Saturable and reverse saturable absorption in silver nanodots at 532 nm using picosecond laser pulses

• Published in: Journal of applied physics 2008-10, Vol.104 (7), p.073107-073107-8
• Main Authors: Gurudas, Ullas, Brooks, Elijah, Bubb, Daniel M., Heiroth, Sebastian, Lippert, Thomas, Wokaun, Alexander
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2990056

Saturable absorption (SA) and reverse saturable absorption (RSA) at 532 nm were observed in Ag nanodots prepared by pulsed laser deposition. The real [ Re χ ( 3 ) ] and imaginary [ Im χ ( 3 ) ] parts of the third order nonlinearity of these films were measured using the Z -scan technique. At low input irradiances, the decrease in absorption near the focal point results from a negative Im χ ( 3 ) and yields SA. At higher input irradiance, RSA becomes dominant. The transition from SA to RSA suggests that there is a threshold irradiance at which additional nonlinear process(es) is (are) involved and become dominant. The recovery time of these nonlinear processes was measured by a degenerate pump-probe experiment. The effects are explained in terms of the electron dynamics in the excited states.