Structural, vibrational, optical and second harmonic generation studies of urea doped single KDP crystals grown by Sankaranarayanan–Ramasamy technique

The method of cooling aqueous solution and the Sankaranarayanan–Ramasamy technique were used for the preparation of urea doped KDP single crystals with additive concentrations of 0.1, 0.5, and 1 mol%. The single crystals were grown unidirectionally from seeds that were inclined to type I phase-matching angle, the requirement for maximal second harmonic generation (SHG) efficiency. The analysis employed to study the chemical composition, crystal structure, bonding vibrations, and optical properties of the crystal samples was energy-dispersive X-ray spectroscopy, X-ray diffraction patterns, Raman spectroscopy, ultraviolet-visible spectroscopy, and SHG measurement respectively. The differences in chemical composition, crystal structure, optical transmittance, and SHG efficiency of the parts on each urea doped KDP single crystal rod were explained by the variation in the growth sector boundary. This work aims to improve the second-order nonlinear optical coefficient of KDP crystals and suggests which part of the urea doped KDP crystal rod grown by the SR technique is most acceptable for frequency-doubling applications.