Second harmonic generation in the surface layers of ferroelectric sodium nitrite

The temperature dependences of the intensities of the second and composite optical harmonics of lines (λ = 510.5 and 578.2 nm) emitted by a copper vapour laser were determined. The harmonics were generated in crystals of ferroelectric sodium nitrite. The dependences were affected significantly by the excitation conditions. The observed effects were attributed to the characteristics of the phase state of the surface layers of the ferroelectric.