Birefringence measurements by means of light deflection at domain walls in ferroelastic crystals

Abstract

The deflection of light in ferroelastic crystals results from refraction and reflection at domain wa lls. When the tilt angle of the principal axes in neighboring domains is small, simple relationships between the crystal birefringences and the angles of the deflected beams can be deduced from Snell's law of r efraction. As a rule, this condition is satisfied a t W -domain w alls i n f erroelastic s pecies t hat h ave a b iaxial p rototype p hase. In this case, measurement of the deflection a ngles p ermits o ne t o d etermine t he b irefringences e asily. This method has as its main advantages independence of the sample thickness and the need for only rough sample preparation. It is absolutely insensitive to temperature fluctuations. We have applied the method to crystals of rubidium hydrogen selenate and dihydrated barium chloride as illustrative examples.