A high average power, high repetition rate, large energy nanosecond pulsed solid state laser

Abstract

The application provides a high average power, high repetition rate and large energy nanosecond pulse solid-state laser, comprising: a confocal unstable resonant cavity; a saturable absorber module, which comprises a laser crystal and a cooled copper heat sink; a bleaching laser, which is vertically irradiated on the saturable absorber; a plurality of laser gain modules, which are sequentially arranged inside the confocal unstable resonant cavity, and any laser gain module comprises a laser medium, a cooled copper heat sink, a diode stack pump source and a two-dimensional cylindrical shaping lens group, the repetition rate pulse pump light shaped by the two-dimensional cylindrical shaping lens group is vertically irradiated on the front surface of the laser medium, and the back surface of the laser medium is welded on the cooled copper heat sink. The application can pulse modulate a single cavity oscillation laser, realize nanosecond pulse laser output with an average power of thousands of watts and a pulse energy of up to 10J.

Description

Technical Field

[0001] This invention relates to the field of pulsed laser technology, and more particularly to a high average power, high repetition rate, high energy nanosecond pulsed solid-state laser. Background Technology

[0002] High-energy, high-pulse nanosecond lasers have wide applications in numerous fields, such as shock strengthening, Thomson scattering as a source for measuring plasma temperature in tokamak experiments, and illumination for long-distance detection. Shock strengthening is the most widespread application. After shock strengthening, the lifespan of components can typically be increased by more than tenfold. It is suitable for easily worn parts such as bearings in high-speed trains, aircraft propeller blades, and machine tool cutting tools. However, in my country, the use of laser shock strengthening technology to improve key components is not widespread. The main reason is that the lasers currently used for shock strengthening typically employ flash-pumped high-energy pulsed solid-state lasers. Their pulse energy can reach the 10 joule range, but the repetition rate is usually in the 1-10 Hz range. Shock strengthening a component, especially a large component like a propeller blade, is very time-consuming, significantly reducing the practical application value of shock strengthening. Therefore, there is an urgent need to develop a high-repetition-rate, high-energy nanosecond pulsed laser to meet its pressing needs in industrial applications and cutting-edge scientific research.

[0003] Currently, high-energy nanosecond pulsed lasers mainly fall into two categories: (1) flash lamp-pumped pulsed solid-state lasers, characterized by relatively high pulse energy. However, the repetition rate is usually less than 10 Hz, and the average power is usually less than 100 W. (2) MOPA-type diode-pumped pulsed solid-state lasers, with a maximum average power of 1 kW, a repetition rate of several hundred Hz, and a pulse energy typically in the range of 1-5 J. These are achieved using the MOPA (first-stage oscillation plus 4-5-stage amplification) method. If a laser with a higher repetition rate or greater pulse energy is required, both of the above methods face significant challenges. Summary of the Invention

[0004] To address the aforementioned technical challenge of achieving high pulse energy and high repetition rate in existing lasers, this invention provides a high average power, high repetition rate, high-energy nanosecond pulsed solid-state laser. This invention employs a large-aperture laser gain medium and a large-aperture saturable absorber to achieve pulse modulation of a diode-pumped high average power solid-state laser. Furthermore, it utilizes a 1μm band low-energy, high-repetition-rate solid-state laser as the active bleaching laser, improving the repetition rate and pulse energy stability of the passively Q-switched laser. Ultimately, this achieves a multi-kilowatt-level average power single-cavity oscillating nanosecond pulsed solid-state laser.

[0005] The technical means employed in this invention are as follows:

[0006] A high average power, high repetition rate, high energy nanosecond pulsed solid-state laser, comprising:

[0007] Confocal unstable resonant cavity;

[0008] A saturable absorber module, comprising a laser crystal and a cooling copper heat sink, wherein the front side of the laser crystal is used to receive the bleaching laser and the back side is soldered to the cooling copper heat sink;

[0009] A bleaching laser is used to bleach the saturable absorber module by vertically irradiating it.

