Nonlinear optical properties of ZnO variants

Abstract

Investigation on nonlinear optical properties of ZnO with Au-Ag NPs was done in this report using a femtosecond laser with a wavelength of 720 nm using Z-scan measurement. ZnO sample was prepared by a two-step process: seeding process via ultrasonic spray pyrolysis and growth process via hydrothermal methods, while ZnO with Au-Ag NPs was done by chemical reduction. ZnO shown saturable absorbance properties with nonlinear absorption coefficient, β = 1.63×10⁻⁶ cm/W, while ZnO deposited with Au-Ag NPs, shows reverse saturable absorption properties, for which ZnO Au NPs have the highest value of 5.60×10⁻⁶ cm/W, nonlinear refractive index response for pristine ZnO gave self-focusing effect with the value of a nonlinear refractive index, γ = 2.29×10⁻¹² cm²/W. In contrast, the rest of ZnO with Au-Ag NPs gave the self-defocusing effect, with the Au NPs having the lowest response with γ = −5.79×10⁻¹² cm²/W. This gives ZnO Au NPs have the highest third-order nonlinear susceptibility, χ(3) = 14.62×10⁻¹⁰ esu, which is an enhancement from pristine ZnO.