Helicity inversion and generation of orthogonal, degenerate index states of generic C points

Abstract

We discuss a technique to invert the helicity of generic C points and generate its orthogonal state of polarization in a single step through a fork grating (FG). It is experimentally demonstrated that the beam in each of its diffraction orders possesses a degenerate C point index state. The diffraction phenomenon reported is helicity-dependent, in which left and right-handed ellipse field singularities are separated. The orthogonal polarization state of the input singularity is produced in one of the first diffracted orders of the grating. For every singularity that the grating produces, its orthogonal polarization state is also available in one of its diffraction orders. In contrast to a half-wave plate, where helicity inversion is accompanied by index inversion, a FG inverts helicity without inverting the index. Therefore, a FG can be used to perform multi-functions under generic C point illumination.