Nonlinear Coefficients of Hafnium doped Lithium Niobate Crystals

The study aims to measure the second-order nonlinear coefficient of LiNbO
₃
:Hf crystals as a function of the doping concentration. Second-harmonic generation measurements are performed using picosecond pulses of an optical parametric oscillator. Results show that doping levels significantly affect the wavelength dependence of refractive indices. Crystals with dopant concentration below 3% exhibits a nonlinear efficiency comparable to congruent crystals which shows enhanced resistance to photorefractive damage.