Analysis of multidielectric thin film based FPI for high reflectivity and lower phase shift

Thin film layers used in design of MEMS based Fabry-Perot Interferometer has been thoroughly analyzed. Reflectivity and phase shift are two important properties that influence the overall performance of the FPI. Effects of phase shift on the FPI performance in the wavelength range 3mum--5mum are discussed. While it is easy to obtain a layer combination to get high reflectivity, finding a layer combination that has high reflectivity and low phase shift is a challenging task. Thin film design equations are obtained and programs are written in Matlab and Mathematica to calculate the reflectivity and phase shift for different layer combinations. Matlab code executes faster but the phase shift results obtained with Mathematica are more accurate. At times reflectivity is calculated using Matlab code and phase shift using Mathematica. Thin film design software Filmstar is used to achieve layer combinations that have higher reflectivity and lower phase shift. The results obtained from Filmstar software are compared with those obtained from Matlab and Mathematica code and very good agreement has been observed.