Tunable Filter Based On Fabry - Perot Cavity Optical Study

To adapt to the development of DWDM,we should cut down the photoelectric devices of the communication system. Now researchers are researching the pratical all optical communication network and the tunable optical filter is indispensable. Based on some general theories about the superprism effect in photonic crystal (PC) and the Fabry-Perot filter. We mainly focused on the study of the incidence angle tunable filter with thin-film Fabry-Perot cavity,the superprism effect in the liquid crystal Fabry-Perot filter,as well as the Multi-Heap tunable filter based on liquid crystal Fabry-Perot cavity.1, Research on the incidence angle tunable filter with thin-film Fabry-Perot cavity. Utilizing the large group delay at the wavelength of peak the transmittance of thin-film Fabry-Perot filter,we presented the method to achieve large spatial dispersion of different wavelength. We can change the incidence angle to get tunable property and achieve spatial demultiplexer. Based on this consideration, we made the analysis on the thin-film Fabry-Perot filter structure Air| (HL)^5 H 6L H(LH)^5| Sub. The device was designed and fabricated, also the measurement setup which is used for detecting the shift caused by spatial dispersion was built. We achieved the spatial shift for the incidence angle 27.8°, 30.9° and 33° , compared the measured values with theoretic values and made the analysis on the error between the measured values and theoretic values.2, Research on the superprism effect in the liquid crystal Fabry-Perot filter. To obtain tunable spatial optical filter.We inserted a liquid crystal layer into one-dimensional thin film photonic crystal and designed a structure of liquid crystal Fabry-Perot filter. Based on its large group delay at wavelength of peak transmittance, the superprism effect in this structure was numerically simulated. Utilizing the electric tunable effect of liquid crystal, the incident lights at various wavelength regions could be spatially separated. The finite-difference iterative method was used tocalculate the distribution of the liquid crystal directors under an applied voltage, and the Berreman 4x4 matrix method was applied to analyze the optical properties of liquid crystal. With 0 to 0.55V voltage applied, the 20 degree oblique incident light in p-polarization state was simulated. Different wavelength lights was separated with spatial dispersion. The tuning range is from 745nm to 780nm.And we also made analysis on the influence of group delay for different incidence agnle and different stack number of dielectric layer at two sides of liquid crystal cavity.3n Research on the Multi-Heap tunable filter based on liquid crystal Fabry-Perot cavity. Utilizing the interfere principle of the Fabry-Perot cavity and the electrooptical effect of liquid crystal , we designed a Multi-Heap tunable filter. This device also could be tuned by the incidence angle. We designed , simulated and fabricated the device. Then we introduced fabricating process of liquid crystal cell and the key factor that effect the property of the liquid crystal cell. Finally, we made measurements and analysis on the tunable property for e light and o light.