CN112490836A - Gas Raman laser based on annular unstable resonator - Google Patents
Gas Raman laser based on annular unstable resonator Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
- H01S3/083—Ring lasers
- H01S3/0835—Gas ring lasers
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/08081—Unstable resonators
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
- H01S3/10023—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by functional association of additional optical elements, e.g. filters, gratings, reflectors
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects
- H01S3/305—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects in a gas
Abstract
The invention provides a gas Raman laser based on an annular unstable resonator, which comprises a fundamental frequency laser plane reflector, a laser gain medium, a fundamental frequency laser plane reflector, a convex lens coated with a fundamental frequency light antireflection film, a plane mirror for increasing the reflectivity of fundamental frequency laser reflection Raman light, a Raman pool, a plane mirror for increasing the reflectivity of fundamental frequency laser reflection Raman light and a convex lens coated with a fundamental frequency light antireflection film. The ring cavity formed by the elements meets the self-imaging condition, so that the focus in the cavity is arranged at the center of the Raman cell, the light-emitting threshold of Raman laser can be reduced, and the conversion efficiency is improved. The Raman light high-reflection mirror is coaxially inserted outside the cavity along the optical axis on the Raman light transmission path, and the Raman light output coupling mirror forms a Raman light resonant cavity, so that lower threshold value and better beam quality can be realized. By inserting the isolator and the etalon at the same optical axis at the proper position in the cavity, spatial hole burning caused by standing wave can be avoided, and fundamental frequency light with stable frequency is realized, so that the spectrum conversion efficiency of the Raman laser is improved.
Description
Technical Field
The invention belongs to the field of laser, and particularly relates to an annular unstable resonator gas Raman laser for generating variable-frequency Raman laser.
Background
The stimulated Raman scattering technology of the Raman active medium is an important technical means for realizing laser frequency conversion. The inherent properties of the gas laser determine the characteristics of high power, high beam quality, high beam uniformity and high damage threshold, and the Raman laser with gas as a gain medium has the same excellent laser characteristics. Compared with other types of Raman laser media, the gas Raman medium can realize large Raman frequency shift and narrower Raman line width. A commonly used Raman medium is N2、H2、CH4Etc. since the concentration of the gas is generally not high, a higher pumping power density is required to reach the threshold.
At present, methods for realizing Raman laser by adopting gas medium are generally divided into several types: the first is an external cavity method, namely, a Raman medium is arranged outside a fundamental frequency light cavity, laser output by an output coupling mirror is focused into a Raman pool and a Raman active medium in the pool to generate stimulated Raman scattering to output Raman laser, and the residual fundamental frequency light can be focused into the Raman pool for multiple times through a reflecting mirror, which is equivalent to increasing the gain length of the Raman medium to realize efficient Raman light conversion. The problem with this approach is that the optical design is too complex and the adjustment is too cumbersome. The second is an intracavity method, that is, the laser medium and the raman medium are both placed in the fundamental frequency cavity, the raman light is output through the dichroic mirror, the designed fundamental frequency laser is not output, only the raman laser is output, and the residual pump light in the raman conversion process continues to oscillate and amplify in the cavity.
The cavity design of the intracavity raman laser is very important for realizing efficient raman conversion. The current high-efficiency gas Raman laser is generally a concentric cavity or an unstable cavity. The concentric cavity is formed by superposing the curvature centers of the two cavity mirrors and is positioned in the Raman cell so as to realize high-efficiency Raman light conversion through the fundamental frequency pumping light with high power density. However, the concentric cavity belongs to a critical cavity type, the positions of the cavity mirrors are difficult to be aligned, and particularly when the raman laser runs at a certain repetition frequency, due to the heat effect, the curvature centers of the two cavity mirrors are dislocated to a certain extent, which has a great influence on the raman efficiency. In contrast, unstable cavities have relatively high alignment stability, better beam quality. The negative-branch confocal unstable cavity generally places the raman cell at the real focus position due to the real focus present in the cavity to achieve high conversion efficiency. Because the mode of laser oscillation in the cavity of the negative branch real confocal unstable resonator is single focusing reflection parallel, the net loss of parallel light passing through the Raman medium can influence the fundamental frequency light efficiency because the lower power density of the parallel light passing through the Raman medium is generally lower than the Raman threshold.
