A large energy nanosecond laser with adjustable repetition frequency and pulse width and a working method thereof

Abstract

The application discloses a large-energy nanosecond laser with adjustable repetition frequency and pulse width and a working method thereof, and relates to the technical field of lasers. The large-energy nanosecond laser comprises, along an optical path, a solid oscillator, an acousto-optic modulation frequency reduction module, an energy attenuation module and a solid amplification module. The solid oscillator is used for outputting nanosecond pulse width tunable laser pulses. The acousto-optic modulation frequency reduction module is used for reducing the frequency of the laser pulses. The energy attenuation module is used for attenuating the laser pulses after frequency reduction to the same energy. The solid amplification module comprises at least one solid pre-amplifier and at least one solid main amplifier. The solid main amplifier comprises a polarizer, a plano-concave lens and a side-pumping module. The laser pulses amplified by the previous stage are injected into the side-pumping module for amplification after collimation and shaping by the polarizer and the plano-concave lens. The fast, online and programmable adjustment of the output pulse width is realized, so that the large-energy nanosecond laser with stable output energy, controllable parameters and excellent beam quality is obtained.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a high-energy nanosecond laser with tunable repetition rate and pulse width, and its operating method. Background Technology

[0002] High-energy nanosecond lasers, due to their high single-pulse energy and peak power, have wide applications in precision machining, laser cleaning, laser-induced breakdown spectroscopy, and nonlinear optics. However, in more complex applications, different requirements necessitate lasers with different repetition rates and pulse widths. For example, in precision machining, the repetition rate and pulse width of the laser are often optimized to achieve the best processing results and efficiency for different materials.

[0003] Traditional Q-switched oscillators used to generate nanosecond pulses typically have output pulse widths determined by the oscillator's inherent physical parameters, such as oscillator length and cavity shape. Once the oscillator structure is designed, the pulse parameters of the output laser are usually difficult to adjust flexibly.

[0004] In existing technologies, adjusting the nanosecond pulse width typically involves mechanically changing the oscillator length. However, relying on mechanical structures to adjust the pulse width not only increases the complexity of the resonant cavity structure and the instability of the system, but also makes the operation cumbersome, disrupts the long-term pointing stability of the system, and makes it difficult to meet the application requirements of fast, online, and programmable pulse width switching.

[0005] In existing technologies, an external cavity modulator is used to shape continuous light or long pulses to achieve adjustable output laser pulse width. However, the resulting seed light is limited by fiber nonlinearity and has low output energy. At the same time, since it is essentially a post-stage shaping of continuous light or long pulses, it suffers from problems such as high loss and high cost, making it difficult to directly obtain high-energy nanosecond pulse width continuously adjustable seed light.

[0006] In summary, whether mechanical methods are used to change the resonant cavity parameters or external modulation methods are used to shape continuous light or long pulses, it is difficult to simultaneously meet the requirements of high structural stability, convenient adjustment, and high output energy. Summary of the Invention

[0007] To address the aforementioned issues, this invention proposes a high-energy nanosecond laser with tunable repetition rate and pulse width, along with its operating method. Without altering the laser's thermal effects, it enables rapid, online, and programmable adjustment of the output pulse width, thereby obtaining a high-energy nanosecond laser with stable output energy, controllable parameters, and excellent beam quality.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a high-energy nanosecond laser with tunable repetition rate and pulse width, comprising: a solid-state oscillator, an acousto-optic modulation down-frequency module, an energy attenuation module, and a solid-state amplification module arranged sequentially along the optical path; The solid-state oscillator includes an acousto-optic Q-switch. By adjusting the driving signal of the acousto-optic Q-switch, the operating repetition rate and on-time of the acousto-optic Q-switch are adjusted to output a nanosecond pulse width tunable laser pulse. The acousto-optic modulation frequency reduction module is used to reduce the frequency of laser pulses; The energy attenuation module is used to attenuate the down-frequency laser pulse to the same energy before it enters the solid-state amplification module; The solid-state amplification module includes at least one solid-state preamplifier and at least one solid-state main amplifier arranged sequentially. The solid-state main amplifier includes a polarizer, a plano-concave lens, and a side pump module. The laser pulse amplified by the previous stage is collimated and shaped by the polarizer and the plano-concave lens and then injected into the side pump module for amplification.

[0009] As an alternative implementation, the solid-state oscillator includes a first LD pump source, a first biconvex lens, a second biconvex lens, a high-reflectivity mirror, a first laser gain crystal, a first polarization beam splitter, a pinhole aperture, an acousto-optic Q-switch, an etalon, and an output coupling mirror arranged sequentially along the optical path; wherein the center points of the high-reflectivity mirror, the first laser gain crystal, the first polarization beam splitter, the pinhole aperture, the acousto-optic Q-switch, and the output coupling mirror are located on the same straight optical path, forming a coaxial resonant cavity structure.

[0010] As an alternative implementation method, the driving period of the driving signal is adjusted according to different target pulse width requirements, the operating repetition frequency of the acousto-optic Q switch is changed, the duty cycle of the driving signal is adjusted within the driving period, and the on-time of the acousto-optic Q switch is controlled.

[0011] As an alternative implementation, the operating repetition rate is adjustable from 1 kHz to 35 kHz, the drive signal duty cycle is adjustable from 80% to 98%, and the pulse width is adjustable from 12 to 100 ns.

[0012] As an alternative implementation, the acousto-optic modulation frequency reduction module includes a second 45° reflector, a second 1064 nm half-wave plate, a first plano-convex lens, an acousto-optic modulator, and a second plano-convex lens arranged sequentially along the optical path, for reducing the laser pulse repetition frequency to the range of 1-1000 Hz.

