Focusing of light by negative refraction in a photonic crystal slab superlens on silicon-on-insulator substrate

We experimentally demonstrate the light focusing by negative refraction in a photonic crystal slab superlens at wavelengths lambda of 1.26-1.42 mu m. The photonic crystal slab was fabricated on silicon-on-insulator substrate with an interface structure optimized for low reflection and diffraction losses. The light focusing in the photonic crystal slab was clearly observed through the intentional out-of-plane radiation or scattering of guided light in the slab. The minimum focused spot width was limited to 1.8 mu m (1.4 lambda) owing to aberrations. The focusing characteristics were in good agreement with those obtained from photonic band and finite-difference time-domain analyses. (c) 2006 Optical Society of America.