阅读说明：本技术 风扇式气体循环高重频拉曼池 (Fan type gas circulation high repetition frequency Raman cell ) 是由 郭敬为 李仲慧 蔡向龙 刘金波 于 2018-06-13 设计创作，主要内容包括：本发明公开了一种能够降低高重频泵浦光在气体介质传播过程中热透镜效应的新型拉曼池,在该设计中最外一层的拉曼池壁为不锈钢材质,拉曼池内放有立体填充物。拉曼池外壁与内置填充物之间的空隙可充高压气体,并且宽窄不一致,将风扇组放置于其中一条窄空隙中,在剩余窄空隙中选择一条作为泵浦光的通光通道。使用高重频泵浦光泵浦气体介质时,泵浦光附近热量逐渐积累,产生热透镜效应,影响输出光的光束质量,当电动风扇运行后,空隙内的高压气体介质按照固定方向流动,带走泵浦光附近的热量,降低拉曼池内热透镜效应,从而提高拉曼光的转换效率。本发明是一种新式拉曼池,通过降低热效应的方法提高拉曼光转化效率及光束质量,有明朗的应用前景。(The invention discloses a novel Raman pool capable of reducing the thermal lens effect of high repetition frequency pump light in the process of gas medium transmission. Gaps between the outer wall of the Raman cell and the built-in filler can be filled with high-pressure gas, the width of the gaps is inconsistent, the fan set is placed in one of the narrow gaps, and one of the remaining narrow gaps is selected as a light passing channel of pump light. When the high repetition frequency pump light is used for pumping the gas medium, heat near the pump light is gradually accumulated to generate a thermal lens effect, the quality of light beams output by the light is influenced, after the electric fan operates, the high-pressure gas medium in the gap flows in a fixed direction to take away the heat near the pump light, the thermal lens effect in the Raman cell is reduced, and therefore the conversion efficiency of the Raman light is improved. The invention is a novel Raman pool, improves the Raman light conversion efficiency and the light beam quality by reducing the thermal effect, and has bright application prospect.)

1. Fan-type gas circulation high repetition frequency Raman pond, its characterized in that: the Raman cell is a closed chamber, two ends of the closed chamber are respectively provided with a laser incidence window and a laser emergent window, a filler is arranged in the Raman cell, a gap is reserved between the cell wall of the Raman cell and the filler, and the gap forms a fixed airflow channel; the channel is internally provided with a fan set.

2. The fan-gas circulation high repetition frequency raman cell of claim 1, wherein: the wall of the Raman tank wall is a stainless steel pipe capable of bearing high pressure of gas.

3. The fan-gas circulation high repetition frequency raman cell of claim 1, wherein: the filler is a solid which can be deformed without high pressure.

4. The fan-gas circulation high repetition frequency raman cell of claim 1, wherein: the fan set is vertically arranged and combined by any small fan blade type electric fan.

5. The fan-gas circulation high repetition frequency raman cell of claim 1, wherein: the window sheets of the laser incidence window and the laser emergent window are white sheets or lenses plated with dielectric films.

6. The fan-gas circulation high repetition frequency raman cell of claim 1, wherein: and a gas pressure gauge for testing the gas pressure in the cell is arranged on the cell wall of the Raman cell.

7. The fan-gas circulation high repetition frequency raman cell of claim 1, wherein: and the wall of the Raman cell is provided with an air vent communicated with the air flow channel.

8. A gas-circulating high repetition frequency raman cell system comprising a high repetition frequency pump light source and a raman cell according to any one of claims 1 to 7.

9. The operation method of the gas circulation high repetition frequency Raman pool system comprises the following steps: sufficient gas medium is filled in the Raman cell, the required air pressure is adjusted, then the fan set is operated, after the gas in the Raman cell is circulated and stabilized, the high repetition frequency pump light is started to completely pass through the Raman cell along a preset light passing path, the shape of a light spot of output light is observed by using spot burning paper at a light outlet and compared with the shape of the pump light spot, if the front light spot and the rear light spot of the Raman cell have no obvious deformation, the heat effect is properly controlled, otherwise, the rotating speed of the fan is further adjusted, and the shapes of the front light spot and the rear light spot are close to be consistent.

10. The fan-type gas circulation high repetition frequency Raman cell of any one of claims 1-7 and the use of the gas circulation high repetition frequency Raman cell system of claim 8 in the fields of basic scientific research, laser frequency conversion, broadening of spectral range and gas concentration detection.

Technical Field

The invention belongs to the technical field of laser, and relates to a fan type gas circulation Raman cell. The invention can be applied to the fields of basic scientific research, laser frequency conversion, spectrum range widening, gas concentration detection and the like.