[0013] As an alternative implementation, the energy attenuation module includes a third 45° reflector, a third 1064 nm half-wave plate, and a second polarizing beam splitter arranged sequentially along the optical path; used to attenuate laser pulses of different energies after frequency reduction to the same energy, so as to amplify the same energy and efficiency in each amplifier stage.

[0014] As an alternative implementation, a first beam isolation system is provided between the solid-state oscillator and the acousto-optic modulation down-conversion module, including a first 1064 nm half-wave plate, a first 45° reflector and a first spatial isolator arranged sequentially along the optical path, for suppressing the backlight of the laser pulse; A second beam isolation system is provided between the last-stage solid-state preamplifier and the first-stage solid-state main amplifier. This system includes a fourth 1064 nm half-wave plate, a second spatial isolator, and a fifth 1064 nm half-wave plate arranged sequentially along the optical path. This system is used to ensure unidirectional transmission of laser pulses between the last-stage solid-state preamplifier and the first-stage solid-state main amplifier.

[0015] As an alternative implementation, the first-stage solid-state main amplifier includes a sixth 45° reflector, a first polarizer, a first plano-concave lens, a seventh 45° reflector, and a first side-pumping module arranged sequentially along the optical path; the laser pulse output from the last-stage solid-state preamplifier is injected into the first side-pumping module via the sixth 45° reflector, the first polarizer, the first plano-concave lens, and the seventh 45° reflector in sequence, and the laser pulse amplified by the first side-pumping module enters the second-stage solid-state main amplifier.

[0016] As an alternative implementation, the second-stage solid-state main amplifier includes a second polarizer, a second plano-concave lens, and a second side pump module arranged sequentially along the optical path; the laser pulse output from the first-stage solid-state main amplifier is collimated and shaped by the second polarizer and the second plano-concave lens and injected into the second side pump module, and finally outputs a laser pulse amplified by the second side pump module.

[0017] Secondly, the present invention provides a method for operating a high-energy nanosecond laser with tunable repetition rate and pulse width, comprising: Based on the target pulse width requirement, the operating repetition rate and on-time of the acousto-optic Q-switch are adjusted by regulating the driving signal of the acousto-optic Q-switch, so as to output a nanosecond pulse width tunable laser pulse. The laser pulse is down-frequencyed, then attenuated to the same energy, and then enters a solid-state preamplifier; The attenuated laser pulse is amplified by at least one solid-state preamplifier and at least one solid-state amplifier to output a high-energy pulsed laser with a tunable nanosecond pulse width. The solid-state main amplifier includes a polarizer, a plano-concave lens and a side pump module. The laser pulse amplified by the previous stage is collimated and shaped by the polarizer and the plano-concave lens and then injected into the side pump module for amplification.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes a high-energy nanosecond laser with tunable repetition rate and pulse width, and its operating method. An acousto-optic Q-switch is incorporated within a solid-state oscillator. By adjusting the driving signal applied to the acousto-optic Q-switch, its operating timing is controlled. Under the condition of constant pumping conditions and consistent laser thermal effects, the accumulation of inverted particles and the energy release process within the cavity are controlled, resulting in a continuously tunable pulse width and stable wavelength laser pulse. This avoids the structural complexity, poor stability, and cumbersome adjustment problems associated with mechanical cavity tuning. Furthermore, an acousto-optic modulation down-frequency module down-frequencys the laser pulse output from the solid-state oscillator, achieving tunable repetition rate. An energy attenuation module attenuates the down-frequency laser pulse to the same energy level before it enters a solid-state preamplifier. The nanosecond pulse with tunable pulse width is amplified by at least one solid-state preamplifier and at least one solid-state main amplifier, resulting in a high-energy nanosecond laser pulse with tunable repetition rate and pulse width, stable energy, and excellent beam quality. This invention employs a digital signal control adjustment method, which features fast response speed, facilitates parameter preset, and allows for synchronous control with external processing systems, making it suitable for systems requiring high-precision time control. Therefore, it is suitable for applications such as high-precision micro-machining, laser cleaning, and medical aesthetics, and has good engineering application value.

[0019] This invention proposes a high-energy nanosecond laser with tunable repetition rate and pulse width, and its operating method. The driving signal parameters of the acousto-optic Q-switch within the oscillator are adjusted according to different target pulse width requirements. Specifically, the operating repetition rate of the acousto-optic Q-switch is adjusted by changing the driving period to control the accumulation process of inverted particles in the resonant cavity during the energy storage phase; the on-time of the acousto-optic Q-switch is adjusted by changing the duty cycle of the driving signal to control the changes in cavity loss and the energy storage and release process. In other words, adjusting the driving signal period and duty cycle allows for dynamic matching between the accumulation process of inverted particles and the energy storage and release process within the cavity, thereby meeting the laser output requirements under different target pulse widths. Furthermore, by optimizing the driving signal duty cycle, the on-time of the acousto-optic Q-switch and the cavity gain build-up process can be controlled, which helps reduce amplified spontaneous emission and improves the signal-to-noise ratio of the output laser while ensuring stable pulse build-up.

[0020] The pump source of the solid-state oscillator of this invention adopts a continuous pumping mode, which is beneficial to keep the pumping conditions constant and the thermal effect of the laser consistent when outputting lasers with different pulse widths. This improves the consistency of output parameters and output stability during pulse width adjustment. The pump source of each stage amplifier adopts a pulse pumping mode, which helps to reduce the thermal load of the gain crystals at each stage and alleviate the influence of thermal effects on the amplification process, thereby obtaining high beam quality laser output.

