Nonlinear optical properties of laser synthesized Pt nanoparticles: saturable and reverse saturable absorption

In this paper, the spectral and nonlinear optical properties of a colloidal solution of platinum nanoparticles (Pt NPs) in water are presented. The Pt NPs were prepared by laser ablation of a Pt metallic target in distilled water using a 1064 nm high frequency Nd:YAG laser. The intensity-dependent nonlinear optical absorption and nonlinear refraction behaviors of the sample exposed to the 532 nm nanosecond laser pulses were investigated by applying the Z-scan technique. The saturated nonlinear absorption coefficient 5.4 x 10(7) cm W-1 was obtained in a saturation intensity of 1.8 x 10(7) W cm(-2). The saturable absorption response of the Pt NPs was switched to the reverse saturable absorption in the higher laser intensities. The nonlinear refractive index that has a negative value was increased from 3.5 x 10(-13) cm(2) W-1 up to 15 x 10(-13) cm(2) W-1 by increasing the laser intensity.