2024-03-29T11:52:18Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/301572022-11-17T02:08:08Zhdl_2115_20053hdl_2115_145Realistic Design of Large-Hollow-Core Photonic Band-Gap Fibers With Suppressed Higher Order Modes and Surface ModesSaitoh, KunimasaFlorous, Nikolaos JohnMurao, TadashiKoshiba, Masanori007This paper theoretically describes effective suppression of higher order modes (HOMs) in realistic large-hollow-core photonic band-gap fibers (PBGFs) and utilizes the use of this class of waveguides for low-loss data-transmission applications and high-power beam delivery systems. The proposed design strategy is based on the resonant-coupling mechanism of central air-core modes with defected outer core modes. By incorporating six 7-unit-cell air cores in the cladding of the PBGF with sixfold symmetry, it is possible by resonantly coupling the light corresponding to the HOMs in a central 19-unit-cell core into the outer 7-unit-cell core, thus significantly increasing the leakage losses of the HOMs in comparison to those of fundamental mode. We consider a realistic PBGF structure with hexagonal airholes having rounded corners and derive a surface-mode-free condition of a silica-ring thickness surrounding the hollow core for both 7-unit-cell and 19-unit-cell cores. Verification regarding the propagation properties of the proposed design is ensured with a PBGF analysis based on a finite element modal solver. Numerical results show that the leakage losses of the HOMs can be enhanced in a level of at least three orders of magnitude over 200-nm wavelength range in comparison to those of the fundamental mode, while in addition, we show that the incorporation of a realistic air core with optimized silica-ring thickness can eliminate surface modes and achieve strong confinement into the central core and very low $eta$ -factor for the fundamental mode.IEEEJournal Articleapplication/pdfhttp://hdl.handle.net/2115/30157https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/30157/1/JLT25-9.pdf0733-8724Journal of Lightwave Technology259244024472007-09enginfo:doi/10.1109/JLT.2007.902749©2007 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.publisher