[0021] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] 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 only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a high-energy nanosecond laser with tunable repetition rate and pulse width provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the pulse width of the solid-state oscillator provided in Embodiment 1 of the present invention, when the repetition rate is 35 kHz, and the final amplified output laser pulse width is 101 ns. Figure 3 This is a schematic diagram showing the pulse width of the solid-state oscillator provided in Embodiment 1 of the present invention, when the repetition rate is 27 kHz, and the final amplified output laser pulse width is 84.9 ns. Figure 4 This is a schematic diagram of the pulse width of the solid-state oscillator provided in Embodiment 1 of the present invention, when the repetition rate is 22 kHz, and the final amplified output laser pulse width is 70 ns. Figure 5 This is a schematic diagram showing the pulse width of the solid-state oscillator provided in Embodiment 1 of the present invention, when the repetition rate is 17 kHz, and the final amplified output laser pulse width is 55.8 ns. Figure 6 This is a schematic diagram showing the pulse width of the solid-state oscillator provided in Embodiment 1 of the present invention, when the repetition rate is 12 kHz, and the final amplified output laser pulse width is 40.27 ns. Figure 7 This is a schematic diagram showing the pulse width of the solid-state oscillator provided in Embodiment 1 of the present invention, when the repetition rate is 6 kHz, and the final amplified output laser pulse width is 25.3 ns; Figure 8 This is a schematic diagram showing the pulse width of the solid-state oscillator provided in Embodiment 1 of the present invention, when the repetition rate is 1 kHz, and the final amplified output laser pulse width is 11.95 ns. Figure 9 A schematic diagram of the center wavelength and spectral width of the output laser pulse of a high-energy nanosecond laser with tunable repetition rate and pulse width provided in Embodiment 1 of the present invention; Figure 10 This is a schematic diagram of the output beam quality of a high-energy nanosecond laser with tunable repetition rate and pulse width provided in Embodiment 1 of the present invention. Figure 11 This is a schematic diagram of the output energy of each stage of the amplification stage of a high-energy nanosecond laser with tunable repetition rate and pulse width provided in Embodiment 1 of the present invention; In the figure, 1. First LD pump source; 2. First biconvex lens; 3. Second biconvex lens; 4. High-reflection mirror; 5. First laser gain crystal; 6. First polarization beam splitter; 7. Pinhole aperture; 8. Acousto-optic Q-switch; 9. Erebaum; 10. Output coupling mirror; 11. First 1064 nm half-wave plate; 12. First 45° reflector; 13. First spatial isolator; 14. Second 45° reflector; 15. Second 1064 nm half-wave plate; 16. First plano-convex lens; 17. Acousto-optic modulator; 18. Second plano-convex lens; 19. Third 45° reflector; 20. Third 1064 nm half-wave plate; 21. Second polarizing beam splitter; 22. Second LD pump source; 23. Third biconvex lens; 24. Fourth biconvex lens; 25. First 45° dichroic mirror; 26. Second laser gain crystal; 27. Third plano-convex lens; 28. Fourth 45° reflector; 29. ​​Third LD pump source; 30. Fifth biconvex lens; 31. Sixth biconvex lens; 32. Second 45° dichroic mirror; 33. Third laser gain crystal; 34. Fifth 45° reflector; 35. Fourth plano-convex lens; 36. Fourth LD pump source; 37. Seventh biconvex lens; 38. Eighth biconvex lens; 39. Third 45° dichroic mirror; 40. Fourth laser gain crystal; 41. Fourth 1064nm half-wave plate; 42. Second spatial isolator; 43. Fifth 1064nm half-wave plate; 44. 45° half-wave plate; 46. 47. 48. 45° sixth reflector; 49. 40. 41. 42. 45° first polarizer; 40. 41. 42. 43. 44. 45° seventh reflector; 42. 43. 44. 45° first side pump module; 46. 47. 48. 49. 40. 51. 52. 43. 44. 45° second polarizer; 50. 51. 52. 45. 56. 47. 48. 49. 40. 51. 42. 45° second reflector; 52. 43. 44. 45° second reflector; 53. 44. 45° second reflector; 54. 45. 46. 47. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form as well. Furthermore, it should be understood that the terms “comprising” and “including”, and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0028] Example 1 This embodiment provides a high-energy nanosecond laser with tunable repetition rate and pulse width, including a solid-state oscillator, an acousto-optic modulation down-frequency module, an energy attenuation module, and a solid-state amplification module arranged sequentially along the optical path; The solid-state oscillator includes an acousto-optic Q-switch. By adjusting the driving signal of the acousto-optic Q-switch, the operating repetition rate and on-time of the acousto-optic Q-switch are adjusted to output a nanosecond pulse width tunable laser pulse. The acousto-optic modulation frequency reduction module is used to reduce the frequency of laser pulses; The energy attenuation module is used to attenuate the down-frequency laser pulse to the same energy before it enters the solid-state amplification module; The solid-state amplification module includes at least one solid-state preamplifier and at least one solid-state main amplifier arranged sequentially. The solid-state main amplifier includes a polarizer, a plano-concave lens, and a side pump module. The laser pulse amplified by the previous stage is collimated and shaped by the polarizer and the plano-concave lens and then injected into the side pump module for amplification.

