Effects of phase-conjugate feedback on the modal content and noise characteristics of a cw argon ion laser: experimental results

摘要

Significant optical noise reduction can occur in a continuous wave argon ion laser when a very small fraction of the output beam is reinjected inside the laser cavity. Noise reduction reaching 15 dB for the low-frequency components (below 1 MHz) and reaching 58 dB at the frequencies corresponding to the beating of longitudinal modes has been obtained by optimizing the external cavity length and the feedback level. It has been possible to reduce the number of oscillating longitudinal modes from 174L?0 to 2 without loss of power. We have compared the optical noise reduction for an external cavity terminated by a phase-conjugate mirror and by a conventional plane mirror.