Polarization-insensitive terahertz array-induced transparency in diffractively coupled metasurface of embedded square lattice

Most of terahertz lattice-induced transparency behaviors are investigated under the lattice modes matching the plasmonic modes. Alternatively, we propose terahertz polarization-insensitive array-induced transparency effect due to diffractive coupling in between two collective eigenmodes of meta-atoms on sublattice-sites in the metasurface of embedded square lattice. Aforementioned two collective eigenmodes destructively interfere each other so as to induce a transparency window in frequency spectrum. A large positive group delay (30 ps) is foreseen in the vicinity of the induced transparency window (0.37 THz), where the electric susceptibility is zero. Our finding manifests a new design of terahertz polarization-insensitive slow light device.