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

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 tell uride (CdTe) attractive materials for the fabrication of electro-optical de vices. In this context we characterized both acoustic and optical phonon co ntributions to the electro-optic coefficient of CdTe and GaAs. Accurate mea surements of n(0)(3)r(41) as a function of modulation frequency and tempera ture were carried out on CdTe:ln and GaAs crystal at 1.5 mum. For CdTe, to the best of our knowledge, this is the first time that a contribution to th e electro-optic coefficient due to optical phonons has been determined. A p ositive value for the ionic contribution, due to optical phonons in GaAs, i s obtained, in disagreement with that previously inferred from Raman scatte ring efficiency measurements. The pure electronic contribution was then iso lated, and the second-order non-linear optical coefficient was derived. The latter was compared to previously reported data from non-linear wavelength conversion measurements. (C) 2001 Elsevier Science B.V. All rights reserve d.