Investigations on synthesis, growth, crystal structure, thermal, Dielectric and Terahertz Transmission properties of Organic NLO Crystal : (2-(2-hydroxy-3-methoxystyryl)-1-methylquinolinium-4-methylbenzenesulfonate (O-HMQ)

Abstract We investigate an organic nonlinear optical (NLO) crystal, (2-(2-hydroxy-3-methoxystyryl)-1-methylquinolinium-4-methylbenzenesulfonate (O-HMQ) suitable for Terahertz applications. The present study elaborates the synthesis, crystal structure, thermal stability and dielectric and transmission properties of O-HMQ crystal at terahertz frequencies. O-HMQ is successfully synthesized in our Laboratory. H1-NMR and FTIR results revealed the molecular structure. O-HMQ single crystals of size 7 × 3 × 3 mm3 are grown from methanol solution by solvent evaporation technique. Single crystal X-ray diffraction data shows that O-HMQ belongs to a monoclinic crystal structure with space group C 2/c. The melting point analysis shows a phase transition around 72°C and a mesophase. The temperature-dependent dielectric study has been carried out for different frequencies ranging from 1kHz to 1 MHz proved the phase transition. The real part of the dielectric constant (erʹ), imaginary part (ei″) and dielectric loss (tanδ) are estimated. Further, we demonstrate Terahertz (THz) transmission characteristics of our as-grown O-HMQ single crystal using 50 fs ultra-short two-color laser plasma source in a broad spectral range of 0.1–50 THz, proving its suitability for THz related applications.