Research On Diffraction Characteristics Of Vortex Beam Possessing Different Topological Charge

A vortex beam possesses spiral phase factor exp(ilθ)(l is topological charge ofvortex beam). The photon orbital angular momentum of every photon is l. Thespecial orbital angular momentum of vortex beam make it have wide applicationprospects in atom optics, biomedical, quantum information coding, photoninformation processing and optical micromanipulation. We can observe highertransfer rate than ordinary single frequency beam when the vortex beam with spiralphase factor is applied to communication system. The communication system basedon orbital angular momentum is applied to optical frequency range and radiofrequency. We study the external form of the vortex beam topological charges toconfirm the orbital angular momentum of vortex beam. It is valuable for studyingthe vortex beams are applied to communication for improving the data transfer rate.This paper focus on calculating and analyzing diffraction patterns of vortex beamthrough different apertures, obtained a counting method of determining thetopological charge number of vortex beam.In this paper, according to the research objectives, the main research workwould be carried out as following four aspects.1、Introduced the development history and research status of optical vortex, andexplained the main work of this article.2、In this paper, vortex beam is described with mathematics, and the commonmethods to generate vortex beams are summed, such as mode conversion methods,hologram methods, spatial light modulator method, spiral phase plate method,andusing a laser resonator output vortex beam. Relative merits of various methods areanalyzed. 3、The diffraction light intensity distribution characteristics of vortex beampossessing different topological charge numbers through special aperture arecalculated and analyzed, and obtained a conclusion that the topological chargecorresponds with the light intensity distribution. The result can be used to measurethe number of topological charge by diffraction experiment.4、Analyzed the diffraction characteristics of vortex beam through a apertureconsist of four arched holes, hexagonal array aperture consist of circular holes andsquare holes. The analysis showed that the light intensity in a ring distribution oflight and dark, and with the number of topological charge increasing, increasesdiffraction series. Diffracted by hexagonal array aperture consist of consist of fourarched holes, a kind of Rotating Tail phenomenon existed in the diffraction pattern.It’s direction corresponds with the positive and negative of topological charge.Diffracted by hexagonal array aperture consist of square holes, the diffractionpatterns are complex, the diffraction light intensity distribution depends on parity ofthe topological charge.