Abstract

We report photorefractive passive phase conjugation¹ of GaAIAs laser radiation at 815-865 nm and Ar⁺ laser radiation at 1090 nm. A ring passive phase conjugate mirror was used with BaTiO₃ as the real-time holographic gain medium. At least 1.5 mW (50 mW/cm²) was required for the PPCM to begin operation. At 3.6 mW (126 mW/cm²) the reflectivity reached 16%, corresponding to 25% after correction for Fresnel reflections. The rise time, defined here as time taken to 90 % of steady state, was approximately 5/1 s W/cm² at 514.5 and 815 nm, where /is the incident intensity. When the GaAIAs laser was replaced by an Ar⁺ laser emitting 35 mW (1.4 W/cm²) at 1090 nm the rise time measured 500// s W/cm². In spite of the length of this time, the steady-state reflectivity reached 18% uncorrected for Fresnel reflections. We describe effects of the phase conjugate feedback into GaAIAs lasers and attempts at active mode locking. The fact that the PPCM operates at 1090 nm indicates that it can be used to correct distortions in Nd:YAG laser systems where aberrations in the solid-state gain medium might possibly be severe.

© 1985 Optical Society of America