We build on former results from our work on parity-time symmetric gratings implemented in 1550 nm distributed-feedback laser diodes to address the design issues raised by the first trends we observed. These laser diodes are of a complex-coupled nature, with modulations of both real and imaginary parts of the effective index, with a relative phase related to the parity-time symmetry. The unidirectionality of the photonic behavior in the reflection mode is dependent on the level of extra losses incurred by the metallic grating used to implement fixed loss modulation onto a nearly uniform gain, either as a first-order or a third-order grating. The observed behavior suggests that facets play a large role in setting the desired unidirectional lasing operation points, with preferential emission on one side. We explore this issue, which is of generic interest for the coupling of parity-time symmetric structures to open space.

中文翻译：

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1550 nm 分布式反馈激光二极管中的奇偶时间对称光栅：对器件设计规则的洞察

我们基于之前在 1550 nm 分布式反馈激光二极管中实现的奇偶时间对称光栅的工作结果，以解决我们观察到的第一个趋势引起的设计问题。这些激光二极管具有复耦合性质，有效折射率的实部和虚部均进行调制，相对相位与奇偶时间对称性相关。反射模式中光子行为的单向性取决于用于将固定损耗调制到几乎均匀的增益上的金属光栅所产生的额外损耗水平，无论是作为一阶还是三阶光栅。观察到的行为表明，刻面在设置所需的单向激光操作点方面发挥着重要作用，一侧具有优先发射。我们探讨这个问题，