Characteristics Of Optical Transmission With Bandgap Control In Bragg Fiber And Its Fabrication

Thank to the unique structure of one-dimensional photonic crystal in the cladding and the mechanism of optical guidance with wide spectra and wide angular direction, Bragg fiber becomes the hotspot in research and innovation of the next-generation microstructured bandgap fibers.Based on the light guidance with wide-spectral and wide- or omni-directional bandgap guidance, the modal cutoff inside the bandgap, and the interaction between the core-guiding mode and the defect-guiding mode, a few key problems in the physical functional devices based on Bragg fibers are investigated theoretically, and the key technologies in the fabrication of semiconductor-polymer Bragg fibers are promoted and verified experimentally.The dependence of between one-dimensional photonic bandgap on the structure parameters are investigated theoretically, the nature of optical guidance by bandgap within wide spectra and wide angular directions is demonstrated; the idea of an open waveguide based on Bragg fiber array is proposed, theoretical analysis supports that the low-loss mode transmission is achievable by properly designing the waveguide structure, and an 0.07-dB/cm leakage loss is accessible.The influences of modal cutoff inside the bandgap on the optical transmission in the fiber are analyzed theoretically, the conditions to realize single fundamental mode (HE11) transmission are founded; with analysis of relation between transmission bandwidth and fiber parameters, the design principles of Bragg fiber for broadband single fundamental mode transmission are proposed, and a 215-nm bandwidth around 1550 nm is achieved; meanwhile, the idea of a three-dimensional micro resonator based on the variation of modal cutoff in bandgap induced by dual tapering of the Bragg fiber is proposed, and the tunability of resonant wavelength and Q-value by the taper structures is verified.The effect of interation between core-guiding mode and defect-guiding mode in Bragg fiber, as well as the controllability of group velocity and dispersion of the core mode, are analyzed theoretically, the achievability of broadband flat and zero dispersion slow light transmission in Bragg fiber by optimization of fiber structures is verified; as a result, a vg=c/5 slow light with 90-nm bandwidth and a vg=0.074c slow light with both zero dispersion and zero dispersion slope are achieved.With choice of As2Se3 and PEI as materials, a manufacture system for semiconductor-polymer Bragg fiber is designed and founded, the key technologies including large-area uniform film evaporation, univorm preform consolidation and uniform fiber drawing are solved primarily, the feasibility of Bragg fiber fabrication is verified experimentally, and a prototype of Bragg-structured fiber is obtained for the first time domestically.