One of the major advantages of utilizing atmospheric pressure plasma processing(APPP) technology to fabricate ultra-precision optics is that there is no subsurface damage during the process.In APPP,the removal footprint and removal rate are critical to the capability and efficiency of the figuring of the optical surface.In this paper,an atmospheric plasma torch,which can work in both remote mode and contact mode,is presented.The footprints and the removal rates of both modes are compared by profilometer measurements.The influences of process recipes and substrate thickness for both modes are investigated through a series of experiments.When the substrate is thinner than 12 mm,the removal rate in contact mode is higher.However,the removal rate and width of the footprint decrease dramatically as the substrate thickness increases in contact mode.
In order to get ultra-smooth fused silica surface without subsurface damage efficiently, the atmospheric pressure plasma processing( APPP) method has been developed. It is based on chemical reaction between active radicals excited by plasma and workpiece surface atoms,so the subsurface damage caused by contact stress can be avoided and atomic-level precision can be ensured. In this paper,based on the spectral quantitative analysis theory,the influence laws on material removal rate by the key factors of APPP including the flow rate of reaction gases,the input power,the processing distance and time are discussed. In addition,the results that APPP can remove the damaged surface layer and do not introduce secondary damage are proved via the nanoindentation technology.
