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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800nm时,耦合长度小于100μm.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 550nm时,二者分别为28.2和26.2μm(两狭缝波导间的耦合间距为0.5μm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 550nm时,TE及TM模式的振幅衰减系数分别为5.65和3.16dB/cm.
Using the Helmholtz equation and the finite difference method, a numerical method for analyzing the directional coupling characteristics of a dual-slot waveguide filled with a polymer SU-8 is given. The eigenvalue equation of the mode characteristic of a double-coupled slot waveguide is derived. The discretization and sparsity processing are done to obtain the mode field distribution and the effective refractive index of the coupled waveguide.The coupling between TE and TM directional coupler can be obtained by solving the effective refractive index of the highest order symmetry and the highest order odd symmetry mode Length.The numerical results show that the coupling length is less than 100 μm when the coupling distance is less than 800 nm.The optical parameters of the materials of the slit waveguide are measured by ellipsometry with the dispersion relation of the working wavelength.The influence of coupling length And loss of mode dispersion.The analysis shows that as the working wavelength increases, the coupling length decreases in both polarization modes and the coupling length in TM mode is greater than the coupling length in TE mode. When the operating wavelength is 1 550 nm, the two are 28.2 and 26.2 μm, respectively (the coupling pitch between the two slot waveguides is 0.5 μm), while the mode loss also decreases with increasing wavelength and the TE mode loss is greater than the TM mode Loss, when the operating wavelength of 1 550nm, TE and TM mode amplitude attenuation coefficient of 5.65 and 3.16dB / cm.