Topological photonic crystal fiber with near-zero flattened dispersion

• Topological photonic crystal fiber with guiding corner mode. • Non-zero bulk polarization and corner charge. • Structural defects-immune near-zero flattened dispersion. • Symmetric supercontinuum and frequency comb. Robustness against structural disorder or defects is a fascinating feature of topological photonic systems, triggering the extensive investigations in modern photonics. Recently, the marriage of topological photonics and fiber optics resulted in a new research direction of photonics with promising applications. In this work, we propose a new type of topological photonic crystal fiber (PCF) with guiding topological corner mode, which has near-zero flattened dispersion. Due to the design flexibility of the fiber cross-section and topological robustness of waveguiding modes, the topological PCF exhibits near-zero flattened dispersion immune to structural disorder and defects at telecommunication wavelength for proper structural parameters. In the dispersion-flattened topological PCFs, symmetric supercontinuum (SC) and frequency comb based on four-wave mixing (FWM) spanning from 1300 nm to 1800 nm can be generated for short fiber lengths in the range of 1–1.5 m. The presented results will broaden the applications of topological PCFs for nonlinear fiber optics due to the structural defects-immunity.