Half-wave plate based on a birefringent metamaterial in the visible range

In this paper, a half-wave plate (HWP) based on a birefringent metamaterial is numerically designed to operate in the visible range. The proposed structure consists of an array of double-pattern perpendicular rectangular apertures (RAA) engraved into opaque silver film deposited on a glass substrate. One of the apertures is glass filled. The operating principle is based on the excitation and the propagation of one guided mode inside each aperture but with different effective indices. After transmission, a phase difference is obtained between the two transverse components, which value depends mainly on the metal thickness. We have investigated the simplest configuration using a homemade code based on the finite difference time domain method to design a half-wave plate with optimized efficiency resulting in transmission coefficient of more than 60% together with a birefringence of 2.1 at an operation wavelength of 737nm. This kind of anisotropic metasurfaces promises a wide range of applications in integrated photonics.