Theoretical Analysis And Fabrication Technique Research Of Highly Nonlinear Photonic Crystal Fiber

Supercontinuum sources have great advantages of broadband radiation, stability and spatially coherent. They are starting to be used in applications such as optical communications, the generation of ultra-short pulse, optical coherence tomography(OCT), optical frequency metrology, and so on. Recent research efforts have been focus on the development of supercontinuum sources using micro-structured fibers. Wide Supercontinuum spectrum has been successfully generated by photonic crystal fiber (PCF) owing to its highly nonlinearity and flexible design of the dispersion profile. In addition, the tailorability of the cladding structure enables high flexibility in the design of the dispersion profile facilitating different nonlinear effect, especially the zero-dispersion wavelength(ZDW) can be shifted into short wavelength band(670-880nm)because of the large waveguide contribution to the dispersion which will be suitable for supercontinuum generation with Ti: sapphire laser pulses.Recently Photonic crystal fiber has attracted of a lot of researchers interests and theoretical analysis and fabrication study have been carried on by a lot of research groups. Nowadays new sorts of fiber are continuously appearing. In this thesis, the methods of structure design, the transmission characteristics, the fabrication process and the key technique in fiber splicing will be discussed. The main parts are as follows:(1) The mathematical methods used in the investigation of photonic crystal fiber are deduced and analyzed. Chapter 2 has introduced the beam propagation method, plane wave method and finite element method respectively. And in Chapter 3 these methods are used to simulate the fiber characteristics with chromatic dispersion, nonlinear coefficient and confinement loss respectively.(2) The relationship between fiber structure parameter and optical transmission characteristics are discussed using Rsoft software. Basing on the theoretic simulation, a highly nonlinear photonic crystal fiber is designed for supercontinuum generation with Ti: sapphire laser pulses.(3) The fabrication process of photonic crystal fiber is introduced. And with the technique mentioned in Chapter 4 the photonic crystal fibers have been fabricated according to the theoretical design. (4) The key technique of photonic crystal fiber splicing with normal single mode fiber is discussed theoretically and experimentally.(5) The characteristics of fiber chromatic dispersion, nonlinear coefficient and confinement loss are measured. The fiber for commercial application is expected by optimizing the fiber structure and fabrication technique.The thesis draws a conclusion that a highly nonlinear photonic crystal fiber is designed and fabricated, of which the zero-dispersion wavelength is around 860nm and the dispersion curve at 800nm wave band is flattened. Supercontinuum emission with spectrum stretching over 900nm is obtained by injecting Ti: sapphire laser pulses.