半导体光调制器波导的输出模斑通常是直径为2~3μm的椭圆形, 与光纤进行耦合时会因模斑不匹配而产生严重的耦合损耗, 并影响对准容差。为降低光纤与调制器波导的耦合损耗, 同时改善对准容差, 设计了两种应用于光调制器中的模斑变换器(Spot-size Converter), 通过仿真对其传输损耗和模场耦合效率进行了比较, 其中采用混合结构的模斑变换器具有更优的性能。

Semiconductor optical modulators generally have an elliptical output mode field with a diameter about 2~3μm. Due to the mode mismatch between the waveguide of a modulator and that of a fiber, a serious coupling loss will be induced along with a small alignment tolerance. To reduce the coupling loss and improve the alignment tolerance, two types of spot-size converters(SSCs) are designed for semiconductor modulators, while their propagation loss and fiber coupling efficiency are compared based on numerical simulations. It is concluded that the hybrid-taper based SSC exhibits superior performance.