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-orde r nonlinear optical autocorrelation method in the fs regime. In order to pr event 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 obtaine d by nanoparticles produced by an electron beam lithographic method, which enables us to fabricate a two-dimensional array of nearly identical, parall el oriented particles of designed shape without centrosymmetry, essential f or high SHG efficiency and the tuning of the plasmon resonance to the drivi ng laser wavelength of 780 nm.