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 × 10−7 cm W−1 was obtained in a saturation intensity of 1.8 × 107 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 × 10−13 cm2 W−1 up to −15 × 10−13 cm2 W−1 by increasing the laser intensity.

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