High-speed electro-optic diffraction modulator for baseband operation

A new kind of laser-beam modulator is described. An interdigital electrode structure deposited on an electro-optic crystal is used to produce a spatially periodic electric field which diffracts the laser beam within the crystal. Baseband operation is possible, and optical-pulse risetimes of 1.5 ns have been observed. The required drive power is only 7.5 nJ per pulse at 25 V, but this could be improved by scaling. The measured extinction ratio is 25 dB and this varies by less than ±1dB for a 10 K temperature change. The form of the modulator lends itself to inclusion in thin-film optical circuits.