High-Coherence Supercontinuum Generation Using Orbital Angular Momentum Modes in Gas-Filled Hollow-Core Fibers

We numerically demonstrate supercontinuum generation in an argon-filled hollow-core fiber using orbital angular momentum (OAM) modes. By solving the generalized nonlinear Schrödinger equation, we demonstrate that OAM modes with topological charge l=2 exhibit significantly enhanced spectral coherence compared to the fundamental Gaussian mode (l=0). The reduced effective nonlinear coefficient γ in OAM modes (γₗ₌₂ ≈ γₗ₌₀/3) provides dual advantages: suppression of modulation instability leading to more deterministic spectral broadening, and inherent robustness against higher-order effects such as self-steepening, whose cumulative impact scales as N². Our results show that the first-order coherence degree |g₁₂⁽¹⁾| remains above 0.9 across the generated supercontinuum for l=2, while dropping below 0.3 for l=0 under identical pump conditions. This work establishes OAM modes in gas-filled hollow-core fibers as a promising platform for highly coherent supercontinuum generation.