Nonlinear optical properties of Ag nanoparticles prepared by laser ablation in liquids
V.A. Karavanskii 1* , A.V. Simakin 2 , V.I. Krasovskii 1 , P.V. Ivanchenko 1
1 Natural Sciences Center of A.M.Prokhorov General Physics Institute,
Russian Academy of Sciences, 38/L2 Vavilov str., Moscow, 119991 Russia
2 Wave Research Center of A.M.Prokhorov General Physics Institute,
Russian Academy of Sciences, 38, Vavilov str., Moscow, 119991 Russia
* e-mail: karavan@kapella.gpi.ru
Optical properties and third order optical nonlinearity (ONL) of liquid metal colloids prepared by laser ablation in water and ethanol are investigated. It was shown that fresh colloids undergo full or partial sedimentation with changing of ONL characteristics. It was found out that water colloids took stable state after partial sedimentation with changing of ONL sign during sedimentation process. The induced nonlinear optical absorption inherent for fresh colloids transformed to induced nonlinear transparency after sedimentation. The optical absorption spectra are interpreted within the framework of Drude model for metallic particles with taking into account the effect of nanoparticles sizes on optical properties. The evolution of ONL sign is explained by the coexistence of two type Ag particles in colloid solution after ablation in water. The large particles undergo the sedimentation and the small Ag particles with presumable oxide shell form stable colloid. The sizes of small Ag particles were calculated and nonlinear optical absorption parameters were measured by z-scan technique. The nature of induced transparency is discussed.