Improvement of 2-D Luneburg Lens Focusing Ability with the Aid of Conformal Graphene Strip

We consider the plane wave focusing characteristic of layered cylindrical Luneburg lens equipped with conformal strip of graphene, in the H-polarization case. The surface impedance of the strip is characterized with the aid of the quantum-physics Kubo formalism. We use mathematically accurate full-wave analytical regularization technique, which is based on the inversion of the problem static part. This guarantees the convergence of the resulting numerical algorithm. We compute the focusing ability of a microsize lens as a function of the frequency in a wide range up to 60 THz. This analysis shows that a graphene strip, placed into the focal area of the Luneburg lens, enhances its focusing ability at the plasmon-mode resonance frequency proportionally to the quality factor of the plasmon mode of the strip.