Fabrication and laser-assisted modification of the Ag particles ensembles supporting quadrupole plasmon oscillations

摘要

A combination of physical vapour deposition, thermal annealing and laser irradiation was used to tailoring of the silver nanoparticles array on a quartz substrate. This method for control of optical properties is exploit 355-nm pulsed laser irradiation. Experimental separation of three main overlapped plasmonic modes, dipoles that correspond to parallel and perpendicular oscillations and quadrupole with maximum wavelength at 355 nm, in extinction spectrum of Ag nanoparticles ensembles was demonstrated. It was shown that the laser post-processing of the nanoparticles array in spectral vicinity of the quadrupole band leads to selective ablation of nanometer particles. This process resulted to close-packing of the nanoparticles ensemble on top of the substrate causing, in turn, formation of 'hot-spots' and absorptive bands in the near IR range. Using the laser postprocessing as persistent spectral hole burning technique, a dephasing time of quadrupole plasmon resonances was experimentally defined for the first time.