Nanocoaxial Waveguide Grating as Quarter-Wave Plates in the Visible Range

A geometrical artificial anisotropy can be controlled through polarization and propagation properties of guided modes inside annular nanocavities with elliptical core. In this paper, we theoretically demonstrate the principle of obtaining this anisotropy by exploiting such guided modes. We present the control of this birefringence through an example of a quarter-wave plate exhibiting a transmission of about 83% in the visible range associated with a giant effective birefringence of around Δ
n
= 0.75.