Analysis on linear and nonlinear optical properties of an efficient semi-organic crystal: Thiourea borate

Single crystals of thiourea borate, a novel semi organic nonlinear material has been grown by slow evaporation method at ambient temperature. The compound has been subjected to single crystal XRD to characterise the lattice parameters. Results show that the crystal belongs to Triclinic crystal structure. FTIR spectra were recorded to identify the functional groups present in the sample. The transparency of the optical material was analysed by the UV-Vis-NIR studies. The absorption studies illustrate the UV cut-off wavelength to be 255 nm. The transmission studies indicate rapid and intensive transition to maximum transmission at the cut-off wavelength. The third order nonlinear optical properties of the crystal were studied by Z scan technique using continuous wave 532 nm diode pumped Nd:YAG laser. Closed aperture Z scan studies reveal the crystal to possess negative nonlinearity. Open aperture Z scan pattern indicate saturation absorption within the material. The nonlinear optical parameters such as nonlinear refractive index n2, nonlinear absorption coefficient β and nonlinear susceptibility χ(3) were also determined.