“…The significance of vortex beams has led to a variety of techniques to measure their phase profile. Representative examples include interference with a planewave [16] or a mirror image copy [17], a rotational symmetry analysis [18], multipoint interferometry [19], diffraction from an annular [20] or triangular aperture [21], an angular to linear momentum mapping [22], a full modal decomposition [23], an off-axis superposition of vector modes [24], and a Stokes parameters based method [25], among others.…”