Abstract
In this work, a circular dual-core photonic crystal fiber is proposed for dispersion compensation for the controllable orbital angular momentum (OAM) mode by the inner-outer core mode coupling. This design can simultaneously realize a negative dispersion of up to −3039.45 ps nm−1 km−1 for OAM mode HE31 and a high effective index separation of 2.15 × 10−3 within scalar linearly polarized (LP)21 mode group (HE31 and EH11) at 1.55 µm, ensuring HE31 vortex mode robust propagation without channel crosstalk. Evolution of the combined effective index, OAM phase, and electric field is systemically verified functioning as wavelength during the inner-outer mode coupling. Structural parameter dependence of negative dispersion is demonstrated with respect to lattice constant, air hole size and air-filling fraction, remarkably suggesting that negative dispersion dip at phase-matching wavelength exhibits an enhanced blue shift with lattice constant of inner cladding increasing but a red shift with lattice constant of outer cladding. The feasibility of this design is demonstrated with an achievement of negative dispersion of −1773.21 ps nm−1 km−1 for EH11 mode at wavelength 1.55 µm by tuning the structural parameter. This design is expected for fiber applications in OAM-based optical communication systems.
Published Version
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