Room-temperature heterodyne terahertz detection with quantum-level sensitivity


Our Universe is most radiant at terahertz frequencies (0.1–10.0 THz) (ref. 1), providing critical information on the formation of the planets, stars and galaxies, as well as the atmospheric constituents of the planets, their moons, comets and asteroids2,3,4,5,6,7,8,9. The detection of faint fluxes of photons at terahertz frequencies is crucial for many planetary, cosmological and astrophysical studies10,11,12,13,14. For example, understanding the physics and molecular chemistry of the life cycle of stars and their relationship with the interstellar medium in galaxies requires heterodyne detectors with noise temperatures close to the quantum limit15. Near-quantum-limited heterodyne terahertz detection has so far been possible only through the use of cryogenically cooled superconducting mixers as frequency downconverters15,16,17,18. Here we introduce a heterodyne terahertz detection scheme that uses plasmonic photomixing for frequency downconversion to offer quantum-level sensitivities at room temperature. Frequency downconversion is achieved by mixing terahertz radiation and a heterodyning optical beam with a terahertz beat frequency in a plasmonics-enhanced semiconductor active region. We demonstrate terahertz detection sensitivities down to three times the quantum limit at room temperature. With a versatile design capable of broadband operation over a 0.1–5.0 THz bandwidth, this plasmonic photomixer has broad applicability to astronomy, cosmology, atmospheric studies, gas sensing and quantum optics.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Principles of heterodyne terahertz detection through plasmonic photomixing.
Fig. 2: Terahertz-to-RF conversion using the fabricated plasmonic photomixer.
Fig. 3: Noise temperature characteristics of the fabricated plasmonic photomixer.

Data availability

The authors declare that all data supporting the conclusions of the manuscript are present in the manuscript and the supplementary materials.


  1. 1.

    Neugebauer, G. et al. Early results from the Infrared Astronomical Satellite. Science 224, 14–21 (1984).

  2. 2.

    Mahieu, E. et al. Recent Northern Hemisphere stratospheric HCl increase due to atmospheric circulation changes. Nature 515, 104–107 (2014).

  3. 3.

    Manney, G. L. et al. Unprecedented Arctic ozone loss in 2011. Nature 478, 469–475 (2011).

  4. 4.

    Solomon, S. et al. Contributions of stratospheric water vapor to decadal changes in the rate of global warming. Science 327, 1219–1223 (2010).

  5. 5.

    Phillips, T. G. & Keene, J. Submillimeter astronomy (heterodyne spectroscopy). Proc. IEEE 80, 1662–1678 (1992).

  6. 6.

    Hartquist, T. W. & Williams, D. A. The Molecular Astrophysics of Stars and Galaxies (Oxford Univ. Press, 1998).

  7. 7.

    van Dishoeck, E. F. & Blake, G. A. Chemical evolution of star-forming regions. Annual Rev. Astron. Astrophys. 36, 317–368 (1998).

  8. 8.

    Dutrey, A., Guilloteau, S. & Guelin, M. Chemistry of protosolar-like nebulae: the molecular content of the DM Tau and GG Tau disks. Astron. Astrophys. 317, L55–L58 (1997).

  9. 9.

    Biver, N. et al. Evolution of the outgassing of Comet Hale-Bopp (C/1995 O1) from radio observations. Science 275, 1915–1918 (1997).

  10. 10.

    Hartogh, P. et al. Ocean-like water in the Jupiter-family comet 103P/Hartley 2. Nature 478, 218–220 (2011).

  11. 11.

    Küppers, M. et al. Localized sources of water vapour on the dwarf planet (1) Ceres. Nature 505, 525–527 (2014).

  12. 12.

    Brünken, S. et al. H2D+ observations give an age of at least one million years for a cloud core forming Sun-like stars. Nature 516, 219–221 (2014).

  13. 13.

    Falgarone, E. et al. Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies. Nature 548, 430–433 (2017).

  14. 14.

    Hogerheijde, M. R. et al. Detection of the water reservoir in a forming planetary system. Science 334, 338–340 (2011).

