Design And Nonlinear Research Of Subwavelength Core Photonic Crystal Fiber

Photonic crystal fiber(PCF)has excellent optical properties and flexible design,which makes it a typical photonic device for application in optical fiber communication and optical fiber sensing systems.Recent years,with improvement of the theory and fabrication techniques of PCF,sub-wavelength core photonic crystal fiber(SCPCF)with silica substrate and non-silica core has attracted more and more attention.Compared with traditional silica PCF,SCPCF has a wider optical propagation band width,higher nonlinearity coefficient and greater flexibility to adjust the birefringence and dispersion of fiber.Therefore,the SCPCF is becoming research hot in design of photonic device and optical nonlinear application.In this paper,structural design and nonlinear optical characteristic of SCPCF are deeply investigated theoretically.The main works as follows:1.First,we introduce the concept,characteristics and fabrication of PCF.Then on this basis,the forming background and concept of SCPCF are introduced.Based on light-wave equations,we derived the optical pulse transmission equation in fibers,and expound several nonlinear effect in fiber.2.Several common analysis methods of PCF are briefly introduced.And among these methods,we discussed the full-vector finite element method(FV-FEM)in detail which lay a solid theoretical foundation for numerical simulation of SCPCF in this paper.And we discussed the numerical computation method of nonlinear Schrodinger equation in which Raman response function is included.3.Based on tellurite ellipse core,we design a SCPCF with high birefringence and high nonlinearity by introduce four asymmetric holes between the core and the octagonal cladding.With full-vector finite element method,we investigate influence of the structure parameter of proposed fiber(such as,size of core,eccentricity of core,and size of inner cladding)to the birefringence,nonlinearity coefficient and dispersion.This work is meaningful for the research of relationship between the structure parameter and optical characteristic.4.A liquid-core photonic crystal fiber is designed for supercontinuum.The substrate material of proposed fiber is silica,and the core is filled with CS2.By adjusting the structure parameter reasonably,fiber with all-normal dispersion in 1200-2500 nm is obtained.With split-step Fourier method,supercontinuum(SC)generation and its physical mechanism in proposed fiber is investigated.Besides,we study the influence of pump parameters(fiber length,pump power and pulse duration)to the bandwidth and coherence of generated SC,and summarize the change rule of spectrum feature with different pump parameters.All these works have great guiding significance for parameter selection of SC generation and quality optimization of generated SC.