COMPLETE HIGH-FREQUENCY MEASUREMENT OF MUELLER MATRICES BASED ON A NEW COUPLED-PHASE MODULATOR

A new polarization modulator is presented. It uses two phase-locked id entical electro-optic phase modulators at 50 kHz. Thanks to a coupling object introduced between the two phase modulators, the four Stokes p arameters of the light beam are independently modulated on the basis o f the first and second complex harmonics of the modulation signal. A M ueller matrix ellipsometer (MME) using this new modulation and a multi channel polarimeter are also described. The data processing and the fe edback control of Pockels cells is based on a numerical Fourier transf orm system. It allows one to measure simultaneously, in one modulation period (20 mu-s), the 16 coefficients of any Mueller matrix. This MME takes advantage of an easy-to-operate calibration method. The high-fr equency modulation of the four parameters of the polarization enables low-light-level measurements (without any chopper and lock-in) and pre sents spectroscopic capabilities. It provides a promising tool for the study of many subjects of growing interest like, for example, rough s urfaces treatment or particle characterization. (C) 1997 American Inst itute of Physics.