Linear and nonlinear optical properties of WO3 nanoparticles synthesized at different fluences of pulsed Nd:YAG laser

Abstract

Here in this paper, synthesis of WO3 nanoparticles (NPs) by laser ablation of a pure tungsten plate immersed in water is reported. For this purpose, the first harmonic of an acousto-optically Q-Switched Nd:YAG laser is utilized at 13, 18 and 23 J/cm2 laser fluences. X-ray diffraction (XRD) and transmission electron microscopy (TEM) associated with dynamic light scattering (DLS) techniques show that while the laser fluence increases from 13 to 23 J/cm2, the crystallinity, length of particle chains and average particle size of the products increase, respectively. UV–Vis spectra indicate a red shift on the absorption edge towards the visible region for the samples produced at higher laser fluences attributed to the particle size increment and energy band gap decrement, subsequently. Also other linear optical parameters including Urbach energy, refractive index dispersion, relaxation time, complex dielectric and conductivity functions are derived and discussed. Z-scan analysis is carried out to determine the nonlinear refraction index, nonlinear absorption coefficient and third-order nonlinear susceptibility. It is found that WO3 NPs can be considered for optical limiting performance because of the high nonlinear absorption. Furthermore, the specimens prepared at higher laser fluences are more applicable due to the larger particle size and higher nonlinear absorption, consequently.