Nonlinear optical properties of new ferroelectric LaBGeO5

Abstract

The crystal quality of new nonlinear-optical/ferroelectric crystal LaBGeO₅ was examined by measuring wavelength dependence of the second harmonic intensity under the phase matching condition at λ = 1.314 μm. The effective interaction length I _eff was determined as 1.28 mm, which was 73% of the actual length. The ferroelectric phase transition nature was also investigated by measuring temperature dependence of quadratic nonlinear optical constants. The result confirmed that LBGO exhibits a ferroelectric phase transition of the second-order at 531.5°C and showed that the spontaneous polarization calculated by the Jerphagnon relation agrees well with the value estimated from the specific heat measurement. The point group of the high temperature phase was determined as D ₃ as a result of the observable nonlinear component in the high temperature phase.