Two photon absorption induced optical limiting action of L-Aspartic acid monohydrate

Abstract

The organic l-Aspartate Monohydrate (L-AspMH) crystal is grown by slow evaporation technique. Single crystal XRD analysis reveals that L-AspMH belongs to an orthorhombic system with P 21 21 21 space group. The inter-contacts in the crystal structure are analyzed using the Hirshfeld surface analysis. To support the experimental results, quantum chemical calculations using the density functional theory (DFT) are done. The molecular structure of L-AspMH crystal is optimized by DFT/B3LYP functional, 6–311G++(d,p) basis set. The FT-IR and FT-Raman spectra are also stimulated and validated experimentally. The blue-shift in the O–H stretching wavenumbers is due to the presence of O–H⋯O hydrogen bonding. The highest occupied molecular orbital (HOMO: −7.409 eV) energy, lowest unoccupied molecular orbital (LUMO: −0.927 eV) energy and energy gap (6.483 eV) of the AspMH crystal is calculated. The hyper conjugative and inter/intra molecular interactions have been investigated through the Natural Bond Orbital (NBO) analysis. UV–vis absorption studies shows the material exhibit absorbance maxima in the UV (204 nm) region and high transmittance in the Visible-NIR (340–900 nm) region. The predicted first order hyperpolarizability is found to be 13 times greater than that of urea. Third-order nonlinear optical property of the crystal is studied using Z-scan technique under nanopulsed Nd:YAG laser. L-AspMH exhibit intensity dependent nonlinear absorption behaviour was witnessed with M-type (2.46 × 1012 W/m2) at lower on-axis input intensity and reverse saturable absorption (4.98 × 1012 W/m2) at higher on-axis input intensity. The material demonstrates sequential two absorption induced optical limiting action. Higher two-photon absorption coefficient (0.56 × 10−10 m/W) and lower onset optical limiting threshold (5.41 × 1012 W/m2) makes AspMH a potential candidate for optical limiting devices.