Supercontinuum generation from Topological Edge Supermodes in a short SSH Photonic Crystal Fiber

Abstract: We introduce a topological photonic-crystal fiber that embeds a short Su-Schrieffer-Heeger (SSH) chain and supports two edge supermodes. Using full-vector modal analysis and a coupled generalized nonlinear Schroedinger equation, we show that each supermode provides an independent nonlinear channel with a distinct broadening mechanism: the even supermode features two zero-dispersion wavelengths and yields degenerate four-wave mixing sidebands, whereas the odd supermode is all-normal-dispersion and generates a smooth, flat ANDi-type continuum. Exciting a single core prepares a coherent superposition of the two supermodes; cross-phase modulation and inter-parity four-wave mixing then enable energy transfer across detunings inaccessible to either mode alone, producing the broadest and flattest spectrum with new short wavelengths components. Our results establish topology-enabled modal control as a scalable knob for engineering supercontinuum generation in short SSH topological fibers.