[0029] The following is combined with Figure 1 This embodiment provides a detailed description of a high-energy nanosecond laser with tunable repetition rate and pulse width. Specifically, it includes a solid-state oscillator, a first beam isolation system, an acousto-optic modulation down-frequency module, an energy attenuation module, a solid-state preamplifier, a second beam isolation system, and a solid-state main amplifier, arranged sequentially along the optical path.

[0030] In this embodiment, a solid-state oscillator is used to output a nanosecond pulse width tunable and wavelength stable laser pulse. The solid-state oscillator includes a first LD pump source 1, a first biconvex lens 2, a second biconvex lens 3, a high-reflection mirror 4, a first laser gain crystal 5, a first polarizing beam splitter 6, a pinhole aperture 7, an acousto-optic Q-switch 8, an etalon 9, and an output coupling mirror 10 arranged sequentially along the optical path.

[0031] Among them, the first LD pump source 1 is a continuous pump, and nanosecond pulse laser is generated under the fixed oscillator structure and thermal effect by using the continuously pumped LD pump source.

[0032] The pump light output from the first LD pump source 1 passes sequentially through a focusing system composed of a first biconvex lens 2 and a second biconvex lens 3 and a high-reflection mirror 4 before entering the first laser gain crystal 5. The center points of the high-reflection mirror 4, the first laser gain crystal 5, the first polarization beam splitter 6, the pinhole aperture 7, the acousto-optic Q-switch 8, and the output coupling mirror 10 are located on the same straight optical path to form an oscillator with a fixed physical structure. This ensures that a coaxial resonant cavity structure is formed inside the oscillator, allowing the oscillating beam inside the cavity to pass through the central light-transmitting area of ​​each optical element in sequence, thereby reducing cavity loss and improving the modulation efficiency and pulse establishment stability of the acousto-optic Q-switch 8.

[0033] Meanwhile, a small aperture 7 is used for spatial filtering to suppress higher-order modes and improve the output beam quality, achieving a laser beam quality close to the diffraction limit of the solid-state oscillator, so as to obtain high-energy laser output with high beam quality.

[0034] In this embodiment, an acousto-optic Q-switched laser is used as the seed source, and high-efficiency and narrow-spectrum nanosecond laser pulse output is achieved by optimizing parameters such as cavity length and output mirror transmittance.

[0035] In Q-switched mode, nanosecond laser pulses can be generated by applying a driving signal to the acousto-optic Q-switch 8 according to different target pulse width requirements. Under the condition of keeping the laser thermal effect basically consistent, the working sequence of the acousto-optic Q-switch 8 can be controlled by adjusting the driving signal applied to the acousto-optic Q-switch 8, changing the on-time of the acousto-optic Q-switch 8, and thus controlling the accumulation of inverted particles and the energy storage and release process in the cavity, thereby realizing the continuous adjustment of the output laser pulse width.

[0036] Specifically: By adjusting the driving cycle of the driving signal, the operating repetition rate of the acousto-optic Q-switch 8 is changed, thereby controlling the accumulation time of inverted particles in the gain medium during the low-Q energy storage stage. At the same time, the duty cycle of the driving signal is adjusted within the driving cycle to control the opening duration of the acousto-optic Q-switch 8, the change process of intracavity loss, and the energy storage and release process.

[0037] When the pump power remains constant, when the target pulse width decreases, the repetition rate of the acousto-optic Q-switch 8 is reduced and the duty cycle is increased, so that the inverted particle accumulation process and the energy storage and release process are adjusted to a narrower pulse width output state; when the target pulse width increases, the repetition rate of the acousto-optic Q-switch 8 is increased and the duty cycle is reduced, so that the inverted particle accumulation process and the energy storage and release process are adjusted to a wider pulse width output state.

[0038] Therefore, by coordinating the adjustment of the working repetition frequency and the duty cycle of the driving signal, the inversion particle accumulation process, the cavity gain establishment process, the cavity loss modulation process, and the energy storage and release process are dynamically matched, thereby realizing the continuous adjustment of the output pulse width of the solid-state oscillator.

[0039] The preferred adjustment range for the operating repetition frequency is 1 kHz to 35 kHz, and the preferred adjustment range for the drive signal duty cycle is 80% to 98%.

[0040] As a preferred implementation, by optimizing the fill factor of the pump spot and the laser pulse mode field to achieve optimal spatial mode matching, and by introducing a pinhole aperture 7 for spatial filtering to suppress higher-order spatial modes, the beam quality can be significantly improved while maintaining high energy extraction efficiency.

[0041] As a preferred implementation, by optimizing the duty cycle of the driving signal applied to the acousto-optic Q-switch 8, both the suppression of spontaneous emission (ASE) and the stable establishment of the target pulse width laser pulse are considered. When the solid-state oscillator operates at a low repetition rate, ASE is more easily accumulated due to the longer energy storage time between adjacent pulses. Therefore, the turn-off time of the acousto-optic Q-switch 8 needs to be extended to improve the turn-off capability. When the solid-state oscillator operates at a high repetition rate, ASE accumulation is relatively reduced. Under the premise of meeting the turn-off requirements of the acousto-optic Q-switch 8, the turn-off time of the acousto-optic Q-switch 8 can be appropriately reduced.

[0042] As a preferred embodiment, the high-reflectivity mirror 4 is coated with HR@1064 nm and HT@808 nm films, with an incident light angle of 0°. The high-reflectivity mirror 4 is used to transmit 808 nm wavelength light and reflect 1064 nm laser light, and has high transmittance and high reflectance, ensuring that the solid-state oscillator can output nanosecond adjustable laser pulses.