Disclosure of Invention
Aiming at the problems of the Raman laser adopting the gas Raman medium, in order to reduce the Raman threshold and improve the Raman conversion efficiency, the invention provides the high-efficiency low-threshold gas Raman laser based on the annular unstable resonator.
The invention provides a gas Raman laser based on an annular unstable resonator, which comprises a pumping source, a fundamental frequency laser plane reflector 1, a laser gain medium 2, a fundamental frequency laser plane reflector 3, a convex lens 4 plated with a fundamental frequency light antireflection film, a fundamental frequency laser reflection Raman light antireflection plane mirror 5, a Raman pool 6, a fundamental frequency laser reflection Raman light antireflection plane mirror 7 and a convex lens 8 plated with a fundamental frequency light antireflection film, wherein the fundamental frequency laser plane reflector 3 is a concave mirror; the mirror for reflecting Raman light by fundamental frequency laser and increasing the reflection is a mirror plated with a fundamental frequency laser reflection film and a Raman laser reflection increasing film;
after the pump light of the pump source passes through the laser gain medium 2, the output fundamental frequency laser can be transmitted along two opposite directions;
when the laser light propagates along the clockwise direction, the laser light sequentially passes through a fundamental frequency laser plane mirror 3, a convex lens 4 coated with a fundamental frequency light antireflection film, a plane mirror 5 coated with a fundamental frequency laser reflection Raman light antireflection film, a Raman pool 6, a plane mirror 7 coated with a fundamental frequency laser reflection Raman light antireflection film, a convex lens 8 coated with a fundamental frequency light antireflection film, a Brewster angle window 9 coated with a fundamental frequency light antireflection film and a fundamental frequency laser plane mirror 1, and then passes through a laser gain medium 2 again to complete one-time propagation;
when the transmission is carried out along the anticlockwise direction, the transmission is carried out again through the laser gain medium 2 after sequentially passing through the fundamental frequency laser plane reflecting mirror 1, the convex lens 8 plated with the fundamental frequency light antireflection film, the plane mirror 7 for the fundamental frequency laser reflection Raman light antireflection, the Raman pool 6, the plane mirror 5 for the fundamental frequency laser reflection Raman light antireflection, the convex lens 4 plated with the fundamental frequency light antireflection film and the fundamental frequency laser plane reflecting mirror 3;
the Raman laser generated after the fundamental frequency laser enters the Raman pool can be transmitted to two opposite directions, and the Raman laser is transmitted after passing through the mirror 5 for reflection of the fundamental frequency laser and reflection of Raman light or the mirror 7 for reflection of the fundamental frequency laser and reflection of Raman light, and the Raman laser is output from two directions. The Raman laser comprises a fundamental frequency laser plane reflecting mirror 1, a laser gain medium 2, a fundamental frequency laser plane reflecting mirror 3, a convex lens 4 coated with a fundamental frequency light antireflection film, a fundamental frequency laser reflection Raman light antireflection plane mirror 5, a Raman pool 6, a fundamental frequency laser reflection Raman light antireflection plane mirror 7 and a convex lens 8 coated with a fundamental frequency light antireflection film, wherein an annular unstable resonator of the Raman laser can be formed.
