Abstract
Photoelastic modulators are studied here as both birefringence (or polarization) and phase modulators. In the first part of this work we have determined the influences of time dependent variations of index and thickness, for an ideal modulator where oscillation is supposed to be perfectly longitudinal. An interferometric experiment allowed the validation of the results obtained. In the second part, we have calculated the exact modes of oscillation of the modulator by means of a software based on the method of finite elements. We have determined in this way the homogeneity of stresses and deformations in the modulator and the distribution of indices and birefringences. This allowed us to define the limits of validity of the generally used ideal model, previously studied.