SPATIAL-MODE CLEANUP OF A PULSED LASER-BEAM THROUGH MUTUALLY PUMPED PHASE CONJUGATION WITH A CW REFERENCE

A method of cleaning up the spatial mode of a pulsed laser beam without using a pinhole is proposed and demonstrated. The method consists of performing mutually pumped phase conjugation (MPPC) between the pulsed laser beam and a cw reference, thereby transferring the desirable spatial mode of the cw beam onto the pulsed beam. In these experiments MPPC is observed in a photorefractive BaTiO3 crystal between the beams from a Q-switched flash-lamp-pumped Nd:YAG laser and a diode-pumped cw Nd:YAG laser, both operating at 532 nm. The experimental results showed convincing spatial-mode cleanup of the pulsed beam, with an -3% conversion efficiency. A method of significantly increasing the overall efficiency is discussed. To the author’s knowledge, this is the first reported MPPC between pulsed and ow laser beams. © 1990 Optical Society of America.