Custom designed and unstrained SESAMs for fiber based shortpulse lasers

用于基于光纤的短脉冲激光器的定制设计和无应变 SESAM

• 批准号: 510095359
• 负责人: Professor Dr.-Ing. Franz Xaver Kärtner
• 金额: --
• 依托单位: Institut für Experimentalphysik
• 依托单位国家: 德国
• 项目类别: Research Grants (Transfer Project)
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/510095359?language=en
• 关键词: Custom; designed; unstrained; SESAMs; fiber

Ultrashort pulse lasers with pulse lengths in the femtosecond range are used in industry and research, e.g. as seed lasers in materials processing, biophotonics and quantum sensing. To generate ultrashort pulses from solid-state and fiber lasers, saturable absorber mirrors (SESAMs) are typically used for passive mode coupling. The advantages of SESAMs are their versatile adaptability to a wide variety of laser systems and their ease of integration into the laser cavity, since as passive components they do not require any further control. However, for fiber-based ultrashort pulse lasers operating in the wavelength range around 1550 nm, there are two key challenges that have so far hampered the use of SESAMs or led to premature laser failure in the field. First, the dynamic behavior of mode-locked ultrashort pulse lasers is complex, i.e., in principle very close to a chaotic state. To keep the laser robust and stable in a desired well-defined operating state, the mode-locking SESAM must be tuned to the specific laser. To do this, the entire laser system must be fully understood not only in the stable state of mode-locked pulse generation, but especially in the startup phase. This stage of maturity has not yet been reached for fiber-coupled pulse lasers with wavelengths around 1550 nm. Instead, one currently works with empirically determined requirements and assigns specially selected SESAMs to a particular laser.Second, on the standard GaAs substrate used for SESAMs, there is no strain-free and long-term stable absorber material for 1550 nm. For this wavelength, the required fast absorber consists of In0.47Ga0.53As with strong crystal bias of +3.5% to the GaAs substrate. Although the bias can be reduced by incorporating small amounts of nitrogen, the resulting dilute nitrides have not been shown to have long-term stability. In commercial systems, the failure rate of 1550 nm SESAMs is increased 40-fold compared to 1030 nm SESAMs. Nevertheless, commercially available 1550 nm SESAMs are based on GaAs. Both limiting aspects are addressed in this project to overcome the hurdles for the use of fiber-based ultrafast lasers at 1550 nm in close collaboration with TOPTICA Photonics AG. There is a DFG precursor project for both. Using a numerical model of the SESAM mode-locked fiber laser, optimized laser and absorber parameters are to be determined for the desired single-pulse operation of the fiber laser. These optimized absorbers will then be grown at the Fraunhofer Institute and tested at TOPTICA and University of Hamburg in designated fiber lasers for startup behavior, dynamics and aging. Several of these cycles will be run to achieve an overall optimized system.

在工业和研究中使用了脉冲长度的超短脉冲激光器，例如作为种子激光器在材料加工，生物素化和量子传感中。为了从固态和纤维激光器产生超短脉冲，通常使用饱和吸收镜（SESAM）进行被动模式耦合。 SESAM的优势是它们对各种激光系统的多功能适应性及其易于整合到激光腔的功能，因为作为被动组件，它们不需要任何进一步的控制。但是，对于在1550 nm左右在波长范围内运行的基于纤维的超短脉冲激光器，到目前为止，有两个关键的挑战阻碍了sesams的使用或导致该田中的早产激光失效。首先，模式锁定的超短脉冲激光器的动态行为是复杂的，即原则上非常接近混乱状态。为了将激光稳定和稳定保持在所需的明确定义的工作状态，必须将模式固定的SESAM调整为特定的激光器。为此，不仅必须在模式锁定的脉冲产生的稳定状态下，尤其是在启动阶段中完全理解整个激光系统。对于纤维耦合脉冲激光器，尚未达到这个成熟度，波长约为1550 nm。取而代之的是，当前有一个经验确定的要求，并将特殊选择的SESAM分配给特定的激光。对于此波长，所需的快速吸收剂由In0.47Ga0.53AS组成，其强晶体偏置为GAAS底物 +3.5％。尽管可以通过掺入少量氮来减少偏差，但所得稀氮尚未证明具有长期稳定性。在商业系统中，与1030 nm的塞萨姆相比，1550 nm塞萨姆的故障率增加了40倍。然而，市售的1550 nm SESAMS基于GAAS。在该项目中解决了这两个局限性方面，以克服与Toptica Photonics AG密切合作使用基于纤维的超快激光器的障碍。两者都有一个DFG前体项目。使用SESAM模式锁定的纤维激光器的数值模型，为纤维激光器的所需单脉冲操作确定优化的激光和吸收参数。然后，这些优化的吸收剂将在Fraunhofer Institute生长，并在Toptica和Hamburg University进行指定的纤维激光器，以实现启动行为，动力学和衰老。这些周期中的几个将运行以实现整体优化系统。