Based on the above technical solution, preferably, the gas raman laser based on the annular unstable resonator further includes a brewster angle window 9 coated with a fundamental frequency light antireflection film, the brewster angle window 9 coated with the fundamental frequency light antireflection film is disposed between the fundamental frequency laser plane mirror 1 and the convex lens 8 coated with the fundamental frequency light antireflection film, and the purpose of adding the brewster angle window 9 coated with the fundamental frequency light antireflection film into the fundamental frequency cavity is to generate laser with linear polarization, and the raman light threshold can be greatly reduced by the linear polarization fundamental frequency light. The Brewster's angle window 9 plated with the fundamental frequency light antireflection film can be arranged in any non-Raman laser transmission area, and the laser in the cavity sequentially passes through the fundamental frequency laser plane reflecting mirror 1, the laser gain medium 2, the fundamental frequency laser plane reflecting mirror 3, the convex lens 4 plated with the fundamental frequency light antireflection film, the flat mirror 5 for antireflection of fundamental frequency laser reflection Raman light, the Raman pool 6, the flat mirror 7 for antireflection of fundamental frequency laser reflection Raman light, and is coaxial with the initial fundamental frequency laser beam after passing through the convex lens 8 plated with the fundamental frequency light antireflection film and the Brewster's angle window 9 plated with the fundamental frequency light antireflection film.
Based on the above technical scheme, preferably, when the positions of the convex lens 4 plated with the fundamental frequency light antireflection film and the convex lens 8 plated with the fundamental frequency light antireflection film satisfy the following conditions, propagation of fundamental frequency light in the cavity can satisfy a circular self-imaging in the cavity:
wherein L is1、L2、L3The optical path propagation distance from the space virtual image point to the convex lens 8 coated with the fundamental frequency light antireflection film, the optical path propagation distance between the convex lens 4 coated with the fundamental frequency light antireflection film and the convex lens 8 coated with the fundamental frequency light antireflection film, and the optical path propagation distance from the convex lens 4 coated with the fundamental frequency light antireflection film to the space virtual image point are respectively, wherein M is f2/f1Magnification; the space virtual image point is the focus of a convex lens 4 of a fundamental frequency light antireflection film in the Raman cell. And the distance L between the convex lens 4 plated with the antireflection film for fundamental frequency light and the convex lens 8 plated with the antireflection film for fundamental frequency light2The confocal condition is satisfied:
L2＝f1+f2
wherein f is1And f2The focal lengths of the convex lens 4 plated with the antireflection film for fundamental frequency light and the convex lens 8 plated with the antireflection film for fundamental frequency light are respectively.
Based on the technical scheme, M is preferably 1-3. It is believed that M should be chosen close to 1, which greatly increases the conversion efficiency, but leads to increased cavity sensitivity and difficult adjustment, and the choice should be made in combination with practical conditions.
Based on the above technical scheme, preferably, the raman pool is filled with raman medium, the focal points of the convex lens 4 plated with the fundamental frequency light antireflection film and the convex lens 8 plated with the fundamental frequency light antireflection film are located inside the raman pool, and particularly, the focal point is located at the center of the raman pool in order to improve the raman laser conversion efficiency.
Based on the above technical solution, preferably, a raman light high-reflection mirror 10 and a raman light output coupling mirror 11 are further coaxially arranged on the optical axis of the output raman laser transmission path; the raman light high-reflection mirror 10 and the raman light output coupling mirror 11 are arranged on a raman laser transmission path outside the annular cavity, raman laser can be transmitted through the fundamental frequency laser reflection raman light anti-reflection plane mirror 5 and the fundamental frequency laser reflection raman light anti-reflection plane mirror 7, the raman light high-reflection mirror 10 is arranged on a raman laser transmission path of the fundamental frequency laser reflection raman light anti-reflection plane mirror 5, the raman light output coupling mirror 11 is arranged on the raman laser transmission path of the fundamental frequency laser reflection raman light anti-reflection plane mirror 7, conversely, the raman light high-reflection mirror 10 and the raman light output coupling mirror 11 can be replaced, the raman light high-reflection mirror 10 and the raman light output coupling mirror 11 form a raman light resonant cavity, and the length of the resonant cavity is equal to the sum of the curvature radii of the raman light high-reflection mirror 10 and the raman light output coupling mirror 11; the reflecting surfaces of the Raman light high-reflection mirror 10 and the Raman light output coupling mirror 11 share a curvature center, and the curvature center is superposed with the focus of the convex lens 4 of the fundamental frequency light antireflection film in the Raman cell.
