CN113097851B

CN113097851B - Compact carbon dioxide pumping terahertz dual-frequency laser

Info

Publication number: CN113097851B
Application number: CN202110326765.4A
Authority: CN
Inventors: 刘海庆; 解家兴; 张际波; 魏学朝; 揭银先; 王宏北
Original assignee: Hefei Institutes of Physical Science of CAS; Institute of Energy of Hefei Comprehensive National Science Center
Current assignee: Hefei Institutes of Physical Science of CAS; Institute of Energy of Hefei Comprehensive National Science Center
Priority date: 2021-03-26
Filing date: 2021-03-26
Publication date: 2022-09-16
Anticipated expiration: 2041-03-26
Also published as: CN113097851A

Abstract

The invention relates to a compact carbon dioxide pumping terahertz double-frequency laser, which comprises a double-laser main body, a carbon dioxide laser pumping optical path and a laser auxiliary system, wherein the double-laser main body is provided with a first laser and a second laser; the dual laser main body comprises a pumping end vacuum cavity, an output end vacuum cavity, 2 laser tubes, 4 invar steels and a pumping end vacuum cavity; the whole pumping light path of the carbon dioxide pumping light path and the double-laser main body are fixed on the optical panel, and laser emitted by the carbon dioxide laser enters the cavity through light condensation, beam splitting and different Boonst windows; the output end vacuum cavity is shared by the two terahertz lasers, the terahertz double-frequency laser device further comprises a high-precision three-dimensional adjusting mechanism which is used for fixing the center hole copper mirrors, the lengths of the resonant cavities of the two lasers are adjusted in a remote mode under a sealed condition, namely the distance between the two center hole copper mirrors at the pumping end and the output end is adjusted accurately, and the output power and the difference frequency of the terahertz double-frequency laser device are controlled.

Description

Compact carbon dioxide pumping terahertz dual-frequency laser

Technical Field

The invention relates to the technical field of optics, in particular to a compact carbon dioxide pumping terahertz double-frequency laser.

Background

Terahertz waves refer to electromagnetic radiation with a frequency in the range of 0.1-10 THz (wavelength of 3000-30 microns), and are located in a relatively wide electromagnetic radiation region between microwave and infrared light. It encompasses a range of electromagnetic spectrum from a portion of the millimeter wave band (about 0.1THz) to the far infrared region (about 25 THz). A light source capable of generating terahertz frequency band laser is called a terahertz laser, and the terahertz laser is an important light source of a far infrared laser interferometer in the plasma diagnosis technology.

The electron density of the plasma is an extremely important physical parameter in the experimental research of a Tokamak fusion device, is associated with a plurality of physical phenomena, can measure the experimental level of the device, and generally uses a far infrared laser interferometer to diagnose the electron density of the plasma in the magnetic confinement fusion research. For example, far-infrared DCN interferometer provided on JET device, far-infrared CH provided on LHD and RFX device ₃ OH interferometers, and the like. The development of interferometer diagnostic techniques is extremely fast, which makes diagnostic interferometers of many types, the most widely used, of the Mach-Zehnder type, heterodyne interferometers. The method mainly obtains the required electron density parameter by calculating the detected phase shift according to the different refractive indexes generated when far infrared light propagates in vacuum and plasma and different phase shifts generated in the propagation direction of the far infrared light. For heterodyne interferometer systems, a difference signal is generated during the actual measurement, and the magnitude of the difference determines the time resolution. There are various methods for modulating the difference frequency by interferometer, such as a rotating grating method, a twin laser method, and the like.

At present, double-light-color laser interferometers and polarimeters are researched and developed at home and abroad, and the technology is more and more important for magnetic confinement fusion experiments. In future ITER and CFETR fusion devices, efforts are underway to develop a two-color laser interferometer using a far infrared band light source in order to meet the demand for high parameter plasma physical diagnostics. And compact carbon dioxide pumping terahertz double-frequency laser compares with traditional single-frequency laser, has following advantage: 1. compared with the method for modulating the intermediate frequency signal by using the rotating grating, the method has the advantage of good signal-to-noise ratio due to the fact that mechanical vibration of the rotating grating is reduced. 2. The time resolution of the dual laser system is high and can easily reach megahertz level. 3. Compared with the super vacuum rotary grating, the optical system and the mechanical structure are simpler.

