Terahertz laser frequency combs

Abstract

Terahertz light can be used to identify numerous complex molecules, but has traditionally remained unexploited due to the lack of powerful broadband sources. Pulsed lasers can be used to generate broadband radiation, but such sources are bulky and produce only microwatts of average power. Conversely, although terahertz quantum cascade lasers are compact semiconductor sources of high-power terahertz radiation, their narrowband emission makes them unsuitable for complex spectroscopy. In this work, we demonstrate frequency combs based on terahertz quantum cascade lasers, which combine the high power of lasers with the broadband capabilities of pulsed sources. By fully exploiting the quantum-mechanically broadened gain spectrum available to these lasers, we can generate 5 mW of terahertz power spread across 70 laser lines. This radiation is sufficiently powerful to be detected by Schottky-diode mixers, and will lead to compact terahertz spectrometers.

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Figure 1: GVD of laser gain medium.
Figure 2: Continuous-wave spectrum and beat notes.
Figure 3: Results of SWIFT measurement.
Figure 4: Bias dependence of beat-note and SWIFT spectra.
Figure 5: Heterodyne beat note between single-mode laser and comb.

References

  1. 1

    Udem, Th., Holzwarth, R. & Hänsch, T. W. Optical frequency metrology. Nature 416, 233–237 (2002).

    ADS  Article  Google Scholar 

  2. 2

    Mandon, J., Guelachvili, G. & Picqué, N. Fourier transform spectroscopy with a laser frequency comb. Nature Photon. 3, 99–102 (2009).

    ADS  Article  Google Scholar 

  3. 3

    Ferguson, B. & Zhang, X.-C. Materials for terahertz science and technology. Nature Mater. 1, 26–33 (2002).

    ADS  Article  Google Scholar 

  4. 4

    Shen, Y.-C. et al. Detection and identification of explosives using terahertz pulsed spectroscopic imaging. Appl. Phys. Lett. 86, 241116 (2005).

    ADS  Article  Google Scholar 

  5. 5

    Schmuttenmaer, C. A. Exploring dynamics in the far-infrared with terahertz spectroscopy. Chem. Rev. 104, 1759–1780 (2004).

    Article  Google Scholar 

  6. 6

    Köhler, R. et al. Terahertz semiconductor‐heterostructure laser. Nature 417, 156–159 (2002).

    ADS  Article  Google Scholar 

  7. 7

    Brandstetter, M. et al. High power terahertz quantum cascade lasers with symmetric wafer bonded active regions. Appl. Phys. Lett. 103, 171113 (2013).

    ADS  Article  Google Scholar 

  8. 8

    Kourogi, M., Nakagawa, K. & Ohtsu, M. Wide-span optical frequency comb generator for accurate optical frequency difference measurement. IEEE J. Quantum Electron. 29, 2693–2701 (1993).

    ADS  Article  Google Scholar 

  9. 9

    Kippenberg, T. J., Holzwarth, R. & Diddams, S. A. Microresonator-based optical frequency combs. Science 332, 555–559 (2011).

    ADS  Article  Google Scholar 

  10. 10

    Yeh, K.-L., Hoffmann, M. C., Hebling, J. & Nelson, K. A. Generation of 10 µJ ultrashort terahertz pulses by optical rectification. Appl. Phys. Lett. 90, 171121 (2007).

    ADS  Article  Google Scholar 

  11. 11

    Pearson, J. C. et al. Demonstration of a room temperature 2.48–2.75 THz coherent spectroscopy source. Rev. Sci. Instrum. 82, 093105 (2011).

    ADS  Article  Google Scholar 

  12. 12

    Drouin, B. J., Maiwald, F. W. & Pearson, J. C. Application of cascaded frequency multiplication to molecular spectroscopy. Rev. Sci. Instrum. 76, 093113 (2005).

    ADS  Article  Google Scholar 

  13. 13

    Ippen, E. P. Principles of passive mode locking. Appl. Phys. B 58, 159–170 (1994).

    ADS  Article  Google Scholar 

  14. 14

    Wang, C. Y. et al. Coherent instabilities in a semiconductor laser with fast gain recovery. Phys. Rev. A 75, 031802 (2007).

    ADS  Article  Google Scholar 

  15. 15

    Wang, C. Y. et al. Mode-locked pulses from mid-infrared quantum cascade lasers. Opt. Express 17, 12929–12943 (2009).

    ADS  Article  Google Scholar 

  16. 16

    Barbieri, S. et al. Coherent sampling of active mode-locked terahertz quantum cascade lasers and frequency synthesis. Nature Photon. 5, 306–313 (2011).

    ADS  Article  Google Scholar 

  17. 17

    Hugi, A., Villares, G., Blaser, S., Liu, H. C. & Faist, J. Mid-infrared frequency comb based on a quantum cascade laser. Nature 492, 229–233 (2012).

    ADS  Article  Google Scholar 

  18. 18

    Keilmann, F., Gohle, C. & Holzwarth, R. Time-domain mid-infrared frequency-comb spectrometer. Opt. Lett. 29, 1542–1544 (2004).

    ADS  Article  Google Scholar 

  19. 19

    Bernhardt, B. et al. Cavity-enhanced dual-comb spectroscopy. Nature Photon. 4, 55–57 (2010).

    ADS  Article  Google Scholar 

  20. 20

    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 

  21. 21

    Kärtner, F. X. et al. Ultrabroadband double-chirped mirror pairs for generation of octave spectra. J. Opt. Soc. Am. B 18, 882–885 (2001).

