Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 13: Symposium: Ultrafast Nanooptics II
O 13.4: Vortrag
Montag, 26. März 2007, 16:15–16:30, H38
Ultrafast Spectroscopy of Single Gold Nanoparticles — •Markus Lippitz1,2,3, Meindert van Dijk1, and Michel Orrit1 — 1Huygens Laboratory, University of Leiden, The Netherlands — 24. Physics Institute, University of Stuttgart — 3Max Planck Institute for Solid State Research, Stuttgart
Metal nanoparticles in the size of 1-100 nm have properties different from bulk metal. The particle size distribution present in even the best chemical preparation methods blurs the picture one can get. Optical spectroscopy of a single particle at a time removes the sample inhomogeneity and gives direct access to the individual particle's properties. We present nonlinear optical experiments on single gold nanoparticles.
We reported the first observation of third-harmonic signals from individual gold particles. Excited with short pulses (100 fs) at 1600 nm, the particles generate 533-nm light, close to the plasmon resonance. Contrary to our expectation, we found the third-harmonic intensity to vary as the fourth power of the diameter of the particles, which can be explained by the nonlinear optical response of the free electrons.
In another experiment we performed time-resolved absorption measurements of single gold nanoparticles, with a sensitive common-path interferometer. The variation of the plasmon resonance after absorption of a near-infrared pump pulse is probed in the visible wavelength range. At short times, the signal of the hot electrons dominates. At longer delay times, mechanical oscillations of the whole particle can be detected by periodic shifts of the plasmon frequency.