Optical, structural and Near-IR NLO properties of gold nanoparticles doped sodium zinc borate glasses

Abstract

Gold (Au) nanoparticles (NP) embedded borate glasses with the molar composition of (x‒0.1)Na2O‒10ZnO‒(90‒x)B2O3‒0.1AuCl3 (x = 10, 20, 30 mol %) have been prepared via melt quench technique. The effect of Na2O content on properties such as optical, structural and nonlinear optical (NLO) properties of gold NPs containing sodium zinc borate glasses were studied using UV‒Visible absorption, Fourier Transform Infrared spectroscopy (FTIR), High Resolution-Transmission Electron Microscope (HR‒TEM) and Z-scan measurements. X‒ray diffraction (XRD) measurements confirmed the glassy nature of the samples. UV‒Visible absorption spectra of glasses comprising Au NPs demonstrated a broad surface plasmon resonance (SPR) absorption peak near 577 nm due to the transition from d‒band to the Fermi level and this SPR peak demonstrated a red‒shift with increase in Na2O concentration. HR‒TEM micrographs revealed the presence of uniformly distributed and spherical shaped Au nanoparticles with an estimated average particle size of ∼6 nm (±1.5 nm). Nonlinear Optical (NLO) measurements were performed at three different off‒resonant wavelengths (750 nm, 800 nm, 850 nm) using femtosecond (fs) pulses (150 fs, 80 MHz) delivered by aTi:sapphire oscillator. Saturable Absorption (SA) kind of nonlinearity has been observed in the open aperture (OA) Z-scan data and is attributed to intraband transition within the Au NPs, while the closed aperture (CA) Z-scan data illustrated a negative type of nonlinear refraction attributed to effect of self-defocusing. NLO studies and the obtained nonlinear coefficients suggest that, the NZB glasses are potential candidates for mode-locking and switching applications in near-infrared spectral region.