Quasi-BIC-enhanced integrated sensing dielectric metasurfaces 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 by enhancing light–matter interaction and detecting weak intrinsic chiroptical signals. However, the use of separate platforms for molecular concentration detection and chiral identification often impedes system integration. Here, we proposed an integrated dielectric metasurface sensor that enabled both surface-enhanced infrared absorption (SEIRA) and surface-enhanced vibrational circular dichroism (SEVCD) sensing. The metasurface featured quasi-bound states in the continuum (quasi-BIC) resonances with tunable, high-quality (Q) factors in the mid-infrared (MIR) region. Importantly, a switchable superchiral field could 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 demonstrated 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 in broadband fingerprint retrieval and chiral identification, paving the way for advancements in chemical applications and biomedical diagnostics.