Task-based assessment of phase-shifting interferometer/ellipsometer

Abstract

In this presentation, I present a novel phase-shifting interferometer/ellipsometer. The uniqueness arises from the fact that this study is the consolidation of four distinct ideas drawn from the field of optics and the field of statistics. A conventional four-step phase-shifting interferometer is modified to allow for both TE and TM polarized measurements. Maximum-likelihood estimation theory is then used to extract the three parameters of interest, namely the real and imaginary components of the complex index of refraction and the surface profile. Finally, Cramer-Rao lower bounds serve as a quantitative means of assessing the particular system design at the task of estimating the three parameters in question. I will demonstrate the feasibility of the proposed technique with a Mach-Zehnder prototype, and show how three system parameters, namely the incident amplitude and the relationship between the TE and TM polarized light in terms of amplitude and phase, affect the performance. I also show how quantization of the measured irradiance affects the performance.