Magnetically tunable chiral near-fields in magneto-plasmonic nanocavities for giant enhancement in enantioselective biosensing.

Chiral near-fields are crucial for chiroptical sensing and nanophotonic applications but are often limited by weak intensity and confinement. Here, we numerically investigate a magneto-plasmonic nanocavity comprising a plasmonic (gold) holey disk (HD) on a magnetic Ce:YIG substrate. The magneto-plasmonic HD exhibits approximately 3-fold enhancement of chiral near-field intensity compared with a bare plasmonic HD. Furthermore, chiral near-fields of magneto-plasmonic HD can be actively tuned by an external magnetic field. The giant enhancement in chiral near-fields leads to a biomolecular CD enhancement factor of 106. Moreover, by systematically varying the molecular chirality parameter, the proposed magneto-plasmonic HD exhibits an approximately 150-fold larger analyte-dependent optical response than the bare HD. The results demonstrate the potential of magneto-plasmonic nanocavities for tunable and highly sensitive chiral biosensing.