Mid-infrared silicon metasurfaces for near-field enhancement of molecular fingerprints

Mid-infrared dielectric metasurfaces are promising promising fundamental building blocks for integrated sensing with high sensitivity and compositional selectivity. We have designed and fabricated a silicon metasurface with resonance properties in the 4 ~ 5 μm mid-infrared region. Benchmark FTIR characterizations on solutions of tungsten hexacarbonyl molecules showed a detection limit at 1 mg/mL, without any surface functionalization. We further rationalize the detection limit of the molecules-nanostructure open interface with volume field enhancement analysis. Our results show that mid-infrared silicon metasurfaces may be a suitable platform for potential integration with microfluidic for in-vivo detection.