Temporal characteristics of quantum cascade laser frequency modulated combs in long wave infrared and THz regions.
Temporal characteristics of quantum cascade laser frequency modulated combs in long wave infrared and THz regions.
复制标题
长波红外和太赫兹区域量子级联激光调频梳的时间特性。
作者：
Nathan Henry;D. Burghoff;Q. Hu;J. Khurgin
在这里，我们考虑了一个描述量子级联激光器(QCL)在太赫兹和长波红外(LWIRλ=8-12µm)光谱范围内产生频率梳(FC)的动力学的时域模型。利用这些QCL的共同规范，我们证实了自由运转的激光器进入了在与FCS对应的时间域产生伪随机调频(FM)辐射的运行区域，并且在频域中具有稳定的相位关系。我们为这种不寻常的行为提供了一个解释，这是竞争最有效的运营制度的结果。扩展先前在[Opt.英语。57(1)，011009(2017年)]我们分析了现实的太赫兹和长波红外QCL的性能，并表明，尽管许多参数的规模非常不同，但这两种类型的激光器具有非常相似的特征，即FM运行的FM周期与增益恢复时间相称，FM幅度与增益带宽相当。我们还确定了调频梳子伪随机动力学背后的真正罪魁祸首是空间烧孔，而不是更普遍的光谱烧孔。
We consider here a time domain model representing the dynamics of quantum cascade lasers (QCLs) generating frequency combs (FCs) in both THz and long wave infrared (LWIR λ = 8-12µm) spectral ranges. Using common specifications for these QCLs we confirm that the free running laser enters a regime of operation yielding a pseudo-randomly frequency modulated (FM) radiation in the time domain corresponding to FCs with stable phase relations in the frequency domain. We provide an explanation for this unusual behavior as a consequence of competition for the most efficient regime of operation. Expanding the model previously developed in [Opt. Eng. 57(1), 011009 (2017)] we analyze the performance of realistic THz and LWIR QCLs and show, despite the vastly different scale of many parameters, that both types of lasers offer very similar characteristics, namely FM operation with an FM period commensurate with the gain recovery time and an FM amplitude comparable with the gain bandwidth. We also identify the true culprit behind pseudo-random dynamics of the FM comb to be spatial hole burning, rather than the more pervasive spectral hole burning.