Study On The Properties Of Band Gap And Waveguide Slow Light In Two Dimensional Photonic Crystals

Photonic crystals are synthetic crystals, made of two or more kinds of dielectric building blocks arried in 1D, 2D and 3D period structure. The velocity of the light in photonic crystals can be controlled with the band gap and the slow light propoties of photonic crystals. Relative to other slow-light technologies, the greatest advantage of slow light in photonic crystal waveguides is that it can produce slow light at room temperature in compact in size, and the light velocity can be modified by designing deffernt photonic crystal structures. Then photonic crystals can be applied in optical delay line, optical buffering, all-optical storage, optical communication and etc. Different optical function devices with great behaviors can be made, and there applications will be widely and important in high speed information processing and data transport fields.In this thesis, properties of two-dimensional photonic crystal band-gap and waveguide slow light are analyzed. New photonic crystal structures with better band gap characteristics and performance of slow light, have been designed through studying the structure parameters on band-gap size and waveguide properties of slow light, as well as the coupling of conventional waveguide and photonic crystal waveguide. The contents are as follows:1. Band gap characteristics of two-dimensional hexagon column (air hole) photonic crystals is analyzed with PWE. The relationship between the change of band gap and fill factor as well as crystal lattice constant is reserached; The influence of difference between the background refraction and the column (air hole) refraction on band gap is also analyzed; when the air holes are overlapped, the reason of the band gap appearance is explained.2. Investigate the characteristics of slow light in the 2D triangular rods photonic crystal line defected waveguide using PWE (Plane Wave Expansion method) . We analyze the effect of the filling factor and radius of the defect rods on the group velocity of guided mode separately, and compare the effect. The waveguide structure with group velocity smaller than 0.01c is demonstrated through detuning the filling factor and defect rods size. Characters of GVD (Group Velocity Dispersion) of slow light are also analyzed, and the magnitude of second-order coefficient of GVD value in the area of ultra slow light is about 10~5-10~6 ps~2/km ,which can guarantee the propagation with efficiency.3. The field distribution is simiulated with FDTD (Finite Difference Time Domain method) when the light transmits in the line defected PCW (Photonic Crystal Waveguide) . And the coupling between the normal waveguide and the photonic crystal waveguide is studied. Mode field impedance mismatch problem are founded because of the coupling of different structural parameters or geometry. And we also point out the direction for further research.