Semi-organic nonlinear optical material, 𝐿-lysine 𝐿-lysinium dichloride nitrate (2C₆H₁₅N₂O$^{+}_{2}$.H⁺.NO$^{-}_{3}$.2Cl^-) was synthesized at room temperature. Single crystals of 𝐿-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies. The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The frequency and temperature dependence of dielectric constant (𝜀_r), dielectric loss (tan 𝛿) and a.c. conductivity (𝜎_ac) were also measured.

Bulk single crystal of 4-aminobenzophenone with a size of 25 mm dia. and 35 mm length has been grown by vertical Bridgman technique. The crystal system of the grown crystal was confirmed by X-ray diffraction analysis. Crystalline perfection was analysed by high resolution X-ray diffraction studies. Chemical etching was carried out for the first time in 4-aminobenzophenone single crystal to study the defects presented in the grown crystal and the growth mechanism involved. Several organic etchants were employed with different etching time to select suitable etchant for studying dislocation pattern and other structural defects existing in the grown crystal. Etch patterns such as spirals and striations observed for the selective etchants provide considerable information on growth mechanism of the crystal.

In the present work, benzimidazole (BMZ), a well known nonlinear optical material, thin films were deposited using the modified liquid phase growth technique at different solution temperatures. The prepared samples were subjected to spectral, structural and surface analyses. Linear optical properties and third-order optical nonlinearity of the deposited BMZ thin films were analysed using UV–visible–NIR spectrum and 𝑍-scan technique, respectively. The experimental results show that the BMZ films exhibit reverse saturable absorption and positive nonlinearity at 650 nm CW laser of power 5 mW. The measured third-order nonlinear susceptibility of the films is about 10⁻¹⁰ esu. Optical limiting studies were performed using the same laser source and the potentiality of the BMZ films is reported.

L-arginine monohydrobromide monohydrate (LAHBr) single crystals were grown from two molar mixtures of L-arginine and HBr acid in 1 : 2 and 1 : 3 ratios. The solution pH of the above molar ratios was measured to be 7.2 and 1.8, respectively. This drastic change in pH has modified the morphology of LAHBr single crystal and influenced the mechanical stability, optical transparency, refractive index, birefringence and laser damage threshold. The decrease in pH from 7.2 to 1.8 has enhanced the optical transparency and laser damage threshold of LAHBr crystal.