Measuring the topological charge of vortex beams by using an annular ellipse aperture |
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Authors: | H Tao Y Liu Z Chen and J Pu |
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Institution: | (1) College of Information Science and Engineering, Institute of Optics and Photonics, Huaqiao University, Xiamen, Fujian, 361021, China; |
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Abstract: | We theoretically and experimentally investigate the Fraunhofer diffraction pattern of a vortex beam passing through an annular
ellipse aperture. It is found that the pattern of the far-field diffraction intensity distribution exhibits some dark spots,
which become clearer with increasing the value of the ellipticity factor of the annular ellipse aperture. The diffraction
phenomenon is more obvious with increasing the value of the ratio of the inner long axis (or short axis) to the outer side
of the annular ellipse aperture. The number of the dark spots in the Fraunhofer diffraction intensity distribution is just
equal to the topological charge value of the measured optical vortex, and the centre of each dark spot is just a phase-singularity
point. Based on this property, we can measure the topological charge of an optical vortex beam. |
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Keywords: | |
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