Unidirectional growth of L-cysteine hydrochloride monohydrate: first time observation as nonlinear optical material and its characterization

A bulk size (∼60 mm length and 20 mm diameter) single crystal of L-cysteine hydrochloride monohydrate has been successfully grown for the first time by the unidirectional Sankaranarayanan–Ramasamy method and found to be a nonlinear optical material by observing the second harmonic generation (SHG). The crystal structure has been confirmed by single-crystal as well as powder X-ray diffraction analysis. The Fourier transform–Raman technique was used to study the vibrational modes and functional groups. The grown crystal was found to be highly transparent. The crystalline perfection has been evaluated by high-resolution X-ray diffractometry and the grown crystal was found to be free from macroscopic defects such as structural grain boundaries. The relative SHG efficiency and laser damage threshold values were found to be 1.2 and 5.5 times that of a potassium dihydrogen phosphate crystal, respectively. The dielectric constant, dielectric loss and alternating current conductivity were measured by an impedance analyser over a wide range of frequency between 100 Hz and 5 MHz. The dielectric constant was found to be stable for the entire range of frequency with very small dielectric loss, making this material suitable for device applications. The present investigation reveals that the title compound, since it can be grown with desirable size along a predetermined direction and it is a good nonlinear optical material with the prerequisite optical and dielectric properties, is a good candidate for photonic or opto-electronic applications.