Letter | Published:

Highly power-efficient quantum cascade lasers

Nature Photonics volume 4, pages 9598 (2010) | Download Citation


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.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    et al. Quantum cascade laser. Science 264, 553–556 (1994).

  2. 2.

    , , & Recent progress in quantum cascade lasers and applications. Rep. Prog. Phys. 64, 1533–1601 (2001).

  3. 3.

    et al. High performance quantum cascade lasers based on three-phonon-resonance design. Appl. Phys. Lett. 94, 011103 (2009).

  4. 4.

    , , & Room temperature continuous wave operation of quantum cascade lasers with 12.5% wall plug efficiency. Appl. Phys. Lett. 93, 021103 (2008).

  5. 5.

    et al. Role of interface roughness in the transport and lasing characteristics of quantum-cascade lasers. Appl. Phys. Lett. 94, 091101 (2009).

  6. 6.

    et al. Resonant tunneling in quantum cascade lasers. IEEE J. Quantum Electron. 34, 1722–1729 (1998).

  7. 7.

    Wallplug efficiency of quantum cascade lasers: critical parameters and fundamental limits. Appl. Phys. Lett. 90, 253512 (2007).

  8. 8.

    et al. Digital alloy interface grading of an InAlAs/InGaAs quantum cascade laser structure studied by cross-sectional scanning tunneling microscopy. Appl. Phys. Lett. 83, 4131–4133 (2003).

  9. 9.

    et al. Bound-to-continuum and two-phonon resonance quantum-cascade lasers for high duty cycle, high-temperature operation. IEEE J. Quantum Electron. 38, 533–546 (2002).

  10. 10.

    , , & Quantum cascade lasers with large optical waveguides. IEEE Photon. Tech. Lett. 18, 544–546 (2006).

Download references


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.

Author information


  1. Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, 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, Maryland 21218, USA

    • Jacob B. Khurgin
    •  & Yamac Dikmelik
  3. AdTech Optics Inc., City of Industry, California 91748, USA

    • Xiaojun Wang
    •  & Jen-Yu Fan


  1. Search for Peter Q. Liu in:

  2. Search for Anthony J. Hoffman in:

  3. Search for Matthew D. Escarra in:

  4. Search for Kale J. Franz in:

  5. Search for Jacob B. Khurgin in:

  6. Search for Yamac Dikmelik in:

  7. Search for Xiaojun Wang in:

  8. Search for Jen-Yu Fan in:

  9. Search for Claire F. Gmachl in:


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.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Peter Q. Liu.

Supplementary information

About this article

Publication history






Further reading