Fabrication of optical element from unidirectional grown imidazole–imidazolium picrate monohydrate (IIP) organic crystals for nonlinear optical applications

Abstract

Nonlinear optical bulk single crystal of Imidazole–imidazolium picrate monohydrate (IIP) has been grown by Sankaranarayanan–Ramasamy (SR) method using acetonitrile as solvent. First time we report the bulk growth of IIP crystal by SR method. The transparent IIP single crystal of maximum diameter 21 mm and length 46 mm was obtained by employing SR method. The grown crystal was subjected to high resolution X-ray diffraction, UV–vis–NIR transmittance, refractive index, hardness, dielectric and laser damage threshold studies. The crystalline perfection of the grown crystal was analyzed using HRXRD. Cut off wavelength and optical transmission window of the crystal was assessed by UV–vis–NIR and the refractive index of the crystal was found. The mechanical property of the crystal was estimated by Vicker׳s hardness test. The dielectric property of the crystal was measured as a function of frequency. The laser damage threshold value was determined. The particle size dependent second harmonic generation efficiency for IIP was evaluated with standard reference material potassium dihydrogen phosphate (KDP) by Kurtz–Perry powder method using Nd:YAG laser, which established the existence of phase matching. The second harmonic generation (SHG) of IIP crystal was investigated by the SHG Maker fringes technique. The mechanism of growth is revealed by carrying out chemical etching using acetonitrile as etchant. • SR method grown bulk IIP crystal of 46 mm length, 21 mm diameter. • The refractive index of IIP crystal by solid prism method is 1.738. • The full width at half maximum of the diffraction curves is 49.25″. • The laser damage threshold of SR method IIP crystal is 0.252 GW/ cm 2 .