[0010] Several laser gain modules are arranged sequentially inside a confocal unstable resonant cavity. Each laser gain module includes a laser medium, a cooled copper heat sink, a diode array pump source, and a two-dimensional cylindrical shaping lens group. The repetition rate pulse pump light shaped by the two-dimensional cylindrical shaping lens group irradiates the front side of the laser medium perpendicularly, and the back side of the laser medium is welded to the cooled copper heat sink.

[0011] Furthermore, the laser medium is 90.8×60×5mm. 3 1% doped Nd 3+ YAG crystal, the Nd 3+ A 2mm thick layer of undoped YAG crystal is bonded around the YAG crystal.

[0012] The back side of the laser medium is coated with an 808nm wavelength 0° high reflectivity film and a 1064nm 23° high reflectivity film, and is soldered onto a copper heat sink. The front side is coated with an 808nm wavelength 0° anti-reflection film and a 1064nm 45° anti-reflection film, and the sides are roughened.

[0013] Furthermore, the diode array pump source is a diode array with a center wavelength of 808nm, the peak power of the diode array is 30kW, the operating mode is a repetition frequency pulse, and the maximum duty cycle is 10%.

[0014] The two-dimensional cylindrical shaping lens group includes a fast-axis collimating cylindrical lens and a slow-axis collimating cylindrical lens;

[0015] The fast axis spacing of the diode array pump sources of the adjacent laser gain modules is set to be horizontal and vertical.

[0016] Furthermore, the laser crystal of the saturable absorber module is a Cr-doped crystal. 4+ YAG crystal, with a 1064nm 23° high-reflectivity film deposited on its back side and soldered onto a copper heat sink, and a 1064nm 45° anti-reflection film deposited on its front side; the Cr... 4+ YAG crystals have a transmittance of 20%–60% at 1064 nm.

[0017] Furthermore, the bleaching laser is a 500Hz pulsed solid-state laser; the bleaching laser beam is synchronized with the diode array pump source by a time synchronizer.

[0018] Furthermore, the confocal unstable resonant cavity is a positive branch confocal unstable cavity with an amplification of M = 1.1, including an output coupling mirror and a concave high-reflection mirror, wherein one side of the output coupling mirror is convex and the other side is concave.

[0019] The outer diameter of the output coupling mirror is 90mm, and the radius of curvature of both sides of the cavity mirror is 30m.

[0020] The reflectivity of the convex coating area of ​​the output coupling mirror is 95% at the center and 70% on a square with a side length of 52mm. Its reflectivity varies linearly according to Gaussian. An anti-reflection coating is deposited in the area outside the square area with a side length of 56mm, and there is a reflectivity transition zone between the two.

[0021] The concave surface of the output coupling mirror is coated with a 1064nm antireflection film, and the outer diameter of the concave high-reflection mirror is 90mm, with a 1064nm high-reflection film coated on the concave surface.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention provides a diode-pumped single-cavity oscillating high-repetition-rate, high-energy nanosecond pulsed solid-state laser with an average power of several kilowatts. The principle is to achieve nanosecond pulse output through passive pulse Q-switching of a large-aperture laser crystal and a saturable absorber; to increase the energy storage of the laser crystal by increasing the modulation depth of the saturable absorber (reducing the initial transmittance of the saturable absorber), thereby increasing the pulse energy; to improve frequency stability and pulse energy stability by actively bleaching a 1μm band high-repetition-rate pulsed laser, and to further compress the laser pulse width, thereby increasing the pulse energy; and to achieve high beam quality solid spot output by combining a Gaussian mirror with an unstable cavity design. A higher average power, high-energy nanosecond pulsed laser can be achieved by appropriately reducing the doping concentration of the laser medium, increasing the aperture of the laser crystal and saturable absorber, and simultaneously increasing the number of gain modules. Furthermore, the single-pulse energy of the laser can be further increased by employing the MOPA method.

