“…Apertures of different shapes ranging from triangular [81,343], circular [344,345], diamond-shaped [161], hexagonal [346], regular polygon [347], and annular [151,155,348,349] were also used in diffraction experiments. Additional methods for vortex charge determination based on using twisted phase element [350], hyperbolic grating [351], axicon [352], spiral spectra [353], single point detector [354], and Talbot effect [355] were also reported in literature. 10.1.3.…”