Based on the above technical solution, preferably, the gas raman laser based on the annular unstable resonator further includes a polarizer 12 plated with a fundamental frequency light antireflection film, a faraday optical rotator 13, an analyzer 14, an optical rotator 15, and an etalon 16 plated with an antireflection film at any non-raman light transmission position in the annular cavity, where the polarizer 12 plated with a fundamental frequency light antireflection film, the faraday optical rotator 13, the analyzer 14, the optical rotator 15, and the etalon 16 plated with an antireflection film are sequentially arranged in a counterclockwise direction; the fundamental frequency laser passes through the polarizer 12, passes through the Faraday optical rotator 13, and penetrates through the analyzer 14 and the optical rotator 15, and the polarizer 12, the Faraday optical rotator 13, the analyzer 14, the optical rotator 15 and the etalon 16 plated with the antireflection film of the fundamental frequency light are arranged in the non-overlapping area of any fundamental frequency light and Raman laser.
Based on the above technical solution, preferably, the gas raman laser based on the ring-shaped unstable resonator further includes two Q crystals; taking the polarizer 12 plated with a fundamental frequency light antireflection film as a starting point, and arranging the two Q crystals between the analyzer 14 and the etalon 16 plated with the antireflection film along the counterclockwise direction; the two Q crystals are arranged in a non-overlapping area of any fundamental frequency light and Raman laser; the two Q crystals are active or passive Q switches. The active or passive Q switch is inserted into the non-Raman optical transmission path in the annular unstable cavity, and pulses generated by Q regulation have higher peak power, so that higher conversion efficiency of Raman laser can be obtained.
Based on the above technical solution, preferably, the active or passive Q-switch is an electro-optical Q-switch element, an acousto-optical Q-switch element, a saturable absorber, or the like.
Advantageous effects
(1) The gas Raman laser based on the annular unstable resonator provided by the invention has the advantages that the fundamental frequency light circularly oscillates in the cavity in a traveling wave mode, compared with a non-circular negative-branch real confocal unstable resonator gas Raman laser, the design can realize that the fundamental frequency laser forms a focus every time the fundamental frequency laser passes through the Raman cell, the annular cavity meets the self-imaging condition, the focus in the cavity is arranged at the center of the Raman cell, the light-emitting threshold of the Raman laser can be reduced, the conversion efficiency is improved, the power density is favorably improved, and the Raman light conversion is realized.
(2) Compared with a standing wave cavity, the gas Raman laser based on the annular unstable cavity provided by the invention can avoid space hole burning caused by standing waves by inserting the polarizer, the Faraday optical rotator, the analyzer and the isolator consisting of the optical rotator and inserting the etalon into the appropriate position in the cavity along the same optical axis, thereby realizing fundamental frequency light with stable frequency and improving the spectrum conversion efficiency of the Raman laser.
(3) According to the gas Raman laser based on the annular unstable resonator, the annular cavity and the unstable resonator are combined, the advantages of good laser frequency stability of the annular cavity, no overlapping of lasers in the cavity and good self-imaging unstable resonator light beam quality are considered, and efficient Raman laser conversion is achieved.
(4) According to the gas Raman laser based on the annular unstable resonator, the Raman light high-reflection mirror and the Raman light output coupling mirror are coaxially inserted outside the cavity along the optical axis of the Raman light transmission path to form a Raman light resonant cavity, so that a lower threshold value and better beam quality can be realized. Two Q crystals are inserted into a non-Raman optical transmission path in the cavity, pulses generated by Q modulation have higher peak power, and higher conversion efficiency of Raman laser can be obtained.
