Regensburg 2007 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 2: Internal Symposium “Nonlinearities of Photonic Materials”

DF 2.3: Talk

Monday, March 26, 2007, 11:00–11:20, H11

Mechanisms of holographic grating formation in silver nanoparticle suspensions * — •Helge Eggert¹, James Adleman², Demetri Psaltis², and Karsten Buse¹ — ¹Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn — ²Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125

Colloidal suspensions of metal nanoparticles have interesting thermal and nonlinear-optical properties. The high third-order nonlinearity of metal nanoparticles at wavelengths close to the surface plasmon resonance makes such suspensions attractive, e.g., for optical switching applications. However, the optical response of these materials is still not completely understood, especially on the nanosecond time scale. To study silver nanoparticle suspensions, holographic experiments are conducted: Holographic gratings are recorded utilizing interfering nanosecond pulses. The diffraction efficiency is measured with continuous-wave light. An instantaneous response together with a longer lasting but also transient grating are observed: The nanoparticles absorb the pump light and heat up, which yields a response on the time scale of the laser pulse duration. Heat is transferred to the solvent, and a delayed thermal grating appears. The final decay time constant of this grating depends quadratically on the period length of the interference pattern and has a typical value of 1 ms for grating spacings of several micrometers. This are indications for thermal gratings.

*Financial support by the DFG (BU 913/17) and by the Deutsche Telekom AG is gratefully acknowledged.