Photorefractive energy exchange requiring optical activity and an electric field

Optical-activity-supported energy transfer is explained, and a transfer of 4% is observed in bismuth silicon oxide with same-frequency equal-intensity beams having the same circular polarization. The direction of energy exchange can be controlled by the sign of the electric field or the sense of the circularity. In general, energy exchange occurs by destructive and constructive interference between diffracted and transmitted beams; here, with the induced grating vector along the [110] direction, interference cannot occur unless optical activity and an external electric field are present.