Tunable Mid‐Infrared Phase‐Change Metasurface

Abstract The intense light–matter interaction of plasmonic metasurfaces provides an appealing platform for optical sensing. To date, most metasurface sensors are not spectrally tuned. Moreover, they operate in a total reflection mode, which complicates the optical setup. Transmissive tunable filters are therefore desirable. A mid‐infrared (M‐IR) tunable metasurface is described that operates in transmission mode. The resonant frequency of the filter is tuned by nonvolatile phase transitions to the dielectric properties of the chalcogenide material Ge 2 Sb 2 Te 5 . A broad transmittance spectral shift of 500 nm across the M‐IR region is experimentally demonstrated. This shift is in good agreement with finite‐difference time‐domain simulations of the same structure. The design paves the way for on‐chip M‐IR multispectral interferometry and provides a promising approach for compact real‐time M‐IR measurements.