The Theoretical Study Of Two Dimensional Photonic Crystals And Its Waveguides Used For Optical Amplification

Photonic crystals are artificial crystals in which the materials with different refractive indices are regular arranged. Due to the capability to control the propagation of electromagnetic wave, optical devices based on photonic crystals have potential huge application. At present, photonic crystal waveguides,which are fabricated by introducing linear defects in two dimensional photonic crystals, have become an important research direction in this field. BandSOLVE and FULLWAVE are simulator of Rsoft, base on Plane Wave Expansion (PWE) method and Finite-Difference Time-Domain (FDTD) method, respectively. The two simulators are adopted to model and analyze photonic crystal waveguides.Square lattice, triangular lattice and honeycomb lattice have been studied in this work. The photonic bandgap(PBG) of 2D photonic crystal structures are derived and analyzed using PWE. According to the computed results, the relationship between bandgap and lattice structure, fill ratio, refractive index of substrate is studied. Finally, the structures have been found which could be used as photonic crystal waveguide.The representative triangular lattice photonic crystal composed of circular air-cylinders has been constructed as a photonic crystal waveguide by introducing a line defect and setting the fill ratio r/a=0.42 and refractive index of substrate n=5. Through the simulation of photonic bandgap of the structure with a line defect, two localized defect models with dimensionless frequency of 0.47 and 0.3 in the PBG are found to match the 980nm pumping light and 1530nm signal light respectively. According to PBG=α/λ, the lattice constant corresponding to pumping and signal light is 460 nm. We reset the lattice constant and radius to be 460nm and 193nm respectively in the photonic crystal structure we chose before. Some waveguides are designed including line waveguide,60°bend waveguide,120°bend waveguide, Y-junction waveguide and multi-bend waveguide. Transmission characteristics of pumping and signal light have been simulated (signal light only in multi-bend waveguide). Optimization are done on some photonic structures, through the introduction of a new air-cylinder in bend finally we have got a comparatively good light propagation outcome.