Differential detection of polarization-modulated optical signals

Optical polarization analyzers designed for measuring small birefringence of transparent objects are analyzed theoretically. Analyzers that combine methods of polarization modulation and differential suppression of excess noises are considered. Generalizations of two configurations of polarization circuits commonly used in measurements of this type are discussed. Analytical expressions for observable birefringence signals have been derived for these cases. The paper shows the coincidence of maximum signals achievable in those circuits.