[0043] In a preferred embodiment, the output coupling mirror 10 is coated with PR@1064 nm (T=50%) and HT@808 nm films, with an incident light angle of 0°. The output coupling mirror 10 is used to transmit 808 nm wavelength light and partially reflect 1064 nm laser light, ensuring that the solid-state oscillator can output nanosecond adjustable laser pulses.

[0044] In this embodiment, the first beam isolation system includes a first 1064 nm half-wave plate 11, a first 45° reflector 12 and a first spatial isolator arranged sequentially along the optical path, for suppressing the backlight of the laser pulse output by the solid-state oscillator.

[0045] The laser pulse output from the solid-state oscillator passes sequentially through the first 1064 nm half-wave plate 11, the first 45° reflector 12, and the first spatial isolator 13. The first spatial isolator 13 has high isolation and low insertion loss, which can effectively suppress the backlight of the laser pulse.

[0046] In this embodiment, the acousto-optic modulation frequency reduction module includes a second 45° reflector 14, a second 1064 nm half-wave plate 15, a first plano-convex lens 16, an acousto-optic modulator 17, and a second plano-convex lens 18 arranged sequentially along the optical path, which are used to reduce the frequency of the laser pulses output by the solid-state oscillator in order to adjust the repetition frequency of the laser pulses.

[0047] The laser pulses, whose repetition frequency range is adjustable from 1 kHz to 35 kHz, are sequentially passed through the second 45° reflector 14, the second 1064 nm half-wave plate 15, the first plano-convex lens 16, the acousto-optic modulator 17, and the second plano-convex lens 18, and the repetition frequency can be flexibly reduced to the range of 1-1000 Hz.

[0048] In this embodiment, the energy attenuation module includes a third 45° reflector 19, a third 1064nm half-wave plate 20, and a second polarizing beam splitter 21 arranged sequentially along the optical path; The laser pulses output by the acousto-optic modulation down-conversion module pass sequentially through the third 45° reflector 19, the third 1064nm half-wave plate 20, and the second polarizing beam splitter 21. This process attenuates the laser pulses of different energies after down-conversion to the same energy so that they can enter the solid-state preamplifier. This ensures that the same energy and efficiency are amplified in each stage of the amplifier, preventing damage to the device due to excessive energy.

[0049] In this embodiment, the solid-state preamplifier includes at least one stage and adopts a single-pass structure. Each stage includes a dichroic mirror, a laser gain crystal, a focusing system composed of two biconvex lenses, and an LD pump source. The laser pulse amplified by the previous stage and the pump light output from the LD pump source pass through the focusing system and the dichroic mirror in sequence, and then are coupled into the laser gain crystal through the dichroic mirror for amplification.

[0050] This embodiment takes a three-stage solid-state preamplifier as an example, including a first-stage solid-state preamplifier (PRE.1), a second-stage solid-state preamplifier (PRE.2), and a third-stage solid-state preamplifier (PRE.3).

[0051] The first-stage solid-state preamplifier includes a second LD pump source 22, a third biconvex lens 23, a fourth biconvex lens 24, a first 45° dichroic mirror 25, a second laser gain crystal 26, a third plano-convex lens 27, and a fourth 45° reflector 28.

[0052] The second-stage solid-state preamplifier includes a third LD pump source 29, a fifth biconvex lens 30, a sixth biconvex lens 31, a second 45° dichroic mirror 32, a third laser gain crystal 33, a fifth 45° reflector 34, and a fourth plano-convex lens 35.

[0053] The third-stage solid-state preamplifier includes a fourth LD pump source 36, a seventh biconvex lens 37, an eighth biconvex lens 38, a third 45° dichroic mirror 39, and a fourth laser gain crystal 40.

[0054] Specifically: The laser pulse output by the energy attenuation module is focused into the second laser gain crystal 26 through the first 45° dichroic mirror 25. At the same time, the pump light emitted by the second LD pump source 22 passes through the focusing system composed of the third biconvex lens 23 and the fourth biconvex lens 24 in sequence, passes through the first 45° dichroic mirror 25 and is also focused into the second laser gain crystal 26. The laser pulse amplified by the second laser gain crystal 26 then passes through the third plano-convex lens 27 and the fourth 45° reflector 28 and enters the second-stage solid-state preamplifier.

[0055] The laser pulse amplified by the first-stage solid-state preamplifier passes through the second 45° dichroic mirror 32 and enters the third laser gain crystal 33. At the same time, the pump light emitted by the third LD pump source 29 passes through the focusing system composed of the fifth biconvex lens 30 and the sixth biconvex lens 31, passes through the second 45° dichroic mirror 32 and is also focused into the third laser gain crystal 33. The laser pulse amplified by the third laser gain crystal 33 then passes through the fifth 45° reflecting mirror 34 and the fourth plano-convex lens 35 and enters the third-stage solid-state preamplifier.

[0056] The laser pulse amplified by the second-stage solid-state preamplifier passes through the third 45° dichroic mirror 39 and enters the fourth laser gain crystal 40. At the same time, the pump light emitted by the fourth LD pump source 36 passes through the focusing system composed of the seventh biconvex lens 37 and the eighth biconvex lens 38, and is also focused into the fourth laser gain crystal 40 after passing through the third 45° dichroic mirror 39. The laser pulse amplified by the fourth laser gain crystal 40 then enters the second beam isolation system and enters the solid-state main amplifier through the second beam isolation system.

[0057] In this embodiment, the second beam isolation system includes a fourth 1064 nm half-wave plate 41, a second spatial isolator 42 and a fifth 1064 nm half-wave plate 43 arranged sequentially along the optical path, which are used to suppress the backlight of the laser pulse and ensure unidirectional laser transmission between the pre-amplification stage and the main amplification stage.

