阅读说明：本技术 电激励非链式脉冲hf激光器被动脉宽压缩方法及激光器 (Passive pulse width compression method for electric excitation non-chained pulse HF laser and laser ) 是由 陶蒙蒙 黄超 黄珂 朱峰 马连英 李高鹏 沈炎龙 易爱平 冯国斌 于 2020-05-06 设计创作，主要内容包括：本发明涉及一种电激励非链式脉冲HF激光器被动脉宽压缩方法及激光器,针对传统压缩电激励非链式脉冲HF激光器输出脉冲宽度的方法存在的工艺繁杂、设计成本高及实施复杂的问题,通过将可饱和吸收体置于电激励非链式脉冲HF激光器谐振腔内部,实现激光器谐振腔内的激光光斑整形及激光脉宽压缩后输出。激光器包括HF激光器本体及设置在其谐振腔内设置脉宽压缩装置,脉宽压缩装置包括缩束模块和可饱和吸收体。该方法属于被动式的脉冲压缩,对不同脉宽的HF激光器均可适用,可实现自跟踪式的脉宽压缩。(The invention relates to a passive pulse width compression method of an electric excitation non-chain type pulse HF laser and the laser, aiming at the problems of complicated process, high design cost and complex implementation of the traditional method for compressing the output pulse width of the electric excitation non-chain type pulse HF laser. The laser comprises an HF laser body and a pulse width compression device arranged in a resonant cavity of the HF laser body, wherein the pulse width compression device comprises a beam shrinking module and a saturable absorber. The method belongs to passive pulse compression, is applicable to HF lasers with different pulse widths, and can realize self-tracking pulse width compression.)

1. The pulse width passive compression method of the electric excitation non-chain type pulse HF laser is characterized in that the pulse width of the pulse laser of the electric excitation non-chain type pulse HF laser is 100ns magnitude: the saturable absorber is placed in a resonant cavity of the electric excitation non-chained pulse HF laser, and laser spots in the resonant cavity of the laser are shaped and the laser pulse width is compressed and then output.

2. Realize passive form pulse width compression's electric excitation non-chain pulse HF laser, its characterized in that: comprises an electrically excited non-chained pulse HF laser and a pulse width compression device;

the electro-excitation non-chained pulse HF laser comprises a gas chamber (2), a high-reflection mirror (3), an output mirror (4) and a high-voltage discharge module (1); the gas chamber (2) is filled with working gas, the high reflecting mirror (3) is positioned at the high reflecting end of the laser pulse, the output mirror (4) is positioned at the output end of the laser pulse, and the high reflecting mirror (3) and the output mirror (4) form a resonant cavity which is coaxial with the gas chamber (2); the high-voltage discharge module (1) is a pumping source and is used for exciting working gas;

the pulse width compression device comprises a beam-shrinking module (5) and a saturable absorber (6), is positioned in a laser pulse light path in front of the output mirror (4), and is coaxial with the gas chamber (2); the beam-shrinking module (5) is used for compressing pulse laser spots in a laser resonant cavity, and the saturable absorber (6) is used for shaping the laser spots in the laser resonant cavity and compressing laser pulse width;

charging and discharging the high-voltage discharge module (1), pumping working gas to an excited state to generate a laser signal, and generating oscillation of the laser signal in a resonant cavity formed by the high reflector (3) and the output mirror (4) to output laser pulses; in the oscillation process, laser beams pass through the beam-shrinking module (5) and the saturable absorber (6) for multiple times to realize spot shaping and pulse width compression of laser pulses.

3. An electrically excited non-chained pulsed HF laser with passive pulse width compression according to claim 2, characterized in that: the pulse width compression device is positioned between the air chamber (2) and the output mirror (4), and the pulse laser realizes light spot compression through the beam shrinking module (5); and then spot shaping and pulse width compression are realized through a saturable absorber (6), and finally output is realized through an output mirror (4).

4. An electrically excited non-chained pulsed HF laser with passive pulse width compression according to claim 2, characterized in that: the pulse width compression device is positioned between the air chamber (2) and the high-reflection mirror (3), and the pulse laser realizes light spot compression through the beam shrinking module (5); and then the light spot shaping and the pulse width compression are realized through a saturable absorber (6), and then the light spot shaping and the pulse width compression are reflected to the air chamber (2) again through a high-reflection mirror (3) and then output through an output mirror (4).

