Filtering and Modulation from the Infrared to the Terahertz using Phase‐Change Extraordinary Optical Transmission Metasurfaces

Periodic arrays of sub‐wavelength‐scale holes in plasmonic metal films are known to provide resonant transmission peaks via the extraordinary optical transmission (EOT) effect. Active control of the spectral position of such transmission peaks can be obtained by adding a layer of phase‐change material (PCM) to the EOT device. Switching the PCM layer between its amorphous and crystalline states can shift the spectral position of the resonance, enabling potential applications in the fields of active filtering and sensing (e.g., multispectral sensing), and for signal modulation. Here, the design, fabrication, and characterization of active EOT devices are targeted at various important regions of the optical spectrum. Tunable mid‐ and long‐wave infrared optical bandpass filters with potential applications in the area of multispectral sensing are designed and fabricated. The filters are based on the extraordinary optical transmission effect, with active tuning control provided by thermally switchable chalcogenide phase‐change materials (PCMs). Similar devices are also shown to act as useful modulators in the THz waveband.