Recognition of fractional topological charge through self-rotating beam phase

Abstract

Fractional vortex beams exhibit unique physical properties, including radially notched intensity distributions, complex phase structures, and higher-dimensional orbital angular momentum modulation compared to integer vortex beams. Accurately measuring fractional topological charges (TCs) is essential for harnessing their application potential. This Letter introduces a useful method for recognition of fractional TCs using the self-rotating beam phase. By analyzing the far-field intensity peak of the self-rotating beam phase modulated fractional vortex beam and performing cross correlation operations on diffraction patterns with a hybrid digital-optical correlator, this method achieves precise fractional TC recognition. It is characterized by simplicity, effectiveness, and the elimination of complex interferometer setups. The experimental results show good agreement with theoretical predictions, offering a convenient approach for precise measurement of fractional TCs.