Study On Key Technology Of Ion Beam Polishing Of Single Crystal Silicon Mirror

The single crystal silicon mirror is an extremely important optical component in the laser system,and its processing quality is directly related to the performance of the whole laser system.Due to the manufacturing of optics,various defects are introduced,resulting in a significant reduction of the laser damage threshold compared to the intrinsic surface.Because of the unique material removal mechanism,Ion Beam Polishing(IBP)can achieve high modification precision and does not introduce any subsurface damage during processing.So it has great advantages in low-defect surface process.However,the limitations are low processing efficiency and possible induced surface microtopography.In this paper,the key process in IBP of single crystal silicon mirror is taken as the research object.The removal function of ion beam processing cylindrical mirror is simulated.And the influences of IBP with oblique incident angles on the surface quality of single crystal silicon optics is studied,which can guide the optimization of process parameters.A combined process based on IBP and Plasma Cleaning(PC)was explored and verified by single crystal silicon cylindrical mirror processing experiment.This paper mainly includes the following contents:1.The modeling and simulation of removal function of the ion beam when machining the mirrors.The accuracy of removal function is fundamental to the realization of high precision surface fabrication and is of great significance.According to the basic model of removal function deduced by Sigmund Theory and BH Theory,the transformation equation from the removal function of plane mirrors to the cylindrical mirrors is derived considering the impact of incident angle,surface shape and target distance on removal function.Therefore the removal function during cylindrical mirrors process can be obtained through simulation and the machining efficiency also the precision of the single crystal mirror are guaranteed.2.The evolution of the surface quality of single crystal silicon under the ion beam oblique sputtering.In the experiment where the incident angle is a single variable,the variation of the surface quality of single crystal silicon optics at different angles is monitored.According the results,the surface quality can be maintained at a small angle and 45°,even with a certain degree of improvement.3.Research on combination process of single crystal silicon mirror.The PC is combined with IBP to realize the control and improve of the surface quality.Finally,the IBP combination process of single crystal silicon mirror was formed and the process flow was established.4.The combined process was verified through the processing of single crystal silicon cylindrical mirror.After 229 min processing,the surface accuracy of single crystal silicon cylindrical mirror is reduced from 0.786λ to 0.244λ,and the surface quality is improved to some extent.