Influence of Zn2+ doping on the nonlinear optical limiting characteristics of Bi2WO6 nanostructures for optical device applications

The concentration-dependent non-linear absorption and optical limiting action of Zn-doped Bi2WO6 nanostructures synthesized by co-precipitation method is reported. The incorporation of Zn2+ ions in the host matrix was confirmed by X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analysis. The optical properties and charge transfer mechanism were analyzed by UV-DRS and Photoluminescence studies. The surface morphology was studied by HRTEM and HRSEM techniques. The Nonlinear optical characteristics of the nanostructures were investigated by Q-switched nanosecond Nd: YAG laser pulses at 532 nm using Z-Scan technique. The open aperture Z-scan results exhibited reverse saturable absorption (RSA) for all the samples. The mechanism for RSA is attributed to Two-Photon Absorption (2 PA) via sequential process. The non-linear absorption coefficient (β) of Zn-doped Bi2WO6 nanostructure was found to increase while the optical limiting threshold decrease with increase in Zn doping concentration. The observed nonlinear absorption can be attributed to the impact of dopants on crystal structure, particle size, creation of oxygen vacancies, and defects on the host lattice.