Broadband diffraction in a photorefractive asymmetric coupled quantum well structure

We report a new approach to expand the diffraction bandwidth of a photorefractive device in the longitudinal-field geometry by using asymmetric coupled quantum well (ACQW) structures. The longitudinal-field geometry is another configuration of PR MQW devices. Compared with devices in the transverse-field geometry, larger diffraction efficiency is obtained with a smaller operating voltage (10-20V) in the longitudinal-field geometry. The device has a photorefractive p-i-n structure.