[0024] Based on the above reasons, this invention can be widely applied in fields such as impact strengthening, plasma measurement, and long-distance detection. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the high average power, high repetition rate, and high energy nanosecond pulse solid-state laser of the present invention.

[0027] Figure 2 This is a schematic diagram of the Nd:YAG crystal with undoped YAG crystal bonded around its perimeter according to the present invention.

[0028] Figure 3 This is a schematic diagram of the convex coating area of ​​the output coupling mirror of the present invention.

[0029] Figure 4 These are reflectance curves at different locations within the reflective region of this invention.

[0030] In the figure: 1. Concave high-reflectivity mirror; 2. Saturable absorber; 3. Cooling copper heat sink; 4. Bleached laser; 5. Laser medium; 6. Diode pump source; 7. Two-dimensional cylindrical shaping lens group; 8. Gaussian output coupling mirror. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] 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, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0033] like Figure 1 As shown, the present invention provides a high average power, high repetition rate, high energy nanosecond pulse solid-state laser, including several laser gain modules, a saturable absorber module, a bleached laser, and a set of confocal unstable resonant cavities.

[0034] In a preferred embodiment of the present invention, the number of laser gain modules is preferably eight. Each laser gain module includes an Nd:YAG crystal, a cooled copper heat sink, a diode array pump source, and a set of two-dimensional cylindrical shaping lenses.

[0035] Specifically, the laser medium is 90.8×60×5mm. 3 1% doped Nd 3+ YAG crystal, with a 2mm thick layer of undoped YAG crystal bonded around its perimeter, resulting in a final crystal size of 94.8×64×5mm. 3 ,like Figure 2 As shown. A crystal measuring 94.8 × 64 mm. 2 The surface is coated with an 808nm wavelength 0° high-reflectivity film and a 1064nm wavelength 23° high-reflectivity film, and soldered onto a copper heat sink. The heat sink adopts a plate heat exchanger structure and is cooled by water. When irradiated by a pump source with an average power of 3000W, even if it is completely converted into heat, it is far below the heat transfer limit of the gain module, thus allowing the laser gain module to operate under low heat load conditions and ensuring good beam quality. The other crystal measures 94.8×64mm. 2 The crystal is coated with an 808nm wavelength 0° anti-reflection film and a 1064nm 45° anti-reflection film. The remaining four faces of the crystal are roughened to suppress parallel oscillations. This design also ensures that overemission does not occur even under saturated pump conditions. Preferably, in this embodiment, the laser propagation direction is substantially consistent with the thermal gradient direction, which does not significantly affect the laser wavefront and avoids obvious thermal lensing effects, thus achieving high beam quality output.

[0036] The diode array pump source is a diode array with a center wavelength of 808nm and a peak power of 30kW. It operates in repetitive pulse mode with a maximum duty cycle of 10%, typically set to 200μs × 500Hz. The pump light shaping system is a two-dimensional cylindrical shaping lens group, including a fast-axis collimating cylindrical lens (FAC) and a slow-axis collimating cylindrical lens (SAC), ensuring that over 95% of the pump light can illuminate the 90.8 × 60mm area. 2 On the crystal surface. Preferably, in this embodiment, the fast axes of the four pump sources are in the horizontal direction and the fast axes of the four sources are in the vertical direction, and they are arranged at intervals to homogenize the wavefront distortion and thermal lensing efficiency caused by pump inhomogeneity, thereby improving beam quality. The current pulse synchronization of all diode arrays is controlled by a time synchronizer, and the current pulse misalignment is less than 1%.

