Striving towards a periodicity breaking of the photonic crystal fibers microstructuration for an unprecedented singlemode robustness

Abstract : We report in this communication on the investigation of novel triple-clad Very-Large-Mode-Area (VLMA) largepitch- fibers demonstrating numerically a strengthening of the fiber singlemodeness. The practical feasibility of the proposed fiber designs is ensured by taking into account the specifications of the resorted manufacturing technique. After a brief discussion about the mechanism of modal filtering into state-of-the-art air-silica leaky structures, we will present a novel kind of VLMA fibers. Here, the standard 6-fold symmetry as well as the periodic photonic crystal cladding are removed in profit to a totally aperiodic inner cladding microstructuration. This aperiodicity enables to exacerbate the singlemode robustness by maximizing the high-order-modes (HOMs) leakage out of the gain region in favour of the Gaussian fundamental mode. The behaviour of two different aperiodic LPFs is reported in regard to the refractive index of the inclusions, the doped core diameter and the operating wavelength. Thus, the scalability of these novel structures is evidenced. Finally, the manufacturability challenge is estimated by taking into account small index-mismatch between the active core and the background material.