Quasi-BIC-empowered integrated sensing dielectric metasurface for molecular fingerprint retrieval and chiral detection

Abstract

Precise detection and classification of chiral enantiomers are essential for pharmaceutical development and disease diagnosis. Nanophotonics provides a promising approach enhancing the light-matter interaction and detecting intrinsic weak chiroptical signals. However, the use of separate platforms for molecular concentration detection and chiral identification often impedes system integration. Here, we propose an integrated sensing dielectric metasurface that enables both surface-enhanced infrared absorption (SEIRA) and surface-enhanced vibrational circular dichroism (SEVCD) sensing. The metasurface features quasi-bound states in the continuum (quasi-BIC) resonances with tunable and high quality (Q) factors in the mid-infrared (MIR) region. Importantly, a switchable superchiral field can be generated under off-axis linear polarization by adjusting the period aspect ratio of the unit cell, achieving a volume-averaged chirality enhancement of 195-fold. Coating the metasurface with chiral Thalidomide demonstrates its capability for molecular detection, with a 9-order increase in absorbance and over 160-fold enhancement in VCD signals. This work presents a high-performance platform for function multiplexing of broadband fingerprint retrieval and chiral identification, paving the way for advancements in chemical applications and biomedical diagnostics.