[0037] In a preferred embodiment of the present invention, the saturable absorber module includes a Cr-doped core. 4+ YAG crystal and a cooling copper heat sink. Characterized by Cr... 4+YAG crystal has a transmittance of 20%–60% at 1064 nm and its dimensions are 94.8 × 64 × 5 mm. 3 A crystal measuring 94.8 × 64 mm. 2 A 1064nm 23° high-reflectivity film is deposited on the surface and soldered onto a copper heat sink. The heat sink employs a plate heat exchanger structure and is cooled by water. The other crystal measures 94.8 × 64 mm. 2 The surface is coated with a 1064nm wavelength 45° antireflective film, and the 0° 1064nm wavelength is required to have the highest possible transmittance. The characteristic is that when the initial transmittance is as low as 20%, the highest pulse energy of 10J output can be achieved, but the laser's photo-to-photon conversion efficiency is low; when the initial transmittance is as high as 60%, the laser's photo-to-photon conversion efficiency can be improved, but the pulse energy is significantly reduced.

[0038] In a preferred embodiment of the present invention, the bleaching laser uses a 500Hz pulsed solid-state laser to vertically irradiate a saturable absorber, with a pulse energy of not less than 40mJ and a pulse width on the order of approximately 10ns. A convex lens is used to focus the bleaching laser, resulting in a spot diameter of approximately 2mm on the front surface of the saturable absorber. A time synchronizer controls the synchronization of the bleaching laser pulse with the diode array pump source, with the bleaching laser pulse start time delayed by approximately 200μs compared to the start time of the driving current pulse of the diode array pump source. The key feature is that the bleaching laser can reduce (or even eliminate) the repetition rate instability and pulse energy instability caused by passive Q-switching of conventional saturable absorbers, making its repetition rate stability and energy stability comparable to those of actively Q-switched lasers. Furthermore, actively bleaching the saturable absorber can significantly shorten the on-time of the Q-switching switch, thereby compressing the laser pulse width, reducing losses, and significantly increasing the pulse energy.

[0039] In a preferred embodiment of the present invention, the confocal unstable resonant cavity is a positive-branch confocal unstable cavity with an amplification M = 1.1, comprising a crescent-shaped (one side convex, the other concave) output coupling mirror and a concave high-reflectivity mirror. The output coupling mirror has an outer diameter of 90 mm, and the radii of curvature on both sides of the cavity mirror are 30 μm. The shape of the coating area on its convex surface and its reflectivity curve for 1064 nm are shown below. Figure 3-4 As shown. The reflectivity at the very center of the region is 95%, and the reflectivity on a 52mm square is 70%, with the reflectivity varying linearly according to a Gaussian distribution. An anti-reflection coating is deposited in the region outside the 56mm square area, creating a reflectivity transition zone between the two. A 1064nm anti-reflection coating is deposited on the concave surface of the coupling mirror. The concave high-reflectivity mirror has an outer diameter of 90mm and is coated with a 1064nm high-reflectivity film on its concave surface; its typical radius of curvature is 33m, and the unstable cavity length is 1.5m. Its equivalent output coupling efficiency is approximately 30%, allowing for a near-flat-top beam distribution.

[0040] It should be noted that in this invention, the number of gain modules can be increased, which requires correspondingly reducing the doping concentration, increasing the aperture of the laser gain crystal and the saturable absorber, reducing the initial transmittance of the saturable absorber, increasing the amplification of the confocal unstable cavity and the equivalent output coupling rate, and ultimately achieving higher average power and greater energy nanosecond pulsed laser output.

[0041] The following specific application examples will further illustrate the solution of the present invention.

[0042] Example 1

[0043] The first embodiment of the present invention is as follows: Figure 1 As shown, this embodiment provides a nanosecond pulsed laser with high average power, high repetition rate, and large pulse energy, including: a concave high-reflectivity mirror 1, a saturable absorber module, a bleached laser 4, eight laser gain modules, and a Gaussian output coupling mirror 8.

