Influence of bismuth nitrate doping towards the characteristics of L-Alanine nonlinear optical crystals

In the present study, an amino acid derivatives, L-alanine (LA) and Bismuth nitrate-doped L-alanine (BNLA) crystals were grown by the slow evaporation technique. The crystal structure and quality of the grown crystal were examined by single-crystal X-ray diffraction (XRD) and powder XRD. The X-ray diffraction analysis of LA and BNLA crystals confirmed the orthorhombic crystal system without any internal structural grain boundaries. The optical properties of the LA and BNLA crystals have been determined using UV-Visible spectroscopy and Photoluminescence (PL). The second harmonic generation (SHG) efficiency of the crystal was measured using Kurtz powder technique. The dielectric constant measurement was performed at room temperature for different frequencies. Photoconductivity tests show that the LA and BNLA crystals have negative photoconductivity value. On testing of the retentivity or remanent magnetization, the BNLA crystal has increased values as compared to the pure LA crystals, in addition to the observation of changes in coercivity. Further, the observation of maximum intensity peak for the BNLA crystal at 346.9 nm pointed out that the crystal has blue fluorescence emission. The third-order nonlinear optical properties of the grown crystal were studied using Z-scan technique. The enhancement in nonlinear refractive index and third-order NLO susceptibility value shows that the grown BNLA crystals may be of good quality and less in defect than that of pure LA crystals.