根据光波模在光子晶体线缺陷波导和环形谐振腔之间的耦合原理, 在二维三角晶格光子晶体中设计了一款由线缺陷主波导、环形谐振腔、60°弯下载波导组成的多信道下载滤波器。利用平面波展开方法计算了完整光子晶体及线缺陷波导的能带结构; 基于时域有限差分方法计算了各目标频率光信号在器件中的传输特性, 分析了影响器件耦合效率的因素并对其进行了改进。分析表明: 通过改变环形谐振腔内介质柱的半径可以调节光子晶体环形谐振腔的谐振频率, 而改变线缺陷主波导与环形谐振腔之间耦合区域中介质柱的形状以及将直下载波导改换成60°弯下载波导可以提高线缺陷主波导、60°弯波导与环形谐振腔之间的耦合效率。计算结果显示: 优化后的多信道二维光子晶体滤波器具备优良的选频功能, 各目标频率光信号的透射率均达90%以上。与传统半导体介质材料器件相比, 该器件体积较小, 结构简单, 易于大规模集成, 很有应用前景。

On the basis of the resonant coupling principle of light wave modes between the defect modes of line-defect waveguides and the ring resonators, a multi-channel drop filter consisting of a line-defect waveguide, ring resonators and 60°bend waveguides was designed by using the two-dimension triangular lattice photonic crystals. The energy structures of a complete photonic crystal and a line-defect waveguide were calculated by the plane-wave expansion method. The transmission characteristic of the filter was investigated with the two-dimensional finite difference time domain method. Then, the effect factors on coupling efficiency of devices were analyzed and an improved method was proposed. The analysis shows that the resonance frequencies of photonic crystal ring resonator depend on the radius of dielectric rods in the resonators and the coupling efficiencies between the line-defect waveguides and the ring resonators are improved by changing the shapes of dielectric rods in coupling region and replacing the straight waveguide with a 60°bend waveguide. The simulation results show that the optimized multi-channel two dimensional photonic crystal filter has good wavelength selection frequency performance, and the transmission efficiencies of all the resonance wavelengths are above 90%. The filter is characterized by a smaller size, simple structure, easy integration and good application prospects.