Refraction and Reflection of Light at Ferroelastic Domain Walls in Rochelle Salt Crystal

When a laser beam transmits through an a -cut plate of Rochelle salt in the ferroelectric (simultaneously ferroelastic) phase, two types of weak intensity beams deflected from the direct beam direction are observed. The relation between the angle of incidence and the angle of deflection, and polarizing directions of light are satisfactorily explained by refraction and reflection at a domain wall, on both sides of which refractive indicatrices are mutually inclined a few degrees. The refraction and reflection occur at equal angles, and the respective polarizing directions are symmetrical with respect to the wall. There exists a critical angle of incidence, above which one type of deflection beams appears. Diffraction effects due to multi-walls do not account for the experimental results.