Magnetochiroptical nanocavities in hyperbolic metamaterials enable sensing down to the few-molecule level

William O F Carvalho; Osvaldo N Oliveira Jr; J R Mejía-Salazar

doi:10.1063/5.0183806

Magnetochiroptical nanocavities in hyperbolic metamaterials enable sensing down to the few-molecule level

J Chem Phys. 2024 Feb 21;160(7):071104. doi: 10.1063/5.0183806.

Authors

William O F Carvalho¹, Osvaldo N Oliveira Jr¹, J R Mejía-Salazar²

Affiliations

¹ Sao Carlos Institute of Physics, University of Sao Paulo, CP 369, 13560-970 São Carlos, SP, Brazil.
² National Institute of Telecommunications (Inatel), Santa Rita do Sapucaí, MG 37540-000, Brazil.

PMID: 38380755
DOI: 10.1063/5.0183806

Abstract

In this work, we combine the concepts of magnetic circular dichroism, nanocavities, and magneto-optical hyperbolic metamaterials (MO-HMMs) to demonstrate an approach for sensing down to a few molecules. Our proposal comprises a multilayer MO-HMM with a square, two-dimensional arrangement of nanocavities. The magnetization of the system is considered in polar configuration, i.e., in the plane of polarization and perpendicular to the plane of the multilayer structure. This allows for magneto-optical chirality to be induced through the polar magneto-optical Kerr effect, which is exhibited by reflected light from the nanostructure. Numerical analyses under the magnetization saturation condition indicate that magnetic circular dichroism peaks can be used instead of reflectance dips to monitor refractive index changes in the analyte region. Significantly, we obtained a relatively high sensitivity value of S = 40 nm/RIU for the case where refractive index changes are limited to the volume inside nanocavities, i.e., in the limit of a few molecules (or ultralow concentrations), while a very large sensitivity of S = 532 nm/RIU is calculated for the analyte region distributed along the entire superstrate layer.