Great efforts have been made to explore the Fano resonances in two-dimensional transition metal dichalcogenides (TMDs) coupled with plasmonic nanostructures in the visible region. However, the intrinsic losses of metallic materials and the TMD exciton linewidths of at least tens of meV at room temperature (RT) inevitably limit the achievable Q factor of the Fano resonance. Herein, we integrate a monolayer WS2 with single hydrogenated amorphous silicon nanospheres (SiNSs) in water. Pronounced asymmetric Fano resonances with a Q factor up to 104 at the A exciton frequency (2.0 eV) are observed at RT. Fano fitting and modified coupled-mode theory both suggest a decreased A exciton linewidth of ~10 meV as compared to the reported value (~60 meV). This is attributed to the enhanced decay of trion in WS2. Moreover, directional Fano coupling can be achieved by exciting the hybrid from the SiNS or WS2 side, providing more possibilities in device implementation.
Mid-infrared (MIR) spectroscopy is a powerful technique for molecular sensing through identifying the vibrational fingerprints of analyte molecules. However, the sensing efficiency drops dramatically at the nanoscale due to the poor interaction between MIR light and nanometric molecules. Here we exploit the MIR magnetic dipole resonance in a single silicon Mie antenna to demonstrate enhanced molecular sensing. We show that an ultra-sensitive measurement of a sub-10-nm PMMA layer can be achieved by positioning the antennas at the anti-node of a standing wave, which enables light-matter interactions under enhanced resonance conditions. Our results provide a new approach towards high-sensitivity MIR molecular sensing based on a miniaturized photonic platform.
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