SRS crystal anti-damage laser energy homogenizing device based on microlens array

Abstract

The invention relates to an SRS crystal anti-damage laser energy homogenizing device based on a microlens array, and belongs to the technical field of short pulse laser. A pump laser, a light beam isolation system, a light beam energy adjusting system, a color separation mirror, a micro-lens array and a stimulated Raman scattering medium pool are sequentially arranged in the light path direction. The micro-lens array integrates a plurality of micro-lens units and is used for dividing a pump beam emitted by the pump laser into a plurality of sub-beams. The method is used for solving the technical problems that in the pulse compression technology, energy of Gaussian beams at a focus is highly concentrated, local power density is extremely prone to exceeding a crystal damage threshold value, irreversible permanent damage is caused, and energy conversion efficiency is low.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of short pulse laser, and particularly relates to a SRS crystal anti-damage laser energy homogenization device based on a microlens array. BACKGROUND

[0002] High-power lasers, as key tools, play a vital role in the fields of industrial manufacturing, space exploration and national defense applications. Achieving high-power operation while obtaining high brightness, narrow linewidth and multi-wavelength output capability is always the core parameter for evaluating the performance of a laser and is also the focus of continuous research in this field. However, the heat bearing capacity of the laser gain medium constitutes a major constraint: as the pump power increases, the thermal effect inside the medium significantly increases, thereby causing the degradation of beam quality and reducing the brightness of the output beam. The beam quality degradation caused by thermal effects limits the effectiveness of high-power lasers in applications such as directed energy weapons, space exploration and other scenarios that require laser transmission over long distances.

[0003] CN111641098A discloses a device for generating high-energy ultrashort pulses and a working method thereof, which comprises a femtosecond laser front end, a pre-chirp management unit, a pulse separation unit, a nonlinear fiber amplification unit, a pulse synthesis unit and a pulse compression unit. The femtosecond laser front end emits a linearly polarized pulse sequence. The pre-chirp management unit adjusts the pulse pre-chirp amount of the linearly polarized pulse sequence. The pulse separation unit separates the pre-chirped pulse into multiple pulses in time. The nonlinear fiber amplification unit amplifies the separated pulses in power. The pulse synthesis unit combines the amplified pulses in time to obtain a pulse with higher energy. The pulse compression unit is used to compress the synthesized high-energy pulse to obtain an ultrashort high-energy pulse.

[0004] The prior art has at least the following problems in use:

[0005] In the pulse compression technology, the energy of the Gaussian beam is highly concentrated at the focal point, and the local power density is extremely easy to exceed the damage threshold of the crystal, causing irreversible permanent damage.

[0006] In the pulse compression technology, the conversion efficiency of high-order Stokes light is significantly attenuated. As the number of Raman cascade orders increases, the quantum loss and phonon scattering loss intensify, resulting in an exponential decline in energy conversion rate. SUMMARY

[0007] The application provides a SRS crystal anti-damage laser energy homogenization device based on a microlens array, which is used to solve the technical problems of irreversible permanent damage caused by the high concentration of energy of the Gaussian beam at the focal point in the pulse compression technology and the low energy conversion efficiency.

[0008] In order to achieve the above object, the present application is realized by the following technical scheme:

[0009] A SRS crystal anti-damage laser energy homogenization device based on a microlens array is provided, which is sequentially provided with a pump laser, a beam isolation system, a beam energy adjustment system, a color separation mirror, a microlens array and a stimulated Raman scattering medium pool along the optical path direction; the microlens array is integrated with a plurality of microlens units for dividing the pump light beam emitted by the pump laser into a plurality of sub-beams.

[0010] Further, the number of microlens units is N, corresponding to the division of the pump light beam emitted by the pump laser into N sub-beams, and the local power density of the crystal is reduced to 1 / N of the designed intersection point.

[0011] Further, the medium in the stimulated Raman scattering medium pool is selected from nitrate crystals, silicate crystals, vanadate crystals, tungstate crystals or diamond; the nitrate crystal includes , the silicate crystal includes Nd: , the vanadate crystal includes , the tungstate crystal includes .

