| Popis: |
Vortex beams have attracted attention due to their unique properties and wide applications. In this paper, a novel scheme for generating the first-order orbital angular momentum (OAM) modes based on anti-resonant reflecting guidance mechanism in ring-core fibers (RCFs) is proposed and experimentally demonstrated. By directly fusion splicing with the standard single-mode fiber (SMF), anti-resonant reflecting guidance of guided-core modes in RCF can be basically motivated. Consequently, the excited modes can well transmit inside the low-refractive-index central core of the RCFs with exhibiting a Gaussian field distribution (defined as the anti-resonant mode, AR mode). Because of different mode coupling coefficients under external pressure on the RCF, these AR modes can be coupled to the HE11 and HE21 modes, respectively. Results show that, by adjusting the polarization state of injected light beams as well as the pressure on the RCF, OAM modes with topological charge numbers of both the positive (L = +1) and negative (L = -1) can be separately generated at efficiencies of 63.2% and 61.7%, respectively |