5. An electrically excited non-chained pulsed HF laser with passive pulse width compression according to claim 3 or 4, characterized in that: the size of the saturable absorber (6) is larger than the spot size of the pulse laser after passing through the beam-shrinking module (5).

6. An electrically excited non-chained pulsed HF laser with passive pulse width compression as claimed in claim 5, characterized in that: the saturable absorber (6) is of a plano-concave lens structure or a biconcave lens structure with a thin middle part and a thick edge; or a plano-convex lens structure or a biconvex lens structure with thick middle and thin edge.

7. An electrically excited non-chained pulsed HF laser with passive pulse width compression as claimed in claim 5, characterized in that: the saturable absorber (6) has saturable absorption characteristics in a wave band of 2.6-3.1 mu m.

8. An electrically excited non-chained pulsed HF laser with passive pulse width compression according to claim 7, characterized in that: the beam shrinkage range of the beam shrinkage module (5) is 1.5: 1-5: 1; the working gas is SF of 10kPa₆And C₂H₆Gas, SF₆And C₂H₆Has a gas-component ratio of 92: 8.

9. An electrically excited non-chained pulsed HF laser implementing passive pulse width compression according to claim 8, characterized in that: the high reflection mirror (3) is a gold-plated reflection mirror, and the reflectivity of the high reflection mirror at a wave band of 2.6-3.1 mu m is higher than 95%; the output mirror (4) is CaF₂A flat mirror having a reflectance of 7%; the saturable absorber (6) is Fe: ZnSe crystal with thickness of 1.5mm, cross-sectional dimension of 7mm, initial transmittance of 60%, or the saturable absorber (6) is ZnS, ZnSe or CaF coated with graphene or graphene oxide film layer₂And (4) crystals.

Technical Field

The present invention relates to a method and an apparatus for passive pulse width compression based on a saturable absorber, and more particularly, to a method for passive pulse width compression of an electrically-excited non-chained pulse HF laser and the electrically-excited non-chained pulse HF laser.

Background

The discharge-excited non-chain type pulse HF laser has output spectrum covering 2.6-3.1 microns, large output energy, high peak power and good beam quality, has wide application prospect in the fields of laser spectroscopy, laser biomedicine, laser radar, photoelectric countermeasure and the like, and is a medium-infrared large-energy pulse laser light source which is concerned by much.

Under normal operation, the output pulse width of discharge-excited non-chained pulsed HF laser is generally over 100ns (Huang-super, Huang-Ke, Yiei-Ping, etc.. 100Hz repetition frequency pulse mid-infrared HF chemical laser, Chinese laser, 2019, 46(2): 0201002. Pan-Checkland, Xie-Jiang, Chen-Fei, etc.. mid-infrared room temperature high energy Fe²⁺: ZnSe laser, Chinese laser, 2018, 45(11):1101001, Koehex, Kuaihai, Sunji, et al, pulsed HF (DF) laser induced by repetitive frequency discharge, Infrared and laser engineering, 2007, 36: 36-38. S D Velikanov, V P Danilov, N G Zakharov, et al^{2 +}ZnSe laser pumped by a non-resonant electric-discharge HF laser at random temperature Electronics 2014,44(2): 141-144). However, in some effect studies, a narrower laser pulse width is required, which requires pulse width compression of the output pulses of the HF laser.

Pulse width compression methods can be divided into active and passive solutions. Active switching devices such as acousto-optic switching-on and electro-optic switches (sclarem, extra waves, willow strength, Yan level, yellow epitaxy, billows, Liuhuan, a laser pulse width and waveform control method based on Q-switched switch step opening, Chinese patent application No. 201210159255.3, Chenpekuang, Lanxinwu, a Q-switched laser pulse waveform adjustment method, Chinese patent application No. 87103899.4) can control the output pulse width of a laser, but in a non-chain type pulse HF laser excited by discharge, instantaneous high-voltage discharge can generate serious interference on acousto-optic and electro-optic switching-on crystals, so passive switching devices are used as much as possible in the non-chain type pulse HF laser excited by electric discharge to prevent electromagnetic interference generated by the high-voltage discharge. According to the research of the inventor, the existing passive pulse width compression technology is mostly based on the dispersion compensation principle, and the adopted specific methods comprise dispersive optical fibers (Ping Tong Chong, tail hydroscopic, Guze Jian Tailang, optical pulse compressor; Chinese patent, application number: 200910009704.4) and gratings (Zhou Chang He, Jiawei, femtosecond pulse compression device; Chinese patent, application number: 200710048185.3), and the like, but the method is only suitable for the pulse width compression of ultra-short pulses such as ps and fs, and cannot realize effective compression on pulses of 100ns magnitude. In a conventional electrically-excited non-chained pulse HF laser, the discharge pulse time is shortened by changing the design of the discharge circuit of the laser to achieve a compression of the output pulse width of the laser. However, this method requires redesign and processing of the entire discharge circuit, electrodes and resonator parameters of the laser, involving a number of links that are particularly complex to implement.

