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Femtosecond pulses from a mid-infrared quantum cascade laser

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The quantum cascade laser has evolved to be a compact, powerful source of coherent mid-infrared light; however, its fast gain dynamics strongly restricts the formation of ultrashort pulses. As such, the shortest pulses reported so far were limited to a few picoseconds with some hundreds of milliwatts of peak power, strongly narrowing their applicability for time-resolved and nonlinear experiments. Here we demonstrate an approach capable of producing near-transform-limited subpicosecond pulses with several watts of peak power. Starting from a frequency-modulated phase-locked state, ultrashort high-peak-power pulses are generated via spectral filtering, gain modulation-induced spectral broadening and external pulse compression. We assess their temporal nature by means of a novel asynchronous sampling method, coherent beat note interferometry and interferometric autocorrelation. These results open new pathways for nonlinear physics in the mid-infrared.

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Fig. 1: Diffraction grating compressor.
Fig. 2: Complex comb spectrum and coherence before and after pulse compression as measured by SWIFTS.
Fig. 3: Asynchronous upconversion sampling.
Fig. 4: Compressed and uncompressed QCL intensity profile as measured by ASUPS.
Fig. 5: Compressed QCL pulses as measured by IAC.
Fig. 6: Shortest compressed QCL pulses.

Data availability

The measurement data that support the plots within this paper are available at and from the corresponding author on reasonable request. Data that support the findings in this article are also available in the ETH Research Collection43.

Code availability

The analysis codes will be made available on reasonable request.

Change history

  • 24 November 2021

    In the HTML version of this Article published online, the copyright information was in error; the copyright information has now been corrected.


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This work was supported by the BRIDGE program, funded by the Swiss National Science Foundation and Innosuisse, in the scope of the CombTrace (no. 176584; P.T., M.Bertrand, F.K.) project. Further financial support was provided by the Swiss National Science Foundation (no. 165639; M.S., P.J.) and the European Union’s Horizon 2020 research and innovation program Qombs (no. 820419; B.S.). We would like to gratefully thank J. Hillbrand for helpful advice and discussion while conducting the experiments and for proofreading the manuscript. Moreover, we express gratitude to S. Markmann and A. Forrer for their careful reading of the paper, S. Wang for his preliminary work on ASUPS and R. Wang for providing QCLs in an early stage of the work. We thank E. Gini of the FIRST—Center for Micro- and Nanoscience for the MOVPE regrowths.

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Authors and Affiliations



P.T. built the upconversion, SWIFTS and autocorrelation set-up, performed the experiments and wrote the manuscript with editorial input from M.Bertrand, B.S. and J.F. M.Bertrand characterized the normal buried heterostructure device (LIV, optical spectra) used for this publication, performed preliminary IAC experiments and helped with the set-up of the radiofrequency-optimized device. B.S. was involved in the SWIFTS analysis, characterized the radiofrequency-optimized laser (LIV, optical spectra, beat note), helped with its set-up and performed preliminary strong microwave modulation experiments. M.S. dimensioned the grating compressor. P.J. and F.K. processed the QCLs used in this work. M.Beck was responsible for MBE growth. J.F. supervised this work.

Corresponding authors

Correspondence to Philipp Täschler or Jérôme Faist.

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The authors declare no competing interests.

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Peer review informationNature Photonics thanks Stefano Barbieri, Benedikt Schwarz and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Sections 1–5 and Figs. 1–5.

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Täschler, P., Bertrand, M., Schneider, B. et al. Femtosecond pulses from a mid-infrared quantum cascade laser. Nat. Photon. 15, 919–924 (2021).

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