Quantum-dot-based semiconductor saturable absorber mirrors (SESAMs) with fast response times were developed by molecular beam epitaxy (MBE). Using quantum dots (QDs) in the absorber region of the SESAMs instead of quantum wells, enables additional degrees of freedom in the design, the control of saturation parameters and the recovery dynamics. However, if one wants to integrate such a SESAM element into semiconductor surface emitting lasers such as a mode-locked integrated external-cavity surface-emitting laser (MIXSEL), the saturable absorber layers have to withstand a longer high-temperature growth procedure for the epitaxial formation of distributed Bragg reflectors (DBR). Typically defect related SESAMs will be annealed at those growth temperatures and lose their high-speed performance. Here we present a systematic study on the growth parameters and post-growth annealing of SESAMs based on high-quality In_xGa_1−xAs/GaAs quantum dots (QDs) grown by MBE at growth temperatures of 450 °C or higher. The good quality enables the QDs to survive the long DBR overgrowth at 600 °C with only minimal shifts in the designed operation wavelength of 1030 nm required for growth of MIXSEL devices. The introduction of recombination centers with p-type modulation doping and additional post-growth annealing improves the absorption of the high-quality QDs. Hence, low saturation fluences < 10 µJ/cm² and a reduction of the τ_1/e recovery time to values < 2 ps can be achieved.

中文翻译：

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用于外延集成到半导体表面发射激光器中的耐高温In _x Ga _1-x As / GaAs量子点可饱和吸收剂

通过分子束外延（MBE）开发了具有快速响应时间的基于量子点的半导体可饱和吸收镜（SESAM）。在SESAM的吸收体区域中使用量子点（QD）代替量子阱，可以在设计，饱和度参数控制和恢复动力学方面实现更多自由度。但是，如果要将这种SESAM元件集成到诸如锁模集成外腔表面发射激光器（MIXSEL）之类的半导体表面发射激光器中，则可饱和吸收层必须承受更长的高温生长过程，才能承受较高的温度。外延形成分布式布拉格反射器（DBR）。通常，与缺陷相关的SESAM将在那些生长温度下退火，并失去其高速性能。MBE在450°C或更高的生长温度下生长的_x Ga _1-x As / GaAs量子点（QD）。优良的品质使QD能够在600°C的长时间DBR过度生长下生存，而MIXSEL器件的生长所需的1030 nm设计工作波长只有很小的偏移。引入带有p型调制掺杂的重组中心和额外的生长后退火可改善高质量QD的吸收。因此，可以实现<10 µJ / cm ^2的低饱和能量通量，以及将τ1 _{/ e}恢复时间减少至<2 ps的值。