Focusing surface waves with an inhomogeneous metamaterial lens.

We propose a new type of surface wave lens that is made of a circular in-plane inhomogeneous metamaterial slab and numerically demonstrate its capability to focus surface waves at optical frequencies. This approach can achieve a smaller focal spot size than the previously demonstrated Ag plasmonic lens. The use of inhomogeneous metamaterials is to decrease the high losses that are usually associated with metamaterials that support large surface k vectors by reducing the propagation distance in high loss metamaterials.