Modeling of realistic cladding structures for air-core photonic band-gap fibers

Abstract

Cladding structures of photonic band-gap fibers often have air-holes of non-circular shape and, typically, close-to-hexagonal air holes with curved corners are observed. We study photonic band-gaps in such structures by aid of a two-parameter representation of the size and curvature. For the fundamental band-gap we find that the band-gap edges (the intersections with the air line) shift toward shorter wavelengths when the air-filling fraction f is increased. The band-gap also broadens and the relative band-width increases exponentially with f^2. Comparing to recent experiments [Nature 424, 657 (2003)] we find very good agreement.