Drawings
FIG. 1 is a schematic structural diagram of a gas Raman laser based on an annular unstable resonator according to the present invention;
FIG. 2 is a schematic structural diagram of a gas Raman laser based on an annular unstable resonator according to the present invention;
FIG. 3 is a schematic structural diagram of a gas Raman laser based on an annular unstable resonator according to the present invention;
FIG. 4 is a schematic structural diagram of a gas Raman laser based on an annular unstable resonator according to the present invention;
wherein: 1. a fundamental frequency laser plane mirror; 2. a laser gain medium; 3. a fundamental frequency laser plane mirror; 4. a convex lens plated with a fundamental frequency light antireflection film; 5. a mirror for reflecting Raman light and increasing the transmission of fundamental frequency laser; 6. a Raman pool; 7. a mirror for reflecting Raman light and increasing the transmission of fundamental frequency laser; 8. a convex lens plated with a fundamental frequency light antireflection film; 9. a Brewster angle window plated with a fundamental frequency light antireflection film; 10. a Raman light high-reflection mirror; 11. a Raman light output coupling mirror; 12. a polarizer plated with a fundamental frequency light antireflection film; 13. a Faraday rotator; 14. an analyzer; 15. an optical rotator; 16. an etalon plated with an antireflection film; 17. a crystal of Q; 18. and (3) Q crystal.
Detailed Description
Embodiments of the present invention are described in further detail below with reference to the accompanying drawings.
Example 1
As shown in fig. 1, a gas raman laser based on an annular unstable resonator includes a fundamental frequency laser plane mirror 1, a laser gain medium 2, a fundamental frequency laser plane mirror 3, a convex lens 4 coated with a fundamental frequency light antireflection film, a flat mirror 5 for antireflection of fundamental frequency laser reflection raman light, a raman pool 6, a flat mirror 7 for antireflection of fundamental frequency laser reflection raman light, a convex lens 8 coated with a fundamental frequency light antireflection film, and a brewster's angle window 9 coated with a fundamental frequency light antireflection film; the intracavity laser sequentially passes through a fundamental frequency laser plane reflector 1, a laser gain medium 2, a fundamental frequency laser plane reflector 3, a convex lens 4 coated with a fundamental frequency light antireflection film, a plane mirror 5 coated with a fundamental frequency laser reflection Raman light antireflection film, a Raman pool 6, a plane mirror 7 coated with a fundamental frequency laser reflection Raman light antireflection film, passes through a convex lens 8 coated with a fundamental frequency light antireflection film and a Brewster's angle window 9 coated with a fundamental frequency light antireflection film along the clockwise direction and is coaxial with the initial laser beam.
The propagation of the fundamental frequency light in the cavity meets the condition of circulating self-imaging in the cavity:
wherein L is1、L2、L3The distance from the virtual image point to the convex lens 8 with the base frequency light antireflection film coated on the lens, the distance between the convex lenses 4 and 8 with the base frequency light antireflection film coated on the lens, and the distance from the convex lens 4 with the base frequency light antireflection film coated on the lens to the virtual image point are respectively. And the distance L between the convex lens 4 plated with the antireflection film for fundamental frequency light and the convex lens 8 plated with the antireflection film for fundamental frequency light2The confocal condition is satisfied:
L2＝f1+f2
wherein f is1And f2The focal lengths of the convex lens 4 plated with the antireflection film for fundamental frequency light and the convex lens 8 plated with the antireflection film for fundamental frequency light are respectively. M ═ f2/f1(assume f)1<f2) To be the magnification. It is believed that M should be chosen close to 1, which greatly increases the conversion efficiency, but leads to increased cavity sensitivity and difficult adjustment, and the choice should be made in combination with practical conditions.
The brewster's angle window 9 is added into the fundamental frequency cavity to generate laser with linear polarization, and the linear polarization of fundamental frequency light can greatly reduce the threshold of raman light.
The Raman medium is filled in the Raman cell, the focuses of the convex lens 4 plated with the fundamental frequency light antireflection film and the convex lens 8 plated with the fundamental frequency light antireflection film are positioned in the Raman cell, and particularly, the focus is positioned in the center of the Raman cell in order to improve the Raman laser conversion efficiency.
