Plasmonic Dipole and Quadrupole Scattering Modes Determine Optical Trapping, Optical Binding, and Swarming of Gold Nanoparticles

Laser trapping at an interface provides a unique platform for assembling novel multiparticle-based optical matter that extends well beyond the irradiated area. Optical binding, resulting from the resonantly scattered photons by gold nanoparticles through the dipolar scattering mode, serves as the primary force for supporting the cohesion of the particles in these optically induced assemblies, which is interpreted in view of the formation of an optical binding network. Unfortunately, the dipole scattering mode is restricted to a narrow range of experimental conditions, limiting its use to specific trapping laser wavelengths and particle sizes. To address this limitation, exploring higher multipole scattering modes, such as the quadrupole, could provide a broader range of experimental conditions. In this work, we will describe how the higher quadrupole scattering mode influences the formation of optical binding and the possibility of extending the optical potential outside the irradiated area for constructing large optically induced assemblies.