CN103928837B - Multi-pass amplifying system for high-power laser separation chirp pulses - Google Patents

Abstract

A multi-pass amplifying system for high-power laser separation chirp pulses is composed of a laser seed pulse source, a pulse stretcher, a DPA regeneration cavity, bi-pass DPA modules and a pulse compressor. Seed pulses are output by the laser seed pulse source and first stretched into the chirp pulses through the pulse stretcher, then the power of the chirp pulses is amplified through the DPA regeneration cavity and the bi-pass DPA modules, and finally the amplified chirp pulses are compressed through the pulse compressor. The multiple levels of DPA modules are connected in series in a CPA module, and the DPA modules have the function of multi-pass pulse amplifying, so that the pulse power amplifying capacity of the multi-pass amplifying system is improved, and the influence of the nonlinear effect is effectively restrained.

Description

High Power Laser Separation Chirped Pulse Multipass Amplification System

technical field

The invention relates to a high-power laser pulse amplification technology, in particular to a high-power laser separation chirped pulse multi-pass amplification system.

Background technique

In 1960, Maiman of Hughes Laboratory in the United States invented the ruby pulse laser. Under the pumping of millisecond-level light pulses, the ruby laser outputs a spike sequence of microsecond level, and its peak power is on the order of kW. Subsequently, Q-switching technology and mode-locking technology developed rapidly, and the peak power of laser pulses can reach the order of GW (10 ⁹ W). When the laser power continues to increase, nonlinear effects such as beam self-focusing will intensify, which will eventually lead to damage to the optical medium. In 1985, D. Strickland and G. Mourou of the University of Rochester in the United States solved the above problems well by using chirped pulse amplification (CPA) technology. The seed pulse is first stretched into a chirped pulse, and then compressed into an ultrashort pulse after power amplification. Using CPA technology can make the laser pulse peak power reach TW (10 ¹² W) or even PW (10 ¹⁵ W) level. The application of CPA technology breaks the limitation of the dielectric tolerance threshold and greatly promotes the development of ultra-intense and ultra-short laser technology. However, for narrow-band laser pulses, the traditional CPA technology is not suitable because it is difficult to widen the pulse width to a sufficient width. In recent years, the development of discrete pulse amplification (DPA) technology has provided a better solution to the problem of narrowband laser pulse amplification.

In 2007, Shian Zhou, Frank W.Wise and Dimitre G.Ouzounov proposed separation pulse amplification (hereinafter referred to as DPA) technology, using yttrium vanadate (YVO4) crystal array to realize pulse separation and recombination (Opticsletters, 2007, 32 (7):871-873). The basic principle of DPA is to first separate the seed pulse into two or more pulses, and then integrate the pulse sequence into one pulse after being amplified. Compared with the CPA technology, it can be seen that the use of the DPA technology can break through the limitation of the spectral bandwidth on the pulse broadening, thus well making up for the shortcomings of the traditional CPA technology. In 2012, S.Roither and A.J.Verhoef et al. used the Sagnac ring optical path to realize the separation and recombination of pulses. Using this method, the pulse separation distance can be expanded and controlled more conveniently and effectively (Optics express, 2012, 20(22) :25121-25129). In the same year, L.J.Kong and F.W.Wise et al. used the method of nonlinear crystal array DPA to obtain picosecond pulses with a peak power of megawatts (Optics letters, 2012, 37(2): 253-255), L. Daniault et al. used a birefringent crystal array and a Sagnac ring optical path structure to separate, amplify and recombine femtosecond pulses (Opticsexpress, 2012, 20(19): 21627-21634). In 2013, Yoann Zaouter, Florent Guichard and others combined CPA technology and DPA technology into CPA-DPA technology (Optics letters, 2013,38(2):106-108), and deeply discussed the compounding and compression of amplified pulses, etc. (Optics letters, 2013, 38(21): 4437-4440). In the same year, Marco Kienel and Arno Klenke et al. also reported researches on improving pulse compounding and compression efficiency (Optics Express, 2013, 21(23): 29031-29042; Optics letters, 2013, 38(22): 4593- 4596). However, most of the above-mentioned systems only include single-stage DPA, and still focus on realizing single-pass or double-pass pulse amplification. Compared with the existing CPA system, the power amplification capability of the existing DPA related system is still insufficient. In order to speed up the practical process of DPA technology, it is urgent to improve the pulse amplification efficiency of DPA and CPA-DPA system.