Specifically, when the laser works, fundamental frequency laser generated by the gain medium circularly oscillates in the cavity along the clockwise direction or the anticlockwise direction, when a stable mode is formed, the laser at the position of the gain medium is parallel light, the parallel light passes through the convex lens 4 or 8 plated with the fundamental frequency light antireflection film and is focused into the Raman pool 6, a focus is formed in the Raman pool, the power density of the fundamental frequency light near the focal depth of the focus reaches a stimulated Raman conversion threshold, the conversion efficiency of the stimulated Raman laser is gradually improved along with the improvement of the pumping power of the fundamental frequency light, and the Raman laser is output left and right along the horizontal direction.
Example 2
As shown in fig. 2, in the gas raman laser of the ring unstable resonator according to embodiment 1, a raman light high-reflection mirror 10 and a raman light output coupling mirror 11 are coaxially inserted outside the ring unstable resonator along an optical axis on a raman light transmission path, and the reflection surfaces of the raman light high-reflection mirror 10 and the raman light output coupling mirror 11 have curvatures and share a curvature center, and the curvature center coincides with an intracavity focal point. The Raman light high reflecting mirror 10 and the Raman light output coupling mirror 11 form a Raman light resonant cavity, and the length of the resonant cavity is the sum of the curvature radii of the Raman light high reflecting mirror 10 and the Raman light output coupling mirror 11. Specifically, when the laser works, the power density of the fundamental frequency light at the focus in the cavity and near the focal depth reaches the threshold value generated by the raman light, and the raman light is reflected back into the cavity through the raman light high-reflection mirror 10 or the raman light output coupling mirror 11 after passing through the plane mirror 5 or 7 for reflection enhancement of the fundamental frequency laser reflection raman light, and because the position of the focus in the cavity coincides with the center of curvature of the raman light high-reflection mirror 10 or the raman light output coupling mirror 11, the reflected raman light can return to the focus again and be amplified as seed light, thereby improving the conversion efficiency of the raman light.
Example 3
In example 1 and example 2, the laser light propagates in the resonant cavity both clockwise and counterclockwise in the form of a traveling wave, wherein the beam size is continuously enlarged to a forward wave and reduced to a backward wave, and the presence of the backward wave causes a standing wave to be likely to exist in the cavity, and most importantly, it generates raman light, but this part of the raman light is not available and reduces the raman conversion efficiency. Therefore, as shown in fig. 3, based on the embodiment 2, the brewster angle window 9 coated with the anti-reflection film for fundamental frequency light is removed, and the circular unstable cavity gas raman laser is inserted with the polarizer 12 coated with the anti-reflection film for fundamental frequency light, the faraday rotator 13, the analyzer 14, and the optical rotator 15 in order on any spatial coaxial axis in the non-raman optical transmission path in the cavity to ensure that the fundamental frequency laser passes through the polarizer 12, the faraday rotator 13, the analyzer 14, and the optical rotator 15, so that the fundamental frequency light traveling counterclockwise establishes oscillation, and the fundamental frequency laser traveling reversely experiences loss and no oscillation. Meanwhile, the etalon 16 plated with the antireflection film is inserted into any non-overlapping area of the fundamental frequency light and the Raman light, the output of the fundamental frequency laser with narrow line width is realized by designing the thickness of the etalon, and the conversion efficiency of the spectrum intensity of the Raman laser is improved.
