Deflection of Light Studies in Ferroelectric Ammonium Hydrogen Selenate Crystal

Deflection of light by AHSe (NH 4 HSeO 4 ) crystal both in the case of (100) domain walls existing at room temperature and in the case of (001) domain walls existing below 250 K was studied. The dependencies of the deflection angles f and g , corresponding to A and B beams, were measured as functions of the incidence angle f i . The results of our measurements allowed us to calculate the birefringences and their temperature dependencies within the different phases with the ferroelastic domain structure. The strong dependence of deflected beam intensity as a function of the electric field applied to the samples in ferroelastic-ferroelectric phase was observed.