阅读说明：本技术 一种像散透镜聚焦的气体受激拉曼散射装置 (Gas stimulated Raman scattering device focused by astigmatic lens ) 是由 郑天成 蔡向龙 郭敬为 李仲慧 沈陈诚 于 2020-06-10 设计创作，主要内容包括：本发明是一种基于像散透镜聚焦的气体受激拉曼散射的装置,高能量激光通过像散透镜进行聚焦,泵浦气体拉曼介质产生受激拉曼效应,实现覆盖较宽光谱范围的多条谱线输出。本发明选用由两面平凸柱面镜正交组合成的像散透镜进行聚焦,通过调节柱面镜之间的间距,可以改变聚焦光斑处的光强分布,改变气体的激光诱导击穿阈值,进而影响各阶拉曼光间的能量输出。该发明是一种有效的多谱线输出方法,本发明的优点在于本发明激光器设计简单,调试便捷,并且可实现多种类型的激光器变频,波长变换跨度比较大,可变波长丰富。(The invention relates to a gas stimulated Raman scattering device based on astigmatic lens focusing, wherein high-energy laser is focused through the astigmatic lens, and a pumped gas Raman medium generates a stimulated Raman effect, so that a plurality of spectral lines covering a wider spectral range are output. The invention selects the astigmatic lens orthogonally combined by two plane convex cylindrical mirrors for focusing, and can change the light intensity distribution at the focusing light spot and change the laser induced breakdown threshold of the gas by adjusting the distance between the cylindrical mirrors, thereby influencing the energy output among various stages of Raman light. The invention is an effective multispectral output method, and has the advantages of simple laser design, convenient debugging, realization of frequency conversion of various types of lasers, large wavelength conversion span and rich variable wavelengths.)

1. An astigmatic lens focused gas stimulated raman light output device, comprising: the device comprises a pump laser (1), a lambda/2 wave plate (2), a polarization beam splitter prism (3), a lambda/4 wave plate (4), an astigmatic lens (5), a Raman pool (6), a plano-convex lens (7), a beam splitter prism (8) and a separation baffle (9), wherein the lambda/2 wave plate, the polariton beam splitter prism, the plano-convex lens (4), the astigmatic lens (5), the Raman pool, the plano-convex lens (7) and the beam splitter prism are sequentially arranged along the laser output direction of the pump laser (1);

laser output by the pump laser (1) sequentially passes through a lambda/2 wave plate (2), a polarization beam splitter prism (3), a lambda/4 wave plate (4), an astigmatic lens (5), a Raman pool (6), a plano-convex lens (7), a beam splitter prism (8) and a separation baffle (9) and then is output;

the astigmatic lens (5) converges the laser light passing through the lambda/4 wave plate (4) to any point in the Raman cell (6); the plano-convex lens (7) collimates the output light of the Raman cell (6); and Raman gain gas is filled in the Raman cell (6).

2. An astigmatic lens focused gas stimulated raman light output device according to claim 1, wherein: the astigmatic lens can be a single coated plano-convex astigmatic lens, or can be formed by combining two plano-convex cylindrical mirrors.

3. An astigmatic lens focused gas stimulated raman light output device according to claim 2, wherein: the two plane convex cylindrical mirrors are orthogonally arranged, and the distance between the two plane convex cylindrical mirrors can be adjusted in a reciprocating mode along the transmission direction of the laser.

4. An astigmatic lens focused gas stimulated raman light output device according to claim 1, wherein: raman gain gas is filled in the Raman cell (6), the gas pressure of the Raman gain gas filled in the Raman cell can be adjusted at will, and the adjustment of the gas pressure of the Raman gain gas in the Raman cell (6) can realize the adjustment of the number and the energy of output spectral lines; the Raman-enhanced gas is CO₂，H₂,CH₄,D₂,SF₆,N₂And one or more kinds of Raman active gases.

5. An astigmatic lens focused gas stimulated raman light output device according to claim 4, wherein: inert gas can be additionally filled into the Raman cell (6); the inert gas is one or more than two of helium, neon, argon, krypton and xenon.

6. An astigmatic lens focused gas stimulated raman light output device according to claim 1, wherein: the pump light of the pump laser (1) can be ultraviolet light, visible light or infrared light.