Saturable absorbers are an effective way to achieve laser pulse width compression. However, the reports of saturable absorbers for laser pulse width compression are mostly focused on their mode-locking applications and pulse width compression of ultrashort pulses of the ps and fs order (T.K. Lim and B.K. Garside.Saturable absorber mode-locking and laser pulse compression, optics Communications,1974,12(1): 8-13; RonaldMuller pulse compression in coherent pulse lasers with a slotted pulsed laser, optics Communications,1979,28(2): 259), while there are few reports in discharge-excited long pulse width (above 100ns order) pulsed gas lasers. In 1982, Thomas Varghese reported research work using dye saturable absorbers to achieve pulse width modulation of a 5ns pulse width XeCl laser. It uses an external cavity structure, i.e. the light beam output from the laser directly passes through the dye saturable absorber to realize pulse width compression (Thomas Varghese. "Temporal tuning" of XeCl laser pulse width from 5ns to less than500ps using structured absorbent articles. In 1984, A.Takahashi et al pulse width compressed and amplified a 1ns pulse width XeCl laser using the same external cavity pulse compression structure (A.Takahashi, M.Maeda, and Y.noda.short pulse generation and compression in XeCl lasers. IEEE Journal of Quantum Electronic,1984,20(10): 1196-) 1201). Also using this external cavity type pulse compression configuration, researchers have also achieved high energy narrow pulse width ultraviolet laser outputs in KrF amplifiers (J.Badziak and S.Jablonski. Generation of ultra short lasers in outside laser systems with a tunable absorber. Proc. SPIE,1995,2202: 42-50.). It can be seen that the reports of pulse width compression using saturable absorbers in gas lasers have all been applied in ns-order short pulse width gas lasers, while no report has been found in 100 ns-order long pulse width compression. In addition, the external cavity structure is reported and adopted, but the pulse width compression structure of the external cavity structure generates large loss to the pulse peak power of the laser.

Disclosure of Invention

Aiming at the problems of complex process, high design cost and complex implementation of the traditional method for compressing the pulse width output by the electric excitation non-chained pulse HF laser, the invention provides an inner cavity type passive pulse width compression method and device for the electric excitation non-chained pulse HF laser, and the pulse width of the HF laser can be compressed without changing the circuit design and the resonant cavity parameters of a laser system. The method belongs to passive pulse compression, is applicable to HF lasers with different pulse widths, and can realize self-tracking pulse width compression; in addition, as the saturable absorber is arranged in the laser resonant cavity, not only can the pulse peak power of the laser not be remarkably lost, but also the pulse peak power of the laser can be greatly improved by selecting proper saturable absorber parameters.

The basic idea of the invention is to utilize the saturable absorption characteristic of a saturable absorber in the time domain, and realize the compression of the pulse width of the HF laser by placing the saturable absorber in a resonant cavity of the non-chained pulse HF laser. In addition, by adjusting the parameters of the saturable absorber, the compressed HF laser output pulse width can also be varied.

The technical scheme of the invention is to provide a method for compressing the passive pulse width of an electric excitation non-chain type pulse HF laser, the pulse width of the pulse laser of the electric excitation non-chain type pulse HF laser is 100ns magnitude, and the method is characterized in that: the saturable absorber is placed in a resonant cavity of the electric excitation non-chained pulse HF laser, and pulse laser spots in the resonant cavity of the laser are shaped and the laser pulse width is compressed and then output.