[0012] Further, the beam isolation system is composed of two half-wave plates, two light polarizers and one Faraday isolator, which is used to block the reverse propagation of light into the pump laser.

[0013] Further, the beam energy adjustment system is composed of one half-wave plate and one light polarizer, and the energy of the output light is adjusted by rotating the half-wave plate.

[0014] Further, the number of microlens units of the microlens array can be adjusted.

[0015] Further, the microlens array is a gradient focal length microlens array; the focal length of the center region unit of the gradient focal length microlens array is 80mm, and the focal length of the edge region unit increases from the center to the edge to 120mm.

[0016] Further, the gradient variation range of the focal length of the gradient focal length microlens array can be adjusted.

[0017] The present application provides a SRS crystal anti-damage laser energy homogenization device based on a microlens array, which has the following beneficial effects:

[0018] The microlens array spatially disperses the pump light energy, decomposes the extremely high power density originally concentrated in a single point into hundreds of parallel sub-action areas, and reduces the local energy load of the crystal to below the safety threshold;

[0019] The multi-focal distributed thermal deposition mechanism of the microlens array homogenizes the internal temperature field of the crystal, eliminates severe temperature gradients in the axial and radial directions, effectively blocks thermal stress cracking and wavefront distortion chain reactions, and further improves energy conversion efficiency. Attached Figure Description

[0020] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of an SRS crystal anti-damage laser energy homogenization device based on a microlens array, provided in an embodiment of the present invention.

[0022] Figure 2 A schematic diagram of the microlens array in an SRS crystal anti-damage laser energy homogenization device based on a microlens array provided in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of a traditional focusing lens;

[0024] Figure 4 A schematic diagram of a gradient focal length microlens array in an SRS crystal anti-damage laser energy homogenization device based on a microlens array provided in an embodiment of the present invention;

[0025] Figure 5 The laser pulse time-domain waveform diagram provided for an embodiment of the present invention.

[0026] In the figure: 1-Pump laser; 2-Beam isolation system; 3-Beam energy adjustment system; 4-Color separator; 5-Microlens array; 6-Stimulated Raman scattering medium cell. Detailed Implementation

[0027] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0028] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application 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. Therefore, they should not be construed as limitations on this application.

[0029] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0030] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to welding, bolting, or riveting; they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0031] Example:

[0032] like Figures 1 to 4 As shown, this embodiment provides an SRS crystal anti-damage laser energy homogenization device based on a microlens array 5. A pump laser 1, a beam isolation system 2, a beam energy adjustment system 3, a color separator 4, a microlens array 5, and a stimulated Raman scattering medium cell 6 are arranged sequentially along the optical path. The microlens array 5 integrates multiple microlens units to divide the pump beam emitted by the pump laser 1 into multiple sub-beams.

[0033] Furthermore, the number of microlens units is N, which corresponds to dividing the pump beam emitted by pump laser 1 into N sub-beams, and the local power density of the crystal is reduced to 1 / N of the intersection design.

[0034] Furthermore, the medium in the stimulated Raman scattering medium cell 6 is selected from nitrate crystals, silicate crystals, vanadate crystals, tungstate crystals, or diamond; nitrate crystals include... Silicate crystals include Vanadate crystals include tungstate crystals include .

[0035] Furthermore, the beam isolation system 2 consists of two half-wave plates, two optical polarizers, and one Faraday isolator, used to block back-propagating light from entering the pump laser 1.

[0036] Furthermore, the beam energy adjustment system 3 consists of a half-wave plate and a light polarizer, and the energy of the output light is adjusted by rotating the half-wave plate.

[0037] Further, the microlens array 5 is a gradient focal length microlens array 5; the central area unit focal length of the gradient focal length microlens array 5 is 80 mm, and the edge area unit focal length increases from the center to the edge to 120 mm.

