On the Power-Bandwidth Trade-off in Bistable Photonic Switches

Low power operation and high speed have always been desirable in applications such as data processing and telecommunications. While achieving these two goals simultaneously, however, one encounters the well-known power-bandwidth trade-off. This is here discussed in a typical bistable switch based on a two-dimensional photonic crystal with Kerr type nonlinearity. The discussion is supported by the nonlinear finite difference time domain (FDTD) simulation of a direct coupled structure with a home-developed code. Two cases of working near resonant and off-resonant are simulated to compare the power and the speed of the device in the two cases. It is shown that working near-resonance reduces the power levels at the expense of reducing the settling time, i.e. the bandwidth limitation. The hystersis loops for the device are also obtained with both coupled-mode theory and quasi-steady state FDTD simulation. The impact of operating near/off resonance on the shape of the hystersis loop is discussed as a confirmation of the previous results. Alternative ways of reducing the power while saving the bandwidth are also examined. The discussion is general and one may investigate other optical switches to obtain similar results.