Surface-mode enhanced photonic-crystal nano-imaging observed by a scanning near-field optical microscope

In this paper, we experimentally demonstrate the sub-wavelength loss-less nano-imaging effect achieved by the surface-mode coupling in a negative refraction silicon photonic crystal at a wavelength of 1100 nm. The surface mode and nano-imaging effect of the photonic crystal are experimentally studied with a scanning near-field optical microscope. The thickness and the wavelength dependence of the full width at half maximum of the focal spot reveal a direct evidence of the surface-mode enhanced nano-imaging effect, which is consistent with the simulation. As a consequence, a focal spot with a lateral resolution of λ/3 at the predicted wavelength has been achieved.