7. An astigmatic lens focused gas stimulated raman light output device according to claim 1, wherein: the deflection angle of the lambda/4 wave plate can be changed within the range of 0-45 degrees; the polarization state of incident light is changed by changing the deflection angle of the lambda/4 wave plate, and the conversion efficiency of output light is further controlled.

8. An astigmatic lens focused gas stimulated raman light output device according to claim 1, wherein:

the polarization beam splitter prism can divide incident unpolarized light into two vertical linearly polarized light beams; the P polarized light passes through completely, the S polarized light is reflected at an angle of 45 degrees, and the emergent direction forms an angle of 90 degrees with the P light.

9. An astigmatic lens focused gas stimulated raman light output device according to claim 1, wherein:

the separating baffle (9) is a flat plate with a through hole in the middle, and the through hole in the middle is a light hole for outputting the gas stimulated Raman light.

Technical Field

The invention relates to a gas stimulated Raman scattering device based on astigmatic lens focusing, which generates a stimulated Raman scattering effect by pumping a gas Raman medium through high-energy laser and realizes output of a plurality of spectral lines covering a wide spectral range.

Technical Field

Stimulated raman is an effective method to broaden the spectral range of high peak power lasers. Both gas and solid media can be used for stimulated Raman conversion, the solid Raman active medium often has the advantages of high gain coefficient, small volume and the like, the damage threshold is low, the Raman frequency shift is small, and the Raman frequency shift is 1000cm^-1Left and right; correspondingly, the gas Raman active medium has the characteristics of lower Raman gain coefficient, larger damage threshold value and the like, the Raman shift is larger, and the Raman frequency shift of the common Raman active gas such as hydrogen in a vibration mode is 4415cm^-1Methane 2917cm^-1And 1388cm for carbon dioxide^-1. Therefore, the spectrum of the gas-stimulated raman laser is often wide in coverage and richer in spectrum.

Pumping the medium with first-order stokes light may then generate second-order stokes light when the first-order stokes raman conversion generated by pumping the gaseous raman-active medium with the focused laser beam is increased. However, when pumping with high energy, laser can breakdown gas, and the generated plasma can often absorb a large amount of pumping photons, which reduces the raman conversion efficiency, and is accompanied by strong thermal effect, which is not favorable for improving the raman conversion and improving the beam quality of raman light. Based on the principle, the invention selects an astigmatic lens to focus in a gas Raman medium, and realizes the output of multispectral lines by utilizing stimulated Raman scattering. The astigmatic lens can change the light intensity distribution at the focus, increase the laser-induced breakdown threshold of the gas, and further influence the energy distribution of different-order Raman light generated by stimulated Raman scattering.

Disclosure of Invention

The invention has the practicability that the monochromatic laser light source is focused in the Raman cell by the astigmatic lens, and a plurality of spectral lines are generated by utilizing gas stimulated Raman scattering. The process is as follows: the pumping laser is focused by the astigmatic lens and then enters the Raman pool filled with Raman active gas, the pumping light and the gas medium act to generate stimulated Raman effect, a plurality of spectral lines are output, and finally the spectral lines are separated by the prism. The gas stimulated Raman device focused by the astigmatic lens mainly comprises four parts: the device comprises a pumping source laser, an astigmatic lens, a gas Raman pool and a separation output system.

Based on the above technical scheme, preferably, the pump light of the pump laser is ultraviolet light, visible light or infrared light, and the multispectral wavelength distribution range can be adjusted by changing the wavelength of the pump light.

Based on the technical scheme, preferably, the beam quality, the pulse width and the repetition frequency of the pump light are changed, the output energy value can influence the output of the Raman light, and the conversion efficiency of the output light can be dynamically adjusted; the pulse width of the pump light can be in a nanometer level, a picosecond level or a femtosecond level, and the repetition frequency can be 1-1000 Hz or even higher; the pump light may also be continuous light. The polarization state of the pump light is linear polarization, circular polarization or elliptical polarization.

Based on the above technical solution, preferably, the astigmatic lens can converge the laser light to any point in the raman pool by changing the focal length. The raman light output can be controlled by varying the focusing parameters.

Based on the technical scheme, the astigmatic lens is preferably composed of two plane-convex cylindrical lenses, and the distance between the cylindrical lenses is adjustable. The light intensity distribution at the focus light spot can be changed by changing the distance between the cylindrical mirrors, so that the energy of the output Raman light of different orders can be regulated and controlled.

