Acousto-optic isolator

摘要

An acousto-optic isolator for a semiconductor laser diode comprises a Fabry-Perot resonator tuned to the laser optical frequency fo followed by an acousto-optic Bragg diffraction device utilizing surface acoustic waves of frequency fa launched from a transducer. Light focussed by a lens to the load has a resultant frequency fo+fa. Any light reflected from the load suffers a further change in frequency to fo+2fa in the diffraction device and hence is blocked by the resonator. Undiffracted light can be detected at a photo-detector and used in a feedback control loop to stabilize the light source to the resonator.