Generation of the second harmonic of laser radiation in powders of pure and doped potassium nitrate in the temperature interval of 25–160 °C

Abstract

The temperature dependence of the intensity of generation of the second harmonic of laser radiation with λ = 1.064 µm in various powders of extra-pure potassium nitrate is studied. The powders are obtained from crystals grown in a KNO3-Ba(NO3)2—H2O water-salt system. It is demonstrated that the centrosymmetric phase is crystallized from pure solutions. If Ba(NO3)2 is added to the solution, non-centrosymmetric phases of KNO3 or 2KNO3 · Ba(NO3)2 double salt are formed. As the crystals are cooled down from the temperature of 160 °C, the samples display a ferroelectric phase transition and a hysteresis relaxation dependence of the nonlinear optical response due to the method of sample preparation.