Phase-modulated temperature scanning interferometry for measurements of electrooptic coefficients: application to KTiOPO4

This work describes an efficient and simple method to determine the effective electrooptic coefficients of crystals, along with the continuous recording of their temperature dependence. A sample with plane and parallel optical end faces acts as a Fabry-Pe´rot resonator, which is submitted to a linear ramp of temperature. The thermooptic effect generates a shift of interference fringes that are phase-modulated by applying an appropriate electric field. Residual absorption of the material is considered to achieve the best accuracy. The case of KTiOPO₄ is given as an example to illustrate the method; first results on the thermal behavior of its effective coefficients r_i3 are presented.