Ultrafast spatiotemporal chiroptical response of dielectric and plasmonic nanospheres

We theoretically examine the spatiotemporal evolution of enhanced near-field optical chirality (OC) in both plasmonic and dielectric nanospheres when excited by ultrashort optical pulses. We demonstrate distinct spatiotemporal variations in near-field OC arising from the differing natures of plasmonic and dielectric resonators. The electric dipole resonant plasmonic nanosphere generates instantaneous near-field OC that relies on the interference between incident and scattered (induced) fields. Conversely, a resonant dielectric nanosphere sustains long-lasting OC even after the incident field diminishes due to the scattered field from resonant electric and magnetic dipole modes. We further demonstrate the control over the near-field OC using vector beams. Our work opens up opportunities for spatiotemporal control of nanostructure-enhanced chiral-light matter interactions.