Optically controlling photonic band gap logic elements

The change in the refractive index of GaAs due to the light-induced generation of nonequilibrium charge carriers is shown to substantially change the transmission of a one-dimensional GaAs/GaAlAs photonic band-gap structure, allowing low-threshold photonic-crystal optical logic gates to be created. Elementary logic operations of the Boolean algebra performed with nonlinear PBG structures, including the biconditional implication, module-two addition, Peirce's arrow, and disjunction, are demonstrated. We show how different logic operations can be performed with the same GaAs/GaAlAs PBG structure at different power densities of logic pulses.