Optical and terahertz characterisation of efficient NLO single crystal: (E)-2-(4-(dimethyl amine) styryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (P-BI).

We report the terahertz (THz)-based characterisation of a highly efficient non-linear optical compound (E)-2-(4-(dimethyl amino) styryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (P-BI) single crystal. The crystallographic structure of the grown crystal was confirmed by single-crystal X-ray diffraction analysis. Based on the obtained diffraction analysis, the title crystal belongs to the space group P21 and possesses good optical transmission between 700 and 1500 nm. The most important impedance spectroscopy-based parameters such as dielectric constant and dielectric losses show lower values which are an essential requirement for general non-linear optical (NLO) materials. The femtosecond oscillator has helped us to ascertain the transmission/absorption and generation in the 0.2–2.0 THz range. The obtained experimental data were used for the measurement of real and imaginary parts of the refractive index and absorption coefficients of the crystal. Finally, the crystal was subjected to the femtosecond laser amplifier for measuring the efficiency, maximum generated power and effect of vertical rotation of the crystal on THz radiation. The output power was measured using a pyroelectric detector and the generated maximum power was of the order of 1.9 µW at 150 mW incident pump power. The corresponding efficiency of the generated THz signal is of the order of 1.26 × 10–3%. [ABSTRACT FROM AUTHOR]