Interferometric detection method for orbital angular momentum of vortex beams

This study proposes a new method to detect the orbital angular momentum of vortex beams using interferometry. Experimentally, when a spatial light modulator is used to generate a vortex beam, coaxial interference directly occurs only by a modulated vortex beam and an incident Gaussian beam which is not fully modulated, producing a perfect petal-like interference pattern. The number of interfering petals coincides with the value of the orbital angular momentum carried by the vortex beam; thus, a separate reference beam is not required when we detect the orbital angular momentum of vortex beams produced by the spatial light modulator. This study analyzes the interference pattern of Bessel-Gaussian and Laguerre-Gaussian beams, which can reflect the orbital angular momentum of the beam, i.e. , the azimuth factor and the positive and negative values of the orbital angular momentum together with the radial factor of the Laguerre-Gaussian beam. Notably, the interference results are clear, and the stability is high.