Photonic crystal fiber metasurface for orbital angular momentum mode generation

Orbital angular momentum (OAM) mode generators have attracted considerable interest due to their unique properties and various applications in optical communication systems to improve the data transmission capacity. However, the reported OAM generators have focused on free-space-based OAM generation. In this study, we propose metasurface-based OAM generators directly deposited on the facet of a large core area photonic crystal fiber. These in-fiber OAM generators provide a very high modal purity of 99% for the OAM(1) and OAM(2) modes with high transmission at an operating wavelength of 1.55 mu m. In addition, the proposed OAM generator provides a high purity (> 90%) over a wide wavelength bandwidth from 1.5 mu m to 1.6 mu m. We believe that this scheme may pave the way for in-fiber metasurface applications.