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Nanocrystalline silicon films were prepared by radio frequency plasma enhanced chemical vapor deposition(RF-PECVD)technique with SiH4and H2precursors.The micro-structure and the bonding characteristics of deposited films with different hydrogen dilution ratios were studied by Raman scattering spectroscopy and Fourier transform infrared absorption(FTIR)spectroscopy.The results show that with the increase of hydrogen dilution ratios,the thin film crystallization rate obviously improves to a certain extent,however,with the further increase,the film crystallization rate shows a downward trend.The analysis of infrared absorption spectra shows there is a close relationship between the silicon-hydrogen bonding model and the crystallization characteristics.With the continuous improvement of the hydrogen dilution ratios,the SiH2bond density and the total hydrogen content in the film reduce significantly.In conditions of high hydrogen dilution ratios,the intensification of dehydrogenation reaction lead to the SiH2 bond density and the total hydrogen of film increases,and lead to a decline in the rate of film crystallization.

Dynamic formulas of acoustic frequency and diffraction efficiency are proposed.Distributions of diffraction efficiency of the acousto-optic cell at different driving frequencies are analyzed,and its approximate expression is also given.However,it is found that the non-reciprocal effect also appears at low frequency(e.g.100 MHz),which usually occurs at above 1 GHz frequency.Through introducing scale factor δF/ΔF,the non-reciprocal effect experiment is carried out with the laser wavelengths of 532 nm and 632.8 nm in Tellurium dioxide crystals.The obtained results show that the total change in the diffraction bandwidth is 50% to 60%,which basically matches the calculated result.According to this result,the non-reciprocal effect can be applied in the development of directional couplers(optical router) and other optoelectronic devices.