[0038] Further, the number of microlens units of the microlens array 5 and the focal length gradient variation range of the gradient focal length microlens array 5 can be adjusted.

[0039] In the embodiment, as shown in the specific embodiment, Figure 1 The device includes, in sequence, a pump laser 1, a beam isolation system 2, a beam energy adjustment system 3, a color separation mirror 4, a microlens array 5, and a stimulated Raman scattering medium pool 6. The Raman scattering medium in the stimulated Raman scattering medium pool 6 can be replaced according to actual needs, and the carrying power of the device is improved through the microlens array 5.

[0040] The pump laser 1 is a large-energy single-longitudinal-mode laser, the beam isolation system 2 is a system composed of a Faraday isolator, two half-wave plates, and two optical polarizers, and the function of the beam isolation system 2 is to prevent light in the opposite direction of the pump light propagation direction from entering the pump laser 1 to cause damage to the light source when the device is working. The beam energy adjustment system 3 is a system composed of a half-wave plate and an optical polarizer, which can change the energy passing through the optical polarizer by rotating the angle of the half-wave plate, thereby realizing the energy adjustment function of the device. The 1064 nm / 1198 nm color separation mirror 4 can realize the function that the incident wavelength 1064 nm light passes through the separation system, while the returned 1198 nm wavelength light is separated by the mirror. After the incident pump light successfully passes through the color separation mirror 4, the laser continues to propagate forward into the stimulated Raman scattering medium pool 6, and after the Raman conversion is completed in the stimulated Raman scattering medium pool 6, the wavelength of the backward propagating Stokes light changes. When the backward light reaches the polarization beam splitter lens, it is reflected to the output light path due to the change in wavelength, thereby effectively isolating the interference of the backward transmission light on the front-stage system.

[0041] The core improvement lies in the microlens array 5, which adopts a circular arrangement to integrate about 200 microlens units with the same focal length of 100 mm. The microlens array 5 divides the pump light beam into 200 sub-beams and forms a uniformly distributed focal point group inside the Raman crystal. The power density of each sub-beam is only 1 / 200 of that of the traditional single focal point design, which fundamentally avoids crystal damage caused by local overheating. The microlens array 5 can be replaced by a gradient focal length microlens array 5.

[0042] As shown in the specific embodiment, Figure 4As shown, the focal length of the central region unit is set to 80mm, while the focal length of the edge region units increases to 120mm. This design addresses the Gaussian energy distribution characteristics of the pump laser by shortening the central focal length to increase the focal spot size and disperse energy accumulation, while simultaneously extending the edge focal length to reduce the boundary power density. This allows the energy deposition within the crystal to match its heat dissipation efficiency. The problem of excessively high energy density in the central region is alleviated by increasing the focal spot size, while the edge region, due to its superior heat dissipation, avoids overcooling by reducing the power density. This achieves a uniform temperature field across the entire cross-section, eliminating the radial temperature gradient generated by traditional equal-focal-length arrays. Under the same pump power, the maximum crystal temperature is reduced by more than 20%, effectively suppressing thermal stress cracking and improving the operational stability of the device. The crystal lifespan is increased by more than 3 times, and the output beam quality M² factor fluctuation range is controlled within ±0.1.

[0043] Stimulated Raman scattering medium cell 6 is selected The crystal, coated with antireflective films at both ends, significantly reduces the internal hot spot temperature through the energy homogenization effect of the microlens array 5, suppressing thermal lensing and thermal stress cracking, while maintaining the optical homogeneity of the crystal to ensure Raman conversion efficiency. The beam-splitting lens adopts a dichroic mirror design, efficiently transmitting the remaining pump light and reflecting the forward Raman scattered light to the output end, which together with the reverse Raman light constitutes the system output; this structure controls the local load of the crystal within a safe threshold through spatially discrete energy distribution, improving the overall power carrying capacity and long-term operational stability of the device.

[0044] For heat-sensitive crystals, a gradient focal length microlens array 5 can be further employed, such as... Figure 4 As shown, the radial temperature field distribution is optimized by combining the short focal length (80mm) in the central region with the long focal length (120mm) in the edge region.

