Terahertz metal grid polarizer with bridges on quartz substrate

Abstract

The metal wire-grid polarizer is a venerable device that is used on radiation throughout the electromagnetic spectrum. It usually consists of a 1D-periodic array of subwavelength metallic wires in free space or mounted on a low-loss dielectric substrate, the plane of the grid being oriented perpendicular to the propagation direction. Herein is presented a new structure, a subwavelength wire-grid polarizer for the terahertz region that acts not only as a wideband polarizer but also as a transparent electrode. This function is achieved by the addition of periodically placed metallic bridges that connect the parallel metal wires of the polarizer. The bridges allow for the uniform distribution of an electrostatic potential over all wires while maintaining the polarizing functionality of the metal wire grid polarizer. Full-wave electromagnetic simulations were performed on the device. The transmittance was computed in both perpendicular polarization and parallel polarization from 100 to 4000 GHz, and the extinction ratio was calculated across the same range. Furthermore, fill-factor studies were performed to understand how device performance is affected by varying slot width and bridge length, as well as bridge offset. The simulation results showed extraordinary optical transmission through the device for perpendicular polarization, creating excellent transmittance and extinction ratios over the frequency range. The perpendicular polarization transmittance and extinction ratio at 1 THz was calculated to be -1 dB and -36 dB respectively. Meanwhile, the bridges allow the device to behave like a DC electrode.