Light-induced torque at multipolar plasmon resonance

Abstract

Light-matter interaction provides a powerful means to control mechanical excitation in the nanoscale. The efficiency of this interaction reaches maximum at optical resonance. By understanding and designing the electromagnetic resonance of nanostructures, we can manipulate the electromagnetic field distribution as desired, with the benefits of enhancing the field strength and squeezing the field spot to be tighter than the diffraction limit. This thesis focuses on the enhanced mechanical effects arising at multipolar plasmon resonance of a subwavelength plasmonic resonator. We perform Finite Difference Time Domain (FDTD) simulation and show that the discrete rotational symmetry of the resonator determines the possible output modes in angular momentum conversion at non-dipolar plasmon resonance. Next, we analyze the efficiency of this conversion for a single, subwavelength nanoparticle in free space. Finally, we calculate the mechanical effects and report that scattering-induced transfer of torque can be unusually enhanced at non-dipolar resonance due to the effects of angular momentum conversion.