Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Broadband continuous single-mode tuning of a short-cavity quantum-cascade VECSEL


Changing the length of a laser cavity is a simple technique for continuously tuning the wavelength of a laser but is rarely used for broad fractional tuning, with a notable exception of the vertical-cavity surface-emitting laser (VCSEL)1,2. This is because, to avoid mode hopping, the cavity must be kept optically short to ensure a large free spectral range compared to the gain bandwidth of the amplifying material. Terahertz quantum-cascade lasers are ideal candidates for such a short cavity scheme as they demonstrate exceptional gain bandwidths (up to octave spanning)3 and can be integrated with broadband amplifying metasurfaces4. We present such a quantum-cascade metasurface-based vertical-external-cavity surface-emitting laser (VECSEL) that exhibits over 20% continuous fractional tuning of a single laser mode. Such tuning is possible because the metasurface has subwavelength thickness, which allows lasing on low-order Fabry–Pérot cavity modes. Good beam quality and high output power are simultaneously obtained.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Metasurface cavity design and electromagnetic simulations.
Fig. 2: Measurement results on longitudinal mode m = 4 with 19% fractional tuning at 77 K.
Fig. 3: Measurement results on longitudinal mode m = 2 with 25% fractional tuning at 77 K.

Data availability

The data that support the plots within this study are available from the corresponding author upon reasonable request.


  1. 1.

    Wu, M. S., Vail, E. C., Li, G. S., Yuen, W. & Chang-Hasnain, C. J. Tunable micromachined vertical-cavity surface-emitting laser. Electron. Lett. 31, 1671–1672 (1995).

    Article  Google Scholar 

  2. 2.

    Huang, M. C. Y., Zhou, Y. & Chang-Hasnain, C. J. A nanoelectromechanical tunable laser. Nat. Photon. 2, 180–184 (2008).

    ADS  Article  Google Scholar 

  3. 3.

    Rosch, M., Scalari, G., Beck, M. & Faist, J. Octave-spanning semiconductor laser. Nat. Photon. 9, 42–47 (2015).

    ADS  Article  Google Scholar 

  4. 4.

    Xu, L. Y. et al. Metasurface external cavity laser. Appl. Phys. Lett. 107, 221105 (2015).

    ADS  Article  Google Scholar 

  5. 5.

    Jayaraman, V. et al. OCT imaging up to 760 kHz axial scan rate using single-mode 1310 nm MEMS-tunable VCSELs with >100 nm tuning range. In Conference on Lasers and Electro-optics (CLEO) (IEEE, 2011).

  6. 6.

    Lee, A. W. M., Kao, T. Y., Burghoff, D., Hu, Q. & Reno, J. L. Terahertz tomography using quantum-cascade lasers. Opt. Lett. 37, 217–219 (2012).

    ADS  Article  Google Scholar 

  7. 7.

    Coldren, L. A. et al. Tunable semiconductor lasers: a tutorial. J. Light. Technol. 22, 193–202 (2004).

    ADS  Article  Google Scholar 

  8. 8.

    Duarte, F. J. Tunable Laser Optics 2nd edn (CRC Press, 2015).

  9. 9.

    Godard, A. Infrared (2–12 μm) solid-state laser sources: a review. C. R. Phys. 8, 1100–1128 (2007).

    ADS  Article  Google Scholar 

  10. 10.

    Jayaraman, V., Chuang, Z. M. & Coldren, L. A. Theory, design, and performance of extended tuning range semiconductor-lasers with sampled gratings. IEEE J. Quantum Electron. 29, 1824–1834 (1993).

    ADS  Article  Google Scholar 

  11. 11.

    Kundu, I. et al. Quasi-continuous frequency tunable terahertz quantum cascade lasers with coupled cavity and integrated photonic lattice. Opt. Express 25, 486–496 (2017).

    ADS  Article  Google Scholar 

  12. 12.

    Slivken, S. et al. Sampled grating, distributed feedback quantum cascade lasers with broad tunability and continuous operation at room temperature. Appl. Phys. Lett. 100, 261112 (2012).

    ADS  Article  Google Scholar 

  13. 13.

    Liu, A. Q. & Zhang, X. M. A review of MEMS external-cavity tunable lasers. J. Micromech. Microeng. 17, R1–R13 (2007).

    Article  Google Scholar 

  14. 14.

    Wysocki, G. et al. Widely tunable mode-hop free external cavity quantum cascade lasers for high resolution spectroscopy and chemical sensing. Appl. Phys. B 92, 305–311 (2008).

    ADS  Article  Google Scholar 

  15. 15.

    Turitsyn, S. K. et al. Random distributed feedback fibre laser. Nat. Photon. 4, 231–235 (2010).

    ADS  Article  Google Scholar 

  16. 16.

    Vijayraghavan, K. et al. Broadly tunable terahertz generation in mid-infrared quantum cascade lasers. Nat. Commun. 4, 2021 (2013).

    ADS  Article  Google Scholar 

  17. 17.

    Jayaraman, V., Cole, G. D., Robertson, M., Uddin, A. & Cable, A. High-sweep-rate 1,310 nm MEMS-VCSEL with 150 nm continuous tuning range. Electron. Lett. 48, 867–868 (2012).

    Article  Google Scholar 

  18. 18.

    Qiao, P. F., Cook, K. T., Li, K. & Chang-Hasnain, C. J. Wavelength-swept VCSELs. IEEE J. Sel. Top. Quantum Electron. 23, 1700516 (2017).