In the prior art, journal articles "g.li, x.c.wei, h.q.liu, Development of an HCN dual laser for the interferometer on EAST, Plasma Science and Technology, vol.19, jun.20, 2017" introduced the Development of an electrically excited HCN dual-frequency laser and its intermediate frequency stability control, but the frequency stability of the HCN laser as an electrically excited HCN gas laser is far less than that of a carbon dioxide pump laser and the requirement for the intermediate frequency control Technology is very high. The paper, "zhou shigao.east polarization interferometer development [ D ], chinese science and technology university, 2018" introduced a polarization interferometer developed using a three wave method of the dual laser principle to achieve plasma electron density diagnosis on EAST fusion devices, but the light source carbon dioxide pumped formic acid laser of the polarization interferometer in this paper was developed in the united states and is a separate three lasers.

The technology of the carbon dioxide pump terahertz laser is monopolized by developed countries such as Europe, America and the like for a long time, is listed as a technology of 'neck' in China, and greatly limits the development of the domestic terahertz technology. The compact double-frequency laser technology of the carbon dioxide pump is also a technology which can not be applied to plasma electron density diagnosis or is deficient on the basis of the development of the terahertz single-frequency laser of the carbon dioxide pump, so that the development of the instrument has extremely high application value.

Disclosure of Invention

The invention aims to develop a carbon dioxide pumping terahertz double-frequency laser with small volume and compact structure, the laser can simultaneously output two terahertz lasers, and the accurate difference frequency output can be realized by remotely adjusting a three-dimensional adjusting mechanism in a cavity; and the working gas is replaced and each optical device is adjusted, so that terahertz laser with different wavelengths can be output, and the terahertz laser is an ideal light source of the far infrared laser interferometer.

The invention is realized by the following technical scheme: a compact carbon dioxide pumping terahertz double-frequency laser comprises a double-laser main body, a carbon dioxide laser pumping optical path and a laser auxiliary system;

the dual laser main body comprises a pumping end vacuum cavity, an output end vacuum cavity, 2 laser tubes, 4 invar steels and a pumping end vacuum cavity;

the whole pumping light path of the carbon dioxide pumping light path and the double-laser main body are fixed on the optical panel, laser emitted by the carbon dioxide laser is divided into two beams by the first light splitting sheet, one of the two beams is split again by the second light splitting sheet and respectively enters the carbon dioxide power meter and the wavelength meter, and the wavelength meter and the power meter are used for monitoring the wavelength and the output power of the carbon dioxide laser and ensuring the stability of the pumping light; the other beam of laser split by the first light splitting piece is incident on a third light splitting piece through a first reflecting mirror and a focusing mirror, and is split into two beams again through the third light splitting piece, wherein one beam enters a first Boonst window of the first laser, and the other beam enters a second Boonst window of the second laser through a second reflecting mirror;

the output end vacuum cavity is shared by the two terahertz lasers, the three-dimensional adjusting mechanism is used for fixing the center hole copper mirrors, the lengths of the resonant cavities of the two lasers are remotely adjusted under a sealed condition, namely the distance between the two center hole copper mirrors at the pumping end and the output end is adjusted, and the output power and the difference frequency of the terahertz double-frequency lasers are controlled by accurately adjusting the lengths of the resonant cavities.

Further, the invar is made of invar alloy materials.

Further, 1 carbon dioxide laser is adopted to pump two terahertz laser cavities simultaneously.

Furthermore, the laser auxiliary system comprises an air inlet system, a vacuum system and a water cooling system.

Furthermore, the pumping end vacuum cavity is shared by two terahertz lasers, and carbon dioxide light after light splitting enters the pumping end vacuum cavity through the first and second Bootstone windows on the pumping end vacuum cavity and then enters the laser tube to pump working gas, so that energy level transition of the working gas is realized.

Further, when the pumping terahertz dual-frequency laser is used, the output power of the two lasers is adjusted to be optimal to obtain a difference frequency signal of the dual-frequency laser, and then one of the two lasers is adjusted with high precision to obtain a desired intermediate frequency.

Furthermore, the vacuum chambers at the output end are horizontally connected through 4 invar steel, 2 laser tubes are hermetically connected between the two vacuum chambers, the 2 laser tubes are horizontally arranged, and a stainless steel water cooling tube is fixed outside each tube wall.

Furthermore, the air inlet system comprises an air bottle, a flow valve and a flow controller; the gas in the gas cylinder is connected to the output end vacuum cavity through the flow valve and the gas pipe, the flow controller controls the air inflow of the flow valve, energy pole transition of different gas molecules is realized by replacing the working gas used in the gas cylinder, and terahertz laser outputting different wavelengths can be realized by the terahertz laser.

