Spontaneous electrooptical absorption effect in a barium-strontium niobate crystal

Spontaneous changes of the Basub(0.25)Srsub(0.75)Nb2O6 single crystal absorption coefficient are under investigation in the 300-400 K temperature range. The measurements have been performed using polarized light with wavelengths (390-400 nm) belonging to the crystal self-absorption edge. Temperature dependence of the absorption coefficient has been observed as the edge shift towards greater wavelengths with increasing temperature. The phenomenon is treated as the electrooptical absorption effect due to spontaneous polarization of the crystal during para-ferroelectric phase transformation. Electrooptical coefficients are calculated for the load-free crystal