Nonlinear switching behaviours in a compact all-semiconductor optical-amplifier Sagnac interferometer device

Nonlinear switching effects in a GaAs-AlGaAs all-semiconductor optical-amplifier loop device with a multimode interference waveguide amplifier (MMIWA) for closing the loop was investigated experimentally and numerically. The miniaturized device, designed to imitate a nonlinear optical loop mirror (NOLM), has a latency more than one hundred times smaller than that of a NOLM. Also, because it used an MMIWA for replacing a coupler in a conventional NOLM, its operation was quite different from that previously reported. In CW signal operation, the nonlinear switching behaviour resulted from the combined effect of nonlinear coupling in the MMIWA and the amplification and lateral field redistribution of the signal through the loop structure. Efficient self-switching and cross-polarized switching were observed. Numerical simulations showed consistent trends in varying device parameters.