower surface of the solid laser medium. The laser device includes multiple pump source optical paths and a curved surface reflector.

2. The laser device according to claim 1, characterized in that, The curved surface of the surface reflector is hemispherical, ellipsoidal, or bell-shaped.

3. The laser device according to claim 1, characterized in that, A transmission film is disposed on the surface of the solid laser medium near the curved reflective device; and / or or A reflective film is provided on the surface of the solid laser medium on the side away from the curved reflective device.

4. The laser device according to claim 1, characterized in that, The waveguide is a plate waveguide, and the light-transmitting body is integrally formed with the plate waveguide; or The plate waveguide is disposed within the through hole of the reflective cavity.

5. The laser device according to claim 1, characterized in that, The light-transmitting body is either a plane or an arc surface convex to the solid-state laser medium on the side closest to the solid-state laser medium.

6. The laser device according to claim 1, characterized in that, The laser device also includes The first cooling module is disposed on the surface of the solid laser medium near the curved reflective device.

7. The laser device according to claim 1, characterized in that, The laser device includes a first pump optical path and a second pump optical path respectively disposed on both sides of the solid-state laser medium. The first pump optical path includes a first pump light source and a first curved surface reflector disposed on the same side. The second pump optical path includes a second pump light source and a second curved surface reflector disposed on the same side, wherein the first curved surface reflector, the second curved surface reflector and the solid laser medium form a blackbody structure.

8. The laser device according to claim 1, characterized in that, Each light source optical path includes a pump light source, a focusing lens and a waveguide arranged in sequence, and each waveguide incident the pump light from the corresponding light source onto the solid laser medium.

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