[0058] The laser pulse output from the third-stage solid-state preamplifier passes sequentially through the fourth 1064 nm half-wave plate 41, the second spatial isolator 42, and the fifth 1064 nm half-wave plate 43. The second spatial isolator 42 has high isolation and low insertion loss, which can effectively suppress reverse light.

[0059] In this embodiment, the solid-state main amplifier includes at least one stage with a single-pass structure, used to progressively increase the energy of the output laser pulse of the solid-state preamplifier in order to output a high-energy nanosecond laser with repetition rate and tunable pulse width.

[0060] This embodiment takes a two-stage example, including a first-stage solid-state main amplifier (MA.1) and a second-stage solid-state main amplifier (MA.2).

[0061] The first-stage solid-state main amplifier includes a sixth 45° reflector 44, a first polarizer 45, a first plano-concave lens 46, a seventh 45° reflector 47, and a first side pump module 48 arranged sequentially along the optical path.

[0062] The second-stage solid-state main amplifier includes a second polarizer 49, a second plano-concave lens 50, and a second side pump module 51 arranged sequentially along the optical path.

[0063] Specifically: The laser pulse output by the second beam isolation system passes sequentially through the sixth 45° reflector 44, the first polarizer 45, the first plano-concave lens 46, and the seventh 45° reflector 47, and is collimated and shaped before being injected into the first side pump module 48. The laser pulse amplified by the first side pump module 48 then enters the second-stage solid-state main amplifier.

[0064] The laser pulse output from the first-stage solid-state main amplifier is collimated and shaped by the second polarizer 49 and the second plano-concave lens 50 and injected into the second side pump module 51, and finally outputs a laser pulse amplified by the second side pump module 51.

[0065] As a preferred implementation, both the solid-state preamplifier and the solid-state main amplifier employ pulse pumping to reduce the thermal load on the gain crystals at each stage, alleviate the accumulation of thermal effects, and improve the output beam quality.

[0066] In a preferred embodiment, the first laser gain crystal 5, the second laser gain crystal 26, the third laser gain crystal 33, and the fourth laser gain crystal 40 are all machined with 2° wedge angles at both ends and doped with Nd. 3+ ion.

[0067] In a preferred embodiment, the first polarizing beam splitter 6 and the second polarizing beam splitter 21 are coated with HT@1064 nm, which has a high polarization extinction ratio and low insertion loss.

[0068] As a preferred embodiment, the first spatial isolator 13 and the second spatial isolator 42 have high isolation and low insertion loss, which can effectively suppress reverse light.

[0069] In a preferred embodiment, the first 1064 nm half-wave plate 11, the second 1064 nm half-wave plate 15, the third 1064 nm half-wave plate 20, the fourth 1064 nm half-wave plate 41, and the fifth 1064 nm half-wave plate 43 have high transmittance and low polarization-dependent loss, and are used to adjust the polarization state of the 1064 nm laser.

[0070] In a preferred embodiment, the first plano-convex lens 16, the second plano-convex lens 18, the third plano-convex lens 27 and the fourth plano-convex lens 35 are all coated with an HT@1064 nm film layer with an incident light angle of 0°, which is used to focus and collimate the 1064 nm laser, and has high transmittance and low aberration.

[0071] In a preferred embodiment, both the first plano-concave lens 46 and the second plano-concave lens 50 are coated with an HT@1064 nm film layer, with an incident light angle of 0°, for focusing and collimating 1064 nm laser light, and have high transmittance and low aberration.

[0072] As a preferred embodiment, both ends of the laser gain crystal are coated with HT@1064 nm and HT@808 nm films, which have high gain coefficient and excellent thermal stability, and can effectively amplify 1064 nm laser.

[0073] In a preferred embodiment, the first biconvex lens 2, the second biconvex lens 3, the third biconvex lens 23, the fourth biconvex lens 24, the fifth biconvex lens 30, the sixth biconvex lens 31, the seventh biconvex lens 37, and the eighth biconvex lens 38 are all coated with an HT@808 nm film, with an incident light angle of 0°. The biconvex lenses are used to focus and shape the 808 nm pump light, exhibiting high transmittance and low aberrations.

[0074] In a preferred embodiment, the first polarizer 45 and the second polarizer 49 are coated with HT@1064nm, which has a high polarization extinction ratio and low insertion loss.

[0075] In a preferred embodiment, the first LD pump source 1 has a center wavelength of 808.3 nm, a numerical aperture NA of 0.22, a core diameter of 400 μm, and an output power of 100 W; the second LD pump source 22 has a center wavelength of 808.5 nm, a numerical aperture NA of 0.22, a core diameter of 105 μm, and an output power of 100 W; the third LD pump source 29 and the fourth LD pump source 36 have a center wavelength of 808.5 nm, a numerical aperture NA of 0.22, a core diameter of 200 μm, and an output power of 170 W. The LD pump sources are used to provide high-energy pump light, and the pump light is shaped by a biconvex lens to ensure efficient coupling of the pump light into the laser gain crystal.

[0076] In a preferred embodiment, the focused spot diameters of the pump light emitted from the first LD pump source 1, the second LD pump source 22, the third LD pump source 29, and the fourth LD pump source 36 are 400 μm, 540 μm, 810 μm, and 1000 μm, respectively.

[0077] In a preferred embodiment, the first 45° reflector 12, the second 45° reflector 14, the third 45° reflector 19, the fourth 45° reflector 28, the fifth 45° reflector 34, the sixth 45° reflector 44, and the seventh 45° reflector 47 are all coated with an HR@1064 nm film, with an incident light angle of 45°. The 45° reflectors are used to reflect 1064 nm laser light and feature high reflectivity and low loss.

