Fast Modulator for Extraction of Internal Laser Power

Abstract

General design considerations for internal laser acousto-optic modulators are given. Calculations are carried out for the time dependence of the power within the cavity and of the external pulsed power. Based on these calculations, acousto-optic quartz modulators were designed to be inserted inside He–Ne and argon folded cavities. Light pulses, with duration continuously variable from 15 nsec to cw and with repetition rate variable from single pulses to a few MHz have been extracted from the cavities. After dumping out most of the cavity energy, the time required for the internal power to rise from 10% to 90% of its steady-state value is of the order of 3 μsec. With a pulse repetition rate of 1 MHz, the average light power was essentially the same as of the cw power capability of the lasers. The peak power intensity of the scattered light could reach the value of more than 50 times the cw power which was about 5 W for a 100mW He–Ne laser and 100 W for a 2-W argon laser. The ability to pulse modulate the laser power at high repetition rates with negligible sacrifice in average power is important in many applications, including optical memories and laser machining.