Using the method of double-sided polishing with oscillating and rotating upper disk, we have investigated the material removal behavior of flat fused silica. It is suggested that the material removal characteristics of the optics depend on the positon and size of the upper polishing disk. Measurements together with the kinematic model results show that the effect of the swing position and size of upper polishing disk similar to sub-aperture polishing, leading to the non-uniformity distribution of the material removal on the surface of the optic component. the surface figure errors of 0.5 wavelengths is achieved after polishing process. The efficiency and quality of double-sided polishing can be improved through changing polishing disk and swing position according to this study.
o achieve the positioning and multi-degree-of-freedom machining of rotary micro-feature structures on the five- axis motion table in the focused ion beam micro-nano machining system, a high-precision sample rotator based on worm gear drive in vacuum environment is designed. The finite element method is used to simulate and optimize the key components. After loading, the maximum deformation of the component is less than 0.2μm, and the natural frequency is more than 10000Hz, which meet the requirements of the working accuracy and strength of the component. The focused ion beam machining experiment of high aspect ratio microstructure of metal material was carried out by using this sample rotator, and the surface roughness of metal material after machining was better than 5nm. The developed sample rotator expands the processing range of focused ion beam processing system.
In order to study the lattice damage caused by low-energy argon ions on the single crystal silicon substrate and the influence of incident energy on the substrate damage during the ion beam polishing process, the molecular dynamics (MD) was used to simulate the incidence of a single argon ion on the single crystal silicon substrate. Compare the lattice defects produced by the bombardment of single crystal silicon by ions of different incident energy. Ion beams with different incident energy were used to polish the surface of single crystal silicon, and the surface roughness after polishing was compared. Experimental and simulation results show that ion bombardment will cause lattice damage to the surface of the substrate. As the energy increases, the range of lattice damage will expand and the resulting lattice defects will be more dispersed. The use of low-energy (200~600eV) ion beams can further reduce the surface roughness of the substrate on the basis of reducing lattice damage
Surface of fused silica optical components were polished by Ion Beam Figuring (IBF) ultra-precision process. Based on the analysis of the relationship between the ion beam current density distribution parameters obtained by faraday scan and the removal function, the removal function model for IBF was established. The IBF experiment for fused silica optical materials were carried out. The experimental results show that the IBF method based on faraday scan can achieve the same figure correcting ability as the traditional IBF method based on line scan experiment. But the offline calculation time of the removal function can be reduced from 2 hours to 5minutes, which improves the efficiency of IBF greatly. After several cycles the initial surface figure error of the optical element before processing, with a PV value from more than 500 nm to less than 15nm and an RMS value from more than 120nm to less than 1.5 nm. Ultra-precision surface of fused silica optical components with nanometer scale were obtained by IBF.
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