Simultaneous measurements of crystal optical characteristics of deuterated triglycine sulphate

The birefringence, rotation angle of the optical indicatrix and the gyration along the polar direction are studied in the paraelectric and ferroelectric phases of deuterated triglycine sulphate crystals using the HAUP‐type universal null‐polarimetric technique. The gyration effect in the multidomain ferroelectric phase is found to be negligibly small, in accordance with the symmetry considerations, while the changes in the birefringence and the indicatrix rotation occurring in the course of the phase transition may be described by electrooptical coupling due to the quadratic spontaneous effect.