Spatially-resolved insulator-metal transition for rewritable optical gratings

Abstract

Optical relief gratings are usually composed of physical grooves with a constant periodicity, and typically suffer from light scattering, are mechanically fragile and are single function. Here, we develop WO3-based gratings by using a recently reported electron-proton synergistic doping route under ambient conditions. This doping strategy is compatible with conventional ultraviolet photolithography, and we show that it induces a selective insulator-metal phase transition and coloration in WO3, with spatial-resolution up to micron-scale. Due to the electrochromic-induced-contrast, a WO3 volume phase grating without grooves and a WO3 relief grating with tunable periodicity are demonstrated. Both gratings can be rewritten after a reset procedure by annealing in air. Our experiments demonstrate WO3–based gratings and an attractive technique for rewritable oxides. Optical gratings are typically composed of periodic grooves, but these suffer from issues with light scattering and are fragile. Here, a groove-less WO3 grating is demonstrated, which uses electron-proton synergistic doping to spatially tune a rewritable insulator-metal transition and coloration.