Low-dimensional III-V InAs/GaAs quantum dots (QDs) have been successfully applied to semiconductor saturable absorber mirrors (SESAMs) working at a 900-1310-nm wavelength range for ultrafast pulsed laser applications benefitting from their broad bandwidth, wavelength flexibility, and low saturation fluence. However, it is very challenging to obtain a high-performance QD-SESAM working at the longer wavelength range around 1550 nm due to the huge obstacle to epitaxy growth of the QD structures. In this work, for the first time, it is revealed that, the InAs/GaAs QD system designed for the 1550-nm light emission range, the very weak carrier relaxation process from the capping layers (CLs) to QDs is mainly responsible for the poor emission performance, according to which we have developed a short-period superlattice (In0.20Ga0.80As/In0.30Ga0.70As)5 as the CL for the QDs and has realized ~ 10 times stronger emission at 1550 nm compared with the conventional InGaAs CL. Based on the developed QD structure, high-performance QD-SESAMs have been successfully achieved, exhibiting a very small saturation intensity of 13.7 MW/cm2 and a large nonlinear modulation depth of 1.6 %, simultaneously, which enables the construction of a 1550-nm femtosecond mode-locked fiber lasers with excellent long-term working stability.

中文翻译：

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具有飞秒光纤激光器应用的短周期超晶格封盖结构的1550 nm InAs / GaAs量子点可饱和吸收镜的开发。

低维III-V InAs / GaAs量子点（QD）已成功应用于工作在900-1310 nm波长范围的半导体可饱和吸收镜（SESAM），得益于其宽带宽，波长灵活性，和低饱和通量。然而，由于QD结构的外延生长的巨大障碍，要获得在1550 nm左右更长波长范围内工作的高性能QD-SESAM极具挑战性。在这项工作中，首次揭示了为1550 nm发光范围设计的InAs / GaAs QD系统，从覆盖层（CL）到QD的非常弱的载流子弛豫过程是造成这种现象的主要原因。较差的发射性能，据此我们开发了一种短周期超晶格（In0.20Ga0.80As / In0.30Ga0。70As）5作为QD的CL，与传统的InGaAs CL相比，在1550 nm处实现了约10倍的强发射。基于已开发的QD结构，已经成功实现了高性能QD-SESAM，其同时具有13.7 MW / cm2的非常小的饱和强度和1.6％的大非线性调制深度，从而可以构建1550 nm飞秒锁模光纤激光器具有出色的长期工作稳定性。