Beyond the effective index method: improved accuracy for 2D simulations of photonic crystal waveguides

Simulation of photonic structures is a necessary step in the design of devices with tailored optical properties. As 3D simulations are time-intensive, the effective index method (EIM) is widely used to reduce systems to 2D models, including in the design of photonic crystal devices. We show that the EIM is poorly suited to model photonic crystal waveguides, giving inaccurate approximations of group velocity and propagation loss. The proposed effective period method provides significantly more accurate estimations of device behaviour without any increase of computation time.