Cladding structures of photonic bandgap fibers often have airholes of noncircular shape, and, typically, close-to-hexagonal airholes with curved corners are observed. We study photonic bandgaps in such structures by aid of a two-parameter representation of the size and curvature. For the fundamental bandgap we find that the bandgap edges (the intersections with the air line) shift toward shorter wavelengths when the air-filling fraction ƒ is increased. The bandgap also broadens, and the relative bandwidth increases exponentially with ƒ<sup>2</sup> . Compared with recent experiments [Nature <i>424,</i> 657 (2003)] we find very good agreement.
© 2004 Optical Society of America
Niels Asger Mortensen and Martin Dybendal Nielsen, "Modeling of realistic cladding structures for air-core photonic bandgap fibers," Opt. Lett. 29, 349-351 (2004)