[0078] As a preferred embodiment, the laser gain crystal is encapsulated in a high thermal conductivity copper heat sink by thermal welding, and a water-cooling channel is integrated in the heat sink. The waste heat generated by the crystal is efficiently removed by circulating cooling water, thereby effectively maintaining the stability of the crystal's operating temperature.

[0079] In a preferred embodiment, the laser gain crystals in the first side pump module 48 and the second side pump module 51 are both coated with HT@1064 nm and HT@808 nm films, which have high gain coefficients and excellent thermal stability, and can effectively amplify 1064 nm laser.

[0080] Figures 2-8 This is a schematic diagram showing different pulse widths of the laser pulses ultimately output by a high-energy nanosecond laser. It can be seen that this embodiment can achieve pulse width... It offers high flexibility and adaptability with continuous adjustment in the range of 12 ns to 100 ns.

[0081] By using etalon 9, a narrow-spectrum wide laser pulse output is obtained. Figure 9 As can be seen, this embodiment achieves the center wavelength. spectral width High-energy nanosecond laser output with a wavelength of less than 0.04 nm.

[0082] pass Figure 10 As can be seen, the amplifiers in this embodiment adopt pulse pumping mode, which helps to reduce the thermal load on the gain crystals of each stage. Combined with thermal lens compensation technology, the final beam quality is achieved as follows: , High-energy nanosecond laser output with high beam quality.

[0083] pass Figure 11As can be seen, the laser in this embodiment achieves efficient energy amplification in each amplification stage, and the final output energy is greater than 60 mJ, which meets the requirements of high-energy laser applications.

[0084] The high-energy nanosecond laser with tunable repetition rate and pulse width proposed in this embodiment employs a master oscillation power amplification structure based on a nanosecond pulse width tunable resonator and a solid-state amplifier, significantly improving the pulse energy of the output laser and making it suitable for high-energy laser applications. By strictly controlling the pump intensity and crystal wedge angle design, ASE (laser-induced breakdown) is effectively suppressed, further improving the signal-to-noise ratio of the output laser pulse and ensuring the purity and stability of the laser output. Simultaneously, it achieves high-energy nanosecond pulse width tunable laser output with pulse widths of 12 ns to 100 ns, repetition rates of 1 Hz to 1000 Hz, laser spectral width less than 0.04 nm, and pulse energy greater than 60 mJ, meeting the needs of industrial processing, scientific research, and high-precision measurement, and showing broad application prospects in laser-induced breakdown spectroscopy, photoconductive switching, and nonlinear optics.

[0085] Example 2 This embodiment proposes a method for operating a high-energy nanosecond laser with tunable repetition rate and pulse width, including: A solid-state oscillator generates nanosecond pulsed lasers by using a continuously pumped LD pump source under a fixed oscillator structure and thermal effects.

[0086] Based on different target pulse width requirements, the operating repetition rate of the acousto-optic Q-switch and the duty cycle of the driving signal are synergistically optimized by adjusting the driving signal applied to the acousto-optic Q-switch. Under the condition of keeping the pump conditions constant and the laser thermal effect consistent, the accumulation and energy release process of inverted particles in the cavity are controlled, and the accumulation process of inverted particles, the cavity gain establishment process, and the on-time of the acousto-optic Q-switch are matched under different operating conditions to achieve continuously adjustable output pulse width. Among them, the repetition rate adjustment range is 1-35 kHz, the duty cycle adjustment range is 80%-98%, and the pulse width adjustment range is 12-100 ns.

[0087] Specifically: By adjusting the driving cycle of the driving signal to change the operating repetition rate of the acousto-optic Q-switch, the accumulation time of inverted particles in the gain medium during the low-Q energy storage stage can be controlled. At the same time, the duty cycle of the driving signal can be adjusted within the driving cycle to control the on-time of the acousto-optic Q-switch, the change process of intracavity loss, and the energy storage and release process.

[0088] When the pump power remains constant, when the target pulse width decreases, the inversion particle accumulation process and the energy storage and release process are adjusted to a narrower pulse width output state by decreasing the operating repetition frequency of the acousto-optic Q switch and increasing the duty cycle; when the target pulse width increases, the inversion particle accumulation process and the energy storage and release process are adjusted to a wider pulse width output state by increasing the operating repetition frequency of the acousto-optic Q switch and decreasing the duty cycle.

[0089] Therefore, by coordinating the adjustment of the working repetition frequency and the duty cycle of the driving signal, the inversion particle accumulation process, the cavity gain establishment process, the cavity loss modulation process, and the energy storage and release process are dynamically matched, thereby realizing the continuous adjustment of the oscillator output pulse width.

[0090] Then, after passing through the first beam isolation system, it enters the acousto-optic modulation and frequency reduction module. The acousto-optic modulation and frequency reduction module reduces the frequency of the laser pulse, reducing the repetition frequency of the laser pulse from 1-35 kHz to 1-1000 Hz, corresponding to an output energy of 0.759-0.157 mJ.

[0091] The down-frequency laser pulses enter the energy attenuation module, which attenuates the lasers of different energies output after down-frequency reduction to a uniform 0.157 mJ before entering the solid-state amplification module.

