Transmissive metasurface focusing elements thinner than a wavelength hold significant promise for replacing conventional free-space components in wavefront and polarization control. Here, we propose an inverse-designed ultrathin terahertz metalens comprising air via-cuboids on a silica wafer. A novel approach that leverages electromagnetically induced transparency (EIT) for ultrathin lens design is presented at the working frequency of 220 GHz. By exploiting the “slow-light” effect associated with EIT, the terahertz metalens is less than 260 μm-thick, and it can focus incident light onto a diffraction-limited spot. A key advantage of this metalens design is the reduction of the aspect ratio to ∼3, which substantially alleviates the fabrication challenges associated with metalenses.
Zeng et al. (Fri,) studied this question.