Potassium trihydrogen dioxalate dihydrate (KTO) nonlinear optical (NLO) single crystal for optical limiting application

Abstract

In nonlinear optics, optical power limiting (OPL) compounds are known to be an important class of materials because it has the ability to protect the optical sensor components as well as human eyes from the abrupt intense laser power. Here, we have grown such optical limiting material so called potassium trihydrogen dioxalate dihydrate (KTO) single crystal from the aqueous solution by slow cooling method and other aspects such as recrystallization, solubility, nucleation rate, metastable zonewidth and induction period were analysed. Single crystal X-ray diffraction analysis results in triclinic crystal system with centrosymmetric space group P 1¯ of KTO single crystal. The electronic band structure shows that KTO single crystal exhibits an insulating nature with band-gap energy of 3.436 eV (DFT).The strong observation of second harmonic generation (SHG) signal of 79 mV output from the centrosymmetric system is quite surprising and the efficiency of it is also almost equivalent to that of the standard KDP material. And this signal may be attributed due to the dehydration of the crystal under laser irradiation (centrosymmetric to non-centrosymmetric) and the third order nonlinear χ(3) is found to be 1.82 × 10−6 esu. Apart from that, the material shows optical limiting behaviour at which it deviates from the linear response at 3.25 mW of input fluence (nonlinear origin) which further confirms that all nonlinear material will always be coupled with both linear and nonlinear property. In addition, optical, mechanical and dielectric properties of KTO single crystal are discussed in detail.