研究・研究者
研究会・セミナー
| 演 題 | 「Second harmonic generation in noble metal nanoparticles: the "small particle limit"」 |
|---|---|
| 日 時 | 2008年10月22日(水) 13:30 より 14:30 まで |
| 講演者 | Prof. P. K. Das (Indian Institute of Science) |
| 場 所 | 研究棟201号室 |
| 概 要 | All spherical noble metal nanoparticles show large second harmonic generation efficiency although this process is supposed to be very inefficient for perfectly symmetric shapes such as a sphere. In search of the origin of such large SH responses, we prepared spherical copper nanoparticles of various size (5-100 nm) with and without stabilizers and probed their second harmonic generation efficiency by the two photon Rayleigh scattering or the hyper-Rayleigh scattering (HRS) technique at several wavelengths spanning from 738 nm in the visible to 1907 nm in the infrared. At small particle sizes the second harmonic generation originates from the particle surface and is predominantly dipolar in character which changes when we go to larger size or shorter wavelength of measurement. We have, by polarization resolved SH experiments, found the size to wavelength (d/l) limits where the mechanism changes from predominantly dipolar to predominantly quadrupolar. Retardation of light becomes important when the d/l increases. The d/l ratio for the "small particle limit" in copper has been compared to that of gold and silver from the literature. We find that nanoparticles of copper and gold are similar in their nonlinear optical behaviour but silver is qualitatively different. |
| その他 |
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