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.