Switchable wire-grid polarizer based on phase-change material GST

Wire-grid polarizers, which consist of a one-dimensional periodic metasurface, are convenient polarising elements used in many optical applications.However, these metasurfaces are still incapable of switching the polarisation state of transmitted light without mechanical rotation.This article presents the design of a switchable wire-grid polariser based on a one-dimensional metasurface composed of the phase-change material Ge-Sb-Te (GST).Using the Fourier modal method and genetic-algorithm-based optimisation, we designed a metasurface that transmits two orthogonal linear polarisations of light in different phase states.We demonstrate that the designed metasurface is stable with respect to variations in wavelength and angle of incidence, as well as variations in the geometrical parameters of the metasurface.This concept was verified by measuring the transmission characteristics of a GST metasurface fabricated using magnetron sputtering on a glass substrate.The experimental extinction ratio of the fabricated samples in both polarisation states ranged between 10 and 14~dB, depending on the specific sample.Because the phase transition in GST films can occur on a sub-microsecond timescale, the developed switchable wire-grid polariser offers significant potential for creating a fast, compact polarisation modulator for telecommunication wavelengths.