Contents of the invention

The invention provides a high-power laser separation chirped pulse amplification system, which greatly improves the pulse power amplification capability of the CPA-DPA system, which will promote the popularization and application of the CPA-DPA and DPA technology in the high-power laser technology field.

Technical solution of the present invention is as follows:

A high-power laser separation chirped pulse multi-pass amplification system is characterized in that its composition includes a laser seed pulse source, a pulse stretcher, a DPA regeneration cavity, a dual-pass DPA module and a pulse compressor. The laser seed pulse source outputs a seed pulse, which is first stretched into a chirped pulse by a pulse stretcher, then its power is amplified by a DPA regeneration cavity and a dual-pass DPA module, and finally the amplified chirped pulse is compressed by a pulse compressor.

The pulse stretcher and pulse compressor can refer to the technical solution in the traditional CPA system (Optik & Photonik, 2010, 5(4):30-33).

The composition of the DPA regeneration cavity: the first thin-film polarizer, the first Pockels cell, the first λ/4 wave plate, the first 0° reflector, the first The included angle between the fast (slow) axis direction of the λ/4 wave plate and the polarization direction of the p-polarized light is 45°, and the returning s-polarized light is reflected at the first film polarizer, and the first Pulse splitter/recombiner, first laser gain medium, second λ/4 wave plate, second 0° mirror, the difference between the fast (slow) axis direction of the second λ/4 wave plate and the polarization direction of p-polarized light The angle between them is 45°. Its working process can be described as, the p-polarized light pulse enters the cavity through the first thin-film polarizer, then passes through the first Pockels cell without voltage applied, the first λ/4 wave plate, and the first λ/4 The included angle between the fast (slow) axis direction of the wave plate and the polarization direction of the p-polarized light is 45°, so the p-polarized light pulse becomes a circularly polarized light pulse, and the circularly polarized light pulse is reflected by the first 0° mirror and passes through the first λ/4 wave plate, the first Pockel cell with no voltage applied, the circularly polarized pulse becomes the s-polarized pulse, the polarization direction of the s-polarized pulse is perpendicular to the polarization direction of the p-polarized light, and the s-polarized pulse is at the first film polarizer reflection, and then the first pulse splitter/recombiner generates a linearly polarized pulse sequence composed of s-polarized pulses and p-polarized pulses, the pulse sequence is amplified at the first laser gain medium and passes through the second λ/4 wave plate, the The angle between the fast (slow) axis direction of the second λ/4 wave plate and the polarization direction of p-polarized light is 45°, so the linearly polarized light pulse sequence becomes a circularly polarized light pulse sequence, and the circularly polarized light pulse sequence passes through the second 0° After being reflected by the mirror, it passes through the second λ/4 wave plate again, and the circularly polarized pulse sequence becomes a linearly polarized pulse sequence composed of s-polarized pulse and p-polarized pulse. The pulse sequence is amplified again at the first laser gain medium and The s-polarized pulse is synthesized by the pulse splitter/recombiner, and the s-polarized pulse is reflected by the first thin-film polarizer, and then passes through the first Pockels cell and the first λ/4 wave plate with a λ/4 voltage applied sequentially, s The polarized pulse becomes a p-polarized pulse, and the p-polarized pulse is reflected by the first 0° mirror and then passes through the first λ/4 wave plate and the first Pockels cell with a λ/4 voltage, and the p-polarized pulse becomes Then the s-polarized pulse is locked in the cavity and continues to amplify. When the λ/4 voltage applied to the first Pockels cell is removed, the regenerated amplified pulse can be output at the first film polarizer.

