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Mid-infrared quantum cascade lasers

The design flexibility of quantum cascade lasers has enabled their expansion into mid-infrared wavelengths of 3–25 μm. This Review focuses on the two major areas of recent improvement: power and power efficiency, and spectral performance.

Abstract

Mid-infrared quantum cascade lasers are semiconductor injection lasers whose active core implements a multiple-quantum-well structure. Relying on a designed staircase of intersubband transitions allows free choice of emission wavelength and, in contrast with diode lasers, a low transparency point that is similar to a classical, atomic four-level laser system. In recent years, this design flexibility has expanded the achievable wavelength range of quantum cascade lasers to 3–25 μm and the terahertz regime, and provided exemplary improvements in overall performance. Quantum cascade lasers are rapidly becoming practical mid-infrared sources for a variety of applications such as trace-chemical sensing, health monitoring and infrared countermeasures. In this Review we focus on the two major areas of recent improvement: power and power efficiency, and spectral performance.

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Figure 1: Concept of a QC laser.
Figure 2: WPE.
Figure 3: DFB QC lasers.
Figure 4: EC QC lasers, broadband QC laser design and wavelength tuning ranges achieved in QC lasers.

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Acknowledgements

The authors acknowledge collaborations with colleagues at Princeton University and associated with the NSF Engineering Research Center MIRTHE. A.J.H. thanks S. Howard for valuable discussions. They also acknowledge partial support by MIRTHE (NSF-ERC) and DTRA.

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Yao, Y., Hoffman, A. & Gmachl, C. Mid-infrared quantum cascade lasers. Nature Photon 6, 432–439 (2012). https://doi.org/10.1038/nphoton.2012.143

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