Qi Xiaoqiong, Loh Hui Yi, Taimre Thomas, Bertling Karl, Indjin Dragan, Rakić Aleksandar D
School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia.
Sensors (Basel). 2022 Nov 4;22(21):8501. doi: 10.3390/s22218501.
We have recently reported the self-pulsation phenomenon under strong optical feedback in terahertz (THz) quantum cascade lasers (QCLs). One important issue, however, we left open: the effect of multiple round trips in the external cavity on the laser response to feedback. Our current analysis also casts additional light on the phenomenon of self-pulsations. Using only one external cavity round trip (ECRT) in the model has been the common approach following the seminal paper by Lang-Kobayashi in 1980. However, the conditions under which the Lang-Kobayashi model, in its original single-ECRT formulation, is applicable has been rarely explored. In this work, we investigate the self-pulsation phenomenon under multiple ECRTs. We found that the self-pulsation waveform changes when considering more than one ECRT. This we attribute to the combined effect of the extended external cavity length and the frequency modulation of the pulsation frequency by the optical feedback. Our findings add to the understanding of the optical feedback dynamics under multiple ECRTs and provide a pathway for selecting the appropriate numerical model to study the optical feedback dynamics in THz QCLs and semiconductor lasers in general.
我们最近报道了太赫兹（THz）量子级联激光器（QCL）在强光学反馈下的自脉动现象。然而，我们留下了一个重要问题未解决：外腔中多次往返对激光器反馈响应的影响。我们目前的分析也为自脉动现象提供了更多见解。自1980年Lang - Kobayashi发表开创性论文以来，在模型中仅使用一次外腔往返（ECRT）一直是常见的方法。然而，很少有人探究原始单ECRT形式的Lang - Kobayashi模型适用的条件。在这项工作中，我们研究了多次ECRT情况下的自脉动现象。我们发现，当考虑不止一次ECRT时，自脉动波形会发生变化。我们将此归因于外腔长度增加以及光学反馈对脉动频率的频率调制的综合作用。我们的研究结果增进了对多次ECRT情况下光学反馈动力学的理解，并为选择合适的数值模型来研究太赫兹QCL以及一般半导体激光器中的光学反馈动力学提供了一条途径。
