Anti-reflection method for beam sampling grating in intense laser system

Abstract

The invention provides an anti-reflection method for a beam sampling grating in an intense laser system. The method comprises the following steps: to begin with, preparing a sub-wavelength grating template on a fused quartz substrate through a holographic ion beam etching method; dropping a little PUA UV imprinting photoresist on the sub-wavelength grating template, and then, covering a PET film on the PUA; curing the PUA through UV irradiation, and separating the cured PUA from the grating template to obtain a sub-wavelength grating soft template; clearing the surface of the beam sampling grating, and then, spin coating PMMA imprinting photoresist on the surface; covering the sub-wavelength grating soft template on the PMMA, wherein soft template grating fringe direction can be parallel, vertical or form angle with the fringe direction of the beam sampling grating; clamping the two through a clamping mechanism and placing the two into a baking oven for heating and curing; separating the sub-wavelength grating soft template from the substrate, and forming a sub-wavelength grating on the PMMA; then, removing bottom residual photoresist of the PMMA grating through oxygen plasma ashing; by utilizing a to-the-bottom PMMA subwavelength grating mask, carrying out CHF3 reaction ion beam etching; and finally, carrying out cleaning to remove residual photoresist to obtain the beam sampling grating having an anti-reflection effect.

Description

technical field [0001] The invention relates to an anti-reflection and anti-reflection method for the surface of an optical element, in particular to an anti-reflection and anti-reflection method for the grating surface of a light beam sampling grating in a strong laser system. Background technique [0002] Beam sampling gratings are a type of optical element used in powerful laser systems to diagnose the energy, power, and spatial distribution of incident beams. For the diagnostic incident wavelength of 351nm, the -1 order diffracted light is focused on the surface of the light intensity detector, and the diffraction efficiency is about 0.2%. The relevant characteristics of the incident light are calculated from the detector measurement results. [0003] In a strong laser system, a large number of optical components need to be used. Therefore, in this complex optical system, the reflection of the beam on the surface of the optical component cannot be ignored, which directly...

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Problems solved by technology

[0004] However, due to its loose and porous structure, the silica sol-gel anti-reflection film will absorb organic matter in the environment and cause its own pollution, resulting in transmittance and damage severe drop in threshold

The adsorbed organic matter will change its own refractive index (equivalent refractive index). If the anti-reflection coating is used on the beam sampling grating surface, it will change the -1 order diffraction efficiency and the overall uniformity, which will lead to inaccurate diagnosis. Therefore, the actual In use, only the back of the beam sampling grating is coated with anti-reflection coating, while the grating surface is left untreated

[0005] At present, the anti-reflection solution adopted in the powerful laser system is to use the sol-gel film, but the film is easily polluted, which leads to the decrease of the transmittance and the laser damage threshold. Decrease, and the refractive index changes after contamination, if used on the grating surface of the beam sampling grating, it will cause inaccurate diagnosis

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