[0044] The laser gain module system includes: a laser crystal 5, a cooled copper heat sink 3, a diode pump source 6, and a two-dimensional cylindrical shaping lens group 7. The laser crystal has dimensions of 94.8×64×5mm. 3 YAG crystal. Center size: 90.8 × 60 × 5 mm 3 Partially doped with 1% Nd 3+ The surrounding 2mm thick area is composed of undoped YAG crystal. The crystal measures 94.8 × 64mm. 2 The surface is coated with 808nm 0° and 1064nm 23° high-reflectivity films, which are then soldered onto a copper heat sink. The heat sink employs a plate heat exchanger structure and is cooled by water. The other crystal measures 94.8 × 64 mm. 2 The crystal is coated with 808nm 0° and 1064nm 45° anti-reflective coatings. The four sides of the crystal are roughened. The pump source is an 808nm diode array with a spectral half-width at half-maximum (FWHM) ≤ 3nm; the peak power of the diode array is 30kW, operating in repetitive pulse mode with a maximum duty cycle of 10%, typically set to 200μs × 500Hz. The pump light shaping system includes a fast-axis collimating cylindrical lens (FAC) and a slow-axis collimating cylindrical lens (SAC), ensuring that over 95% of the pump light can illuminate the 90.8 × 60mm crystal. 2 On the crystal plane, the fast axes of four pump sources are in the horizontal direction, and the fast axes of four other pump sources are in the vertical direction, arranged alternately. The pulse current synchronization of all diode arrays is controlled by a time synchronizer, with current pulse misalignment less than 1%.

[0045] The saturable absorber module system includes: a module with dimensions of 94.8 × 64 × 5 mm. 3 Cr 4+2. YAG crystal and 3. Copper heat sink cooled by water; Cr 4+ A 94.8×64mm YAG crystal 2 A 1064nm 23° high-reflectivity film is deposited on the surface and soldered to a copper heat sink, which is cooled by high-speed flowing cooling water. The other crystal measures 94.8 × 64 mm. 2 A 1064nm 45° antireflective coating is applied to the surface, and the transmittance at 0° 1064nm is required to be as high as possible. The initial transmittance of the crystal is 20% to achieve maximum energy storage. A 500Hz high-repetition-rate pulsed solid-state laser is used as the bleaching laser to vertically irradiate the saturable absorber, with a pulse energy of not less than 40mJ and a pulse width on the order of approximately 10ns. A convex lens is used to make the spot diameter on the front surface of the saturable absorber approximately 2mm. The bleaching laser pulse is synchronized with the diode pump pulse by a time synchronizer, and its pulse time is delayed by approximately 200μs compared to the leading edge of the diode array output time.

[0046] Based on the above technical solutions, preferably, a laparoscope adopts a crescent-shaped design with an outer diameter of 90mm (one side is convex and the other is concave), and the radius of curvature of both sides of the laparoscope is 30m. The shape of the coating area on its convex surface and its reflectance curve for 1064nm are shown below. Figure 3 As shown. The reflectivity at the very center of the region is 95%, and the reflectivity on a square with a side length of 52 mm is 70%. An anti-reflection coating is applied to the area outside the 56 mm square region, with a reflectivity transition zone between the two. The concave surface of the coupling mirror is coated with a 1064 nm anti-reflection coating. The other cavity mirror uses a plano-concave lens with an outer diameter of 90 mm and a 1064 nm high-reflectivity coating on its concave surface; the typical radius of curvature is 33 m, and the unstable cavity length is 1.5 m. Under negligible thermal load, an unstable cavity with a magnification M = 1.1 can be formed. Combined with the Gaussian reflection coating on the output coupling mirror, the equivalent output coupling efficiency is approximately 30%. Due to the inhomogeneity of the laser pump, a slight lensing effect occurs, which can be achieved by finely adjusting the cavity length to achieve confocality. It is expected to achieve nanosecond-level pulsed laser output with an average power of 5 kW (10 J / 500 Hz) and an output spot size of 60 × 60 mm. 2 A square.

[0047] Example 2

[0048] The second embodiment of the present invention is as follows Figure 1 As shown, this invention provides a nanosecond pulsed laser with high average power, high repetition rate, and large pulse energy. Only the diode pump source (6) differs; all other aspects are the same as in Example 1. The pump source uses a diode array with a center wavelength of 885 nm and a spectral half-width of 3 nm.

