Studies on semi-organic non linear optical single crystal: Lithium formate monohydrate (HCO2Li⋅H2O)

Abstract

A semi-organic nonlinear optical single crystal, of lithium formate monohydrate (LFMH), has been grown by slow evaporation solution growth technique. The single crystal XRD analysis confirms that the crystal belongs to the orthorhombic system with non-centrosymmetric space group Pbn21. Powder X-ray diffraction analysis was carried out for the grown crystal in the 2θ range 20–80°. The crystalline perfection was analyzed by high-resolution X-ray diffraction (HRXRD) and found that the quality of the grown single crystal is quite good. The UV–Vis spectrum shows that it has a good transmittance in the entire visible region with the lower cut-off wavelength at 240nm. The presence of the functional groups was confirmed by using FT-IR spectral analysis. The thermal characteristics of LFMH were analyzed by thermogravimetric (TGA) and differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Dielectric studies have been carried out for the grown crystal at different frequencies from 100Hz to 5MHz. Both dielectric constant and dielectric loss values are found to decrease with increasing frequency. The mechanical behavior of the grown crystal was studied using Vickers microhardness tester. Nonlinear optical characteristics of LFMH have been studied using Q-switched Nd:YAG laser (λ=1064nm). The second harmonic generation conversion efficiency of LFMH is 0.9 times that of standard KDP crystal. The laser damage threshold value of LFMH is found to be 1.5GW/cm2.