Nanophotonic-Enhanced\nThermal Circular Dichroism for\nChiral Sensing

Circular dichroism (CD) can distinguish the handedness\nof the chiral\nmolecules. However, it is typically very weak due to vanishing absorption\nat low molecular concentrations. Here, we suggest thermal CD (TCD)\nfor chiral detection, leveraging the temperature difference in the\nchiral sample when subjected to right- and left-circularly polarized\nexcitations. The TCD combines the enantiospecificity of CD with the\nhigher sensitivity of thermal measurements while introducing new opportunities\nin the thermal domain that can be synergistically combined with optical\napproaches. We propose a theoretical framework to understand the TCD\nof individual and arrays of resonators covered by chiral molecules.\nTo enhance the weak TCD of chiral samples, we first used individual\ndielectric Mie resonators and identified chirality transfer and self-heating\nas the underlying mechanisms giving rise to the differential temperature.\nHowever, inherent limitations imposed by the materials and geometries\nof such resonators make it challenging to surpass a certain level\nin enhancements. To overcome this, we suggest nonlocal thermal and\nelectromagnetic interactions in the arrays. We predict that a combination\nof chirality transfer to Mie resonators, collective thermal effects,\nand optical lattice resonance could, in principle, offer more than\nfour orders of magnitude enhancement in TCD. Our thermonanophotonic-based\napproach thus establishes key concepts for ultrasensitive chiral detection.