Technical Field

In the process of Stimulated Raman Scattering (SRS), every stokes photon is generated, a vibrating excited state particle is generated, and the excited state particles release a large amount of heat when relaxing to a ground state through collision; for gaseous raman media, this heat evolved causes them to form a negative temperature gradient and a positive density and refractive index gradient along the beam radius, from the center of the optical axis outwards; the gaseous medium then acts like a negative lens, causing divergence of the incident beam. When the thermal effect in SRS is severe, since the hot gas will rise due to the smaller specific gravity, and the refractive index above the medium is smaller than that below, the whole light beam will diverge and deflect along the direction of the medium with a larger refractive index (i.e. below), and the light spot will usually have an upwardly curved crescent shape, which is generally called thermal defocusing effect or thermal distortion effect.

Thermal defocusing effects often cause divergence and even distortion of various light beams (including pump light and stokes light) in the SRS; thereby reducing the beam power density and raman gain, decreasing the raman conversion efficiency and causing the degradation of the stokes beam quality, and thus eliminating the thermal defocusing effect is very important for the raman conversion. Many researchers in this regard have made attempts to move the medium laterally, move the sample cell laterally mechanically, move the light beam, and so on. In addition, Barry et al use a heating method to accelerate convection to reduce the thermal effect in SRS, improve raman conversion efficiency and improve the spookos beam quality.

Disclosure of Invention

The invention is primarily intended to reduce the thermal lens effect. Through the effect of the electric fan group in the gas Raman cell, heat accumulated in the cell is circularly dissipated along with internal gas, and a serious thermal lens effect cannot be generated even if high-repetition-frequency laser is used for pumping, so that the light beam quality of output light and the conversion efficiency of Raman light are ensured.

The stimulated Raman belongs to the nonlinear effect, and the stimulated Raman scattering can realize laser frequency conversion, so that the device has the advantages of simple design and convenient adjustment; the media capable of realizing stimulated Raman are various, and the Raman media commonly used at present comprise crystals (such as diamond and SrWO)₄) Liquid (e.g.: h₂O，CS₂，C₆H₆) Gas (e.g.: h₂，CH₄) (ii) a Different raman media do not have the same magnitude for pump laser wavelength shifts, some solids can produce shifts of tens of wavenumbers, while gaseous raman media can typically produce shifts of thousands of wavenumbers.

The fan type gas circulation system is characterized in that filler is placed inside a Raman cell, a regular annular airflow channel with uneven width is formed between the filler and the Raman cell wall, a fan set is placed inside one or more narrow channels, and at least one narrow channel is reserved as a light transmission path. When the fan set works, the gas medium can be circulated in the Raman cell to reduce the thermal lens effect generated when the pumping light passes through the medium, and when the high-repetition-frequency pumping light is used for pumping the gas medium, the beam quality of the output light and the conversion efficiency of the Raman light can be still ensured.

In order to achieve the above object, in one aspect of the present invention, a fan-type gas circulation high repetition frequency raman cell is provided, where the raman cell is a closed chamber with a laser incident window and a laser emergent window at two ends, a filler is disposed in the raman cell, a gap is left between a cell wall of the raman cell and the filler, and the gap forms a fixed gas flow channel; the channel is internally provided with a fan set. After the fan runs, stable airflow with a fixed flow direction is formed in the Raman cell, and the thermal lens effect caused when the pump light passes through is weakened.

Furthermore, the wall of the raman pool wall is a stainless steel tube capable of withstanding high gas pressures. The cross section shape can be designed into a geometrical shape with axial symmetry or central symmetry according to requirements. For example: oval, circular, rectangular, etc.

Further, the filler is a solid capable of being deformed without deformation under high pressure conditions. Preferred cross-sections are axisymmetric or centrosymmetric geometries. More preferably, the column is an oval, triangular, or rectangular column, in order to form an airflow channel with different widths between the built-in filler and the raman cell wall, the length of the built-in filler is slightly shorter than that of the raman cell, and the material can be stainless steel, polytetrafluoroethylene, or the like.

Furthermore, the fan set is a vertically arranged combination of any small fan blade type electric fan, and the length of the fan set is slightly shorter than that of the Raman pool.

Furthermore, the window sheets of the laser incidence window and the laser emergent window are white sheets or lenses plated with dielectric films. The diameter of the window sheet is larger than that of the incident laser beam, the thickness is determined according to the air pressure in the Raman cell, and the dielectric film is selected according to the experimental requirements and the incident wavelength. For example: the incident light is 1064nm, the thickness of the two window sheets is 15mm, and the dielectric film T (transmittance) is 99% @1064 nm.

Further, the Raman cell is provided with a gas pressure gauge for testing the gas pressure in the cell. The measuring range can be selected according to the requirement, and the gas pressure in the Raman cell can not exceed two thirds of the measuring range of the barometer.

Further, the pool wall of the Raman pool is provided with an air vent. Preferably a valved vent.

In another aspect of the invention there is provided a gas circulating high repetition frequency raman cell system comprising a high repetition frequency pump light source and a raman cell according to any of claims 1 to 7.

