Abstract

A novel 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)¹ between the pulsed laser beam and a cw reference, thereby transferring the desirable spatial mode of the cw beam onto the pulsed beam. In my experiments, I have observed MPPC in a photorefractive BaTiO₃ crystal between the beams from a Q-switched flashlamp-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. This method can also modify the incident pulsed beam to any desirable spatial pattern by using a spatial light modulator in the cw reference. To my knowledge, this is the first reported MPPC between pulsed and cw laser beams.

© 1990 Optical Society of America