Research On Machanics Of One Dimention Photonic Crystals Q Uality Factor

Terahertz radiation has a broad prospect in scientific research and technical applications, but radiation sources at terahertz are difficult to be realized. Photonic crystals can radiate terahertz wave through difference frequency effect. But the conversion efficiency of this process is very low. The purpose of this thesis is, by improving the quality factor of one-dimensional photonic crystals, to increase the conversion efficiency of the difference frequency process greatly and enhance the terahertz radiation.In this thesis, a conception that only improving the quality factor can conversion efficiency be increased is got by deducting the quasi-phase matching condition and the conversion efficiency formula in one-dimensional photonic crystals. The relationship between structural parameters and the quality factor of one-dimensional photonic crystals band edge resonators and F-P resonators is simulated and some means to improve the quality factor are got. The group velocity and the density of states are used to explain the mechanism of high quality factor for the first time. Bragg photonic crystals with several defect layers are analyzed. For the defect modes, their dependence on odd or even number of the defect layers and their character of degeneration and split are got. The perturbation method in quantum mechanics is used to get the frequency relationship between the degeneration and the split of the defect states. For the first time, a model of one-dimension double square potential wells is used to get the phase relationship between the states. It shows that phase perturbation is the reason for the appearance of the degeneration and the split. Work in this thesis may be helpful for further understanding the mechanism of getting high quality factor in one-dimension photonic crystals, and give some references to the design of photonic crystals with high quality factor.