Tunable Mid‐Infrared Phase‐Change Metasurface

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 Ge2Sb2Te5. 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. A metasurface operating in total reflection mode may complicate the optical setup. Here, a mid‐infrared (M‐IR) tunable metasurface operating in transmission mode is experimentally demonstrated. The resonant frequency of the filter is tuned by nonvolatile phase transitions to Ge2Sb2Te5 permittivity. The design paves the way for on‐chip M‐IR multispectral interferometry and provides an approach for compact real‐time M‐IR measurements.