相位图法研究光子晶体的禁带

给出了一种判断一维光子晶体禁带位置的相位图,利用扩展相位图可方便地描述光子晶体的禁带位置和禁带特征.研究发现,当光子晶体为1/4波片层堆时,光子晶体的禁带最宽;若要进一步展宽禁带,需提高构成周期单元的两种介质的折射率比.对于一般的光子晶体,若周期单元中两种介质的光学厚度不等,则其禁带中心将偏离中心频率的整数倍.此外还研究了禁带中心区的透射率,给出了中心频率附近透射率的一级近似解析解,并由此定性讨论了Fabry-Perot腔的谱线宽度和品质因子.

Study on the band gap of photonic crystals using phase diagram

The phase diagrams are used to ascertain positions of 1 D photonic crystal band gaps. The positions and characteristics of the photonic crystal band gaps can be expediently depicted by using patulous phase diagrams. The band-gap width is largest when the photonic crystal is composed of alternately arranged quarter wave stacks. Increasing the ratio of refractive indices can enlarge the band-gap width. For a conventional photonic crystal, the central position of every band gap will depart from the integral times of the central frequency if the optical thickness of both media in periodic unit is not equal. Furthermore, the transmittance in the central region of the band gap is studied, and the formula of transmittance near the central frequency with the first approximation are deduced. The spectrum line width and quality factor of the Fabry-Perot cavity are qualitatively discussed.