5μm thickness silicon coatings were deposited on RB-SiC、S-SiC、Si and Bk7 substrates using ion-assisted e-beam evaporation method, respectively. Renishaw inVia confocal laser Raman spectrometer was used to study the microstructure of all the samples. The measurement results show that the substrate’s thermal expansion coefficient has great influence on the microstructure of nano-silicon coatings. Owing to 300 degree deposition temperature, there will be thermal stress when the samples are cooled down, which leading to medium-range and short-range order of silicon molecular structure change. Accordingly, TA and TO2 mode will appear or disappear in Raman scattering spectra. Amorphous silicon coating can crystalize after laser irradiation with different Raman scattering TO peak offset for different substrates. Especially for nanosilicon coatings grown on reaction bonded SiC (RB-SiC) and Sintered SiC (S-SiC) under the same deposition conditions, they have different Raman scattering spectra and their thermal stress is different, which will give guidance to deposition and polishing process of nano-silicon layers.
Nowadays, optical elements are often shared in order to improve compactness of optical system and edge filter is one of the core parts. For same spectral system, when half convergence light incidents on edge filter, Sagittal and meridian will have different incident angle range, which cause different polarization characterization for the two directions and is harmful to the optical system’ MTF. In order to improve image quality, all factors affecting MTF are analyzed. When light incidents on edge filter, the difference between P and S polarization’s reflection phase can cause MTF drop. The design process of edge filter is optimized. Optical spectrum and reflection phase are optimized together. The variation is kept in a certain range for reflection phase of P and S polarization when edge filer attains spectrum requirement. The newly designed edge filter is sticked to optical system and carried out simulation. The calculation results showed that the newly designed edge filter has little effect on MTF. Ion-assisted e-beam evaporation method is used to deposit edge filter multilayer and the measurement result is in good accordance with that of the design. We think that a new design method is raised for design wide-incident angle and low polarization aberration edge filter.
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