[0045] During operation, the input power of the beam energy adjustment system 3 is first adjusted, and the position of the microlens array 5 is calibrated so that the sub-focal point uniformly covers the crystal volume. Finally, a stable Raman laser is output by the beam splitter.

[0046] This invention is a solid-state Raman scattering laser that can obtain high-power laser light. It can achieve high-energy output and high-energy-conversion-efficiency Raman scattered light output by using a microlens array 5 with a larger number of microlenses and a focal length gradient distribution.

[0047] Using the above optical path, the pump laser 1 outputs a wavelength of 1064 nm, a repetition rate of 1 Hz, a pulse width of 10 ns, and a single pulse energy of 200 mJ. Its pulsed laser output is as follows: Figure 5 As shown.

[0048] In summary, the present application disperses the pump light energy in space by micro-lens array, decomposes the extremely high power density originally concentrated in a single point into hundreds of parallel sub-action areas, reduces the local energy load of the crystal to below the safety threshold, avoids the instantaneous thermal shock, micro-crack propagation and material phase transition failure caused by energy concentration in the traditional single pool structure, significantly prolongs the service life of the crystal, and ensures the reliability of the industrial large energy laser system under long-term high-frequency operation; the multi-focus distributed heat deposition mechanism of the micro-lens array makes the temperature field in the crystal uniform, eliminates the severe temperature gradient in the axial and radial directions, effectively blocks the chain reaction of thermal stress cracking and wavefront distortion, simultaneously avoids the chemical degradation process such as crystal component volatilization and color center defect generation triggered by high temperature, and maintains the optical uniformity and Raman activity of the gain medium.

[0049] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A damage-resistant laser energy homogenization device based on a microlens array and an SRS crystal, characterized in that, Along the optical path, a pump laser (1), a beam isolation system (2), a beam energy adjustment system (3), a color separation mirror (4), a microlens array (5), and a stimulated Raman scattering medium cell (6) are arranged sequentially. The microlens array (5) integrates multiple microlens units for splitting the pump beam emitted by the pump laser (1) into multiple sub-beams.

2. The SRS crystal anti-damage laser energy homogenization device based on a microlens array according to claim 1, characterized in that, The number of microlens units is N, which corresponds to dividing the pump beam emitted by the pump laser (1) into N sub-beams, and the local power density of the crystal is reduced to 1 / N of the intersection design.

3. The SRS crystal anti-damage laser energy homogenization device based on a microlens array according to claim 2, characterized in that, The medium in the stimulated Raman scattering medium cell (6) is selected from nitrate crystals, silicate crystals, vanadate crystals, tungstate crystals, or diamond; the nitrate crystals include Silicate crystals include Vanadate crystals include tungstate crystals include .

4. The SRS crystal anti-damage laser energy homogenization device based on a microlens array according to claim 3, characterized in that, The beam isolation system (2) consists of two half-wave plates, two optical polarizers and one Faraday isolator, used to block back-propagating light from entering the pump laser (1).

5. The SRS crystal anti-damage laser energy homogenization device based on a microlens array according to claim 4, characterized in that, The beam energy adjustment system (3) consists of a half-wave plate and a light polarizer. Rotating the half-wave plate adjusts the energy of the output light.

6. The SRS crystal anti-damage laser energy homogenization device based on a microlens array according to claim 5, characterized in that, The number of microlens units in the microlens array (5) is adjustable.

7. The SRS crystal anti-damage laser energy homogenization device based on a microlens array according to claim 6, characterized in that, The microlens array (5) is a gradient focal length microlens array (5); the focal length of the central region unit of the gradient focal length microlens array (5) is 80mm, and the focal length of the edge region unit increases from the center to the edge to 120mm.

8. The SRS crystal anti-damage laser energy homogenization device based on a microlens array according to claim 7, characterized in that, The focal length gradient of the microlens array (5) is adjustable.

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