CN-111665623-B - Stray light control system and control method for high-power compact terminal optical system

CN111665623BCN 111665623 BCN111665623 BCN 111665623BCN-111665623-B

Abstract

The invention belongs to the field of high-power laser device optical systems, and discloses a stray light control system and a stray light control method for a high-power compact terminal optical system, which are used for realizing the stray light control system and the stray light control method for the high-power compact terminal optical system. The system comprises a crystal, a focusing lens, an optical flat element and an absorber box, wherein a light source sequentially passes through the crystal and the focusing lens, reaches the optical flat element and is reflected by the optical flat element. The invention provides an optimal design method for high-order stray light and first-order stray light, and provides an optimal design for a beam trap for high-flux first-order stray light, wherein the high-flux first-order stray light is bound in the beam trap, so that the system cleanliness is greatly improved from ISO5 level to ISO3 level, and the method is particularly suitable for stray light control of a high-power compact terminal optical system.

Inventors

ZHU DEYAN
LI PING
WANG FANG
PENG ZHITAO
FENG BIN

Assignees

南京航空航天大学

Dates

Publication Date: 20260505
Application Date: 20200630

Claims (8)

1. A control method for a stray light control system of a high-power compact terminal optical system is characterized in that the system comprises eight optical elements which are longitudinally arranged in a pulling way within a compact distance range, wherein the optical elements are concentrated in two modules, namely a frequency conversion module and a focusing sampling module; the frequency conversion module is formed by installing a plurality of different crystals side by side, is arranged at the front end of the focusing sampling module and is closer to the transmission reflector, and light passes through the frequency conversion module to realize the functions of atmosphere isolation, harmonic conversion and polarization smoothing; the focusing sampling module is close to the vacuum target chamber, and light rays reach the focusing sampling module through the frequency conversion module, so that the functions of light beam focusing, harmonic wave separation, measurement sampling, vacuum sealing and fragment shielding are realized; The control method is used for binding stray light in the light beam trap, and when the control method is used for controlling high-order stray light, in order to ensure that the high-order stray light is far away from elements and structural members, setting parameters among all components need to satisfy the conditions: (1) Wherein f is focal length of the focusing lens, and d 1 、d 2 and d 3 are distances between the focusing lens and the vacuum window, between the vacuum window and the main shielding sheet, and between the main shielding sheet and the secondary shielding sheet respectively; The optimized value of the optical element pitch after focusing the lens is solved as: (2)。
2. A control method for a stray light control system of a high-power compact terminal optical system is characterized in that the system comprises eight optical elements which are longitudinally arranged in a pulling way within a compact distance range, wherein the optical elements are concentrated in two modules, namely a frequency conversion module and a focusing sampling module; the frequency conversion module is formed by installing a plurality of different crystals side by side, is arranged at the front end of the focusing sampling module and is closer to the transmission reflector, and light passes through the frequency conversion module to realize the functions of atmosphere isolation, harmonic conversion and polarization smoothing; the focusing sampling module is close to the vacuum target chamber, and light rays reach the focusing sampling module through the frequency conversion module, so that the functions of light beam focusing, harmonic wave separation, measurement sampling, vacuum sealing and fragment shielding are realized; The control method is used for binding the stray light in the light beam trap, and when the control method is used for controlling the first-order stray light, in order to ensure that the first-order stray light focus of the focusing lens is positioned between the polarized smooth crystal and the focusing lens, the setting parameters among all the components need to satisfy the conditions: (3) Wherein d 4 and d 5 are the distances between the focusing lens and the polarization smoothing crystal, and the distances between the fundamental frequency window and the polarization smoothing crystal, respectively.
3. A method for controlling a stray light control system for a high power compact terminal optical system according to claim 1 or 2, characterized in that the frequency conversion module comprises an isolation window (1), a frequency doubling crystal (2), a frequency tripling crystal (3) and a polarization smoothing crystal (4) arranged side by side.
4. A method for controlling a stray light control system for a high power compact terminal optical system according to claim 3, wherein the focus sampling module comprises a focusing lens (5), a vacuum window (6), a primary shielding plate (7) and a secondary shielding plate (8), and the light rays are refracted by the focusing lens (5) and then pass through the vacuum window (6), the primary shielding plate (7) and the secondary shielding plate (8) which are arranged side by side.
5. The stray light control system for a high power compact terminal optical system of claim 4, wherein the focusing lens (5) is designed in a hollow manner with a thin edge structure, so that the stray light is controllable at the focusing lens.
6. The method for controlling a stray light control system for a high power compact terminal optical system of claim 4 wherein said optical element is AB5 stray light absorbing glass and a fused silica element is added in front of said stray light absorbing glass, and AB5 glass is provided at a position of maximum aperture of stray light beam deviated from a main optical path.
7. A method of controlling a stray light control system for a high power compact terminal optical system as defined in claim 2, wherein the control design process of the method comprises the steps of: s1, optimizing angles of a vacuum window, a main shielding sheet and a secondary shielding sheet, ensuring that first-order stray light is not applied to optical elements and frames in a focusing sampling module, and simultaneously, the stray light is in the same position, so that management is facilitated; S2, adding a fused quartz element in front of each stray light absorbing glass to ensure that damage of AB5 glass does not pollute a terminal system; S3, utilizing the combination design of the paired AB5 glass fused quartz elements as a light beam trap, and absorbing stray light back and forth to ensure that the stray light does not escape out of the light beam trap.
8. The first-order stray light control method of claim 7, wherein an AB5 glass is provided at a position of maximum aperture of the stray light beam deviated from the main optical path.

