Interband Cascade Lasers (ICL) have matured into a versatile technological platform in the mid-infrared spectral domain. To broaden their applicability even further, ongoing research pursues the emission of ultrashort pulses. The most promising approach is passive mode-locking with a fast saturable absorber. However, despite vast attempts no passive mode-locked ICL has been demonstrated up to date. In this study, pump-probe measurements are conducted on the ICL gain, demonstrating that $\approx$60–70% of its dynamic behavior is characterized by a rapid recovery time of 2 ps. The findings explain why passive mode-locking of ICLs has not succeeded so far, shedding a new light on ICL dynamics as strategies are proposed to overcome the current limitations.

中文翻译：

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带间级联激光器中的快速增益动力学


带间级联激光器 （ICL） 已经成熟为中红外光谱领域的多功能技术平台。为了进一步扩大它们的适用性，正在进行的研究追求超短脉冲的发射。最有前途的方法是使用快速可饱和吸收器的无源锁模。然而，尽管进行了大量尝试，但迄今为止还没有证明无源锁模 ICL。在本研究中，对 ICL 增益进行了泵浦探针测量，表明其 $\approx$ 60-70% 的动态行为的特点是 2 ps 的快速恢复时间。研究结果解释了为什么 ICL 的被动锁模迄今尚未成功，这为克服当前限制的策略提出了 ICL 动力学提供了新的思路。