包层调制的聚合物电光调制器及其理论分析

Electro-Optic Polymer Modulators Modulated Only in Claddingand Its Theoretical Analysis

器件损耗偏高是当前聚合物电光调制器的研究中需要解决的问题之一。在调制器的插损之中 ,波导传播损耗 (包括吸收和散射损耗 )的贡献举足轻重。特别是在追求高电光系数的材料同时 ,传播损耗也将会不可避免地增加。如何改善器件的损耗是聚合物调制器实用化的一个重要课题。为此提出了一种在波导包层中调制光波的设想。理论分析表明 ,这种方法能够大幅度降低波导传播性能 ,因而有助于改善器件损耗。由于包层中光波强度比芯层中要弱 ,因此在包层中调制光波会引起场模交叠因子的弱化 ,但是优化计算发现 ,通过调节波导的尺寸尤其是芯层厚度可以控制交叠因子使其弱化程度降低到最小 ,在最优的情况下 ,场 -模交叠因子可达 0 .89。随着波导传播损耗的降低 ,器件调制区的长度可以做得更长 ,有助于进一步降低器件的半波电压。

Now, higher loss in polymer modulators is one of important problems to be solved in the research of electrooptic modulators. The waveguide loss plays an important role in the insert loss. Especially, modulators will inevitably have higher waveguide loss seeking high EO coefficients. It is an important topic to improve the modulators' loss. An idea is proposed that light-wave modulated only in claddings. Analysis shows that this method can decrease largely waveguide loss, so it helps to improve the insert loss. Because the light power in claddings is weaker than one in core, the overlap will weaken when modulation is realized only in cladding. It is found that optimizing the dimensions of waveguide can largely reduce this weakening. Calculation makes the optimum overlap to 0.89. The length of interaction can increase with the decreasing of waveguide loss, which is helpful for decreasing half-wavelength voltage.