Technology Development for Advanced Heterodyne Instruments

  • Our Team

  • Dr. Urs Graf (PI, PH1)
  • Dr. Matthias Justen (PH1)
  • Sajjad Mahdizadeh (PH1)
  • Marc Mertens (PH1)
  • Xiaodong Ren (PH1)
  • Pablo Tapia (PH1)

A short overview

Project D2 concentrates on two major development areas: the creation of powerful monochromatic radiation sources to be used as local oscillators for the highest frequency channels of the upGREAT instrument and the development of the new large format heterodyne array receiver CHAI for the CCAT-prime telescope. In addition D2 takes an active part in the operation and improvements of the GREAT/upGREAT/4GREAT instrument family.

Terahertz sources

In a common effort with the associated project D1, D2 uses quantum cascade lasers (QCL) to develop high power local oscillators (LO). Due to their rapid decrease of output power with frequency, conventional (frequency multiplied) sources cannot provide enough power to feed a heterodyne array above 2 THz. QCLs can produce sufficient output power for our purpose, but special measures have to be taken to control their output beam pattern and their radiation frequency to the accuracy required for astronomical heterodyne spectroscopy. In a joint development effort, the ETHZ group (D1) implements the chip level improvements, which require modifications of the QCL production process, while the UzuK group (D2) builds the embedding hardware, including cryogenics and control electronics.

CCAT-prime and CHAI

On the part of the German CCAT-prime partners, project D2 takes a leading role in the technical definition of the new telescope, its operation and the interfaces to the astronomical receivers. Beyond this participation in the telescope design, D2’s central task is the development of CCAT-prime’s high resolution spectromenter, the dual color large format heterodyne array CHAI (CCAT Heterodyne Array Instrument). D2, in close collaboration with D3, is leading the development of this instrument. While the development of the mixers is located in D3, D2, supported by S, is responsible for the development of the complete receiver system, including optics, cryogenics, electronics and instrument control. D2 is also heading the development of a holographic measurement system to determine errors in the CCAT-prime telescope surface to validate and complement the opto-mechanical surface measurement.


Project D2 provides a large fraction of the operations support for the flight campaigns of the GREAT instrument, with its latest extensions upGREAT and 4GREAT. In addition D2 takes an active part in continuously upgrading the instrument and the operation onboard SOFIA.

Selected Publications (full list)

  • A Laboratory Heterodyne Emission Spectrometer at Submillimeter Wavelengths. N. Wehres, J. Maßen, K. Borisov, B. Schmidt, F. Lewen, U. U. Graf, C. E. Honingh, D. R. Higgins, and S. Schlemmer. Phys. Chem. Chem. Phys. 20, 5530–5544 (2018)
  • Waveguide Embedding of a Double-Metal 1.9-THz Quantum Cascade Laser: Design, Manufacturing, and Results. Justen, M. and Otani, K. and Turcinkova, D. and Castellano, F. and Beck, M. and Graf, U. U. and Büchel, D. and Schultz, M. and Faist, J. IEEE Transactions on Terahertz Science and Technology 7, 609–613 (2017)
  • First Supra-THz Heterodyne Array Receivers for Astronomy With the SOFIA Observatory. Risacher, C. and Güsten, R. and Stutzki, J. and Hubers, H.-W. and Büchel, D. and Graf, U. U. and Heyminck, S. and Honingh, C. E. and Jacobs, K. and Klein, B. and Klein, T. and Leinz, C. and Pütz, P. and Reyes, N. and Ricken, O. and Wunsch, H.-J. and Fusco, P. and Rosner, S. IEEE Transactions on Terahertz Science and Technology 6, 199–211 (2016)
  • A Compact Beam Measurement Setup. Graf, U. U. Journal of Infrared, Millimeter, and Terahertz Waves 37, 770–775 (2016)
  • The upGREAT 1.9 THz multi-pixel high resolution spectrometer for the SOFIA Observatory. Risacher, C. and Güsten, R. and Stutzki, J. and Hübers, H.-W. and Bell, A. and Buchbender, C. and Büchel, D. and Csengeri, T. and Graf, U. U. and Heyminck, S. and Higgins, R. D. and Honingh, C. E. and Jacobs, K. and Klein, B. and Okada, Y. and Parikka, A. and Pütz, P. and Reyes, N. and Ricken, O. and Riquelme, D. and Simon, R. and Wiesemeyer, H. Astron. Astrophys. 595, Art. No. A34 (2016) 
  • 2D patch antenna array on a double metal quantum cascade laser with > 90 % coupling to a Gaussian beam and selectable facet transparency at 1.9 THz. Justen, M. and Bonzon, C. and Ohtani, K. and Beck, M. and Graf, U. and Faist, J. Opt. Lett. 41, 4590–4592 (2016)
  • Terahertz Heterodyne Array Receivers for Astronomy. Graf, U. U. and Honingh, C. E. and Jacobs, K. and Stutzki, J. Journal of Infrared, Millimeter, and Terahertz Waves 36, 896–921 (2015)
  • [12CII] and [13CII] 158 μm emission from NGC 2024: Large column densities of ionized carbon. Graf, U. U., Simon, R. Stutzki, J., et al. A&A, 542, L16 (2012)
  • GREAT: the SOFIA high-frequency heterodyne instrument. Heyminck, S., Graf, U. U., Güsten, R., et al.. A&A, 542, L1 (2012)
  • Phase locking of a 1.5 Terahertz quantum cascade laser and use as a local oscillator in a heterodyne HEB receiver. Rabanus, D., Graf, U. U., Philipp, M., et al. Optics Express, 17, 1159 (2009)
  • A simple method to design astigmatic off-axis mirrors. Wagner-Gentner, A., Graf, U. U., Philipp, M., et al. Infrared Physics and Technology, 50, 42 (2007)
  • Expandable fully reflective focalplane optics for millimeter- and submillimeter-wave array receivers. Lüthi, T., Rabanus, D., Graf, U. U., et al. Review of Scientific Instruments, 77, 4702 (2006)
  • Fourier Gratings as Submillimeter Beam Splitters. Graf, U. U., and Heyminck, S.. IEEE Trans. AP, 49, 542 (2001)

Grambusch, T., Über fokussierende Gitterspiegel zur kontinuierlichen Abstimmung von Quantenkaskadenlasern im Terahertz-Bereich, PhD Thesis, 2014.