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Highly power-efficient quantum cascade lasers

Nature Photonics volume 4, pages 95–98 (2010)Cite this article

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Abstract

Quantum cascade lasers1 are promising mid-infrared semiconductor light sources for molecular detection in applications such as environmental sensing or medical diagnostics. For such applications, researchers have been striving to improve device performance2. Recently, improvements in wall plug efficiency have been pursued with a view to realizing compact, portable, power-efficient and high-power quantum cascade laser systems3,4. However, advances have largely been incremental, and the basic quantum design has remained unchanged for many years, with the wall plug efficiency yet to reach above 35%. A crucial factor in quantum cascade laser performance is the efficient transport of electrons into the laser active regions. We recently theoretically described this transport process as limited by the interface-roughness-induced detuning of resonant tunnelling5. Here, we report that an ‘ultrastrong coupling’ design strategy overcomes this limiting factor and leads to the experimental realization of quantum cascade lasers with 40–50% wall plug efficiency when operated in pulsed mode at temperatures of 160 K or lower.

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Figure 1: A portion of the conduction band diagram of the ultra-strong coupling QCL design at an applied electric field of 102 kV cm−1.
Figure 2: Electroluminescence spectra and laser spectra.
Figure 3: Pulsed light–current–voltage measurements and extracted WPE.
Figure 4: Scatter plot of pulsed peak WPE at 80 K for all tested lasers with cavity lengths ranging from 2.3 to 3.0 mm.
Figure 5: Continuous-wave light–current–voltage measurements and extracted WPE.

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Acknowledgements

The authors would like to acknowledge the collaboration with J. Meyer and his team at the Naval Research Laboratory, Washington, DC. This work is supported in part by the Mid-InfraRed Technologies for Health and the Environment (MIRTHE) Research Center (National Science Foundation—Engineering Research Centers) and the Defense Advanced Research Projects Agency—Efficient Mid-Wave Infrared Lasers Program.

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Authors and Affiliations

  1. Department of Electrical Engineering, Princeton University, Princeton, 08544, New Jersey, USA

    Peter Q. Liu, Anthony J. Hoffman, Matthew D. Escarra, Kale J. Franz & Claire F. Gmachl

  2. Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, 21218, Maryland, USA

    Jacob B. Khurgin & Yamac Dikmelik

  3. AdTech Optics Inc., City of Industry, California, 91748, USA

    Xiaojun Wang & Jen-Yu Fan

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  1. Peter Q. Liu
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Contributions

P.Q.L. carried out the design, fabricated the devices, performed the measurements and analysed the data. A.J.H. and M.D.E. contributed to the measurements and data analyses. K.J.F. developed the design tools. J.B.K. and Y.D. proposed the idea and carried out the theoretical calculations. X.W. conducted the MOCVD growth of the samples. J.-Y.F. contributed to the device fabrication. C.F.G. supervised the whole project and, together with P.Q.L., prepared the manuscript.

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Correspondence to Peter Q. Liu.

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The authors declare no competing financial interests.

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Liu, P., Hoffman, A., Escarra, M. et al. Highly power-efficient quantum cascade lasers. Nature Photon 4, 95–98 (2010). https://doi.org/10.1038/nphoton.2009.262

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