Full-Stokes polarization photodetector based on the hexagonal lattice chiral metasurface

A hexagonal lattice silicon (Si) metasurface formed by the displacement of two mirrored isosceles trapezoid blocks in opposite directions is integrated into an InGaAs/InP photodetector to sense the circularly polarized light, whose optical properties mainly are controlled by the Fabry-Perot (FP) cavity mode supported in the air slit called the Tunnel A. The Si metasurface can also be equivalent to the combination of the electric quadrupole (EQ) and the magnetic quadrupole (MQ) for the right circularly polarized (RCP) mode and the magnetic quadrupole for the left circularly polarized (LCP) mode. The external quantum efficiency of the circular polarization photodetectors is 0.018 and 0.785 for the RCP and LCP incidence, respectively. In addition, the full Stokes pixel based on the six-image-element technique can almost accurately measure arbitrary polarized light at 1550 nm operation wavelength, whose errors of the degree of linear polarizations (Dolp) and the degree of circular polarizations (Docp) are less than 0.01 and 0.15, respectively.