Nanophotonic-Enhanced Thermal Circular Dichroism for Chiral Sensing

TL;DR

This paper introduces Thermal Circular Dichroism (TCD) enhanced by nanophotonics for highly sensitive chiral molecule detection, combining thermal and optical methods to significantly improve detection sensitivity.

Contribution

It presents a theoretical framework and proposes nanophotonic resonator arrays to amplify TCD signals, enabling ultrasensitive chiral sensing beyond current limitations.

Findings

Theoretical model of TCD in resonator systems.

Identification of mechanisms for differential heating.

Prediction of over 10,000-fold enhancement in TCD using arrays.

Abstract

Circular Dichroism (CD) can distinguish the handedness of chiral molecules. However, it is typically very weak due to vanishing absorption at low molecular concentrations. Here, we suggest Thermal Circular Dichroism (TCD) for chiral detection, leveraging the temperature difference in the chiral sample when subjected to right and left-circularly polarized excitations. The TCD combines the enantiospecificity of circular dichroism with the higher sensitivity of thermal measurements, while introducing new opportunities in the thermal domain that can be synergistically combined with optical approaches. We propose a theoretical framework to understand the TCD of individual and arrays of resonators covered by chiral molecules. To enhance the weak TCD of chiral samples, we first use individual dielectric Mie resonators and identify chirality transfer and self-heating as the underlying mechanisms giving rise to the differential temperature. However, inherent limitations imposed by the materials and geometries of such resonators make it challenging to surpass a certain level in enhancements. To overcome this, we suggest nonlocal thermal and electromagnetic interactions in arrays. We predict that a combination of chirality transfer to Mie resonators, collective thermal effects, and optical lattice resonance could, in principle, offer more than 4 orders of magnitude enhancement in TCD. Our thermonanophotonic-based approach thus establishes key concepts for ultrasensitive chiral detection.