Attoliter Mie Void Sensing

TL;DR

This paper introduces Mie void nanostructures in high-index dielectrics for highly sensitive, small-volume refractive index sensing, offering full modal access and potential for biological applications.

Contribution

It demonstrates the use of air-confined Mie voids for refractive index sensing with attoliter volumes and high sensitivity, advancing nanophotonic sensing technology.

Findings

Refractive index sensitivity of ~400 nm per RIU.

Detection of RI changes as small as 6.9 x 10^-4.

Sensor volume as small as 850 attoliters.

Abstract

Traditional nanophotonic sensing schemes utilize evanescent fields in dielectric or metallic nanoparticles, which confine far-field radiation in dispersive and lossy media. Apart from the lack of a well-defined sensing volume that can be accompanied by moderate sensitivities, these structures suffer from the generally limited access to the modal field, which is key for sensing performance. Recently, a novel strategy for dielectric nanophotonics has been demonstrated, namely, the resonant confinement of light in air. So-called Mie voids created in high-index dielectric host materials support localized resonant modes with exceptional properties. In particular, due to the confinement in air, these structures benefit from the full access to the modal field inside the void. We utilize these Mie voids for refractive index sensing in single voids with volumes down to 100 attoliters and sensitivities on the order of 400 nm per refractive index unit. Taking the signal-to-noise ratio of our measurements into account, we demonstrate detection of refractive index changes as small as 6.9 x 10-4 in a defined volume of just 850 attoliters. The combination of our Mie void sensor platform with appropriate surface functionalization will even enable specificity to biological or other analytes of interest, as the sensing volumes are on the order of cellular signaling chemicals of single vesicles in cellular synapses.