Self Bragg matched beam steering using the double color pumped photorefractive oscillator

A new method for steering light beams with automatic (self-aligning) Bragg matching is presented. This device enables, in principle, a large beam deflection range which is not limited by the Bragg condition. It is based on a double color pumped photorefractive oscillator. Two input beams of different colors induce and pump a dynamic four-wave mixing process in a photorefractive BaTiO₃ crystal in which two other beams and a common grating are self-generated. Steering is achieved by wavelength tuning of one of the pump beams. A deflection range of about 1.7°, with an efficiency ranging from 50 to 90%, is measured for a wavelength difference Δλ of ±30 nm for the two pumps (using argon ion laser lines). A deflection of 4.7°with an efficiency of 10% is seen for Δλ=144.8 nm (corresponding to pumps at 488 and 632.8 nm).