  15. 15.

    De Graauw, T. et al. The Herschel–Heterodyne Instrument for the Far-Infrared (HIFI). Astron. Astrophys. 518, L6 (2010).

  16. 16.

    Putz, P. et al. Terahertz hot electron bolometer waveguide mixers for GREAT. Astron. Astrophys. 542, L2 (2012).

  17. 17.

    Heyminck, S. et al. GREAT: the SOFIA high-frequency heterodyne instrument. Astron. Astrophys. 542, L1 (2012).

  18. 18.

    Wootten, A. & Thompson, A. R. The Atacama Large Millimeter/submillimeter Array. Proc. IEEE 97, 1463–1471 (2009).

  19. 19.

    Berry, C. W., Wang, N., Hashemi, M. R., Unlu, M. & Jarrahi, M. Significant performance enhancement in photoconductive terahertz optoelectronics by incorporating plasmonic contact electrodes. Nat. Commun. 4, 1622 (2013).

  20. 20.

    Yardimci, N. T. & Jarrahi, M. Nanostructure-enhanced photoconductive terahertz emission and detection. Small 14, 1802437 (2018).

  21. 21.

    Wengler, M. J. Submillimeter-wave detection with superconducting tunnel diodes. Proc. IEEE 80, 1810–1826 (1992).

  22. 22.

    Gao, J. R. et al. Terahertz superconducting hot electron bolometer heterodyne receivers. IEEE Trans. Appl. Supercond. 17, 252–258 (2007).

  23. 23.

    Kloosterman, J. L. et al. Hot electron bolometer heterodyne receiver with a 4.7 THz quantum cascade laser as a local oscillator. Appl. Phys. Lett. 102, 011123 (2013).

  24. 24.

    Crowe, T. W. et al. GaAs Schottky diodes for THz mixing applications. Proc. IEEE 80, 1827–1841 (1992).

  25. 25.

    Zmuidzinas, J. & Richards, P. L. Superconducting detectors and mixers for millimeter and submillimeter astrophysics. Proc. IEEE 92, 1597–1616 (2004).

  26. 26.

    Semenov, A. D. et al. Superconducting hot-electron bolometer mixer for terahertz heterodyne receivers. Trans. Appl. Supercond. 13, 168–171 (2003).

  27. 27.

    Hubers, H. W. Terahertz heterodyne receivers. IEEE J. Sel. Top. Quantum Electron. 14, 378–391 (2008).

  28. 28.

    Yang, S.-H. & Jarrahi, M. Spectral characteristics of terahertz radiation from plasmonic photomixers. Opt. Exp. 23, 28522–28530 (2015).

  29. 29.

    Wang, N. & Jarrahi, M. Noise analysis of photoconductive terahertz detectors. J. Inf. Mill. THz Waves 34, 519–528 (2013).

  30. 30.

    Kerr, A. R. Suggestions for revised definitions of noise quantities, including quantum effects. Trans. Microw. Theory Tech. 47, 325–329 (1999).

  31. 31.

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

Download references


We gratefully acknowledge financial support from National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) Strategic University Research Partnerships Program. M.J.’s group gratefully acknowledges the financial support from the Office of Naval Research (contract number N00014-14-1-0573) and National Science Foundation (contract number 1305931). S.C. was supported by the Department of Energy (grant number DE-SC0016925).

Author information

N.W. designed and fabricated the device prototypes and performed the heterodyne detector characterization measurements at the University of California, Los Angeles. S.C. performed the noise temperature measurements at the University of California, Los Angeles. Y.-J.L. designed and fabricated the IF circuits. H.J. assisted with project supervision and performed the spectral resolution characterization measurements at JPL. M.J. supervised the project and wrote the manuscript. All authors discussed the results and commented on the manuscript.

Correspondence to Mona Jarrahi.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information: Nature Astronomy thanks Heinz-William Huebers, Juerg Leuthold and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Supplementary information

Supplementary Information

Supplementary Figs. 1–6, Supplementary Table 1

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark