Understanding air-core photonic-bandgap fibers: analogy to conventional fibers

• Published in: Journal of lightwave technology Vol. 23; no. 12; pp. 4169 - 4177
• Main Authors: Digonnet, M.J.F., Hyang Kyun Kim, Kino, G.S., Shanhui Fan
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-12-2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Air-core photonic-bandgap fibers; Analogies; Apertures; Applied sciences; Circuit properties; Computer simulation; conventional solid-core fiber; Cutoff frequency; Electric, optical and optoelectronic circuits; Electronics; Equivalence; Exact sciences and technology; Fibers; Integrated optics. Optical fibers and wave guides; LP modes; Mathematical models; numerical aperture; Optical and optoelectronic circuits; Optical fiber polarization; Optical waveguide components; Optical waveguide theory; Optical waveguides; PBF; Photonic band gap; Predictive models; Simulators; Solid modeling; Surges; Integrated optics; conventional solid-core fiber; Step index; LP mode; Cladding; Air-core photonic-bandgap fibers; Waveguide; LP modes; Numerical aperture; PBF; Fiber core; Simulator; Optical fiber
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2005.859406

It is shown from basic principles that the core modes of an air-core photonic-bandgap fiber (PBF) exhibit similar qualitative and quantitative behavior as the linearly polarized (LP) modes of an equivalent conventional fiber whose step-index profile is entirely determined by the band edges of the PBF. This analogy leads to the concept of effective numerical aperture (NA), which is used to provide an intuitive interpretation of the qualitative behavior of PBF modes. By using this equivalence, several key properties, including the number of modes, their cutoff, effective index, size, and divergence, and the dependence of these quantities on the PBF core and cladding parameters, can be predicted approximately by simulating the LP modes of the equivalent step-index fiber using standard LP-mode simulators or well-known formula. Besides providing a convenient tool to model the modes of a PBF, this analogy gives new physical insight into the fundamental characteristics of these complex waveguides.