Hybrid plasmonic Bound State in the Continuum entering the zeptomolar biodetection range
arxiv(2024)
摘要
Optical Bound States in the Continuum are peculiar localized states within
the continuous spectrum that are unaffected by any far-field radiation and
intrinsic absorption, therefore possessing infinite mode lifetime and Q-factor.
To date they have been widely studied in dielectric structures whereas their
exploitation in lossy media, i.e. plasmonic nanostructures, still remains a
challenge. Here, we show the emergence of a hybrid BIC state in a 2D system of
silver-filled dimers, quasi-embedded in a high-index dielectric waveguide. The
hybrid BIC onset is found to be highly dependent on the bare modes' spectral
and spatial overlap, but particularly on the plasmonic field's intensity. By
tailoring the hybridizing plasmonic/photonic fractions we select an ideal
coupling regime for which the mode exhibits both, high Q-factor values and
strong near-field enhancement tightly confined in the nanogap and a
consequently extremely small modal volume. We demonstrate that this optical
layout can be exploited in a proof-of-concept experiment for the detection of
TAR DNA-binding protein 43, which outperforms the sensitivity of current
label-free biosensing platforms, reaching the zeptomolar range of
concentration.
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