[0049] The 885nm diode pump has a smaller thermal effect than the 808nm pump, and the thermal effect per laser module is smaller, so it can operate at a higher repetition rate (600Hz), thereby achieving a higher average power (6kW) pulsed laser output.

[0050] Example 3

[0051] The third embodiment of the present invention is as follows Figure 1 As shown, this embodiment provides a nanosecond pulsed laser with high average power, high repetition rate, and large pulse energy. The laser gain module is still designed with eight modules. The gain medium is a 2.5% doped Yb:YAG crystal. The laser crystal has dimensions of 36.5 × 24 × 5 mm. 3 YAG crystal. Center size: 32.5 × 20 × 5 mm 3 Partially doped with 2.5% Yb 3+ The surrounding 2mm thick area is composed of undoped YAG crystal. The crystal measures 36.5 × 24mm. 2 The surface is coated with 940nm 0° and 1030nm 23° high-reflectivity films, which are then soldered onto a copper heat sink. The heat sink employs a plate heat exchanger structure and is cooled by water. Another crystal measures 36.5×24mm. 2 The crystal is coated with 940nm 0° and 1030nm 45° anti-reflective coatings. The four sides of the crystal are roughened. The pump source is a 940nm diode array with a spectral half-width at half-maximum (FWHM) ≤ 5nm; the peak power of the diode array is 60kW, operating in repetitive pulse mode with a maximum duty cycle of 5%, typically set to 500μs × 100Hz. The pump light shaping system includes a fast-axis collimating cylindrical lens (FAC) and a slow-axis collimating cylindrical lens (SAC), ensuring that over 95% of the pump light can illuminate the 36.5 × 24mm crystal. 2 On the crystal surface. The rest of the laser gain module design is the same as in Example 1.

[0052] In the design of the saturable absorber module, Cr 4+ The dimensions of the YAG crystal were changed to 36.5×24×5mm. 3 All film systems were changed to 1030nm, and the rest of the design was the same as in Example 1. The design of the bleaching laser was the same as in Example 1.

[0053] One of the cavity mirrors in the optical resonant cavity is a crescent-shaped mirror (one side convex, the other concave) with a diameter of 35 mm. The radius of curvature on both sides of the mirror is 30 μm. The shape of the coating area on its convex surface and its reflectivity curve at 1030 nm are compared with... Figure 3Similarly, the reflectivity at the very center of the region is 95%, and the reflectivity on a square with a side length of 17 mm is 70%. An anti-reflection coating is applied to the area outside the 18.5 mm square region, creating a reflectivity transition zone between the two. The concave surface of the coupling mirror is coated with a 1030 nm anti-reflection coating. The other cavity mirror uses a plano-concave lens with an outer diameter of 35 mm and a 1030 nm high-reflectivity coating on its concave surface; the typical radius of curvature is 33 m, and the unstable cavity length is 1.5 m. Under negligible thermal load, an unstable cavity with a magnification M = 1.1 can be formed. Combined with the Gaussian reflection coating on the output coupling mirror, the equivalent output coupling efficiency is approximately 30%. Due to the inhomogeneity of the laser pump, a slight lensing effect occurs, which can be achieved by finely adjusting the cavity length to achieve confocality. It is expected to achieve nanosecond-level pulsed laser output with an average power of 5 kW (50 J / 100 Hz) and an output spot size of 20 × 20 mm. 2 The shape is square. Due to the extremely high laser power density, all optical components are coated using a process that exceeds the damage threshold.