Furthermore, the vacuum system is connected to the vacuum cavity at the pumping end through a corrugated pipe, and one mechanical pump is used for keeping the two terahertz laser cavities in vacuum.

The water cooling system is connected with the stainless steel water cooling pipe through a water cooling machine, and the temperature of the wall of the laser pipe is kept constant through internal circulating water of the water cooling machine.

Furthermore, three-dimensional adjustment mechanism, the bottom is an electronic translation platform of high accuracy for the mirror holder on the remote control translation platform realizes that the precision is higher than the translation of the front and back of 1 micron, and the mirror holder on the translation platform is two-dimentional and adjusts the mirror holder, realizes the rotation and the pitch angle of mirror through two differential heads of manual regulation and adjusts, through the accurate input and output copper mirror of adjusting of this mirror holder, makes two mirrors keep parallel, and can long-range accurate adjustment resonant cavity length.

Has the advantages that:

the dual-frequency laser has the advantages that the dual-frequency laser developed by the advantage of extremely stable output of the carbon dioxide pump laser has small volume and compact structure, can output extremely stable difference frequency signals, and is an ideal light source of the far infrared laser interferometer. The dual-frequency laser realizes the output function of the two lasers but only uses 1 carbon dioxide laser and 1 set of laser auxiliary system, thus greatly saving the development cost. The dual-frequency laser can output terahertz laser with different wavelengths by replacing the working gas and adjusting the optical device, and the application value of the terahertz gas laser is greatly improved.

Drawings

FIG. 1 is a top view of the overall structure of the present invention;

FIG. 2 is an elevational view of the overall construction of the present invention;

FIG. 3 is a three-dimensional adjustment mechanism for fixing a copper mirror;

FIG. 4 is a center hole copper mirror.

Wherein: the device comprises a pump end vacuum cavity 1, an output

end vacuum cavity

2, 2

laser tubes

3, 4 invar steel 4, an optical panel 5, a carbon dioxide laser 6, a first light splitter 7, a second light splitter 8, a wavelength meter 9, a carbon dioxide power meter 10, a first reflector 11, a focusing mirror 12, a third light splitter 13, a second reflector 14, a first Boonst window 15, a second Boonst window 16, a high-precision three-dimensional adjusting mechanism 17, a gas cylinder 18, a flow valve 19, a flow controller 20, a mechanical pump 21, a water cooler 22 and a stainless steel water cooling tube 23.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention belong to the protection scope of the present invention without creative efforts.

As shown in fig. 1, 2 and 3, a compact carbon dioxide pumping terahertz dual-frequency laser includes a dual-laser main body, a carbon dioxide laser pumping optical path and a laser auxiliary system.

The dual-laser main body comprises a pumping end vacuum cavity 1, an output

end vacuum cavity

2, 2

laser tubes

3, 4 invar steels 4, the pumping end vacuum cavity 1, the output end vacuum cavities 2 are horizontally connected through the 4 invar steels, and the 2 laser tubes are hermetically connected between the two vacuum cavities;

the whole pumping light path of the carbon dioxide pumping light path and the double-laser main body are fixed on the optical panel 5, laser emitted by the carbon dioxide laser 6 is divided into two beams by the first light splitter 7, one of the two beams is split again by the second light splitter 8 and respectively enters the carbon dioxide power meter 10 and the wavelength meter 9, and the wavelength meter and the power meter are used for monitoring the wavelength and the output power of the carbon dioxide laser and ensuring the stability of the pumping light; the other laser beam split by the first light splitter 7 is incident on the third light splitter 13 through the first reflecting mirror 11 and the focusing mirror 12, and is split into two beams again by the third light splitter 13, wherein one beam enters the first bunot window 15 of the first laser, and the other beam enters the second bunot window 16 of the second laser through the second reflecting mirror 14.

The laser auxiliary system comprises an air inlet system, a vacuum system and a water cooling system.

The pumping end vacuum cavity 1 is shared by two terahertz lasers, and carbon dioxide light after light splitting enters the pumping end vacuum cavity 1 through the first and second

Boolean windows

15 and 16 on the pumping end vacuum cavity 1 and then enters a laser tube to pump working gas, so that energy level transition of the working gas is realized.