The composition of the dual-pass DPA module includes: sequentially placing the second thin-film polarizer, the first 45° Faraday rotator, the first λ/2 wave plate, the third thin-film polarizer, and the second pulse polarizer in the direction of the incident p-polarized light Separator/recombiner, second laser gain medium, second 45° Faraday rotator, third 0° mirror, adjust the direction of the fast (slow) axis of the first λ/2 wave plate so that the outgoing light is still p-polarized , the returning s-polarized light is reflected at the third film polarizer, and a fourth 0° reflector is placed in the s-polarized light reflection direction. Its working process can be described as, after the p-polarized light pulse passes through the second film polarizer, then passes through the first 45° Faraday rotator and the first λ/2 wave plate to adjust the fast ( The direction of the slow) axis makes the pulse still p-polarized, and the p-polarized pulse continues to pass through the third film polarizer, and then passes through the second pulse splitter/recombiner to generate a linearly polarized pulse sequence composed of s-polarized pulses and p-polarized pulses. After the sequence is amplified at the second laser gain medium, it passes through the second 45° Faraday rotator and reflects at the third 0° mirror, and the polarization directions of the s-polarized pulse and p-polarized pulse are rotated after passing through the second 45° Faraday rotator twice. After 90°, the pulse sequence is amplified again and synthesized into an s-polarized pulse by the second pulse splitter/recombiner. The s-polarized pulse is reflected by the third thin-film polarizer, the fourth 0° mirror, and the third thin-film polarizer in turn. , and generate a linearly polarized pulse sequence composed of s-polarized pulse and p-polarized pulse through the second pulse splitter/recombiner again. The pulse sequence is amplified at the second laser gain medium and passed through the second 45° Faraday rotator, and then passed through the third After being reflected at the 0° mirror, it passes through the second 45° Faraday rotator again. After the pulse sequence is amplified at the second laser gain medium, it is synthesized into a p-polarized pulse through the second pulse splitter/recombiner, and the p-polarized pulse passes through the second laser gain medium. After the three thin-film polarizers, it continues to pass through the first λ/2 wave plate and the first 45° Faraday rotator to become an s-polarized pulse, and the s-polarized pulse is reflected at the second thin-film polarizer, so that a dual-pass DPA can be realized .

The pulse splitter and the pulse recombiner have the opposite function but the same structure. The pulse splitter/recombiner can be roughly divided into two types: birefringent type and transmission-reflection type. Usually, the birefringent pulse splitter/combiner is mainly composed of a birefringent crystal array (see Optics letters, 2007, 32(7):871-873), and the transmission-reflection pulse splitter/combiner is mainly composed of thin film A polarizer and a λ/2 wave plate or a 45° Faraday rotator (see Opticsexpress, 2012, 20(22): 25121-25129). Assuming that the pulse separator is composed of N pulse separation units, the incident pulse will generate 2 ^N sub-pulses after being acted on by the pulse separator.

Compared with the prior art, the present invention has the following salient features:

1. In the CPA-DPA system, the pulse power amplification capability is improved by connecting multiple DPAs in series.

2. By constructing a DPA regeneration cavity and a dual-pass DPA module, multi-pass DPA is realized, and the pulse amplification efficiency of the CPA-DPA system is further improved.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the high-power laser separation chirped pulse multi-pass amplification system of the present invention.

Fig. 2 is a schematic diagram of the light path structure of the DPA regeneration cavity of the present invention.

Fig. 3 is a schematic diagram of the optical path structure of the dual-pass DPA module of the present invention.

Fig. 4 is a schematic diagram of the optical path of the transmission-reflection pulse separation unit in the embodiment.

detailed description

The present invention will be further described below through the examples and accompanying drawings, but the protection scope of the present invention should not be limited by this.

Please refer to FIG. 1 first. FIG. 1 is a schematic structural diagram of the high-power laser separation chirped pulse multi-pass amplification system of the present invention. It can be seen from the figure that the high-power laser separation chirped pulse multi-pass amplification system of the present invention comprises a laser seed pulse source 1, a pulse stretcher 2, a DPA regeneration cavity 3, a dual-pass DPA module 4 and a pulse compressor 5, and the laser seed The pulse source 1 outputs the seed pulse, which is stretched into a chirped pulse by the pulse stretcher 2, and then the power is amplified by the DPA regeneration cavity 3 and the dual-pass DPA module 4, and finally the amplified chirped pulse is amplified by the pulse compressor 5 compression. Described pulse stretcher 2 and pulse compressor 3 can adopt respectively Type expander and Treacy type compressor.

