Optical Limitation induced by Gold Clusters. 1. Size Effect

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Optical Limitation induced by Gold Clusters. 1. Size Effect
# [7 n: G8 Y( E' }6 [4 ]% MLionel Francüois, Mehran Mostafavi,* and Jacqueline Belloni
Laboratoire de Chimie Physique, UMR 8610 CNRS, UniVersite´ Paris-Sud, 91405 Orsay, Cedex, France
2 p2 C+ W/ B& l& D) n' h2 pJean-Francüois Delouis and Jacques Delaire
Laboratoire de Photophysique et Photochimie Supramole´culaires et Macromole´culaires, UMR 8531,
Ecole Normale Supe´rieure de Cachan, 94235 Cachan Cedex, France
/ g+ m1 s8 }+ mPatrick Feneyrou
Laboratoire Central de Recherches, Thomson-CSF, Domaine de CorbeVille, 91404 Orsay Cedex, France
7 @% Z- d: x- p0 _- i! p  k4 _, VReceiVed: December 20, 1999; In Final Form: March 8, 2000
The nonlinear optical response of gold particles (with 2.5, 9, or 15 nm radius) prepared by ç-radiolysis in
water solution and stabilized by poly(vinyl alcohol) is size-dependent. The 2.5 nm clusters do not limit light
transmission even at very high fluence of nanosecond laser pulses, while the larger clusters strongly limit the
8 n+ m  c- [3 ]0 G5 Wlaser beam transmission at 530 nm. The threshold of limitation and the amplitude depend on the size of the
particles. The rise of the optical limiting effect is measured by picosecond laser spectroscopy. For the largest
9 N4 D2 m" J! s( e( R6 ]/ rparticles, it lasts 1 ns. The limitation effect is attributed to large light-scattering centers induced by the pulse
" D5 y$ k9 d/ F/ U+ r1 V; [6 b& naround the initial particles.