Non-hexagonal Large-Pitch Fibers for enhanced mode discrimination

Photonic-Crystal Fibers (PCF) are among the most promising concepts to achieve large mode field areas suitable for the reduction of nonlinearities in fibers. Differential mode propagation loss is the cornerstone of effective single-mode behavior in passive and core-pumped active PCFs. In this work, we explore non-hexagonal PCF designs with increased mode discrimination in comparison to the classical hexagonal PCF designs. It is shown that a pentagonal design can increase the mode discrimination and, simultaneously, also improve the beam quality of Large-Pitch Fibers with mode field diameters well beyond 100 µm.