Example 4
As shown in fig. 4, in the gas raman laser of the ring unstable resonator according to embodiment 3, Q crystals 17 and 18 plated with antireflection films for fundamental frequency light are sequentially inserted into any space on the same optical axis on the non-raman optical transmission path in the cavity. The Q crystals 17 and 18 are identical. When the laser works, if half-wave voltage is applied to two ends of the Q crystals 17 and 18, linearly polarized light sequentially passes through the Q crystals 17 and 18, the phase in the X direction and the Y direction can be continuously delayed by pi, and the polarization direction of the laser passing through the Q crystals 17 and 18 with the half-wave voltage applied is just vertical to the original polarization direction. When the light propagates to the polarizer 12 plated with the fundamental frequency light antireflection film, the light is lost, and the Q value in the cavity is low; if the half-wave voltage is removed at the two ends of the Q crystals 17 and 18, linearly polarized light sequentially passes through the Q crystals 17 and 18 and cannot be modulated, the polarization of the linearly polarized light is kept unchanged, the linearly polarized light cannot be lost when the linearly polarized light is continuously transmitted to the polarizer 12 plated with the anti-reflection film of the fundamental frequency light along the anticlockwise direction, the Q value in the cavity is high at the moment, a Q-switched pulse is generated, the width of the generated Q-switched pulse is different by changing the application time of the half-wave voltage, the length of the optical cavity is further optimized, and the conversion efficiency of the fundamental frequency light can be improved. Compared with the continuous or quasi-continuous laser operation mode described in the previous scheme, the pulse generated by Q-switching has higher peak power, and higher conversion efficiency of Raman laser can be obtained. The embodiment is only for the purpose of making the content of the patent more detailed and concrete for the person skilled in the art, and the scope of the claims of the patent should not be limited thereby.
Claims (10)
1. A gas Raman laser based on an annular unstable resonator is characterized by comprising a pumping source, a fundamental frequency laser plane reflector (1), a laser gain medium (2), a fundamental frequency laser plane reflector (3), a convex lens (4) coated with a fundamental frequency light antireflection film, a plane mirror (5) for increasing the reflectivity of fundamental frequency laser reflection Raman light, a Raman pool (6), a plane mirror (7) for increasing the reflectivity of fundamental frequency laser reflection Raman light and a convex lens (8) coated with a fundamental frequency light antireflection film; after the pump light of the pump source passes through the laser gain medium (2), the output fundamental frequency laser can be transmitted along two opposite directions;
when the laser light propagates along the clockwise direction, the laser light sequentially passes through a fundamental frequency laser plane mirror (3), a convex lens (4) coated with a fundamental frequency light antireflection film, a plane mirror (5) for increasing the transmission of fundamental frequency laser reflection Raman light, a Raman pool (6), a plane mirror (7) for increasing the transmission of fundamental frequency laser reflection Raman light, a convex lens (8) coated with a fundamental frequency light antireflection film, a Brewster angle window (9) coated with a fundamental frequency light antireflection film and a fundamental frequency laser plane mirror (1), and then passes through a laser gain medium (2) again to complete one-time propagation;
when the laser light propagates along the anticlockwise direction, the laser light passes through the fundamental frequency laser plane reflecting mirror (1), the convex lens (8) plated with the fundamental frequency light antireflection film, the plane mirror (7) for increasing the transmission of the fundamental frequency laser reflection Raman light, the Raman pool (7), the plane mirror (5) for increasing the transmission of the fundamental frequency laser reflection Raman light, the convex lens (4) plated with the fundamental frequency light antireflection film and the fundamental frequency laser plane reflecting mirror (3) in sequence, and then passes through the laser gain medium (2) again to finish one-time propagation;
the Raman laser generated after the fundamental frequency laser enters the Raman pool can be transmitted to two opposite directions, and the Raman laser is transmitted after passing through a plane mirror (5) for reflection and reflection of the fundamental frequency laser and Raman light or a plane mirror (7) for reflection and reflection of the fundamental frequency laser and Raman light respectively, so that the Raman laser is output from two directions.
2. The toroidal unstable cavity-based gas raman laser according to claim 1, wherein: the gas Raman laser further comprises a Brewster angle window (9) plated with a fundamental frequency light antireflection film, and the Brewster angle window (9) plated with the fundamental frequency light antireflection film is arranged between the fundamental frequency laser plane reflecting mirror (1) and the convex lens (8) plated with the fundamental frequency light antireflection film.
