A CNC Chemical Etching Technology Of Optics Suface Based On The Marangoni Effect

Nowadays, advanced optical manufacture technologies have attracted vast interests of researchers, such as CNC polishing, MRP, and ion beam modification technology. Whereas, all of these polishing technologies are expensive for batch production, and process defects are presented in these advanced technologies. The CNC with small tool can't process the super-thin workpiece for the presence of local mechanical stress during processing and can easily induce SSD. The workpiece polished by MRP can't be used in high intensity laser applications because of the metallic particles. As for ion beam modification technology, large vacuum chamber should be included, which is very expensive.The CNC chemical etching technique presented in the paper have a good control of the etching process using the Marangoni effect, referring to CNC with small tool technology. Liquid etchant is used in the method of CNC chemical etching, which can effectively avoid the mechanical stress, and remove the SSD. The technology can be easily implemented with cheap equipments, which is of great significance for the process of the fine optical components and for the components used under the high optical power density.Advanced ultra-precision machining technology of optical material in the world is reviewed, including their advantages and defects. Models for surface tension and chemical polishing are presented based on the technical principles of CNC chemical etching. Detailed studies on SSD of optical components are performed, including the causes and the the vertical variations of the SSD, through micro topographies and quantitative analysis. The structures of SSD are studied in a series of specially designed experiments for etching and the laser damage threshold. Thereafter, removal scheme for SSD is designed.In specially designed experiments, it is demonstrated that Marangoni effect is presented in different etching paths. Other than local etching studies, chemical polishing removal function is fitted from experimental data, and surface refinement is accomplished for large optical components through well-designed etching paths, the P-V value as low as 0.152λ (λ=632.8nm) is reached, without SSD based on the fitted chemical polishing removal function.