High responsivity IR sensing based on reflectometric RF MEMS

Radiofrequency microelectromechanical systems (RF MEMS) integrated with metasurfaces are promising platforms for spectrally selective infrared (IR) sensing. Conventional devices detect IR radiation by tracking resonance frequency shifts. Here, we introduce a reflectometric approach that instead monitors changes in the RF MEMS input impedance and analytically links them to sensing metrics. By coupling a reconfigurable matching network to an RF MEMS resonator, the detector achieves IR responsivities governed by its phase-slope quality factor and tunable to exceptionally high values. Using contour-mode resonators at ambient conditions, we demonstrate responsivities exceeding 11,400 V/W in a 50-Ω readout (>200 A/W), spectral selectivity with a full-width at half-maximum (FWHM) of 0.54 μm at 5.94 μm, noise-equivalent power (NEP) of $~450\mathrm{pW}/\sqrt{\mathrm{Hz}}$ , a ~ 552-μs time constant, and resolve IR power levels down to ~ 740 pW. Reflectometric RF MEMS detectors provide a reconfigurable, spectrally selective, and scalable platform for high-performance on-chip IR spectroscopy and sensing.