Determination of ionic and pure electronic contributions to the electro-optic coefficient of cadmium telluride and gallium arsenide single crystals

Abstract

High electro-optic figure of merit n 0 3 r 41 and the absence of natural birefringence make semi-insulating gallium arsenide (GaAs) and cadmium telluride (CdTe) attractive materials for the fabrication of electro-optical devices. In this context we characterized both acoustic and optical phonon contributions to the electro-optic coefficient of CdTe and GaAs. Accurate measurements of n 0 3 r 41 as a function of modulation frequency and temperature were carried out on CdTe:In and GaAs crystal at 1.5 μm. For CdTe, to the best of our knowledge, this is the first time that a contribution to the electro-optic coefficient due to optical phonons has been determined. A positive value for the ionic contribution, due to optical phonons in GaAs, is obtained, in disagreement with that previously inferred from Raman scattering efficiency measurements. The pure electronic contribution was then isolated, and the second-order non-linear optical coefficient was derived. The latter was compared to previously reported data from non-linear wavelength conversion measurements.