Study Of Dirac Mode Fiber

Photonic crystal fibers have attracted wide attention since they were reported,and they have been widely used in fiber lasers,fiber amplifiers,fiber optic sensing,gas nonlinear optics,and optical communications for their superior optical properties.With the extension of photonic crystal fiber applications,there are increasing demands for photonic crystal fibers which can provide new functions.Traditional light-guidance mechanisms in photonic crystal fibers rely on total reflection and photonic band gap,the discovery of new type Dirac mode photonic crystal fibers can realize the guided mode of light at the Dirac frequency.This novel guided mode has unique power-law decaying profile in the transverse plane and the sensitive narrow sharp frequency response,which make it extremely valuable for long-range interactions of a multiple-core optical fiber and the random laser frequency selection.However,Dirac mode photonic crystal fiber still faces some key technologies that need to be broken.At present,only the triangular lattice photonic crystal fiber can transmit Dirac mode,lacking the support of other fiber structures.In addition,the transmission of Dirac mode requires high refractive index glass to support,which increases the difficulty of fiber fabrication.It is necessary to find a new fiber structure capable of transmitting Dirac mode and broaden the use range of fiber materials.Thus the motivation of the present work is to design and explore different Dirac mode fiber structures from theory.Two kinds of fiber structures,namely the modified honeycomb lattice and the Archimedean-like lattice fiber have been designed.The band structures,Dirac mode conditions,and the corresponding Dirac mode transmission performance of the different lattice type photonic crystal fibers have been simulated.We discovered a new fiber structure capable of transmitting Dirac mode,which reduces the refractive index requirement of matrix materials for Dirac mode fibers,and has successfully widened the choice of materials.Detailed research contents and results are as follows:(1)The band structure and Dirac mode of the triangular lattice photonic crystal fiber with high refractive index glass were researched: The band structure of the triangular lattice photonic crystal fiber with the high refractive index glass was calculated using the plane wave expansion method,and it was found that the bands 10 and 11 can form the second Dirac cone.The new Dirac mode operating wavelength blueshifted with the increasing air-filling fraction of the cladding,and redshifted with the increasing refractive index of the cladding.The error of Dirac frequency is only 1.7%,which calculated by the plane wave expansion method and the finitetime domain-difference method.The new Dirac mode can get leakage-free transmission in the fiber from simulation results of finite-time domain-difference method.(2)The band structure and Dirac mode of the modified honeycomb lattice photonic crystal fiber were researched: An modified honeycomb lattice photonic crystal fiber was designed according to the theory of photonic bandgap.The photonic band structure of the modified honeycomb lattice photonic crystal fiber was calculated using the plane wave expansion method,and it was found that the bands 14 and 15 can form the Dirac cone.The new Dirac mode operating wavelength blueshifted with the increasing air-filling fraction of the cladding,and redshifted with the increasing refractive index of the cladding.The new Dirac mode is not limited by the refractive index of the optical fiber material and can be realized in silica glass.The error of Dirac frequency is only 0.48%,which calculated by the plane wave expansion method and the finite-time domain-difference method.The new Dirac mode can get leakagefree transmission in the fiber from simulation results of finite-time domain-difference method.(3)The band structure and Dirac mode of the Archimedean-like lattice photonic crystal fiber were researched.The photonic band structure of the Archimedean-like lattice photonic crystal fiber was calculated using the plane wave expansion method.It was found that the bands 14 and 15 can form the Dirac cone.The new Dirac mode operating wavelength blueshifted with the increasing air-filling fraction of the cladding,and redshifted with the increasing refractive index of the cladding.The new Dirac mode is not limited by the refractive index of the optical fiber material.The error of Dirac frequency is only 0.12%,which calculated by the plane wave expansion method and the finite-time domain-difference method.The new Dirac mode can get leakage-free transmission in the fiber from simulation results of finite-time domain-difference method.