Anomalous optical resonance on supramolecularly chiral metaspheres with a swirl topology

Abstract

The optics of topological structures have progressed, with the expectation of unprecedented spatiotemporal control of light. Micrometre-scale spheres with a mesoscopic molecular order, as represented by liquid crystalline (LC) droplets, occupy a unique position owing to the prominent appearance of a nontrivial topological surface. However, because of the lack of material rigidity, comprehensive studies on the optical impacts arising from topological spherical textures have not yet been achieved. Here, we show mechanically and optically robust chiral polymer microspheres with mesoscopic supramolecular swirl textures that display anomalous optical resonance behaviours. Spatially resolved hyperspectral camera imaging reveals that the whispering gallery modes (WGMs) on the metasphere surface are azimuthally anisotropic and localize along a diagonal path in an asymmetric manner. Reconstructed polarized fluorescence microscope images clearly visualize the swirl arrangement of polymers at the surface, which explains the azimuthally selective WGMs and their wavelength dependency. These findings expand two-dimensional metasurface studies to quasi-three-dimensional non-Euclidean planes and open up the possibility of anisotropic control of light and directional radiation of WGM lasers.