Studies On The Bandgap Structures Of Photonic Crystal Fiber And Properties Of Directional Coupling Waveguides

Photonic crystal (PC) is a new optical microstructure which is periodically constructed by materials with high-index-constants. PC has unique photonic band gap and light-guiding principle optical properties, so the theory and application research of PC is very active. Presently, the researching of PC has become the most advanced and hottest project in optoelectronic field.Because of their potential ability to control light wave propagation, a lot of novel photonic crystal devices such as photonic crystal fiber, photonic crystal waveguides, optical couplers and optical switches, which are the promising components of PC to be realized in photonic integrated circuits, may be constructed by introducing a point defects or line defects into perfect PCs. The main work of this paper is the analysis of band structure of photonic crystal fiber and the optical propagation properties of photonic crystal waveguides.Firstly, initial introduction about the concept, research status quo and application domain of PC, then a composite triangular lattice photonic crystal which can generate absolute photonic band gap is studied by finite difference time domain method, which is the fundament about PC research.Secondly, according to the different light-guiding principle, we discuss two kinds of photonic crystal fiber. In chapter 3, the band gap distribution and bounded models field distribution on 2D photonic crystal fiber exhibiting a photonic band gap effect are numerically simulated by the plane wave expansion method. In chapter 4, two new photonic crystal fibers structure guiding light by total internal reflection with asymmetry in the vicinity of the core are proposed. There are many unique optical characteristics in the PCF, such as effective refractive index, endless single mode, high birefringence and flexible dispersions, are studied by effective index method and multi-pole method, analyzed and researched the results.Finally, self imaging effect is the primary principle for multi-mode interference (MMI) devices. The general and overlapping self imaging effect have been elucidated in detail in chapter 5. Some novel photonic crystal waveguide multimode interference optical devices based on self-imaging effect are designed and analyzed. The designing principle and optical propagation properties of the devices have been demonstrated by finite difference time domain method and the plane wave expansion method. Meanwhile we analyze in theory the advantages of MMI devices compared with thegeneral optical devices. They are more compact, more robust, higher transmission rate,broader bandwidth, easy manufacturing and easy integration in large scale. Theseexcellent properties can find a wide application in photonic integrate circuits.