Focusing by planoconcave lens using negative refraction

We demonstrate focusing of a plane microwave by a planoconcave lens fabricated from a photonic crystal having a negative refractive index and left-handed electromagnetic properties. An inverse experiment, in which a plane wave is produced from a source placed at the focal point of the lens, is also reported. A frequency-dependent negative refractive index, n ( ω ) < 0 is obtained for the lens from the experimental data which match well with that determined from band structure calculations.