Based On The Key Technologies Of The Thermo-optic Effect Tunable Fabry-perot Thin Film Filter

Tunable optical filters based on thin-film interference filters are extensively researched due to the good characteristics of thin-film interference filters such as narrow bandwidth, low insertion loss and fine temperature stability.In this paper, a tunable Fabry-Perot thin-film filter based on thermo-optic is designed. The filer is made of amorphous silicon and silicon nitride layers grown by PECVD. Due to the excellent thermo-optical property of a-Si, the refractive index of a-Si will be changed by heating; the filter's peaks wavelength will therefore shift substantially.Theoretically, through transfer matrix method of multilayer thin-film interference filter, the tunable Fabry-Perot thin-film filter is analyzed and a vertical structure of the tunable Fabry-Perot thin-film filter based on thermo-optic is designed. A tunable narrow-band thin-film filters based on thermo-optic is obtained by changing the mirrors and the cavity. Multi-cavity Fabry-Perot filters is studied and a vertical structure of dual-cavity Fabry-Perot thin-film filters of flat-top response is designed. Multiple-channel filer is obtained by designing the structure of the cavity. Tuning characteristics of filters is analyzed by changing the temperature of the Fabry-Perot cavity. Theoretically, the good filtering properties and tuning properties of the filter is confirmed.Experimentally, amorphous-silicon and silicon nitride films are deposited by PECVD. By studying, found that power is a very important parameter, it is not only affect the refractive index, but also affect deposition rate and resistance. And pressure, flow rate and temperature have some affection to film's quality too. In silicon nitride film, the ratio of SiH₄ and NH₃ also affects the performance of film.