Nonlinear Optical Property of Sodium Nitrite. I. Second Harmonic Generation at Room Temperature

Abstract

The nonlinear susceptibility describing second harmonic generation in ferroelectric NaNO₂ at fundamental wavelength 1.153μm was measured with a continuous wave He–Ne laser by a phase matching technique. An ambiguity in choice of signs of effective nonlinear coefficients measured leads to four sets of tensor components and |d₁₆|=|d₂₁|=(0.174±0.049)d₃₆(KDP) and |d₂₃|=|d₃₄|=(3.367±0.012)d₃₆(KDP) are chosen on the basis of the Miller law. The signs of d₂₁(=d₁₆) and d₂₃(=d₃₄) are opposite. The nonlinear polarizability of a nitrite ion was found to be |β₁₆(NO₂⁻)|=|β₂₁(NO₂⁻)|=(0.39±0.11)·10⁻²³ cm³d₃₆(KDP), |β₂₃(NO₂⁻)|=|β₃₄(NO₂⁻)|=(6.40±0.23)·10⁻²³ cm³d₃₆(KDP), and |β₂₂(NO₂⁻)|=(0.56±0.14)·10⁻²³ cm³d₃₆(KDP). The anisotropy of the linear and nonlinear susceptibility is ascribed to a π-electron system within the nitrite ion.