    ADS  Article  Google Scholar 

  22. 22

    Kröll, J. et al. Phase-resolved measurements of stimulated emission in a laser. Nature 449, 698–701 (2007).

    ADS  Article  Google Scholar 

  23. 23

    Burghoff, D. et al. A terahertz pulse emitter monolithically integrated with a quantum cascade laser. Appl. Phys. Lett. 98, 061112 (2011).

    ADS  Article  Google Scholar 

  24. 24

    Martl, M. et al. Gain and losses in THz quantum cascade laser with metal–metal waveguide. Opt. Express 19, 733–738 (2011).

    ADS  Article  Google Scholar 

  25. 25

    Burghoff, D., Wang, C. W. I., Hu, Q. & Reno, J. L. Gain measurements of scattering-assisted terahertz quantum cascade lasers. Appl. Phys. Lett. 100, 261111 (2012).

    ADS  Article  Google Scholar 

  26. 26

    Lee, A. W. M. et al. High-power and high-temperature THz quantum-cascade lasers based on lens-coupled metal–metal waveguides. Opt. Lett. 32, 2840–2842 (2007).

    ADS  Article  Google Scholar 

  27. 27

    Kumar, S. & Hu, Q. Coherence of resonant-tunneling transport in terahertz quantum-cascade lasers. Phys. Rev. B 80, 245316 (2009).

    ADS  Article  Google Scholar 

  28. 28

    Gellie, P. et al. Injection-locking of terahertz quantum cascade lasers up to 35 GHz using RF amplitude modulation. Opt. Express 18, 20799–20816 (2010).

    ADS  Article  Google Scholar 

  29. 29

    Zhang, W. et al. Quantum noise in a terahertz hot electron bolometer mixer. Appl. Phys. Lett. 96, 111113 (2010).

    ADS  Article  Google Scholar 

  30. 30

    Baryshev, A. et al. Phase locking and spectral linewidth of a two-mode terahertz quantum cascade laser. Appl. Phys. Lett. 89, 031115 (2006).

    ADS  Article  Google Scholar 

  31. 31

    Gordon, A. et al. Multimode regimes in quantum cascade lasers: from coherent instabilities to spatial hole burning. Phys. Rev. A 77, 053804 (2008).

    ADS  Article  Google Scholar 

  32. 32

    Dhillon, S. S. et al. Terahertz transfer onto a telecom optical carrier. Nature Photon. 1, 411–415 (2007).

    ADS  Article  Google Scholar 

  33. 33

    Hayton, D. J. et al. Phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser using a room-temperature superlattice harmonic mixer. Appl. Phys. Lett. 103, 051115 (2013).

    ADS  Article  Google Scholar 

  34. 34

    Ren, Y. et al. Frequency locking of single-mode 3.5-THz quantum cascade lasers using a gas cell. Appl. Phys. Lett. 100, 041111 (2012).

    ADS  Article  Google Scholar 

  35. 35

    Turčinková, D. et al. Ultra-broadband heterogeneous quantum cascade laser emitting from 2.2 to 3.2 THz. Appl. Phys. Lett. 99, 191104 (2011).

    ADS  Article  Google Scholar 

  36. 36

    Vitiello, M. S. et al. Quantum-limited frequency fluctuations in a terahertz laser. Nature Photon. 6, 525–528 (2012).

    ADS  Article  Google Scholar 

  37. 37

    Consolino, L. et al. Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers. Nature Commun. 3, 1040 (2012).

    ADS  Article  Google Scholar 

  38. 38

    Wu, Q. & Zhang, X.-C. Free-space electro-optic sampling of terahertz beams. Appl. Phys. Lett. 67, 3523–3525 (1995).

    ADS  Article  Google Scholar 

  39. 39

    Amanti, M. I., Fischer, M., Scalari, G., Beck, M. & Faist, J. Low-divergence single-mode terahertz quantum cascade laser. Nature Photon. 3, 586–590 (2009).

    ADS  Article  Google Scholar 

  40. 40

    Kao, T.-Y., Hu, Q. & Reno, J. L. Perfectly phase-matched third-order distributed feedback terahertz quantum-cascade lasers. Opt. Lett. 37, 2070–2072 (2012).

    ADS  Article  Google Scholar 

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Acknowledgements

The work at MIT was supported by NASA and the NSF. The work in the Netherlands was supported by NWO, NATO SFP and RadioNet. This work was performed, in part, at the Center for Integrated Nanotechnologies, a US Department of Energy, Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-programme laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration (contract no. DE-AC04-94AL85000). The authors thank D. Levonian for his help in setting up the FTIR.

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Contributions

D.B. conceived the strategy, designed the devices, performed the measurements and completed the analysis. D.B. and N.H. performed electromagnetic simulations. T.-Y.K., N.H. and C.W.I.C. fabricated the devices. D.B., X.C. and Y.Y. performed the heterodyne beat-note measurements. D.J.H. and J.-R.G. provided the hot electron bolometer mixer. J.L.R. provided the material growth. All work was performed under the supervision of Q.H.

Corresponding author

Correspondence to David Burghoff.

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The authors declare no competing financial interests.

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Burghoff, D., Kao, T., Han, N. et al. Terahertz laser frequency combs. Nature Photon 8, 462–467 (2014). https://doi.org/10.1038/nphoton.2014.85

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