The nonlinear effect from the interplay between the nonlinearity and the supercollimation of photonic crystal

The authors theoretically and numerically investigate the beam propagation near the supercollimation frequency s 0 in a photonic crystal made of nonlinear material. Since the value and sign of the equal-frequency-contour curvature which dominates the beam behaviors can be nonlinearly tuned near s , a kind of nonlinear effect is generated. The envelope equation with unique form is also obtained. Beam-control mechanisms are theoretically predicted and observed in numerical experiments, such as tunable collimation, tunable beam-divergence angle, and self-lock of collimation. These mechanisms can be utilized to function as fiber, lens and coupler, or to design photonic devices. © 2007 American Institute of Physics. DOI: 10.1063/1.2739413