Near-field observation of beam steering in a photonic crystal superprism

The optical near-field technique is applied to provide a direct experimental observation of the refracted beam propagation inside a photonic crystal structure displaying a superprism effect. The obtained results show a 35 degrees light beam angle deviation for a wavelength variation from 1500 to 1600nm. The experimentally determined beam divergence is in good agreement with modeling predictions and previously performed transmittance experiments. A marked self-collimation propagation over a broad 20nm wide spectral range centered at lambda = 1550 nm is experimentally demonstrated. The developed technique opens promising perspectives for the invisibility cloaking structures investigation. (C) 2011 Optical Society of America