Nonlinear Optical Property of Sodium Nitrite. II. Temperature Dependence of Second Harmonic Generation

Abstract

The nonlinear susceptibility describing second harmonic generation in ferroelectric NaNO₂ at the fundamental wavelength 1.153μm was measured as a function of temperature over a range from −100°C to 170°C with a continuous wave He–Ne laser light. Each nonlinear susceptibility component was found to decrease gradually with increasing temperature and not to be linearly proportional to the temperature dependence of the spontaneous polarization. A mechanism of the temperature dependence of the nonlinear susceptibility in NaNO₂ is tried to analyze in terms of the torsional motion of NO₂⁻ ions.