15:00-15:30
Nonlinear Optical Response of Metal Nanoparticles
Dr. Yoshihiko Takeda (Ion Beam Group, Quantum Beam Center)
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Optical nonlinearity of metal nanoparticle materials is one of the charactaric plasmonic properties and is strongly enhanced by the local electric field in a nanoparticle at the localized surface plasmon resonance. The large nonlinearity is expected to be applied to optical nanodevices with picosecond response. For understanding of the origin of optical nonlinearity and the enhanced effect, and design of plasmonic nanodevices, it is significant to evaluate the wavelength dispersion of the nonlinear optical constant with steep changes around the resonance. Here I present the wavelength dispersion of third-order optical susceptibility, χ(3) experimentally evaluated from photo-excited transient response with pump probe method and a femtosecond laser system. Metal (Au, Ag and Cu) nanoparticle materials are fabricated into insulating substrates by 60 keV negative ion implantation at total fluences of 3-10 x 106 ions/cm2. The evaluated spectra are analyzed on hot electron effect using the Maxwell-Garnett approximation with the Drude model for intraband transition and first principles calculation for interband transition. For Au and Cu nanoparticle materials, the interband transition term in hot electron effect dominates the dispersion around the surface plasmon resonance beyond the band edge by Fermi smearing. The large nonlinearity modulates the intensity of local electric field and the nonlinear response is not proportional to input laser power. I also show the power dependence of the third-order nonlinear optical response for all optical switching operation by a single nanoparticle.