When a light beam whose polarization and intensity are weakly modulated at a frequency ωm passes through a periodic analyzer of frequency ωa(<ωm) and the transmitted flux is linearly detected, the resulting total signal St consists of two components: (i) a periodic baseband signal Sbb with harmonics of frequencies nωa (n = 0,1,2,…) and (ii) an amplitude-modulated-carrier signal δSmc with center (carrier) frequency ωm and sideband frequencies at ωm ± nωa(n = 1,2,…). In this paper we show that the average polarization of the beam is determined by a limited spectral analysis of Sbb, whereas the polarization and intensity modulation are determined by a limited spectral analysis of δSmc, or the associated envelope signal δSe, where δSmc = δSecosωmt. The theory of this frequency-mixing detection (FMD) of polarization modulation is developed for an arbitrary periodic analyzer. The specific case of a rotating analyzer is considered as an example. Applications of FMD include the retrieval of information impressed on light beams as polarization modulation in optical communication systems, and the automation of modulated ellipsometry, AIDER (angle-of- incidence-derivative ellipsometry and reflectometry), and modulated generalized ellipsometry.
© 1976 Optical Society of America
R. M. A. Azzam, "Frequency-mixing detection (FMD) of polarization-modulated light," J. Opt. Soc. Am. 66, 735-739 (1976)