Please refer to FIG. 2 . FIG. 2 is a schematic diagram of the optical path structure of the DPA regeneration chamber of the present invention. It can be seen from the figure that the p-polarized light pulse enters the cavity through the first film polarizer 301, passes through the first Pockels cell 302 and the first λ/4 wave plate 303 with no voltage applied in sequence, and the first λ/4 The included angle between the fast (slow) axis direction of the wave plate 303 and the polarization direction of the p-polarized light is 45°, so the p-polarized light pulse becomes a circularly polarized light pulse, and the circularly polarized light pulse is reflected by the first 0° mirror 304 and passes through again With the first λ/4 wave plate 303 and the first Pockels cell 302 without voltage applied, the circularly polarized light pulse becomes an s-polarized light pulse, the polarization direction of the s-polarized light pulse is perpendicular to the polarization direction of the p-polarized light, and the s-polarized light pulse is at the A thin-film polarizer is reflected at 301, and then a linearly polarized pulse sequence composed of s-polarized pulses and p-polarized pulses is generated through the first pulse splitter/recombiner 305. The pulse sequence is amplified at the first laser gain medium 306 and passed through the second λ/4 wave plate 307, the angle between the fast (slow) axis direction of the second λ/4 wave plate 307 and the polarization direction of p-polarized light is 45°, so the linearly polarized light pulse sequence becomes a circularly polarized light pulse sequence , the circularly polarized pulse sequence is reflected by the second 0° mirror 308 and passes through the second λ/4 wave plate 307 again, and the circularly polarized pulse sequence becomes a linearly polarized pulse sequence composed of s-polarized pulses and p-polarized pulses. The sequence is amplified at the first laser gain medium 306 and synthesized into an s-polarized pulse by the first pulse splitter/recombiner 305. The s-polarized pulse is reflected by the first thin-film polarizer 301, and then sequentially passes through the first Pockels cell 302, the first λ/4 wave plate 303, the s-polarized pulse becomes a p-polarized pulse, and the p-polarized pulse passes through the first λ/4 wave plate 303 again after being reflected by the first 0° reflector 304, adding In the first Pockels cell 302 of λ/4 voltage, the p-polarized pulse becomes s-polarized pulse again, so the s-polarized pulse is locked in the cavity and continues to amplify. When the first Pockels cell 302 is removed After the λ/4 voltage, the amplified pulse is transmitted and output at the first film polarizer 301 .

Please refer to FIG. 3 . FIG. 3 is a schematic diagram of the optical path structure of the dual-pass DPA module of the present invention. It can be seen from the figure that after the p-polarized light pulse passes through the second film polarizer 401, it passes through the first 45° Faraday rotator 402 and the first λ/2 wave plate 403 to adjust the fast speed of the first λ/2 wave plate 403. The (slow) axis direction makes the pulse still p-polarized, and the p-polarized pulse continues to pass through the third film polarizer 404, and then passes through the second pulse splitter/complexer 405 to generate a linearly polarized pulse composed of s-polarized pulse and p-polarized pulse Sequence, the pulse sequence is amplified at the second laser gain medium 406 and reflected at the third 0° mirror 408 by the second 45° Faraday rotator 407, and the s-polarized pulse and the p-polarized pulse pass through the second 45° Faraday rotator twice The polarization directions are all turned by 90° after the filter 407, and the pulse sequence is amplified at the second laser gain medium 406 and synthesized into s-polarized pulses through the second pulse splitter/recombiner 405, and the s-polarized pulses pass through the third thin-film polarizer 404 in turn , the fourth 0° reflector 409, and the third film polarizer 404 are reflected, and then the second pulse splitter/recombiner 405 generates a linearly polarized pulse sequence composed of s-polarized pulses and p-polarized pulses. The pulse sequence is in the second After being amplified at the laser gain medium 406, it passes through the second 45° Faraday rotator 407, and after being reflected by the third 0° mirror 408, it passes through the second 45° Faraday rotator 407 again, and the pulse sequence is amplified at the second laser gain medium 406 And through the second pulse splitter/recombiner 405, it is synthesized into a p-polarized pulse. After the p-polarized pulse passes through the third film polarizer 404, it continues to pass through the first λ/2 wave plate 403 and the first 45° Faraday rotator 402. It becomes an s-polarized pulse, and the s-polarized pulse is reflected at the second film polarizer 401 and output.

