利用亥姆霍兹方程和有限差分法，给出一种用于分析聚合物SU8填充的双狭缝波导定向耦合特性的数值方法，推导出双耦合狭缝波导模式特性的特征方程，并做了离散化和稀疏化处理，得到耦合波导的模式场分布和有效折射率.通过求解最高阶偶对称和最高阶奇对称模式的有效折射率，得到TE和TM偏振态下定向耦合器的耦合长度.数值分析结果表明，当耦合间距小于800 nm时，耦合长度小于100 μm.利用椭偏仪测得狭缝波导各层材料的光学参数随工作波长的色散关系，研究分析了双狭缝波导耦合长度和模式损耗的色散特性.分析显示，随着工作波长的增大，两种偏振模式下的耦合长度均减小，且TM模式下的耦合长度大于TE模式下的耦合长度，当工作波长为1 550 nm时，二者分别为28.2和26.2 μm（两狭缝波导间的耦合间距为0.5 μm时）.同时，模式损耗也随波长的增大而减小，且TE模式损耗大于TM模式损耗，当工作波长为1 550 nm时，TE及TM模式的振幅衰减系数分别为5.65和3.16 dB/cm.

In terms of Helmholtz equation and finitedifference timedomain method, a numerical approach for analyzing the directional coupling characteristics based on two SU8 filled slot waveguides was proposed. The mode eigen equation of the coupling slot waveguides was derived and solved, and mode optical field distribution and effective refractive index were achieved. By using the effective refractive indices of the highestorder even symmetric mode and the highestorder odd symmetric modes, the coupling length under TE and TM polarizations was calculated. Numerical simulation results show that when the coupling gap is less than 800 nm, the coupling length is less than 100 μm. The wavelength dispersion characteristics of the used materials were measured with an ellipsoidmeter, and then the wavelength dispersion of coupling length and mode loss of the coupling slot waveguides were investigated. The analytical results reveal that the coupling length decreases as the wavelength increases under both polarizations, and under the same coupling gap, the coupling length under TM polarization is larger than that under TE polarization. The coupling lengths under TM and TE polarizations are 28.2 and 26.2 μm, respectively, when wavelength is 1 550 nm and coupling gap is 0.5 μm. In addition, the mode loss also decreases as wavelength increases, and the mode loss under TE polarization is larger than that under TM polarization. The loss coefficients under TE and TM polarizations are 5.65 and 3.16 dB/cm, respectively, when the wavelength is 1 550 nm.