Anomalous switching in dispersive optical bistability

The response of a dispersive bistable optical device to an instantaneous change in the driving field is studied theoretically. The device is shown to respond in ways that are significantly different from absorptive bistability. Threshold for switching between stable states do not occur at the same values as in the quasi-steady-state. Instead, anomalous thresholds are predicted. It is suggested that this anomalous switching behaviour may place limitations on the possible device applications. It also implies that dispersive bistable devices may be switched merely by an appropriate change of the phase of the driving field.