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 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：

---

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，但迄今为止尚未证明无源锁模 ICL。在这项研究中，对 ICL 增益进行了泵浦探针测量，表明其 60-70% 的动态行为的特点是 2 ps 的快速恢复时间。这些发现解释了为什么 ICL 的被动锁模到目前为止没有成功，随着提出克服当前限制的策略，为 ICL 动力学提供了新的视角。