Abstract
Orbital angular momentum (OAM) is a degree of freedom independent of polarization and frequency of vortex beams. Therefore, the measurement of OAM has attracted great interest. In this paper, we propose a method to detect OAM beams utilizing far-field diffraction feature fringes caused by fork-shaped grating (FSG), which has characteristics of wide-range, high efficiency, and excellent extensibility for detection of high-order OAM beam. We give a detailed explanation of the concept and feature of FSG detection theoretically, and improve detection reliability of fringes by increasing the number of forks and setting appropriate offset. Experimentally, we achieve detection of OAM+50. Moreover, although only two OAMs were detected at the same time in our experiment, FSG can also be used in the detection of multi-OAM beams due to the excellent extensibility of this method. Our finding opens up a new method for the detection of high-order OAM and multi-OAM beams, which is of great significance to the application of FSG.
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