Broadband efficient modulation of light transmission with high contrast using reconfigurable VO2 diffraction grating

Ultra-compact dynamically reconfigurable modulation of optical transmission has been widely studied by using subwavelength-spaced resonant metasurface structures containing reconfigurable optical materials. However, it has been difficult to achieve high transmissivity, large modulation depth, and broad bandwidth simultaneously with the conventional resonance-based metasurface schemes. Here, we propose a reconfigurable phase-transition diffractive grating, made of thick VO 2 ridge waveguides, for achieving the above-mentioned three goals simultaneously in the near-infrared range. Based on the large dielectric-to-plasmonic transition characteristic of VO 2 in the near-infrared range, diffraction directivity of dual-VO 2 ridge waveguide is designed to be tuned by thermally driven phase transition of VO 2 for transverse electrically polarized illumination. Then, the diffractive VO 2 ridge waveguide grating composed of the periodically arranged dual VO 2 ridge waveguides is designed with on-state efficiency around 0.3 and minimum modulation depth about 0.35 over a broad bandwidth of 550 nm (1100-1650 nm). The working principle and excellent modulation performance are thoroughly verified through numerical and experimental studies.