In another aspect of the invention, a method of operating a gas cycle high repetition frequency raman cell system is provided, comprising the steps of: sufficient gas medium is filled in the Raman cell, the required air pressure is adjusted, then the fan set is operated, after the gas in the Raman cell is circulated and stabilized, the high repetition frequency pump light is started to completely pass through the Raman cell along a preset light passing path, the shape of a light spot of output light is observed by using spot burning paper at a light outlet and compared with the shape of the pump light spot, if the front light spot and the rear light spot of the Raman cell have no obvious deformation, the heat effect is properly controlled, otherwise, the rotating speed of the fan is further adjusted, and the shapes of the front light spot and the rear light spot are close to be consistent.

The invention also provides the fan-type gas circulation high repetition frequency Raman cell and application of the gas circulation high repetition frequency Raman cell system according to claim 8 in the fields of basic scientific research, laser frequency conversion, spectrum range widening, gas concentration detection and the like.

The fan-type gas circulation high repetition frequency Raman cell can reduce the thermal lens effect of high repetition frequency pump light in the process of gas medium propagation, the outermost layer of Raman cell wall in the design is made of stainless steel, a three-dimensional filler such as a cube with a regular oval or triangular cross section is placed in the Raman cell, and the material is required to be a solid which can bear high pressure and does not deform such as stainless steel, polytetrafluoroethylene and the like. Gaps between the outer wall of the Raman cell and the built-in filler can be filled with high-pressure gas, the width of the gaps is inconsistent, the fan set is placed in one of the narrow gaps, and one of the remaining narrow gaps is selected as a light passing channel of pump light. When the high repetition frequency pump light is used for pumping the gas medium, heat near the pump light is gradually accumulated to generate a thermal lens effect, the quality of light beams output by the light is influenced, after the electric fan operates, the high-pressure gas medium in the gap flows in a fixed direction to take away the heat near the pump light, the thermal lens effect in the Raman cell is reduced, and therefore the conversion efficiency of the Raman light is improved. The invention is a novel Raman pool, improves the Raman light conversion efficiency and the light beam quality by reducing the thermal effect, and has bright application prospect.

The invention has the advantages that: (1) the cooling time of the thermal effect is greatly reduced, the pump of the high repetition frequency laser can be borne, and the selection range of the pump source is wider; (2) the electric fan set is arranged in the Raman pool, so that the space is saved; 3) gases are less prone to damage than solids, and the use of gases as raman media can withstand higher pumping energies.

Drawings

FIG. 1 is a cross-sectional view of a Raman cell

FIG. 2 is a side view of the exterior of a Raman cell

The device names in the figure are as follows:

1 Raman pool outer wall

2 Raman pool inner filler

3 electric fan set

4 window sheet

5 gas pressure gauge

6 air vent

Detailed Description

As described above, the thermal effect generated by pumping the high pressure gas with the high repetition frequency is a problem. Referring to fig. 1, the present invention provides a fan-type gas circulation high repetition frequency raman cell.

As shown in fig. 2, the raman cell is a closed chamber with a laser entrance window and a laser exit window at two ends, and the interior of the chamber can be filled with high-pressure gas. The gap between the raman cell wall 1 and the cell filling 2 forms a fixed gas flow channel, for example: the Raman pool wall 1 is a cylinder made of stainless steel capable of bearing high pressure, the filler 2 in the Raman pool is an oval cylinder, as can be seen from figure 1, the width of the airflow channels in the Raman pool is inconsistent, the electric fan set 3 is placed in one narrow channel, and the other narrow airflow channel opposite to the narrow channel is used as a passing path of the pumping light. The Raman cell is filled with a gas medium with enough air pressure through the air vent 6, the air pressure in the Raman cell can be displayed by the air pressure gauge 5, when the electric fan set 3 runs, the gas in the Raman cell flows along a fixed direction, and the thermal lens effect generated when the pumping light passes through the medium is weakened.

The cross section of the tank wall 1 can also be regular ellipse, circle, rectangle, etc.; the filler 2 is a cylinder with a cross section of a regular ellipse, an equilateral triangle or other shapes, so that a fixed airflow channel with different widths is formed between the built-in filler and the Raman pool wall, the length of the filler is slightly shorter than that of the Raman pool, and the filler can be made of stainless steel, polytetrafluoroethylene and the like; a small-scale fan blade type electric fan group 3, power, size are chosen according to the concrete experiment; a white sheet or a window sheet 4 plated with a dielectric film, and a gas pressure gauge 5 with a proper measuring range; a vent 6 with a valve.

And adjusting the positions of the filler or the Raman pool wall to ensure that the central axes of the filler and the Raman pool wall are superposed, the specification and the size of each formed narrow channel are the same, the specification and the size of each formed wide channel are the same, and the maximum distance length between the filler and the Raman pool wall is at least twice of the minimum distance length.