The output end vacuum cavity 2 is shared by the two terahertz lasers, and the terahertz dual-frequency laser control device further comprises a high-precision three-dimensional adjusting mechanism 17 which is used for fixing a center hole copper mirror (as shown in figure 4), the length of a resonant cavity (the distance between a pumping end and the two copper mirrors at the output end) of the two lasers can be remotely adjusted under a sealed condition, and the output power and the difference frequency of the terahertz dual-frequency laser are controlled by accurately adjusting the length of the resonant cavity (the adjusting precision is higher than 1 micron). When the length of the resonant cavity of the laser is an integral multiple of the half-wavelength of the laser, the output power of the laser can reach the maximum value, and the relationship between the length of the resonant cavity and the output power of the laser meets a Gaussian distribution curve, so that high-precision adjustment is needed to be used, so that the length of the resonant cavity of the laser is as much as possible equal to the integral multiple of the half-wavelength (the length of the resonant cavity is influenced by environmental temperature, mechanical vibration and the like, can generate small changes during operation, and influences the output power and difference frequency), or about the integral multiple, so that the output power of the laser can be about the peak value, and through calculation, the preferred adjustment precision of the output power is preferably less than or equal to 10 microns; the laser difference frequency adjustment is calculated by a laser resonant cavity length and difference frequency change formula, and the precision of the difference frequency adjustment reaches 1 micron through calculation. When the pumping terahertz double-frequency laser is used, the output power of the two lasers is adjusted to be optimal to obtain a difference frequency signal of the double-frequency laser, and then one of the lasers is adjusted with high precision to obtain a desired intermediate frequency. Because the precision of output power adjustment and intermediate frequency adjustment is different by one magnitude, the influence on the output power is small and can be almost ignored when the intermediate frequency is adjusted.

The 2 laser tubes 3 are hermetically connected between the pumping end vacuum cavity and the output end vacuum cavity, the 2 laser tubes are horizontally arranged (the center heights are consistent), and a stainless steel water cooling tube 23 is fixed outside each tube wall.

The pumping end vacuum cavity 1 and the output end vacuum cavity 2 are fixedly connected through 4 pieces of invar steel 4, and the invar steel 4 is arranged and fixed around the 2 laser tubes 3 in a rectangular mode, so that the whole structure is more compact, and the whole volume is smaller (only 4 pieces of invar steel are used by the two terahertz lasers).

The air inlet system comprises an air bottle 18, a flow valve 19 and a flow controller 20; the gas in the gas cylinder is connected to the output end vacuum cavity through the flow valve and the gas pipe, the flow controller controls the air inflow of the flow valve, energy pole transition of different gas molecules is realized by replacing the working gas used in the gas cylinder 12, and terahertz laser output with different wavelengths can be realized by the terahertz laser.

The vacuum system is connected to the pumping end vacuum cavity 1 through a corrugated pipe, and one mechanical pump 21 is used for keeping the two terahertz laser cavities in vacuum.

The water cooling system is connected with a stainless steel water cooling pipe 23 through a water cooling machine 22, and the temperature of the wall of the laser pipe is kept constant through internal circulating water of the water cooling machine.

As shown in fig. 3, the bottom of the three-dimensional adjusting mechanism 17 of the present invention is a high-precision electric translation stage, which can remotely control the mirror holder on the translation stage to realize the forward and backward translation with the precision higher than 1 micron, the mirror holder on the translation stage is a two-dimensional adjusting mirror holder, and the rotation and pitch angle adjustment of the mirror can be realized by manually adjusting two differential heads. The input end copper mirror and the output end copper mirror can be accurately adjusted through the mirror bracket, so that the two mirrors are kept parallel (the performance of a resonant cavity is ensured, and light energy can resonate between the two mirrors), and the length of the resonant cavity can be remotely and accurately adjusted.

The overall operation mode of the instrument is as follows: and opening a vacuum pump to keep the cavity of the dual laser in a vacuum state, then filling working gas, and adjusting the gas inflow to keep the gas flow and the vacuum degree in the cavity stable. And opening the carbon dioxide laser, dividing the carbon dioxide pumping laser into two paths by the light splitting piece, enabling the two paths to enter the two laser tubes, forming a resonant cavity with the two copper mirrors in front of and behind the laser tubes, and exciting gas molecules to jump from a low energy level to a high energy level by the carbon dioxide laser so as to output the terahertz laser at an output end. During operation, the water cooling system keeps the temperature of the laser tube stable, and the three-dimensional adjusting mechanism adjusts the output power of the lasers and the difference frequency of the two lasers.

Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but various changes may be apparent to those skilled in the art, and it is intended that all inventive concepts utilizing the inventive concepts set forth herein be protected without departing from the spirit and scope of the present invention as defined and limited by the appended claims.

Claims

1. The utility model provides a compact carbon dioxide pumping terahertz is two frequency laser now which characterized in that: the dual-laser device comprises a dual-laser device body, a carbon dioxide laser pumping light path and a laser device auxiliary system;

the output end vacuum cavity is shared by the two terahertz lasers, the carbon dioxide light after light splitting enters the pumping end vacuum cavity through the first and second Boonsted windows on the pumping end vacuum cavity and then enters the laser tube to pump the working gas, and the high-precision three-dimensional adjusting mechanism is further included for fixing the central hole copper mirror, remotely adjusting the resonant cavity lengths of the two lasers under the sealed condition, namely the distance between the two central hole copper mirrors at the pumping end and the output end, and further realizing the control of the output power and the difference frequency of the terahertz double-frequency laser by accurately adjusting the resonant cavity length;

when the length of a resonant cavity of the laser is an integral multiple of the half-wavelength of the laser, the output power of the laser can reach the maximum value, and the relation between the length of the resonant cavity and the output power of the laser meets a Gaussian distribution curve, so that the adjustment is needed, the length of the resonant cavity of the laser is equal to the integral multiple of the half-wavelength, the output power of the laser is in the peak value, and the adjustment precision of the output power is smaller than or equal to 10 micrometers through calculation; the difference frequency adjustment of the laser is calculated by a laser resonant cavity length and a difference frequency change formula, the precision of the difference frequency adjustment is calculated to reach 1 micron, the output power of the laser is adjusted firstly when the pumping terahertz double-frequency laser is used, so that the output power of the two lasers reaches the best, the difference frequency signal of the double-frequency laser is obtained, and then one laser is adjusted with high precision, so that the desired intermediate frequency is obtained;

the three-dimensional adjusting mechanism is provided with a high-precision electric translation table at the bottom and is used for remotely controlling the front and back translations with the precision higher than 1 micron of the mirror frame on the translation table, the mirror frame on the translation table is a two-dimensional adjusting mirror frame, the rotation and pitch angle adjustment of the mirror are realized by manually adjusting two differential heads, the input end and the output end of the copper mirror are accurately adjusted through the mirror frame, the two mirrors are kept parallel, and the length of the resonant cavity can be remotely and accurately adjusted.

2. The compact carbon dioxide pumped terahertz dual-frequency laser according to claim 1, characterized in that: the invar steel is made of invar alloy materials.

3. The compact carbon dioxide pumped terahertz dual-frequency laser according to claim 1, characterized in that: two terahertz laser cavities are pumped simultaneously by adopting 1 carbon dioxide laser.

4. The compact carbon dioxide pumped terahertz dual-frequency laser according to claim 1, characterized in that: the laser auxiliary system comprises an air inlet system, a vacuum system and a water cooling system.

5. The compact carbon dioxide pumped terahertz dual-frequency laser according to claim 1, characterized in that:

when the pumping terahertz double-frequency laser is used, the output power of the two lasers is adjusted to be optimal to obtain a difference frequency signal of the double-frequency laser, and then one of the lasers is adjusted with high precision to obtain a desired intermediate frequency.

6. The compact carbon dioxide pumped terahertz dual-frequency laser according to claim 1, characterized in that: the vacuum chambers at the output end are horizontally connected through 4 invar steel, the 2 laser tubes are hermetically connected between the two vacuum chambers, the 2 laser tubes are horizontally arranged, and a stainless steel water cooling tube is fixed outside the tube wall of each laser tube.

7. The compact carbon dioxide pumped terahertz dual-frequency laser according to claim 4, characterized in that:

the air inlet system comprises an air bottle, a flow valve and a flow controller; the gas in the gas cylinder is connected to the output end vacuum cavity through the flow valve and the gas pipe, the flow controller controls the air inflow of the flow valve, energy pole transition of different gas molecules is realized by replacing the working gas used in the gas cylinder, and terahertz laser outputting different wavelengths can be realized by the terahertz laser.

8. The compact carbon dioxide pumped terahertz dual-frequency laser according to claim 4, characterized in that:

the vacuum system is connected to the pumping end vacuum cavity through a corrugated pipe, and one mechanical pump is used for keeping the two terahertz laser cavities in vacuum;