Effect of manganese ion on structural, linear and nonlinear optical properties of magnesium sulphate heptahydrate crystals

Abstract

The effect of manganese ion on the structural, linear and nonlinear optical characteristics of the magnesium sulphate heptahydrate crystals was investigated. The pure and manganese ion doped magnesium sulphate heptahydrate crystals were grown using the solvent evaporation technique at room temperature. The structural analysis suggested change in the structure symmetry from orthorhombic to monoclinic crystal system by manganese ion doping. The optical constants and parameters were evaluated using Shimadzu UV-1700 Phamaspec UV spectrometer and measurements were performed at a wavelength of 200–800 nm. The obtained UV chromatograph was recorded by Shimadzu UV prob 2.6 software. The optical bandgap showed direct transitions which decreased by manganese ion doping, while steepness parameter for direct transitions showed a contrary attitude. Linear and nonlinear refractive index, extinction coefficient, optical density, optical conductivity, optical susceptibility, optical dielectric properties, inter-band transition strength, energy loss functions and nonlinear susceptibility were found to be greatly influenced by manganese ion doping and were also dependent on the incident wave energy. The optical study of the grown crystals was further extended using various optical dispersion models like Wemple-DiDomenico single oscillator model, Sellmeier dispersion relation and Drude model. The effect of Mn doping on the dispersion of second order refractive index, two photon absorption coefficient, Figure of Merit (FOM) and third order optical susceptibility was studied in a wide range of photon wavelength from 250 to 700 nm.