受光栅制作工艺的影响,光栅参数的轻微偏移极易导致耦合系数偏离设计值从而影响分布式反馈(DFB)半导体激光器性能。通过微扰下的耦合模理论与数值仿真相结合的方式,对侧向非对称光栅的耦合系数特性进行了深入分析。当光栅宽度与脊型区宽度之比在一定范围内时,两个亚光栅之间非对称距离的引入使波导内的光场产生轻微偏移,光场的耦合状态发生改变。这有利于光栅的耦合系数稳定在一个合理的范围内,有效地缓解了占空比等参数对光栅耦合系数的影响,降低光栅工艺误差对DFB半导体激光器性能的影响;此时谐振腔内光子密度均匀分布,避免了常规光栅结构易引发的空间烧孔效应,有助于半导体激光器窄线宽激光的输出。本文工作将为侧向非同步耦合光栅的设计与应用提供理论参考。

Affected by the manufacturing process of gratings, the slight deviation of grating parameters can easily lead the coupling coefficients to deviating from the design values, deteriorating the distributed feedback (DFB) semiconductor lasers. In this paper, the coupling coefficients of lateral asymmetric gratings were analyzed by combining the coupled mode theory in the case of perturbation with numerical simulations. When the ratio of grating width to ridge width is in a certain range, the light fields in the waveguide slightly deviate due to the introduction of the asymmetric distance between two sub-gratings, thus changing the coupling of the light fields. This is beneficial for the coupling coefficients to stabilize in a reasonable range and considerably alleviates the influence of such parameters as duty ratio on the coupling coefficients. Besides, it lowers the influence of errors in the grating process on the properties of DFB semiconductor lasers. Furthermore, the uniform distribution of photon density in the resonator avoids the space hole-burning effect that easily occurs in the conventional grating structure, which is helpful for the output of laser with narrow line width from the semiconductor laser. In conclusion, this work provides a theoretical reference for the design and application of gratings with lateral asynchronous coupling.