Some features of second-harmonic generation in a lithium metaniobate crystal

An investigation was made of the temperature dependences of the phase-matching angle, the angular width of the phase-matching curve, the dispersion of the phase-matching direction, and the temperature derivative of this direction in the generation of the second harmonic of the neodymium laser radiation in a crystal of LiNbO₃. A calculation was made of the parameters K_α and B_α, which were the first and second terms in the expansion of the phase detuning in terms of the angle of deviation from the phase-matching direction. The validity of the linear approximation in this expansion was considered for different values of the phase-matching angle. The dispersion of the phase-matching direction increased ten-fold and the temperature derivative of the phase-matching direction rose twenty-fold on approach to the 90° phase matching. The second harmonic of the neodymium laser radiation was generated with an efficiency of ~40%. The induced inhomogeneity of the refractive index of lithium metaniobate was not observed.