Focusing optical waves via graded-epsilon-near-zero metalens

A parallel plate plasmonic waveguide is proposed in order to emulate the performance of a permittivity-near-zero metamaterial (ENZ) at optical wavelengths by working near the cut-off of the TE1 mode. It is shown that the ENZ region can be tuned by simply modifying the electrical width of the dielectric spacer of the plasmonic waveguide. Also, a graded index (GRIN) epsilon-near-zero lens working at λ0 = 474.9nm is designed by stacking 51 non-uniform plasmonic parallel plates, demonstrating numerically that this structure may be used to focus optical waves.