Reversible Thermal Tuning of High‐Q Non‐Local Lithium Niobate Metasurfaces

Abstract Dynamic control of optical resonances in metasurfaces has become increasingly critical, driven by the growing demand for tunable photonic devices across a wide range of modern nanophotonics applications, including optical switches, displays, and optical communications. Lithium niobate (LN) metasurfaces, featuring a broad transparency window and low optical loss, offer a promising platform for realizing tunable and reconfigurable nanophotonics systems. However, conventional electro‐optic tuning of LN is often limited by high‐voltage requirements and fabrication constraints. In this work, the authors demonstrate reversible thermal tuning of high‐quality factor (high‐Q) guided mode resonances and quasi‐bound states in the continuum (quasi‐BICs) in LN metasurfaces. By employing high‐Q resonances, the thermo‐optic and thermal expansion response is enhanced, achieving modulation of the reflection spectrum from 0 to 1 over an 85 temperature range. At a fixed wavelength, the system exhibits a thermal modulation sensitivity of 1.176% per , allowing for precise and repeatable spectral control. This dual‐channel tuning approach offers precise, reversible control of the optical spectrum. These thermally reconfigurable LN metasurfaces present a robust platform for optical filtering, sensing, and active photonic circuitry. These findings pave the way for thermally reconfigurable metasurfaces, expanding the functional scope of LN‐based nanophotonic devices.