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Topological charge of the vortex beam measurement

Author: LiYangYue
Tutor: PuJiXiong
School: Huaqiao University
Course: Physical Electronics
Keywords: Physical Optics Vortex beams Topological charge Spherical wave interference Diffraction rings Porous film interference Slit interference
CLC: O436
Type: Master's thesis
Year: 2011
Downloads: 83
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Abstract

Since their discovery vortex beams, its transmission characteristics by the people's attention. Research on the vortex beam also has an increasingly important significance. Is a spiral vortex beams of light phase distribution, the phase factor with which the expression exp (ilθ), each photon in the beam orbital angular momentum carrying lh, where l is called the topological charge. Vortex beams in the optical micro-manipulation, biomedicine, information transmission and other fields have important application value. Therefore, the vortex beam has a broad application prospects. In this thesis, vortex beam generation, transmission characteristics, and topological charge vortex beam measurement methods were studied, while the fractional vortex beams were focused on research. The main contents are: 1, based on holographic optical method using a spatial light modulator in the experiment we obtained vortex beam. First, the method of numerical simulation plane wave with vortex beam interference CGH, and loaded into the spatial light modulator. Then after beam expansion nearly plane wave reflected in the spatial light modulator to generate a vortex beam. By changing the calculation of holograms can be produced with different topological charge of the vortex beam. 2, respectively, from the theoretical and experimental research on the generation of vortex beams and interference phenomena. Theoretical analysis of fractional and integer-order vortex beams with spherical wave and plane wave interference, and to experimentally derived from its interference pattern, and the experimental results and theoretical simulations are basically the same. Studies show that, with topological charge vortex beams change will produce changes in the interference pattern. This phenomenon can be used to determine the topological charge vortex beam. 3 to study the vortex beam through an annular aperture diffraction properties after. Purpose is based on the obtained diffraction pattern to determine the topological charge of vortex beams. We theoretically and experimentally studied the vortex beam through an annular aperture diffraction case, the outcome can be achieved through experiments. This paper considers not only the integer order vortex beam also studied the fractional vortex beam diffracted light intensity maps, and discussed the topological charge of the impact of changes in the diffraction patterns, it can be a more comprehensive determination of the topological charge vortex beams . 4, according to the previous single-ring aperture through integer order topological charge of the vortex beam measurements, respectively, in this article we theoretically and experimentally studied the integer order and fractional vortex beams through a single aperture bicyclic ring aperture and after interference pattern. Studies have shown that the interference pattern is not only relevant but also the porous film and the topological charge of vortex beams on. Based on this result, we can measure the integer order and fractional vortex beam topological charge. 5, we propose a new type of angular distribution of the slit, and were theoretically and experimentally studied the vortex beam angular distribution through this slit interference characteristics. Theoretically vortex beam transmitted from the far-field intensity interference pattern of expression was then obtained by experiment experimental results on graph theory has been verified. The results show that the angular distribution of vortex beams through slit interference pattern will increase as the number N of slits and vortex beam topological charge l change varies. This phenomenon is expected to measure the vortex beam topological charge.

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CLC: > Mathematical sciences and chemical > Physics > Optics > Physical optics ( wave optics )
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