Shortening Veselago lenses using variable photonic crystals

Abstract

A photonic crystal can behave like a medium with a negative effective refractive index within certain frequency ranges. As a result, under these conditions, a photonic crystal slab acts as a Veselago lens, which produces images via inverse propagation. To have low reflection the effective index is usually designed to be −1. However, this implies that the lens is half as thick as the distance between the object and its image. We investigate the possibility of varying the refractive index along the propagation direction from −1 at the interfaces to an effective index with a smaller magnitude in the bulk of the medium in order to shorten the Veselago lens while keeping the reflections from the interfaces low. The hole radius in the photonic crystal is varied over the photonic crystal to produce a varying effective refractive index. We present finite-difference time-domain simulations of a Veselago lens with a varying index, demonstrating that Veselago lenses can be shortened in this way.