Research On Supercontinuum Generation In Photonic Crystal Fiber And BK9 Glass

Photonic crystal fibers (PCFs) are established as a novel fiber technology. PCFs,which have been first demonstrated in 1995, are optical fibers with a periodicarrangement of low-index material in a background with higher refractive index. Inorder to achieve a special purpose, researcher can change the internal structure ofPCFs arbitrarily. PCFs possess many novel advantages over ordinary single-modeoptical fiber, for example, Super large single-mode field diameter , tunabledispersion and high nonlinear coefficient and so on.PCF is now finding applications in fiber-optic communications, fiber lasers,nonlinear devices, supercontinuum light source, optical amplifiers, high-powertransmission, highly sensitive gas sensors, and other areas.The application of supercontinuum is a hot research point. Supercontinuum whitelight source generated in PCFs can be used in optical communications, opticalcoherence tomography (OCT), meteorological science, wide spectral detection andso on.The outline of this thesis as follows:(1) The physical mechanisms of ultrashort pulse transmission in photonic crystalfiber are discussed on the basis of Maxwell's equations. Nonlinear Schrodingerequation (NSE) and generalized nonlinear Schr?dinger equation (GNSE) thatinclude high order nonlinear effects are derived. NSE is a nonlinear partialdifferential equations. Split-step Fourier method is used to solve NSE.(2) On the basis of theoretical analysis, we carried out time-domain andspectral-domain simulation by using fast split-step Fourier method coded inMATLAB environment. Experimental platform and optical system are designed.Experiments on supercontinuum generation in PCFs and BK9 glass pumped byfemtosecond pulse are conducted.(3) Supercontinuum generation in photonic crystal fiber pumped by femtosecondpulse in anomalous dispersion region is studied. Experimental results are analyzedincluding high order soliton pulse compression, non-soliton radiation blue shift, redshift of high order soliton splitting, self-phase modulation and other nonlineareffects.(4) Principle of Frequency Resolved Optical Gating (FROG) and inversionalgorithm are reviewed. FROG technique is used to measure temporal characteristicsof supercontinuum generated in K9 glass.