Free–space optical cross–connect switch by use of electroholography

An electrically controlled holographic switch is proposed as a building block for a free–space optical interconnection network. The switch is based on the voltage–controlled photorefractive effect in KLTN crystals at the paraelectric phase. It is built of electrically controlled Bragg gratings stored in the volume of the crystal. A compact switch that connects four high–speed fiber–optic communication channels with high efficiency is demonstrated experimentally. The switch performance is investigated and optimized. This switch is extremely attractive for cascaded switching arrays such as those found in multistage interconnect networks.