Title :
Comparison of zoned microstructure fiber geometries for low-dispersion waveguiding
Author :
Hisatomi, Makiko ; Parker, Michael C. ; Walker, Stuart D.
Author_Institution :
Fujitsu Labs. of Eur. Ltd., Ipswich, UK
Abstract :
This paper presents a comprehensive analysis of zoning in microstructure fiber (MSF) in which parabolic and Gaussian graded-index (GRIN) refractive-index profiles are compared in both continuous and zoned geometries. Ray trajectories were calculated using Fermat´s principle of least time and the paraxial approximation. Optimization of the zoned MSF refractive-index profile revealed that a piecewise Gaussian refractive-index profile exhibits aberration of just 10-nm on-axis focal variation, compared with 40 nm in the zoned parabolic case. In addition, a quarter-period length of the Gaussian-zoned MSF has a 630-nm theoretical spot-size, thus offering efficient coupling between standard single-mode fiber and photonic-crystal devices. A preliminary analysis of a binary radially chirped Bragg fiber geometry is performed using an eigenmode expansion of Maxwell´s equations. Its simpler geometry offers fabrication advantages, but its spot size is closer to 1.2 μm due to its 41-μm quarter-period focal length, and it suffers greater waveguide dispersion compared with the optimized zoned GRIN MSF geometry presented here.
Keywords :
Maxwell equations; aberrations; eigenvalues and eigenfunctions; gradient index optics; lenses; optical fibre couplers; optical fibre dispersion; optical focusing; optical waveguide theory; photonic crystals; ray tracing; refractive index; zone plates; 1.2 mum; 630 nm; Fermat principle; Fresnel zone; GZ-MSF lens; Gaussian refractive index profile; Gaussian-zoned MSF; Maxwell equations; aberration; binary Bragg fiber; continuous fiber geometries; eigenmode expansion; graded-index fiber; least time approximation; low-dispersion waveguiding; microstructure fiber; on-axis focal variation; optical coupling; optimization; parabolic refractive index profile; paraxial approximation; photonic crystal devices; piecewise Gaussian profile; quarter-period focal length; radially-chirped Bragg fiber geometry; ray trajectories; standard single-mode fiber; waveguide dispersion; zoned fiber geometries; zoned microstructure fiber geometries; zoned parabolic MSF; zoning; Geometry; Lenses; Maxwell equations; Microstructure; Optical fiber couplers; Optical fiber devices; Optical refraction; Optical waveguides; Performance analysis; Photonic crystal fibers; Dispersion; Fresnel zone; optimization of fiber geometry; photonic-crystal fiber; propagation characteristics;
Journal_Title :
Lightwave Technology, Journal of
DOI :
10.1109/JLT.2004.841260
