Slow Light Properties Research In Photonic Crystals

All-optical buffer is essential in the realization of all-optical network scheme in future and it will play a more and more important role in all-optical switching system. The concept of photonic crystal with its unique photonic band gap and slow light properties makes it possible to design an optical component which has higher level of integration and better performance. Different function optical devices with great performances can be made, and the applications will be widely and more important in high speed information processing and data transport field.In this thesis, properties of two-dimensional photonic crystal band-gap, waveguide slow light and transmission characteristic is analyzed. Band gap characteristics of two-dimensional hexagon column photonic crystals are analyzed with numerical computation method. The slow light properties of defected photonic crystal waveguide and the influence of defect dielectric column are analyzed by calculating the photonic band, the group velocity and the group velocity dispersion of photonic crystal structures. Then the transfer characteristic of light wave whose frequency is in or out of the photonic band gap is studied and transmission spectrums of different structures are given. Finally, the slow light property of coupled-cavity waveguide is analyzed and a good transmission character of the proposed structure is verified by researching transmission field distribution under different incident wavelength in photonic crystal coupled cavity waveguides.This paper deeply analyzes the structure and properties of two-dimensional photonic crystal waveguide. The main work is done as follows:(1)The characteristics of band in photonic crystal waveguide structure are studied with supercell algorithm of PWE. When shifting the defect rods, the central frequency of guided mode transfers to higher frequency and its group velocity gets smaller as the increase of shifting and the effect of the shifting along y axis dy is more obvious than the shifting along x axis dx. A similar conclusion is get by changing radius of defect rod.(2)The mathematical modeling of two-dimensional photonic crystal waveguide is build with FDTD. The transfer characteristic of light wave whose frequency is in or out of the photonic band gap is studied and transmission spectrums of different structures are given.(3)A slow light photonic crystal coupled-cavity waveguide by introducing two additional holes into the single line-defect structure is proposed. The characteristics of slow light in the coupled-cavity waveguide have been investigated with plane wave expansion (PWE) method. The group velocity is reduced to0.03c (c is the light velocity in vacuum) by modifying the coupled-cavity, meanwhile the effective wavelength range is close to20nm. Finally, the transmission field distribution under different incident wavelength is analyzed with finite difference time domain (FDTD) method. A good transmission character of the proposed structure is verified by researching transmission field distribution under different incident wavelength in photonic crystal coupled cavity waveguides.