Several 7-cell core hollow-core fibers with photonic bandgap spectral positions between 1.4 μm and 2.3 μm were
fabricated. The loss follows the ≈ λ-3 dependency previously reported1 with a minimum measured loss of 9.5 dB/km at
We review recent progress on the understanding of optical guidance mechanisms in hollow-core photonic crystal fibers.
Two classes of hollow-core photonic crystal fiber are identified, one guides via a photonic bandgap and the other guides
by virtue of an inhibited coupling between core and cladding mode constituents. For the former fiber type, we explore
how the bandgap is formed using a photonic analogue of the tight-binding model and how it is related to the antiresonant
reflection optical wave-guidance. For the second type of fiber, which can guide over a broad wavelength range,
we examine the nature of the inhibited coupling.