Photonic logic NOR gate based on two symmetric microring resonators.

We demonstrate an all-optical nor logic gate based on symmetric GaAs–AlGaAs microring resonators whose resonances are closely matched. Two input pump data streams are tuned close to one resonance of the symmetric microrings to switch a probe beam tuned to another resonance by two-photon absorption. The switching energy of the gate is 20 pJ/pulse, and the switching window is 40 ps, limited by the carrier lifetime. The use of two rings provides for better cascading in photonic logic circuits because of the higher number of available ports.