Reconfigurable metasurface for circular dichroism and a polarization converter

We propose a photosensitive silicon terahertz reconfigurable metasurface composed of a silicon substrate, a benzocyclobutene dielectric layer, a U-shaped silicon rod layer, and a metal open square ring layer. When the photosensitive silicon conductivity is σ Si = 5 × 10 5 S/m, the metasurface exhibits strong circular dichroism under the incidence of a circularly polarized wave, with a circular dichroism (CD) value as high as 1 at frequency 4.03 THz. At this time, under linearly polarized wave incidence, the metasurface exhibits linear dichroism, with linear dichroism (LD) values of 0.71, -0.57, and 0.33 at frequencies of 6.76 THz, 7.45 THz, and 8.39 THz, respectively. While the photosensitive silicon conductivity is σ Si = 5 × 10 4 S/m, the metasurface displays a circular-circular polarization converter, and the polarization conversion rate (PCR) is more than 0.9 in the 2.92-6.04 THz and the 2.94-5.68 THz band.