Optical limitation induced by gold clusters.: 1.: Size effect

The nonlinear optical response of gold particles (with 2.5, 9, or 15 nm radius) prepared by gamma-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 laser 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 particles, it lasts 1 ns. The limitation effect is attributed to large light-scattering centers induced by the pulse around the initial particles.