“…Interferometric methods to identify the OAM charges have been proposed using a lateral shear interferometer [6,7], self-interference [8], Mach-Zehnder interferometers [9,10], an inverted field interferometer [11], and a multipoint interferometer [12]. Other approaches to detect OAM state have exploited far-field diffraction patterns with a single slit [13], a double slit [14], and with unique apertures including a triangular aperture [15], a hexagonal aperture [16], a binaural circular aperture [17], a parabolic-line grating [18], a radial grating [19], a selectorial screen of a transparent disk [20], and a metasurface grating [21]. Diffraction has been used for OAM determination not only in the far-field context, but also as near-field diffraction.…”