Affiliation:
1. Swiss Federal Laboratories for Materials Science and Technology, Empa, Laboratory for Transport at Nanoscale Interfaces
2. Swiss Federal Laboratories for Materials Science and Technology
Abstract
Abstract
Light beams that carry Orbital Angular Momentum (OAM) are explored in applications from microscopy to quantum communication. At the same time, a revival of the Talbot effect is seen in modern optics from atomic systems to x-ray phase contrast interferometry. In this paper, we link these two phenomena through a symbiotic interaction in the THz range by means of binary amplitude fork gratings. While the assessment of OAM in the far-field diffraction orders of a fork grating is well-established, here we show how the topological charge of the diffracted beam can be evidenced in the near-field by means of the Talbot effect. For this purpose, the evolution of the diffracted beam behind the fork grating is analysed in Fourier domain. We obtain the typical donut-shaped power distribution and isolate the inherent phase vortex using the Fourier phase retrieval method.
Publisher
Research Square Platform LLC