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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  • 2 A. Hugi, G. Vilares, S. Blaser, H. C. Liu, and J. Faist, Mid-infrared frequency comb based on a quantum cascade laser, Nature 492 (2012), 229–233.
  • 3 V.-M. Gkortsas, C. Wang, L. Kuznetsova, et al., Dynamics of actively mode-locked quantum cascade lasers, Opt. Express 18 (2010), 13616–13630.
  • 4 P. Tzenov, D. Burghoff, Q. Hu, and C. Jirauschek, Time domain modeling of terahertz quantum cascade lasers for frequency comb generation, Opt. Express 24 (2016), 23232–23247.
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  • 6 P. Tzenov, I. Babushkin, R. Arkhipov, M. Arkhipov, N. Rosanov, U. Morgner, and C. Jirauschek, Passive and hybrid mode locking in multi-section terahertz quantum cascade lasers, New J. Phys. 20 (2018), 053055.
  • 7 M. Riesch, N. Tchipev, S. Senninger, H.-J. Bungartz, and C. Jirauschek, Performance evaluation of numerical methods for the Maxwell–Liouville–von Neumann equations, O pt. Quant. Electron. 50 (2018), 112.