title: Appearance of singularities of optical fields under torsion of crystals containing threefold symmetry axes.
abstract: We present an analysis of the effect of torsion stresses on the spatial distribution of optical birefringence in crystals of different point symmetry groups. The symmetry requirements needed so that the optical beam carries dislocations of the phase front are evaluated for the case when the crystals are twisted and the beam closely corresponds to a plane wave. It is shown that the torsion stresses can produce screw-edge, pure screw, or pure edge dislocations of the phase front in the crystals belonging to cubic and trigonal systems. The conditions for appearance of canonical and noncanonical vortices in the conditions of crystal torsion are analyzed.
authors: Institute of Physical Optics, 23 Dragomanov Street, 79005 Lviv, Ukraine.
authors: Ihor
authors: I
authors: Skab
authors: Yurij
authors: Y
authors: Vasylkiv
authors: Bohdan
authors: B
authors: Zapeka
authors: Viktoriya
authors: V
authors: Savaryn
authors: Rostyslav
authors: R
authors: Vlokh