Beam steering in planar-photonic crystals: from superprism to supercollimator

We utilize the anomalous dispersion of planar-photonic crystals (PhCs) near the dielectric band edge to control the wavelength-dependent propagation of light. Light beams with up to 20° divergence were collimated over a 25-nm (1285 nm to 1310 nm) bandwidth using a triangular lattice. The "superprism" phenomenon is demonstrated in the same configuration, simply by tuning the wavelength. Sources of loss are discussed. Both the plane-wave expansion calculation and finite-difference time-domain simulation match well with the experimental results. This is the first experimental demonstration of self-collimating phenomena in a PhC configuration.