Photothermal Circular Dichroism Induced by Plasmon Resonances in Chiral Metamaterial Absorbers and Bolometers

Chiral photochemistry remains a challenge because of the very small asymmetry in the chiro-optical absorption of molecular species. However, we think that the rapidly developing fields of plasmonic chirality and plasmon-induced circular dichroism demonstrate very strong chiro-optical effects and have the potential to facilitate the development of chiral photochemistry and other related applications such as chiral separation and sensing. In this study, we propose a new type of chiral spectroscopy – photothermal circular dichroism. It is already known that the planar plasmonic superabsorbers can be designed to exhibit giant circular dichroism signals in the reflection. Therefore, upon illumination with chiral light, such planar metastructures should be able to generate a strong asymmetry in their local temperatures. Indeed, we demonstrate this chiral photothermal effect using a chiral plasmonic absorber. Calculated temperature maps show very strong photothermal circular dichroism. One of the structures computed in this paper could serve as a chiral bolometer sensitive to circularly polarized light. Overall, this chiro-optical effect in plasmonic metamaterials is much greater than the equivalent effect in any chiral molecular system or plasmonic bio-assembly. Potential applications of this effect are in polarization-sensitive surface photochemistry and chiral bolometers.