All‐Optical Switching of Structural Color with a Fabry–Pérot Cavity

Fine tuning the optical responses of thin‐film devices is highly attractive for emerging applications, such as optical memories, solar cells, nanophotonics, and photodetectors. Even though thin‐film technology is well established, dynamically switching the optical responses of thin films after fabrication remains challenging because of passive materials and device structures. This work demonstrates an approach for all‐optical switching of structural colors excited by a Fabry–Pérot (FP) cavity inside a metal–dielectric–metal (MDM) thin‐film stack. A low‐loss phase‐change material (PCM), that is, antimony trisulfide (Sb 2 S 3 ), which is embedded in the stack, enables efficient FP cavity resonance in the visible spectrum. 1) Color reflectivity of >60%; 2) multistructural colors using a single MDM cavity; 3) a wide dynamic range of colors of up to ≈220 nm; and 4) a gamut coverage of more than 80% of standard RGB (sRGB) are achieved. The all‐optical switching is realized via the crystallization and reamorphization of Sb 2 S 3 using continuous‐wave and pulsed lasers, respectively. The findings provide a framework for the cost‐effective realization of dynamically responsive thin‐film‐based nanophotonic devices.