Nonlinear spatial switching and beaming of light from photonic-crystal waveguides

In our study, we extend the beaming theory in two directions. First, we analyze, by the finite-difference time-domain numerical method, different ways to enhance the directional emission from photonic-crystal waveguides and demonstrate that the substantial enhancement of the light emission can be achieved by adjusting the input wavelength, using a positive surface corrugation, increasing the refractive index of the surface layer, and inducing a near-surface defect mode. We optimize the input wavelength, the corrugation at the surface, and the refractive index of the surface layer and demonstrate the substantial enhancement of the light emission and improved beaming effect. Second, we examine dynamic, all-optical control of the directed emission, leading to an effective free-space switching of the light.