Role of defects on the nonlinear optical properties of La doped Bi2WO6 nanostructures for optical device applications

Lanthanum (La) doped Bismuth tungstate (Bi2WO6) nanostructures was successfully synthesized by chemical method and investigated its third order nonlinear optical properties. The effect of La doping on the optical, structure, chemical composition and morphology of the nanostructures were confirmed by X-ray diffraction (XRD), UV–Visible spectroscopy, Raman, X-ray Photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). The results show that the synthesized samples are highly crystalline and the replacement of Bi3+ by La3+ produces a high degree of Bi2WO6 lattice distortion. The addition of La dopant shifts the absorption edge towards higher wavelength and a decrease in the band gap values was observed. The nonlinear optical properties of the nanostructures were studied by an open and closed aperture Z-scan using a continuous wave Diode Pumped Solid State (DPSS) laser at 532 nm. For all samples the open aperture configuration have shown reverse saturable absorption behavior and the closed aperture scan showed self-defocusing effect. The nonlinear absorption and refraction characteristics are found to increase upon La doping. •The NLO absorption of La doped Bi2WO6 nanostructures were studied by a Z-scan technique at 532 nm.•The nonlinearity is due to reverse saturable absorption nature and self-defocussing nature of the samples.•La3+ doping evidently increases the nonlinear absorption coefficients of Bi2WO6 nanostructures.