The invention also provides an electric excitation non-chained pulse HF laser capable of realizing passive pulse width compression, which is characterized in that: comprises an electrically excited non-chained pulse HF laser and a pulse width compression device;

the electro-excitation non-chained pulse HF laser comprises a gas chamber, a high-reflection mirror, an output mirror and a high-voltage discharge module; the gas chamber is filled with working gas, the high reflection mirror is positioned at the high reflection end of the laser pulse, the output mirror is positioned at the output end of the laser pulse, and the high reflection mirror and the output mirror form a resonant cavity of the laser and are coaxial with the gas chamber; the high-voltage discharge module is a pumping source and is used for exciting working gas;

the pulse width compression device comprises a beam-shrinking module and a saturable absorber, is positioned in a laser pulse light path in front of the output mirror, and is coaxial with the gas chamber; the beam-shrinking module is used for compressing pulse laser spots in the laser resonant cavity, and the saturable absorber is used for shaping the laser spots in the laser resonant cavity and compressing the laser pulse width;

and charging and discharging the high-voltage discharge module, pumping the working gas to an excited state, generating oscillation by a laser signal in a resonant cavity formed by the high reflector and the output mirror, and outputting laser pulse. In the oscillation process, laser beams pass through the beam-shrinking module and the saturable absorber for multiple times, so that spot shaping and pulse width compression of laser pulses are realized.

Furthermore, the pulse width compression device is positioned between the air chamber and the output mirror, the pulse laser realizes light spot compression through the beam shrinking module, realizes light spot shaping and pulse width compression through the saturable absorber, and finally outputs through the output mirror.

Furthermore, the pulse width compression device can be positioned between the air chamber and the high-reflection mirror, and pulse laser realizes light spot compression through the beam shrinking module so as to improve power density; and then the light spot shaping and the pulse width compression are realized through a saturable absorber, and then the light spot shaping and the pulse width compression are reflected to the air chamber again through a high-reflection mirror and then output through an output mirror.

Further, in order to achieve accurate pulse width compression, the size of the saturable absorber should be larger than the spot size of the pulsed laser after passing through the beam-shrinking module.

Further, the structure of the saturable absorber can be designed according to the spot shaping requirement. If the quality of output light spot beams needs to be improved, the saturable absorber is in a plano-concave lens structure or a biconcave lens structure with a thin middle part and a thick edge; if a hollow annular light spot needs to be output, the saturable absorber can be in a plano-convex lens structure or a biconvex lens structure with thick middle and thin edge.

Furthermore, the saturable absorber has obvious saturable absorption characteristics in a wave band of 2.6-3.1 mu m.

Furthermore, in order to improve the power density of the surface of the saturable absorber and enhance the saturable absorption effect, the beam shrinkage range of the beam shrinkage module is 1.5: 1-5: 1. The working gas is SF of 10kPa₆And C₂H₆Gas, SF₆And C₂H₆Has a gas-component ratio of 92: 8.

Furthermore, the high-reflection mirror is a gold-plated mirror, and the reflectivity of the high-reflection mirror in a 2.6-3.1 mu m wave band is higher than 95%; the output mirror is CaF₂A flat mirror having a reflectance of 7%; the saturable absorber is Fe: ZnSe crystal with thickness of 1.5mm, cross-sectional dimension of 7mm, initial transmittance of 60%, or the saturable absorber (6) is ZnS, ZnSe or CaF plated with graphene or graphene oxide film layer₂And (4) crystals.

The invention has the following beneficial effects:

1. the invention can realize pulse width compression of the output pulse of the laser by only inserting a beam shrinking module and a saturable absorber in the resonant cavity of the laser without changing the circuit structure of the electric excitation non-chained pulse HF laser, and has convenient operation and quick implementation.

2. The invention adopts passive pulse width compression and is not interfered by high-voltage discharge of an electrically-excited non-chained pulse HF laser.

3. By changing the parameter of the saturable absorber, the invention can realize the compression of the laser pulse width in different degrees within a certain range, and by selecting the proper parameter of the saturable absorber, the invention can obviously improve the peak power of the output pulse.

4. By changing the structure of the saturable absorber, the invention can improve the output spot beam quality of the non-chained pulse HF laser.

Drawings

Fig. 1 is a schematic diagram of a structure of a center device according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a second centering device according to an embodiment of the present invention.

Fig. 3 shows the pulse width compression results of the HF laser obtained by theoretical simulation.

In the figure: 1-a high voltage discharge module; 2-air chamber; 3-high reflection mirror; 4-an output mirror; 5-a beam shrinking module; 6-saturable absorber.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.