AlGaAs waveguide optically controlled directional coupler latch

A novel AlGaAs optically controlled bistable vertical directional coupler was demonstrated. The optical input can be routed between two outputs by an optical pulse on the input signal or by optical set and reset pulses applied via fiber. Both modes have been experimentally demonstrated. Because of positive optical feedback, the device is bistable and will latch into the set state until assertively reset. The operation is based on electrooptic modification of the phase match between the two waveguides in the directional coupler. Since no Fabry-Perot resonances are involved, the device operates over a fairly wide wavelength (840-880 nm) and applied voltage (2-12 V) range. A switching contrast in the upper waveguide output of 14.7:1 and a throughput of 64% were observed. The critical input power to cause bistable switching is 17 μW. The switching speed (~200 ns) is RC-limited and the set and reset energies are determined by the charging energy of the waveguide capacitance