The pulse splitter/recombiner is composed of several transmission-reflection pulse splitters connected in series. Please refer to FIG. 4 , which is a schematic diagram of an optical path of a transmission-reflection pulse separation unit. It can be seen from the figure that the polarization direction of the incident p-polarized light or s-polarized light pulse is rotated by 45° after passing through the second λ/2 wave plate 0501, and the direction of the fast (slow) axis of the second λ/2 wave plate 0501 is the same as The included angle between the original polarization directions is 22.5°, and the light pulse is separated into a p-polarized sub-pulse and an s-polarized sub-pulse through the fourth film polarizer 0502, and the p-polarized sub-pulse passes through the fourth film polarizer 0502, the first Five thin-film polarizers 0506, the s-polarized sub-pulse is sequentially reflected by the fourth thin-film polarizer 0502, the first 45° reflector 0503, the second 45° reflector 0504, and the fifth thin-film polarizer 0506, and the first 45° reflector 0503 And the second 45° mirror 0504 is installed on the first translation stage 0505, by moving the first translation stage 0505, the optical path of the s-polarized photon pulse can be changed, and the p-polarized photon sub-pulse and the s-polarized photon sub-pulse pass through the fifth film polarizer 0506 And achieve collinear transmission. The polarization directions of the sub-pulses after amplification and return are all rotated by 45°, that is, the original p-polarized photon pulses become s-polarized photon pulses and the s-polarized photon pulses become p-polarized photon pulses. The p-polarized sub-pulse passes through the fifth thin-film polarizer 0506 and the fourth thin-film polarizer 0502, and the s-polarized sub-pulse sequentially passes through the fifth thin-film polarizer 0506, the second 45° reflector 4, the first 45° reflector 0503, and the second 45° reflector 0503. Reflected by four thin-film polarizers 0502, the p-polarized sub-pulse and s-polarized sub-pulse are recombined at the fourth thin-film polarizer 0502 to form a light pulse, and the polarization direction of the light pulse after passing through the second λ/2 wave plate 0501 is the same as the original incident The polarizations of the pulses are either the same or perpendicular.

Claims (1)

1. a kind of high power laser light separation chirped pulse multi-pass amplifier, is characterised by that its composition includes laser seed pulse source (1), pulse stretcher (2), dpa regeneration chamber (3), bilateral dpa module (4) and pulse shortener (5), laser seed pulse source (1) export seed pulse, be chirped pulse through pulse stretcher (2) broadening, then chamber (3) and bilateral dpa mould regenerated by dpa Block (4) carries out power amplification to it, finally utilizes pulse shortener (5) that the chirped pulse after amplifying is compressed；

The composition that described dpa regenerates chamber (3) includes: is sequentially placed the first film polarizer on incident p polarization direction (301), the first Pockels' cell (302), λ/4 wave plate (303), the one 0 ° of reflecting mirror (304), described λ/4 wave plate (303) angle between fast axle or the polarization direction of slow-axis direction and p polarisation is 45 °, returns s polarisation and polarizes in the first film Mirror (301) place is reflected, and is sequentially placed the first pulse separation/recombiner (305), first laser on s polarisation reflection direction Gain media (306), the 2nd λ/4 wave plate (307), the 2nd 0 ° of reflecting mirror (308), the fast axle of described 2nd λ/4 wave plate (307) or Angle between the polarization direction of slow-axis direction and p polarisation is 45 °；

The composition of described bilateral dpa module (4) includes: is sequentially placed the second film polarizer on incident p polarization direction (401), the one 45 ° of Faraday polarization apparatus (402), λ/2 wave plate, the 3rd film polarizer (404), the second pulse separation/ Recombiner (405), second laser gain media (406), the 2nd 45 ° of Faraday polarization apparatus (407), the 3rd 0 ° of reflecting mirror (408), Adjust the fast axle of described λ/2 wave plate (403) or slow-axis direction makes emergent light still for p partially, return s polarisation in the 3rd thin film Polarizer (404) place is reflected, and places the 4th 0 ° of reflecting mirror (409) on s polarisation reflection direction.