[0054] In summary, this invention fills the research gap in high-average-power, high-energy nanosecond pulsed solid-state lasers by employing a large-aperture laser gain medium and a large-aperture saturable absorber to achieve pulse modulation of a diode-pumped high-average-power solid-state laser. Furthermore, it utilizes a 1μm band low-energy, low-repetition-rate solid-state laser as the active bleaching laser, improving the repetition frequency and pulse energy stability of passive Q-switching. Ultimately, a multi-kilowatt-level average-power single-cavity oscillating nanosecond pulsed solid-state laser is achieved. This laser has significant application value and development prospects in industrial applications such as shock reinforcement, plasma measurement, and long-distance detection, as well as in cutting-edge scientific exploration.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high average power, high repetition rate, high energy nanosecond pulsed solid-state laser, characterized in that, include: Confocal unstable resonant cavity; A saturable absorber module, comprising a laser crystal and a cooling copper heat sink, wherein the front side of the laser crystal is used to receive the bleaching laser and the back side is soldered to the cooling copper heat sink; A bleaching laser is used to bleach the saturable absorber module by vertically irradiating it. Several laser gain modules are arranged sequentially inside a confocal unstable resonant cavity. Each laser gain module includes a laser medium, a cooled copper heat sink, a diode array pump source, and a two-dimensional cylindrical shaping lens group. The repetition rate pulse pump light after being shaped by the two-dimensional cylindrical shaping lens group irradiates the front side of the laser medium perpendicularly, and the back side of the laser medium is welded to the cooled copper heat sink. The laser medium is 90.

8. 60 5 mm 3 1% doped Nd 3+ YAG crystal, the Nd 3+ : A 2mm thick layer of undoped YAG crystal is bonded around the YAG crystal. The back of the laser medium is coated with an 808nm wavelength 0° high reflectivity film and a 1064nm wavelength 23° high reflectivity film, and is soldered onto a copper heat sink. The front is coated with an 808nm wavelength 0° anti-reflection film and a 1064nm wavelength 45° anti-reflection film, and the sides are roughened.

2. The high average power, high repetition rate, high energy nanosecond pulsed solid-state laser according to claim 1, characterized in that, The diode array pump source is a diode array with a center wavelength of 808 nm, a peak power of 30 kW, an operating mode of high-repetition-rate pulse, and a maximum duty cycle of 10%. The two-dimensional cylindrical shaping lens group includes a fast-axis collimating cylindrical lens and a slow-axis collimating cylindrical lens; The fast axis spacing of the diode array pump sources of the adjacent laser gain modules is set to be horizontal and vertical.

3. A high average power, high repetition rate, high energy nanosecond pulsed solid-state laser according to claim 1, characterized in that, The laser crystal of the saturable absorber module is a Cr-doped crystal. 4+ YAG crystal, with a 1064nm 23° high-reflectivity film deposited on its back side and soldered onto a copper heat sink, and a 1064nm 45° anti-reflection film deposited on its front side; the Cr... 4+ YAG crystals have a transmittance of 20%–60% at 1064 nm.

4. A high average power, high repetition rate, high energy nanosecond pulsed solid-state laser according to claim 1, characterized in that, The bleaching laser is a 500Hz pulsed solid-state laser; the bleaching laser is synchronized with the diode array pump source by a time synchronizer.

5. A high average power, high repetition rate, high energy nanosecond pulsed solid-state laser according to claim 1, characterized in that, The confocal unstable resonant cavity is a positive branch confocal unstable cavity with an amplification of M=1.1, including an output coupling mirror and a concave high-reflection mirror. One side of the output coupling mirror is convex and the other side is concave. The outer diameter of the output coupling mirror is 90 mm, and the radius of curvature of both sides of the cavity mirror is 30 m. The reflectivity of the center of the convex coating area of ​​the output coupling mirror is 95%, and the reflectivity of the square with a side length of 52mm is 70%, with the reflectivity varying linearly according to Gaussian. An anti-reflection coating is deposited in the area outside the square area with a side length of 56mm, and there is a reflectivity transition zone between the two. The concave surface of the output coupling mirror is coated with a 1064nm antireflection film, and the outer diameter of the concave high-reflection mirror is 90 mm. The concave surface is coated with a 1064nm high-reflection film.

Images