Study On The Band Gap Of Photonic Crystal Fiber

Photonic Crystal Fiber (PCF) is a two-dimensional photonic crystal material, basing on the concept of photonic crystals. Because PCF has so much strange characteristics that the traditional optical fibers do not have, so it has attracted all the world widespread attention. And photonic bandgap is an important feature in photonic crystal fiber, so researching the appropriate bandwidth photonic bandgap of the photonic crystal fiber is a meaningful study. The bandgap of PCF is theoretical analysed and numerical simulated in this paper. The relation between bandgap and structural parameters is investigated mainly. An improved composite honeycomb photonic crystal fiber is designed, which has a wide-band photonic band gap at optical communication.Firstly, research status and development trends of the band gap of photonic crystal fiber are clarified. The application prospects, current problems and fundamental characteristics of optical fiber are introduced. Then, Basing on Maxwell equations, the characteristic equation calculating the bandgap of photonic crystal fiber is derived by full-vector plane wave expansion method, which is the foundation of the simulation of photonic crystal fiber bandgap.Secondly, utilizing the characteristic equation, the one-dimensional and two-dimensional photonic crystal bandgap map is solved by MATLAB language with specific photonic crystal structure. The influence of the filling fraction and the diameter of air holes on the in-plane and off-plane PBG is investigated and analysed, and the relation between effective dielectric constant and the band gap is found.Finally, an improved composite honeycomb photonic crystal fiber is designed by Rsoft CAD software, and the influence of the air hole size of different rings and the doped dielectric cylinders in the cladding on the band gap is stressful investigated, which is compared with the same parameters of the triangular PCF and composite honeycomb PCF. Through improving the arrangement of these dielectric cylinders in structure or doping the high refractive index medium, the band gap can be improved. Comparing with other two structures, photonic crystal fiber with the improved composite honeycomb structure could achieve a wider band gap.