Based on the technical scheme, the deflection angle of the lambda/4 wave plate can be changed optionally. The polarization state of incident light is changed by changing the deflection angle of the lambda/4 wave plate, and the conversion efficiency of output light is further controlled.

Based on the scheme, preferably, the inert gas is filled into the Raman cell, so that the heat effect generated when the gas generates the nonlinear effect can be improved, the conversion efficiency of stimulated Raman can be improved, and the Raman cell can operate at a higher repetition frequency without obvious thermal defocusing.

Based on the technical scheme, preferably, the inert gas is helium, neon, argon, krypton or xenon.

Based on the technical scheme, preferably, the laser separation and output system is formed by combining a prism and a laser selection baffle, the laser separation and output system separates lasers with different wavelengths by using a prism dispersion function, and the laser wavelength to be output can be selected by moving the baffle.

The invention has the advantages that (1) the astigmatic lens is selected to change the light intensity distribution at the focus light spot and regulate the energy output of different orders of Raman light. (2) Compared with a non-astigmatic lens with the same focal length, the astigmatic lens focusing can improve the damage threshold of the gas, bear higher pumping peak power and output higher-energy pumping light. (3) The invention can change the conversion efficiency of Raman light by changing the conditions of pump light energy, pulse width, polarization state, repetition frequency, Raman cell length, gas pressure, focusing parameters, the type and pressure of added buffer gas, and the like. (4) The invention has the advantages of convenient operation, simple device and convenient debugging, and can realize various laser frequency conversion. (5) A separation system may be used to select the spectral range of the output frequency comb, corresponding to different applications. (6) The multispectral generated by the invention can cover ultraviolet, visible and infrared lasers, the Raman wavelength range is changed by changing the wavelength of the pumping light and the type of the Raman medium, and the device has simple design, larger wavelength conversion span and rich variable wavelengths.

Drawings

FIG. 1 is a schematic view of a gas stimulated Raman device focused by an astigmatic lens;

wherein;

1: pump laser, 2: λ/2 wave plate, 3: polarizing beam splitter prism, 4: λ/4 wave plate, 5: astigmatic lens, 6: raman pool, 7: plano-convex lens, 8: beam splitter prism, 9: separating the baffles.

Detailed Description

As shown in fig. 1, the stimulated raman light output device focused by the astigmatic lens of the present invention includes a pump laser 1, and a λ/2 wave plate 2, a polarization splitting prism 3, a λ/4 wave plate 4, an astigmatic lens 5, a raman cell 6, a plano-convex lens 7, a splitting prism 8, and a separation baffle 9, which are sequentially disposed along a laser output direction of the pump laser 1; the astigmatic lens 5 converges the laser light to any point in the raman cell 6; the plano-convex lens 7 collimates the output light of the Raman cell 6; and the Raman cell 6 is filled with Raman gain gas. The combination of the lambda/2 wave plate 2 and the polarization beam splitter prism 3 enables incident light energy to be continuously adjustable.

Example 1

The nanosecond pulse Nd-YAG laser frequency doubling light 532nm laser is used as pump laser, the pulse width is 10ns, the polarization state is vertical polarization, the highest emergent energy is 200mJ, and the repetition frequency is 1 Hz. Pump light is filled with CO₂The raman cell 6. The Raman pool 6 with the length of 80cm is filled with 1MPa CO₂(ii) a Rotating the angle of the lambda/4 wave plate 4 to change the polarization state of the incident light into circular polarization; the focal length of the astigmatic lens 5 is 500mm, and the distance between the two cylindrical mirrors is 2 cm; the pump light is focused in the center of the raman cell 6. The device mainly converts 532nm pump light into 574nm, 624nm and 683nm three-beam Raman laser.

Example 2

A picosecond-level pulse Nd-YAG laser base frequency 1064nm laser is used as a pump laser, the pulse width is 100ps, the polarization state is vertical polarization, and the repetition frequency is 100 Hz. 266nm pump light is filled with H in turn₂The raman cell 6. The Raman pool 6 with the length of 180cm is filled with 1MPa H₂And helium at 0.1 MPa; rotating the angle of the lambda/wave plate 4 to ensure that the polarization state of the incident light is horizontally polarized; the focal length of the astigmatic lens 5 is 1000mm, and the distance between the two cylindrical mirrors is 4 cm; the pump light is focused at 1/4 of the raman cell 6. The device mainly converts 1064nm pump light into 738nm, 1907nm and 9187nm three-beam Raman lasers.