Acousto-optic system for the generation and control of tunable low-frequency signals

An optically efficient interferometric acousto-optic architecture for the tunable generation and control of low-frequency signals is proposed using two radio frequency (rf) or microwave band Bragg cells in an in-line configuration. Critical beam deflection optics, such as a dove prism, ensure that the interfering beams are collinear and stationary, thus providing the high heterodyning efficiency required at the fixed optical detector. Tunable 1- to 15-MHz ultrasonic band signal generation is demonstrated with rf Bragg cells, showing high (107 dB/Hz) carrier-to-noise ratios. This free-space interferometric acousto-optic system with two collinear output beams with a relative color shift is required for making a compact, lightweight, and powerful optical platform for baseband/ low-frequency optical signal processing and control functions, such as required in advanced phased-array systems used in sonar, medical, and industrial applications.