波导耦合多层结构光学微球腔性能分析

Numerical Analysis of Multi-Layer Optical Microsphere Cavity Coupled with a Waveguide

利用时域有限差分(FDTD)法模拟了均匀结构、双层结构和三层结构光学微球腔,得到了各自的能量密度分布,通过对比发现多层结构具有更高的最大能量密度与存储能量和较小的模式体积。波导与多层微球腔之间存在一个最佳间隙,模拟结构的最佳间隙在60～120nm。改变高折射层的厚度和折射率,在特定波长的入射光下可以获得具有较高最大能量密度(大于360)或者较小模式体积的(小于0.03)的微球腔,确定了优化的厚度和折射率。分析高斯光激励的带有导出波导的微球腔,导出波导与微球腔中的光具有相似的激发频谱,表明多层微球腔可以对入射光实现选频并导出。结果显示,多层微球腔具有更好的性能,为光学微球腔后续的结构设计和实际应用提供了一个新的优化思路。

The finite difference time domain（FDTD） method is employed to simulate the homogeneous,two-layer and three-layer microcavities.Via comparing their respective energy density distributions,it is found that the three-layer microcavity has the highest maximum energy density（Imax）,stored energy（En） and the smallest mode volume（Veff）.An optimal gap exists between the multi-layer microcavity and the waveguide,which is 60~120 nm in the paer.A microcavity which has a higher Imax（higher than 360） or a smaller Veff（smaller than 0.03） with particular wavelength can be got by varying the middle layer′s thickness or refractive index.The microcavity with an output waveguide is analyzed with the Gaussian beam excitation.The frequency spectrum in the output waveguide is similar to that in the mircocavity.The multi-layer microsphere cavity can achieve frequency-selecting and light-export.These studies and results show that multi-layer microsphere cavity has better performance and provide new optimizing methods for the design and practical application of microsphere cavity.