The present invention is a system for controlling the power level of a beam exiting an acousto-optic cell and/or a beam delivery device. A beam detector senses the power level of the beam and produces a power signal indicative thereof. An error detector compares the power signal to a predetermined power level. If the power signal and predetermined power level differ, the error amplifier emits a correction signal to a variable amplitude source, which adjusts the amplitude of the acoustic drive frequency such that the power level of the beam exiting the acousto-optic cell and/or the beam delivery device is substantially equal to the predetermined power level.