AMaSiS 2018 Workshop: Abstracts
Modeling of mode-locked and frequency comb quantum cascade lasers
Christian Jirauschek
Technical University of Munich (TUM), Department of Electrical and Computer Engineering
The quantum cascade laser (QCL) relies on intra-conduction-band transitions between quantized energy states in a multi-quantum-well active region. By careful quantum engineering, QCLs can be custom-tailored for a wide range of applications. The coherent nonlinear light-matter interaction is increasingly exploited in a targeted manner to generate mode-locked optical pulses [1] as well as frequency combs [2] in the mid- and far-infrared regime. Simulations provide a detailed understanding of the relevant physical effects and are essential for further systematic development of such QCL sources. In this context, the Maxwell-Bloch (MB) equations, which include the essential coherence and propagation effects at reasonable computational cost, have been used to model both the mode-locked and comb operation dynamics [3, 4].
A main shortcoming of the MB system is its dependence on phenomenological relaxation rate parameters. To eliminate these and thus increase the predictive power, we have recently developed a multi-domain modeling approach which couples generalized multilevel MB equations to carrier transport simulations [4, 5]. We will present MB and multi-domain simulation results for mode-locked as well as comb operation, and compare them to experimental data. A special focus will be on the theoretical exploration of the possibility to obtain passive mode-locking [6], which does not require external pump current modulation as for active mode-locking and can in principle provide shorter pulses, but is widely considered impossible in QCLs due to their inherently short gain recovery times [1]. Moreover, the limitations of the routinely invoked rotating-wave approximation will be discussed, and QCL simulations beyond will be presented based on our open-source project mbsolve [7].
Acknowledgments: This work was supported by the German Research Foundation (DFG) under Grant No. JI 115/4-2 and JI 115/9-1.
References
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