    Article  Google Scholar 

  19. 19.

    Xu, L. Y. et al. Terahertz metasurface quantum-cascade VECSELs: theory and performance. IEEE J. Sel. Top. Quantum Electron. 23, 1200512 (2017).

    Google Scholar 

  20. 20.

    Hugi, A. et al. External cavity quantum cascade laser tunable from 7.6 to 11.4 μm. Appl. Phys. Lett. 95, 061103 (2009).

    ADS  Article  Google Scholar 

  21. 21.

    Lee, A. W. M., Williams, B. S., Kumar, S., Hu, Q. & Reno, J. L. Tunable terahertz quantum cascade lasers with external gratings. Opt. Lett. 35, 910–912 (2010).

    ADS  Article  Google Scholar 

  22. 22.

    Ren, Y. et al. Fast terahertz imaging using a quantum cascade amplifier. Appl. Phys. Lett. 107, 011107 (2015).

    ADS  Article  Google Scholar 

  23. 23.

    Castellano, F. et al. Tuning a microcavity-coupled terahertz laser. Appl. Phys. Lett. 107, 261108 (2015).

    ADS  Article  Google Scholar 

  24. 24.

    Mahler, L., Tredicucci, A., Beltram, F., Beere, H. E. & Ritchie, D. A. Tuning a distributed feedback laser with a coupled microcavity. Opt. Express 18, 19185–19191 (2010).

    ADS  Article  Google Scholar 

  25. 25.

    Qin, Q., Williams, B. S., Kumar, S., Reno, J. L. & Hu, Q. Tuning a terahertz wire laser. Nat. Photon. 3, 732–737 (2009).

    ADS  Article  Google Scholar 

  26. 26.

    Qin, Q., Reno, J. L. & Hu, Q. MEMS-based tunable terahertz wire-laser over 330 GHz. Opt. Lett. 36, 692–694 (2011).

    ADS  Article  Google Scholar 

  27. 27.

    Orlova, E. E. et al. Antenna model for wire lasers. Phys. Rev. Lett. 96, 173904 (2006).

    ADS  Article  Google Scholar 

  28. 28.

    Curwen, C. A., Reno, J. L. & Williams, B. S. Terahertz quantum cascade VECSEL with watt-level output power. Appl. Phys. Lett. 113, 011104 (2018).

    ADS  Article  Google Scholar 

  29. 29.

    Xu, L. Y., Chen, D. G., Itoh, T., Reno, J. L. & Williams, B. S. Focusing metasurface quantum-cascade laser with a near diffraction-limited beam. Opt. Express 24, 24117–24128 (2016).

    ADS  Article  Google Scholar 

  30. 30.

    Xu, L. Y., Curwen, C. A., Reno, J. L. & Williams, B. S. High performance terahertz metasurface quantum-cascade VECSEL with an intra-cryostat cavity. Appl. Phys. Lett. 111, 101101 (2017).

    ADS  Article  Google Scholar 

  31. 31.

    Burnett, B. A., Pan, A., Chui, C. O. & Williams, B. S. Robust density matrix simulation of terahertz quantum cascade lasers. IEEE Trans. Terahertz Sci. Technol. 8, 492–501 (2018).

    ADS  Article  Google Scholar 

  32. 32.

    Gordon, I. E. et al. The HITRAN2016 molecular spectroscopic database. J. Quant. Spectrosc. Radiat. Transf. 203, 3–69 (2017).

    ADS  Article  Google Scholar 

  33. 33.

    Li, L. H. et al. Terahertz quantum cascade lasers with >1 W output powers. Electron. Lett. 50, 309–310 (2014).

    Article  Google Scholar 

  34. 34.

    Amanti, M. I. et al. Bound-to-continuum terahertz quantum cascade laser with a single-quantum-well phonon extraction/injection stage. New J. Phys. 11, 125022 (2009).

    ADS  Article  Google Scholar 

  35. 35.

    Williams, B. S., Kumar, S., Hu, Q. & Reno, J. L. Operation of terahertz quantum-cascade lasers at 164 K in pulsed mode and at 117 K in continuous-wave mode. Opt. Express 13, 3331–3339 (2005).

    ADS  Article  Google Scholar 

Download references


This work was supported by the National Science Foundation (NSF) (1150071, 1407711, 1711892) and the National Aeronautics and Space Administration (NASA) (NNX16AC73G). Microfabrication was performed at the UCLA Nanoelectronics Research Facility, and wire bonding was performed at the UCLA Center for High Frequency Electronics. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US DOE Office of Science. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, a wholly owned subsidiary of Honeywell International, for the US DOE’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in this article do not necessarily represent the views of the US DOE or the United States Government.

Author information




C.A.C. and B.S.W. conceived of the idea. C.A.C. derived the experimental strategy, fabricated the devices, performed the measurements and analysed the data. J.L.R. performed the molecular beam epitaxy growth. C.A.C. and B.S.W. co-wrote the manuscript. All work was done under the supervision of B.S.W.

Corresponding author

Correspondence to Benjamin S. Williams.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary details, Figs. 1–6 and refs. 1–4.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Curwen, C.A., Reno, J.L. & Williams, B.S. Broadband continuous single-mode tuning of a short-cavity quantum-cascade VECSEL. Nat. Photonics 13, 855–859 (2019).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing