Q-Switching and Cavity Dumping of Nd:YAlG Lasers

Abstract

Experiments in Q-switching and cavity dumping of a Nd:YAlG laser have been carried out. The system in either case is composed of a Nd:YAlG folded cavity laser and an intracavity acousto-optic modulator made of fused silica and Brewster cut. Q-switching is achieved by first feeding the modulator with an acoustic pulse of sufficient duration and intensity to keep the laser below threshold (hold off pulse). Termination of the acoustic pulse allows the power inside the laser cavity to build up. A second short acoustic pulse, introduced to the modulator at the time when the internal energy reaches its maximum, couples the energy out of the cavity. This pulse may also be the beginning of the hold off pulse. Cavity dumping is accomplished by feeding the modulator with short acoustic pulses at fixed intervals. In the Q switching mode the system can operate with a maximum repetition rate of about 30 kHz. In the cavity dumping mode of operation the repetition rate of the light pulses can be controlled from 125 kHz to several MHz. The minimum pulse duration obtained in both modes of operation was about 80 nsec. The average power can reach 2 W, which is the maximum cw power capability of the laser used.