Ultra-Pure Chiral Third Harmonic Generation Enabled by Mie-Resonant Dielectric Dimer

Tailoring chiroptical responses at the nanoscale is crucial for on-chip compact polarization manipulation and enantiomer sensing. Efficient chiral second and third harmonic generation has been successfully demonstrated from bulk materials to metamaterials. Here, pronounced linear and nonlinear circular dichroisms are obtained by rotating a dielectric nanocylinder dimer. It is revealed that the giant chiroptical effects originate from multipolar Mie resonances on the dimer, especially the magnetic dipole resonance. The calculated nonlinear g-factor can reach −1.975 in the visible regime, indicating an ultra-pure chiral third harmonic generation in the ultraviolet band. The presented results open new horizons for enhancing and modulating the linear and nonlinear chiroptical responses of nanostructures and can find potential applications in lasing and sensing.