Improvement of power coupling in a nonlinear photonic crystal directional coupler switch

In this paper we try to improve the control signal coupling for a two dimensional all-optical photonic crystal switch, so as to minimize the unwanted control signal reflection. The switch is based on a directional coupler in a triangular lattice of GaAs rods with Kerr optical nonlinearity. Not only can impedance matching affect the characteristics of a switch, but also the unwanted reflection due to poor impedance matching can be a real nuisance in integrated circuits. Since the control signal has usually a low group velocity, matching in control path has also a significant role in reducing operational power. Two dimensional FDTD and PWE methods are used for analyzing the structures. Simulation results show improvement in switching speed and operational power for the proposed structure. The low reflection coefficient for the control signal makes the switch suitable for all-optical integration purposes.

Research highlights▶ An all-optical photonic crystal switch based on a directional coupler is proposed. ▶ The Kerr-type nonlinearity of GaAs rods causes the switching phenomenon. ▶ Some suggestions are made in order to improve the control signal impedance matching. ▶ Time-domain simulations are used to study the effect of matching on switching speed. ▶ An analytical relationship between signal power and switching parameters is derived.