title: Broadband robustly single-mode hollow-core PCF by resonant filtering of higher-order modes.
abstract: We report a hollow-core photonic crystal fiber that is engineered so as to strongly suppress higher-order modes, i.e., to provide robust LP01single-mode guidance in all the wavelength ranges where the fiber guides with low loss. Encircling the core is a single ring of nontouching glass elements whose modes are tailored to ensure resonant phase-matched coupling to higher-order core modes. We show that the resulting modal filtering effect depends on only one dimensionless shape parameter, akin to the well-known d/Λ parameter for endlessly single-mode solid-core PCF. Fabricated fibers show higher-order mode losses some ∼100 higher than for the LP01mode, with LP01losses <0.2  dB/m in the near-infrared and a spectral flatness ∼1  dB over a >110  THz bandwidth.
authors.forename: Patrick
authors.initials: P
authors.lastname: Uebel
authors.forename: Mehmet C
authors.initials: MC
authors.lastname: Günendi
authors.forename: Michael H
authors.initials: MH
authors.lastname: Frosz
authors.forename: Goran
authors.initials: G
authors.lastname: Ahmed
authors.forename: Nitin N
authors.initials: NN
authors.lastname: Edavalath
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Ménard
authors.forename: Philip St J
authors.initials: PS
authors.lastname: Russell