Thermo-Optic Effects in an Electro-Optic Modulation System

Abstract

In this framework, our interest has been focused to the thermo-optic behaviour of an EO modulator crystal as it is expressed by the influence of temperature T on crystal’s optical or electro-optical parameters such as the refractive indices, n 0 and n e , the effective EO coefficient r, the spontaneous birefringence !n(0), the half-wave voltage V , the optical phase retardation #, and the intensity-modulation (IM) depth m of the entire EO-modulation system. After a brief presentation of typical configurations of IM systems, we define the principal thermo-optic and temperature coefficients and we derive useful general equations connecting these parameters in the entire system. Then we present investigations of these equations as regards the above parameters along with calculations of the uncertaintities in the determination of temperature coefficients for the effective EO coefficient r, the half-wave voltage V , and the IM depth m. It is of note that in this publication, the theoretical analysis of the thermo-optic effects in an electro-optic modulation system is only presented. In the experimental field, a determination of various TO coefficients of LiTaO 3 made by the authors, in the case of a transverse EO configuration, has been already published elsewhere [3].