[0092] The laser pulse is amplified by at least one solid-state preamplifier and at least one solid-state amplifier to output a high-energy pulsed laser with tunable nanosecond pulse width. Specifically, the laser energy is amplified to 8.8 mJ by a three-stage solid-state preamplifier, then amplified to 28 mJ by a first-stage solid-state main amplifier after passing through a second beam isolation system, and finally amplified to greater than 60 mJ by a second-stage solid-state main amplifier.

[0093] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A high-energy nanosecond laser with tunable repetition rate and pulse width, characterized in that, It includes a solid-state oscillator, an acousto-optic modulation down-frequency module, an energy attenuation module, and a solid-state amplification module arranged sequentially along the optical path; The solid-state oscillator includes a first LD pump source, a first biconvex lens, a second biconvex lens, a high-reflectivity mirror, a first laser gain crystal, a first polarization beam splitter, a pinhole aperture, an acousto-optic Q-switch, an etalon, and an output coupling mirror arranged sequentially along the optical path. By adjusting the driving signal of the acousto-optic Q-switch, the operating repetition rate and on-time of the acousto-optic Q-switch are adjusted to output a laser pulse with a tunable nanosecond pulse width. The center points of the high-reflectivity mirror, the first laser gain crystal, the first polarization beam splitter, the pinhole aperture, the acousto-optic Q-switch, and the output coupling mirror are located on the same straight optical path, forming a coaxial resonant cavity structure. The acousto-optic modulation frequency reduction module includes a second 45° reflector, a second 1064 nm half-wave plate, a first plano-convex lens, an acousto-optic modulator, and a second plano-convex lens arranged sequentially along the optical path. It is used to reduce the frequency of the laser pulse and reduce the repetition frequency of the laser pulse to the range of 1-1000 Hz. The energy attenuation module is used to attenuate the down-frequency laser pulse to the same energy before it enters the solid-state amplification module; The solid-state amplification module includes at least one solid-state preamplifier and at least one solid-state main amplifier arranged sequentially. The solid-state main amplifier includes a polarizer, a plano-concave lens and a side pump module. The laser pulse amplified by the previous stage is collimated and shaped by the polarizer and the plano-concave lens and then injected into the side pump module for amplification. The energy attenuation module includes a third 45° reflector, a third 1064 nm half-wave plate, and a second polarizing beam splitter arranged sequentially along the optical path. It is used to attenuate laser pulses of different energies after frequency reduction to the same energy so that the same energy and efficiency can be amplified in each stage of the amplifier.

2. A high-energy nanosecond laser with tunable repetition rate and pulse width as described in claim 1, characterized in that, According to different target pulse width requirements, the driving period of the driving signal is adjusted to change the operating repetition frequency of the acousto-optic Q switch. Within the driving period, the duty cycle of the driving signal is adjusted to control the on-time of the acousto-optic Q switch.

3. A high-energy nanosecond laser with tunable repetition rate and pulse width as described in claim 2, characterized in that, The operating repetition frequency is adjustable from 1 kHz to 35 kHz, the drive signal duty cycle is adjustable from 80% to 98%, and the pulse width is adjustable from 12 to 100 ns.

4. A high-energy nanosecond laser with tunable repetition rate and pulse width as described in claim 1, characterized in that, A first beam isolation system is provided between the solid-state oscillator and the acousto-optic modulation down-conversion module, including a first 1064nm half-wave plate, a first 45° reflector and a first spatial isolator arranged sequentially along the optical path, for suppressing the backlight of the laser pulse; A second beam isolation system is provided between the last-stage solid-state preamplifier and the first-stage solid-state main amplifier. This system includes a fourth 1064 nm half-wave plate, a second spatial isolator, and a fifth 1064 nm half-wave plate arranged sequentially along the optical path. This system is used to ensure unidirectional transmission of laser pulses between the last-stage solid-state preamplifier and the first-stage solid-state main amplifier.

5. A high-energy nanosecond laser with tunable repetition rate and pulse width as described in claim 1, characterized in that, The first-stage solid-state main amplifier includes a sixth 45° reflector, a first polarizer, a first plano-concave lens, a seventh 45° reflector, and a first side pump module arranged sequentially along the optical path. The laser pulse output from the last-stage solid-state preamplifier is injected into the first side pump module through the sixth 45° reflector, the first polarizer, the first plano-concave lens, and the seventh 45° reflector in sequence. The laser pulse amplified by the first side pump module then enters the second-stage solid-state main amplifier.

6. A high-energy nanosecond laser with tunable repetition rate and pulse width as described in claim 5, characterized in that, The second-stage solid-state main amplifier includes a second polarizer, a second plano-concave lens, and a second side pump module arranged sequentially along the optical path. The laser pulse output from the first-stage solid-state main amplifier is collimated and shaped by the second polarizer and the second plano-concave lens and injected into the second side pump module, and finally outputs a laser pulse amplified by the second side pump module.

7. A method for operating a high-energy nanosecond laser with tunable repetition rate and pulse width as described in any one of claims 1-6, characterized in that, include: Based on the target pulse width requirement, the operating repetition rate and on-time of the acousto-optic Q-switch are adjusted by regulating the driving signal of the acousto-optic Q-switch, so as to output a nanosecond pulse width tunable laser pulse. The laser pulse is down-frequencyed, then attenuated to the same energy, and then enters a solid-state preamplifier; The attenuated laser pulse is amplified by at least one solid-state preamplifier and at least one solid-state amplifier to output a high-energy pulsed laser with a tunable nanosecond pulse width. The solid-state main amplifier includes a polarizer, a plano-concave lens and a side pump module. The laser pulse amplified by the previous stage is collimated and shaped by the polarizer and the plano-concave lens and then injected into the side pump module for amplification.

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