Nonlinear optical switching behavior of Au nanocubes and nano-octahedra investigated by femtosecond Z-scan measurements

Two types of gold nanoparticles, nanocubes and nano-octahedra were prepared and their nonlinear absorption properties were investigated by using femtosecond open aperture Z-scan experiments. Both nanocubes and nano-octahedra exhibited a shift from saturable absorption (SA) to reverse saturable absorption (RSA) at higher excitation intensities. The SA behavior was ascribed to ground state plasmon band bleaching and RSA was ascribed to excited state absorption and two-photon absorption of these materials. The competition of different processes is responsible for the observed switching behavior.