Synchronization of two photoelastic light modulators to obtain Müeller matrix

We report a method for the temporal synchronization of two photoelastic light modulators. For synchronizing, we used the transistor-transistor logic output signals from each modulator, which contain the information on the light polarization. These signals were introduced in a phase-detector circuit, which provided the phase difference value between both modulators. Three optical devices were used to test the synchronization method proposed: a polarizer, a half-wave, and a quarter-wave retarder plate. The value of each of the elements of the Müeller matrix for these devices was obtained using the method of the 36 measurements. The results show a high correlation between the theoretical and experimental values obtained. The results are also in accordance with other values obtained by different methods reported in the literature. Errors calculated by the proposed method are approximately in the order of a thousandth. The advantages and disadvantages of the method are discussed.