High repetition frequency (HRF) ultrashort pulse fiber laser has been widely used in laser cold processing. The technical solutions such as short cavity length fiber laser have been proposed to achieve HRF ultrashort pulse output recently. However, the application of material-based saturable absorbers in this field has been astricted due to the low modulation depth, low damage resistance threshold, and high saturation fluence. Here, we designed a one-dimensional asymmetric photonic crystal with defect layer (1D-APCDL) as a novel saturable absorber, where the defect layer is Bi1.6Sb0.4Te3 with high modulation depth. The harmonic pulse with 3.82 GHz repetition frequency is achieved at the wavelength of 1562 nm, which is the highest repetition frequency of the topological insulator-based ring fiber laser so far to the best of our knowledge. The research provides a new saturable absorber solution, and provides a new idea for the application of material-based nonlinear optical chip in high-repetition frequency ultrashort pulse fiber lasers.

中文翻译：

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千兆赫飞秒激光器——由一种新型非对称一维光子晶体可饱和吸收体器件与缺陷层

高重复频率（HRF）超短脉冲光纤激光器已广泛应用于激光冷加工。最近提出了短腔长光纤激光器等技术方案来实现HRF超短脉冲输出。然而，基于材料的可饱和吸收体由于调制深度低、抗损伤阈值低和饱和能量密度高，在该领域的应用受到限制。在这里，我们设计了一种具有缺陷层（1D-APCDL）的一维非对称光子晶体作为一种新型可饱和吸收体，其中缺陷层为 Bi1.6锑0.4碲3具有高调制深度。在 1562 nm 波长处实现了重复频率为 3.82 GHz 的谐波脉冲，这是迄今为止我们所知的基于拓扑绝缘体的环形光纤激光器的最高重复频率。该研究提供了一种新的可饱和吸收体解决方案，为基于材料的非线性光学芯片在高重复频率超短脉冲光纤激光器中的应用提供了新思路。