Dynamic Optical Spin Hall Effect in Chitosan-Coated All-Dielectric Metamaterials for a Biosensing Platform

Abstract

The optical spin Hall effect, which describes the spin-dependent and transverse shift of light, has been steadily investigated with the development of sensing applications such as polarization-dependent sensors, material interface analysis, and refractive index spectroscopy. However, practical optical spin Hall effect sensing platforms have not been reported since the previous reports have only focused on passive platforms. Here, we propose a biosensing platform using chitosan-coated all-dielectric metamaterials, which can detect the relative humidity of the surroundings by analyzing the displacement of the spin Hall effect. The chitosan coating provides a high sensitivity of relative humidity with a dynamic optical spin Hall effect in all-dielectric metamaterials. The maximum displacement of the split beam is calculated as 350 nm when the relative humidity changes by 60%, resulting in 8.75 nm shift per 1% of relative humidity change. This mechanism can be further exploited for a biosensing platform since the chitosan-coated all-dielectric metamaterials are biocompatible, biodegradable, and hydrophilic. Considering the chitosan-coated all-dielectric metamaterials have high feasibility with low-cost, high-throughput nanoimprinting methods, the dynamic optical spin Hall effect-based metamaterials will be a candidate of a promising real-time and ultra-sensitive sensing platform for detecting biomolecules.