Effect of structural and optical properties of thiourea doped ammonium dihydrogen phosphate crystals on second order non-linearity

This study highlights the impact of Thiourea on the structural and optical properties of Ammonium Dihydrogen Phosphate (NH₄H₂PO₄) crystals grown by the slow evaporation crystal growth technique. To study the structural properties of pure and doped ADP crystals, X-ray diffraction (XRD) was performed. From XRD analysis, it is found that, relative to pure ADP crystals, the structure of thiourea-added crystals has shown a marginal shift in lattice parameters. The dopant alters the functional group vibrations (FT-IR) of ADP crystals, indicating the inculcation of thiourea into the crystals. The Refractive indices were found to increase with increasing concentration of thiourea. The direct and indirect band gaps of the crystals are found to increase with the increase in dopant concentration. The photoluminescence spectrum shows an increase in the peak intensities after doping. The Kurtz-Perry test was used to determine the influence of thiourea on the Second Harmonic Generation (SHG) efficiency of ADP crystals.