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Dielectric metasurfaces have made significant advancements in the past decade for enhancing light–matter interaction at the nanoscale. Particularly, bound states in the continuum (BICs) based on dielectric metasurfaces have been employed to enhance nonlinear harmonic generation. However, conventional nonlinear metasurfaces are typically fixed in their operating wavelength after fabrication. In this work, we numerically demonstrate tunable third harmonic generation (THG) by integrating a dielectric metasurface with the phase-change material Ge2Sb2Te5 (GST). The hybrid phase-change metasurface can support two BICs with different electromagnetic origins, which are transformed into two high-Q quasi-BICs through the introduction of structural asymmetry. The two quasi-BICs are selectively excited by controlling the polarization of incident light, and their wavelengths are tunable due to the phase transition of GST. Notably, the efficiency of THG is significantly enhanced at the fundamental wavelengths corresponding to the two quasi-BICs, and the operating wavelength for THG enhancement can be dynamically tuned through the GST phase transition. Furthermore, the wavelength of THG enhancement can be further tuned by manipulating the polarization of pump light. Additionally, a high-Q analog of electromagnetically induced transparency is numerically achieved through the interaction between a low-Q Mie resonance and a quasi-BIC mode, which also improves the THG efficiency. The high-Q polarization-controlled hybrid phase-change metasurface holds promise for applications in dynamically tunable nonlinear optical devices.

Abstract Mimicking biological proton pump phenomenon to achieve stimulus‐responsive proton conduction behavior has received long‐term attention. The Pa@Zn‐MOF (Pa = photoacids) composites are successfully prepared through adsorption photoacid in Zn‐MOF, then, the composites are mixed into poly(vinyl alcohol) (PVA) to fabricate hybrid membranes Pa@Zn‐MOF‐PVA. When the hybrid membrane is activated through 375 nm violet light at room temperature, the value of proton conductivity after illumination is always superior to that before light irradiation. This phenomenon is attributed to the light‐induced ring‐closing reaction of the photoacid molecules to give the spiro‐forms (SPs) along with an abundant release of protons. The released protons jump into hydrogen bond networks and conveniently accelerate proton transport, resulting in higher proton conductivity. This is a noteworthy demonstration of dynamic control over proton conduction in composite membrane materials by adsorption of photoacid molecules in metal–organic framework.