Mathematical modelling of extrinsic Fabry-Perot Interferometer cavity

An optical wave when passed through the mirrors of an extrinsic Fabry-Perot interferometer cavity (EFPI) experiences a phase shift in each round trip as a function of the separation between the mirrors are analyzed. Stability as well as the probability of constructive interference in an EFPI is determined using Nyquist stability criterion. The performance when two perfectly parallel surfaces and when there is some tilt between the mirrors in the cavity is also considered with a continuous range of tilt up to which there is possibility of constructive interference.