Description

Stray light control system and control method for high-power compact terminal optical system Technical Field The invention belongs to the field of high-power laser device optical systems, and particularly relates to a stray light management and control method for realizing a high-power compact terminal optical system based on optimized terminal optical system and stray light management device parameters. Background The terminal optical system (Final Optics Assembly, FOA) is the last stage of the high-power laser device, bears the highest laser energy of the device, consists of expensive transmission optical elements such as a frequency doubling crystal, a focusing lens, a vacuum window and the like, and plays important roles of harmonic conversion, light beam focusing, vacuum isolation, debris shielding and the like. When the high-energy laser light passes through the FOA, each surface of each transmissive optical element has residual reflected light (stray light). When the flux of stray light on the terminal optical element and the structural member is strong, hundreds of thousands of pollution particles are added to the optical terminal system, the service life of the terminal optical element is reduced, and the output energy of the laser device is limited. Therefore, avoiding the deterioration of stray light to the clean environment of the system and reasonably controlling the stray light becomes an important problem for the FOA design of the high-power laser device, the life of the optical element and the improvement of the output energy of the system and the safe operation of the laser device. The national ignition device (National Ignition Facility, NIF) contains 192 FOAs, is a compact arrangement in an atmosphere chamber environment, and has a dense and complex stray light distribution. The NIF device starts in 1994 and completes its engineering design in 9 years, the first integration verification on the Beamlet causes serious damage to the optical element, so the FOA is set as a micro-air clean environment under the atmosphere chamber, the second integration verification of the FOA is performed in 2006, a great number of problems are still exposed, the overall shaping of the system is completed in 2007, and the engineering design of the FOA is completed in 2009, but until 2017, it is still reported that terminal pollution caused by stray light and serious damage to the optical element are found. The domestic superlight series device FOA is also compactly arranged, and the continuous design and optimization process is adopted. The light II upgrading device carries out comprehensive control design on the stray light at the beginning of design, but the light II upgrading device carries out new round of optimal design on FOA aiming at the damage of the stray light to the optical element until 2008. The stray light is not absorbed by the light III prototype device, so that the stray light is incident on the inner wall of the terminal, the FOA system is polluted, and the service life of the optical element is greatly reduced. Therefore, the compact FOA stray light distribution is complex, and pollution caused by stray light has a great influence on the service life of terminal optical elements and the output capacity improvement of a laser device, and becomes an important point and a difficult point of the current research work. Compact FOAs are complicated and have a large amount of stray light that interacts multiple times due to the small distance from the frequency doubling band to the focal length. The high-order (twice and more reflected) stray light flux is low, the stray light focus needs to be avoided from not acting on the element and the structural member, and the management and control are mainly focused on the pose optimization design of the vacuum window and the shielding sheet. First order (single reflection) stray light has the characteristic of high flux, and special absorber treatment needs to be designed, and management and control mainly focuses on the design of the distance from a fundamental frequency window to a focusing lens and an absorber. To trap stray light while avoiding contamination of the end system with absorbing glass (AB 5 material). Disclosure of Invention In view of the foregoing background, an object of the present invention is to provide a stray light management method for a high-power compact terminal optical system, which restrains stray light in a beam trap while avoiding contamination of the terminal system by absorbing glass (AB 5 material). The technical scheme adopted by the invention is as follows: a stray light control system for a high power compact terminal optical system includes terminal optical elements arranged in a compact distance range by being pulled apart longitudinally, eight optical elements in total, and two modules, a frequency conversion module and a focusing sampling module, are arranged in a concentrated manner. Further, the frequency conv