Study On Coating Process Of SiO₂ Sol-gel Antireflective Film For Beam Sampling Grating Of ICF

Inertial Confined Fusion(ICF)is one of the effective ways to realize controllable nuclear fusion,which is of great significance in the fields of energy and national defense.There are several optical systems in ICF,among which terminal optical system is critical for laser diagnosis.The parameter of the incident laser in ICF,such as energy,power,spatial distribution and wavelength distortion can be measured with the terminal optical system.Beam Sampling Grating(BSG)is the key components in the terminal optical system,which should meet the requirement of low laser loss and less damage.Coating an antireflective film on the BSG surface was a critical process to solve the problem.A coating method based on meniscus principle was proposed in the SiO2 sol-gel antireflective film process.A coating system based on meniscus method was designed an built,which was validated by coating experiments on flat fused silica plate.The relationship of coating parameters such as coating rate and inclination angle,between coated film quality such as film thichness and uniformity can be concluded through the validating experiments.The optical performance of the BSG with SiO2 sol-gel antireflective film was analysis based on rigorous coupled wave theory.The BSG was coated with SiO2 sol-gel antireflective film and whose surface morphology and diffraction efficiency was tested.Compared with the spin coating method,surface morphology of coated film through meniscus method was smoother,better groove filling consistency and thickness uniformity.Test results showed that,the zero-order diffraction efficiency of BSG is increased by about 3.7%after coating a SiO2 sol-gel antireflective film,which is consistent with the theoretical calculation results.The coating method of SiO2 sol-gel antireflective film based on meniscus principle can provide an effective solution,which can meet the requirement of the ICF.