Optimization of reflectivity, rise time and fidelity of a self-pumped phase conjugate BaTiO_3: Rh ring mirror at 1.06 mum

摘要

It is now well known that rhodium doped barium titanate (BaTiO_3:Rh) exhibits a significant photorefractive response at near infrared wavelengths~1. We studied and characterized this crystal at 1.06 mum by two-wave mixing experiments. In a 45deg-cut crystal with a low absorption (0.1 cm~-1), we measured a photorefractive gain GAMMA of 23 cm~-1 with cw illumination and 16.6 cm~-1 with nanosecond illumination. Using spectroscpic determinations of the photorefractive sites ~2 (Rh~3+, Rh~4+, Rh~5+), we demonstrated that the photorefractive properties~3 of BaTiO_3:Rh are well described by a three charge state model~4. Internal parameters of the material were derived using these experimental characterizations which allowed to accurately predict its performances at 1.06 mum. Comparative characterizations of several BaTiO_3:Rh smaples proved that this material is now well reproducible. Reproducibility, high photorefrctive gain. low absorption and accurate theoretical description make BaTiO_3:Rh a good candidate for realization and optimization of non linear functions like optical phase conjugation. The application we are interested in, is the dynamic wavefront correction of nanosecond Nd:YAG master-oscillator power-amplifier (MOPA) laser sources.