Thermal Nonlinear Refraction and Saturable Absorption of Platinum Nanoparticles under Irradiation of a Continuous Wave Laser and Nanosecond Pulsed Laser

This work focuses on the nonlinear properties of platinum nanoparticles (ptNPs) in the aqueous solution of sodium dodecyl sulfate (SDS) under irradiation of a continuous wave (CW) laser and a nanosecond pulse laser at the wavelength of ۵۳۲ nm. These properties are characterized by means of nonlinear transmittance, Z-scan technique, and scattered intensity assessments when submitted to laser operating at a wavelength of ۵۳۲ nm. The closed Z-scan measurements reveal thermal contribution for the nonlinear refractive index of the platinum nanoparticles in the CW regime and the saturable absorption is observed using the open aperture Z-scan method in the pulsed regime. It will be shown that the thermal thin lens model is in excellent agreement with the experimental results of the sample. A fit has allowed extracting the value of nonlinear refractive index to be -۱.۱×۱۰-۸ cm۲/W. The saturable absorption is analyzed using a phenomenological model based on nonlinear absorption and saturation intensity. The nonlinear absorption coefficient obtains ۳.۲ × ۱۰-۱۰ m-۱.

Keywords:

Platinum nanoparticles , Thermal nonlinear refraction , Saturable absorption , Z-scan technique