All-optical logic in fiber systems using nonlinear refraction

We describe the realization of a nonlinear all-optical logic gate and modulator for use in fiber-optics communication systems. The physical mechanisms for the optical nonlinearities and their influences on device operation and design are considered. Results are presented for the AND, NOR, NOT, and XOR logic functions with a better than 20 dB contrast ratio. The gates and modulators exhibit exceptional stability, because no resonator, feedback, or stringent wavelength control are needed. Silicon at λ = 1.06 μm has been used for these "proof-of- concept" experiments. The feasibility of picosecond operation, multiplexing, and wavelength translation is discussed.