Design of a metallic half-wave plate based on birefringent metamaterial for applications in the visible range

The main objective of this study is to design an artificial birefringent metamaterial to operate within the visible spectrum. This plate consists of a C-Shaped Aperture Array (CSAA) engraved into a silver metallic film deposited on a glass substrate. The artificial anisotropy of this structure is generated by the simultaneous excitation of two guided modes with different effective indices. These excitations occur within the same C-Shaped aperture, at the same wavelength, for two distinct states of orthogonal polarization of the electric field. They propagate at different velocities, resulting in a phase difference Delta phi between the transmitted electric fields. We show that by adjusting the thickness of the silver layer, it is possible to achieve a phase difference of pi corresponding to a Half-Wave Plate (HWP). This design is highly innovative, being more compact and efficient, exhibiting enhanced transmission of T = 75% at a wavelength of lambda = 727nm, with a thickness of H = 146 nm. Such a configuration results in an extraordinary birefringence of Delta n = 2.5.