Realization of an optical vortex from light-emitting diode source by a vortex half-wave retarder and using Talbot effect based detection

An optical vortex with light-emitting diode (LED) as the light source has been studied. The vortex beam is generated by a zero-order vortex half-wave retarder (VHWR). This VHWR generates nondiffracting Bessel beams which can be used in optical tweezers to trap particles. LEDs have a wide range of applications in various fields, and are here used as the source of vortex beam. The characterization of the topological charges and magnitudes of vortex beam has been done using the near-field Talbot effect. The influence of the size of the Gaussian beam is also studied in this work. We provide both theory and experimental demonstration. In addition, we found that the phase selection of the wave function in the Fresnel integral can be used to check the correct direction of topological charge of vortex beam. Our study might be useful for applications in optical communication, microscopic manipulation, and trapping using LED as the light source.