SHG studies of plasmon dephasing in nanoparticles

The decay time of the particle plasmon (dephasing of the coherent electron plasma oscillation) in Au and Ag nanoparticles is measured by a second-order nonlinear optical autocorrelation method in the fs regime. In order to prevent electron heating, the energy fluence from the fs pulses at the sample is kept below 0.5 mu J/cm(2). The necessary high SHG efficiency is obtained by nanoparticles produced by an electron beam lithographic method, which enables us to fabricate a two-dimensional array of nearly identical, parallel oriented particles of designed shape without centrosymmetry, essential for high SHG efficiency and the tuning of the plasmon resonance to the driving laser wavelength of 780 nm.