Comparison of three nonlinear interferometric optical switch geometries

We present an experimental study of ultrafast all-optical interferometric switching devices based upon a resonant nonlinearity in a semiconductor optical amplifier (SOA). We experimentally compare three configurations: one based upon a Sagnac interferometer and the other two based upon Mach-Zehnder interferometers. By using picosecond pulses, we characterize the switching window of the three devices in terms of both temporal width and output peak-to-peak amplitude. These results are found to be in close agreement with a previously developed theoretical model. Since these nonlinear interferometric switches use an active device as the nonlinear element, relatively low control pulse energy is needed to perform switching as compared to other techniques. As a result, these optical switches are practical for all-optical demultiplexing and ultrafast optical sampling for future lightwave communication systems.