为提高分布式反馈(DFB)激光器小信号曲线的通带平坦度和3 dB带宽,利用一维行波模型,研究了一阶和二阶光栅结构下基于push-pull调制原理的DFB激光器,分析了器件参数(如光栅耦合系数、腔长、电极比例等)与激光器频率响应的关系。其中,仿真模型所用的参数是与实际器件的光电特性对照后提取出来的参数。仿真结果表明:对于一阶光栅结构的DFB激光器,在合适的光栅耦合系数、腔长和电极比例下,push-pull调制的带宽比单电极直接调制的带宽大12 GHz;对于二阶光栅结构的DFB激光器,在合适的参数下,push-pull调制的带宽比单电极直接调制的带宽大40 GHz;并且,一阶和二阶光栅结构的push-pull调制激光器的通带平坦度都优于普通的直接调制激光器。同时,实验结果也表明,即使对于普通的有源区设计,采用push-pull调制技术后,其带宽也会大幅提升。

In order to improve the passband flatness and 3 dB modulation bandwidth of the distributed feedback (DFB) lasers, we study the relationship between the device parameters (such as grating coupling coefficient, cavity length and electrode ratio) and the frequency response of 1 st and 2 nd order grating push-pull modulated DFB lasers by using one-dimensional traveling wave model. The parameters used in the simulated model are extracted from the photoelectric characteristics of the actual devices. The simulated results show that, for the DFB lasers with 1 st order grating structure, the push-pull modulation bandwidth is 12 GHz larger than the single-electrode direct modulation bandwidth at the appropriate grating coupling coefficient, cavity length and electrode ratio. For the DFB lasers with 2 nd order grating structure, the push-pull modulation bandwidth is 40 GHz larger than the single-electrode direct modulation bandwidth. Besides, the passband flatness of the 1 st order and 2 nd order grating push-pull modulated lasers is much better than that of the ordinary direct modulation lasers. In addition, the results of the experiments show a substantial increase of the bandwidth with push-pull modulation, even for general design of active region.