Topological Charge And Its Measurement Of Vortex Beam

Vortex beam is a new type of beam newly discovered. Phase vortex beams having a continuous spiral structure, with a phase singularity, and therefore also is called vortex beam is a spiral beam. Due to its special wave front phase structure makes the vortex beam has many advantages compared to other beams. In recent years, vortex beams in optical tweezers, optical fiber operations, laser communications, biomedical, atomic and molecular optics and other fields have a wide range of applications. Various properties of the vortex beam research has become a hot spot. Topological charges vortex beam is a vortex beam of important properties, the topological charge is to distinguish between different vortex beams is an important feature. The focus of this paper is to work on topological charge measurements were vortex beam theory.The first chapter in order to further study the topological charge of the vortex beam, firstly for a brief overview of vortex beams, introduction to the history and current development research vortex beam.The second chapter introduces the theoretical basis of vortex beams, illustrating the vortex beams carrying orbital angular momentum, and angular momentum depends on the size of the topological charge. Systematic method of measuring the vortex beams summarizes the topological charge of recent research findings. Highlights the principle of Mach-Zehnder interferometer, CGH method, vortex beams with plane wave interferometer, Young’s double slit interference method, the Fourier transform method annulus to measure the topological charge of the vortex beams, experimental apparatus and the relevant test results.The third chapter will be on the vortex measuring beam topological charge image recognition technology applications, for the endless belt Fourier transform method further processing by machine identification methods, direct calculation of the topological charge of the vortex beam size. Description of the flow of image processing. Binarization process using Otsu algorithm for the design of the special nature of image recognition algorithm new ring.The fourth chapter design an improved measurement of vortex beams topological charge measurement. First, an improved method of measuring the theoretical analysis. Details of the source of design ideas to design methods of measurement. Then use its methods to the vortex of the topological charge measurement. Then use the Fraunhofer diffraction theory reasoning proof of the feasibility of the method. Then scroll to the incident beam different situations were analyzed and discussed the impact of a single proof seam angle on the measurement results, given the relevant simulation results prove the feasibility of the method. By changing the parameters of design and analysis of the off-axis vortex beam center offset distance measurements relations, vortex beams topological charge distribution on the measurement results validate the single-slit interference point of view of measurement results and describe angles 0.02π to meet the vast majority of cases the measurement.