3. The toroidal unstable resonator-based gas raman laser according to claim 1, wherein the positions of the convex lens coated with a fundamental frequency light antireflection film (4) and the convex lens coated with a fundamental frequency light antireflection film (8) satisfy the following condition:
wherein L is1、L2、L3The optical path propagation distance from the space virtual image point to the convex lens (8) plated with the fundamental frequency light antireflection film, the optical path propagation distance between the convex lens (4) plated with the fundamental frequency light antireflection film and the convex lens (8) plated with the fundamental frequency light antireflection film, and the optical path propagation distance from the convex lens (4) plated with the fundamental frequency light antireflection film to the space virtual image point are respectively; said L2The confocal condition is satisfied:
L2＝f1+f2
wherein f is1And f2The focal lengths of the convex lens (4) plated with the fundamental frequency light antireflection film and the convex lens (8) plated with the fundamental frequency light antireflection film are respectively; m ═ f2/f1To put inHigh rate.
4. The toroidal unstable cavity-based gas raman laser according to claim 3, wherein M is 1 to 3.
5. The toroidal unstable resonator-based gas raman laser according to claim 1, wherein the raman cell is filled with a raman medium.
6. The toroidal unstable resonator-based gas raman laser according to claim 1, wherein the focal points of the fundamental frequency light antireflection film-coated convex lens (4) and the fundamental frequency light antireflection film-coated convex lens (8) coincide with a spatial virtual image point, which is the center of the raman cell.
7. The ring unstable resonator-based gas Raman laser according to claim 2, wherein a Raman light high reflection mirror (10), a Raman light output coupling mirror (11) are further disposed coaxially with the optical axis of the output Raman laser transmission path; the Raman light high-reflection mirror (10) and the Raman light output coupling mirror (11) share a curvature center, and the curvature center is superposed with a space virtual image point; the Raman light high-reflection mirror (10) and the Raman light output coupling mirror (11) form a Raman light resonant cavity, and the length of the resonant cavity is equal to the sum of the curvature radii of the Raman light high-reflection mirror (10) and the Raman light output coupling mirror (11).
8. The toroidal unstable resonator-based gas raman laser according to claim 1, further comprising a raman light high reflection mirror (10), a raman light output coupling mirror (11), a polarizer (12) coated with an antireflection film for fundamental frequency light, a faraday rotator (13), an analyzer (14), an optical rotator (15) and an etalon (16) coated with an antireflection film;
the Raman light high-reflection mirror (10) and the Raman light output coupling mirror (11) are arranged on the same axis of the optical axis of the output Raman laser transmission path; the Raman light high-reflection mirror (10) and the Raman light output coupling mirror (11) share a curvature center, and the curvature center is superposed with a space virtual image point; the Raman light high-reflection mirror (10) and the Raman light output coupling mirror (11) form a Raman light resonant cavity, and the length of the resonant cavity is the sum of the curvature radii of the Raman light high-reflection mirror (10) and the Raman light output coupling mirror (11);
the Faraday optical rotator (13), the analyzer (14), the optical rotator (15) and the etalon (16) plated with the antireflection film of the fundamental frequency light are sequentially arranged along the anticlockwise direction by taking the polarizer (12) plated with the antireflection film of the fundamental frequency light as a starting point; the polarizer (12) plated with a fundamental frequency light antireflection film, the Faraday optical rotator (13), the analyzer (14), the optical rotator (15) and the etalon (16) plated with the antireflection film are arranged in a non-overlapping area of any fundamental frequency light and Raman laser.
9. The toroidal unstable resonator-based gas raman laser according to claim 8, wherein the toroidal unstable resonator-based gas raman laser further includes two Q crystals; taking a polarizer (12) plated with a fundamental frequency light antireflection film as a starting point, and arranging the two Q crystals between the analyzer (14) and an etalon (16) plated with an antireflection film along a counterclockwise direction; the two Q crystals are arranged in a non-overlapping area of any fundamental frequency light and Raman laser; the two Q crystals are active or passive Q switches.
10. The toroidal unstable cavity-based gas raman laser according to claim 9, wherein the active or passive Q-switch is an electro-optic Q-switch element, an acousto-optic Q-switch element, a saturable absorber.
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