Synthesis, growth and physicochemical properties of new organic nonlinear optical crystal l-threoninium tartrate (LTT) for frequency conversion

Abstract

An organic nonlinear optical l-threoninium tartrate (LTT) single crystal was successfully grown by slow evaporation method using de-ionized water as solvent. The orthorhombic structure and non-centrosymmetric space group of P2221 of the grown LTT crystal was confirmed using single crystal X-ray diffraction analysis. The various functional groups and bonding nature of the LTT crystal were realized using FT-IR spectroscopic analysis. The linear optical behavior is examined using UV–Visible spectroscopy revealing the absences of absorbance in the wavelength region of 230–1100 nm. Tauc’s relation is employed to obtain the optical band gap and it is found to be 6.4 eV. The optical parameters like extinction coefficient (K), reflectance (R) and refractive index (n0) are also calculated for the grown LTT crystal. With respect to the frequency and temperature the dielectric constant and dielectric loss were estimated. The Vickers hardness number (Hv), Meyer’s index (n), yield strength (σr), elastic constant (C11), fracture toughness (KC) and Brittle index number (Bi) were calculated using the micro-indentation test. Thermo-gravimetric (TG) and differential thermal (DT) analysis confirm the single stage decomposition and 257 °C melting point of the titular crystal. The exact melting point of the crystal is found to be 268 °C using auto melting point apparatus. The layer growth with 2D nucleation mechanism and less dislocation is confirmed by chemical etching analysis. The surface quality of the titular crystal was studied using laser damage threshold (LDT) measurement and it is found to be 6.57 GW/cm2. Kurtz and Perry method was employed to estimate the second harmonic generation efficiency of the titular crystal and is found to be 2.91 times greater than the KDP crystal. The χ(3), n2 and β of the titular crystal was estimated using Z-scan technique and they are found to be 7.1368 × 10−10 (esu), 0.8466 × 10−12 (cm2W−1) and 3.734 × 10−6 (cmW−1) respectively. Reverse saturable absorption observed in open aperture Z-scan indicates the suitability of titular crystal for optical limiting application.