Single-slit diffraction of an optical beam with phase singularity

Single-slit diffraction of an optical beam carrying phase singularity is presented. Due to azimuthal phase dependence, the diffraction pattern of the singular beam differs from that of a plane wave. The fringes in the diffraction pattern of singular beam undergo continuous bending, while passing through the centre of the pattern and exhibit left to right or right to left shift, depending on the sign of the topological charge of singular beam. It is shown that diffraction of a singular beam through a slit can be used to determine magnitude and sign of its topological charge.