Efficient measurement of the topological charge of partially coherent elliptical vortex beams via twist phase modulation

In this paper, we combined the twist phase with elliptical vortex beams to systematically investigate the evolutionary properties of the spectral density and spectral degree of coherence (SDOC) for the partially coherent twisted elliptical vortex (PCTEV) beam, and realized efficient measurement of the PCTEV beam's topological charge. Our results show that modulating the beam's twist phase and ellipticity, multiple intensity minima emerge in the focal plane, whose number corresponds to the topological charge, which offers an approach for determining the topological charge of partially coherent vortex beams. Moreover, under the condition of consistent sign between the topological charge and twist factor, reduction in ellipticity of the PCTEV beam can enhance the side rings in SDOC, thereby significantly improving the measurement capability for high-order topological charges. Notably, when the sign is opposite, the twist phase will cause a transformation in the form of coherence singularities, changing from a ring-shaped distribution to a dark dot distribution. By analyzing the distribution of these singularities, the topological charge can be determined under different coherence conditions, even in the case of low coherence. Our results can find potential applications in information encryption and free-space optical communication.