Generation and manipulation of high-order orbital angular momentum in helically twisted dual-core photonic crystal fiber based on filling polyglycerol

Abstract

Orbital angular momentum (OAM) technology shows great potential to enhance communication capacity and spectrum utilization. We propose and numerically investigate a polyglycerol-filled dual-core helically twisted photonic crystal fiber (PFH-PCF) for simultaneous realization generating and dynamically manipulating OAM. The proposed structure consists of a hexagonal arrangement of air holes, with the absence of air holes on both sides of the central air hole, forming two solid inner cores, and a filling layer formed by polyglycerol filled in the fourth layer of air holes. Numerical calculations using the finite element method revealed that the higher-order modes of the filling layer couple with different supermodes of the inner cores at the wavelengths of 1101, 1281, 1469, and 1913nm, resulting in OAM generation in the filling layer. The coupling between the dual inner cores and the outer filling core follows the rule of even supermode coupling with even OAM modes and odd supermode coupling with odd OAM modes. The designed fiber can generate OAM modes up to an order of l=+16, with a purity exceeding 94%. Additionally, a temperature change of 20°C results in a spectral shift of 100-200 nm for the OAM operating wavelengths, while a twist rate change of 628.318 rad/m also results in resonance wavelengths shift with a range of 150-250 nm, allowing for free dynamic manipulation of the OAM beam. The excellent results indicate that the presented design has great potential applications in the fields of optical control devices and all-fiber optical communication.