An Investigation on Linear and Nonlinear Optical Properties of Pristine and Co doped MgO

Abstract

Magnesium oxide (MgO) nanoparticles are of special interest in research activity because of their astonishing properties in electronic devices due to their ferromagnetic nature, transparency to visible light and applications in catalysts, solar cells and solid oxide fuel cells. Thus doping of Co may be helpful in interpreting the effect of Co dopant in doped MgO. In this work, synthesis of nanostructures of MgO and Co doped MgO are done using modified auto combustion method using magnesium nitrate hexahydrate, cobalt nitrate hexahydrate and citric acid. Structural, morphological, and optical aspects together with third order optical nonlinearity have been investigated. The crystallite size of Mg(1−x)CoxO (x = 0, 0.01, 0.03, 0.05) are calculated as 10.62 nm, 12.48 nm, 13.19 nm, 13.52 nm respectively. Rietveld refinement confirms the structural parameters of the prepared nanoparticles. FE-SEM images confirm nanostructures with slightly agglomerated nature having flower petal like morphology. Chemical composition of the nanostructures is evaluated by using energy dispersive spectrum, confirms the presence of elements like magnesium, oxygen for pristineMgO and magnesium, cobalt, oxygen for doped samples. Linear optical behaviour of Mg(1−x)CoxO (x = 0, 0.01, 0.03, 0.05) can be identified from the UV-Visible absorbance spectrum. Using the Tauc plot calculations, bandgaps are evaluated and are found to be decreasing with doping concentration. The third order nonlinear properties of the prepared nanoparticles have been measured using the Z-scan method under diode pumped continuous wave laser with 532 nm wavelength. In open aperture Z-scan technique, combined effect of saturable absorption and reverse saturable absorption is observed on doping. On the other hand, a self-defocussing nature with negative refractive index is observed under closed aperture Z-scan method. Pristine MgO and Co-doped MgO are found to be superior candidates for the fabrication of optical limiting devices for protecting human eyes and other sensitive optical detectors from hazardous laser radiation.