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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 (Sb2S3), 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 Sb2S3 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.

We demonstrate compact optically pumped microsquare cavity laser on InP-based multiple-quantum-wells material platform. Continuous-wave operation is achieved for microsquare cavity with footprint as small as 4 × 4 μm2. Numerical mode analysis and experimental characterization of the microsquare laser are conducted, and the results are compared with the commonly used microdisk cavity laser fabricated on the same platform. The microsquare laser shows a lower lasing threshold and infers a higher differential efficiency than the microdisk counterpart. The microsquare cavity laser has also sufficiently high quality factor, and higher pumping injection efficiency due to the more evenly distributed field profile as compared to that of the microdisk. Experimental result also shows that the microsquare laser has better temperature stability than the microdisk. These results promise a potential alternative laser structure for on-chip light source applications. [ABSTRACT FROM PUBLISHER]