Fabry - Perot Film Filter Film Optical Properties Research

With the development of fiber communication, tunable optical filters occupy animportant place, especially those based on F-P cavity. The thermo-optical tunable filterbased on F-P cavity is becoming the focus for its properties such as compact size，easeof integration，low loss and fast tuning speed. This paper is focused on the opticalproperties of amorphous silicon film deposited by PECVD, and obviously, these opticalproperties are the key component of the filter.Firstly, theoretical analysis is given to the thermo-optical tunable filter about itsstructure and materials，through simulation we found a higher refractive index for thecavity material leads to a smaller FWHM and a higher chromatic resolving power, and abigger gap between the refractive indices of the two materials ensures a lower cost. Thedetails of the experiment are given(such as the basic theories of amorphous silicon filmsdeposited by PECVD, and the test instrument used in these experiments), which laytheoretical foundation for further discussion.The following chapter is focused on how the variation on parameters of PECVD(such as pressure, power, substrate temperature, gas temperature and deposition time)affect the optical properties such as refractive index，extinction coefficient and surfacemorphology，and then we give the IR spectrum of the material to carry on these analysis.Then the three chapters below research how other conditions such as differingsubstrate，doping and annealing(by changing annealing time, temperature and gas)affect the optical properties of the film, the results are listed as below: First, the siliconnitride is a suitable substrate for depositing amorphous silicon. Second, the introductionof nitrogen brings adverse effect for the filter. Third, annealing provides the film a bettersurface and a higher refractive index, and the annealing temperature does more impactthan annealing time. All these analysis related above definitely made great progress forthe manufacture of the thermo-optical tunable filter based on F-P cavity.