Structural and Optical Coefficients Investigation of γ-Al2O3 Nanoparticles using Kramers-Kronig Relations and Z-scan Technique

gamma-Al2O3 nanoparticles (NPs) with a mean diameter of 60 nm were prepared through the sol-gel technique and characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), and ultraviolet-visible (UV-Vis) spectroscopy. The formation of cubic structures with the gamma phase for Al2O3 NPs confirms. The average particle size obtained is about 60 nm by the FESEM image. The nonlinear optical properties were examined by a single-beam Z-scan method using a Gaussian visible continuous wave Nd:YAG laser (532 nm). The Z-scan findings indicated a self-focusing nonlinearity and saturable absorption process in order of 10(-8) (cm(2)/W) and 10(-4) (cm/W) in the synthesized gamma-Al2O3 NPs, respectively. Moreover, Kramers-Kronig relations were applied to determine the complex refractive index and dielectric coefficient of the specimens by Fourier-transform infrared spectroscopy. The transversal and longitudinal optical (TO and LO) modes are the two intersection points in the real and imaginary parts of the complex refractive index. Also, the maximum position of the Im(-1/ epsilon) plot is related to LO frequency.

Automated summary

The study focuses on the structure and nonlinear optical properties of γ-Al2O3 nanoparticles prepared by the sol-gel technique, revealing self-focusing nonlinearity and saturable absorption processes. The complex refractive index and dielectric coefficient of the specimens were determined using Z-scan method and Fourier-transform infrared spectroscopy.