Acousto-optic device

An acousto-optic (AO) device, 10, operates by setting up an acoustic standing wave and an optical standing wave in the acousto-optic device. Both acoustic and optical standing waves are set up to be partially co-located within the acousto-optic device so that the optical standing wave interacts with the acoustic standing wave within the acousto-optic device to generate output light which is output from the acousto-optic device. The acoustic and optical standing waves may be internally reflected within the device at a common reflective interface, 14b. Also disclosed is an acousto-optic device comprising first and second electrodes, 12, 14, with a piezoelectric material, 16, between the two electrodes and an acoustic driver which generates an electric field across the piezoelectric material. In one embodiment the second electrode is optically transparent. In a further embodiment the second electrode comprises transparent metal or a doped semi-conductor, such as doped silicon.