- Physical Review Journals
All JournalsPhysics Magazine

Physical Review Accelerators and Beams

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Two-color dual-oscillator infrared free-electron laser

Wieland Schöllkopf*, Sandy Gewinner, Marco De Pas, Heinz Junkes, Sebastian Kray, William Kirstaedter, William B. Colson†, David H. Dowell†, Stephen C. Gottschalk† et al.

John W. Rathke†, Tom J. Schultheiss†, Alan M. M. Todd†, Lloyd M. Young†, Akash Chandra Behera, América Y. Torres-Boy, Martin Wolf, Alexander Paarmann, Gert von Helden, and Gerard Meijer

  • *Contact author: wschoell@fhi-berlin.mpg.de
  • †Consultant to the Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
PDF

Phys. Rev. Accel. Beams 29, 103403 – Published 13 October, 2026

DOI: https://doi.org/10.1103/b27b-9gg1

Abstract

We report on the design and performance of a two-color dual-oscillator infrared free-electron laser (FEL). The midinfrared (MIR) FEL at the Fritz Haber Institute has been upgraded to include a second oscillator FEL beamline that permits lasing in the far-infrared (FIR) regime from 4.5 to 175  μm. In addition, a 500 MHz kicker cavity has been installed downstream of the electron accelerator. It allows deflection of electron bunches of up to 50 MeV energy alternately left and right by an angle of ±2°. It can, thus, split the high-repetition rate (1 GHz) electron bunch train from the accelerator into two bunch trains of 500 MHz repetition rate each; one is steered to the MIR FEL and the other one to the new FIR FEL. In this two-color mode of simultaneous, synchronized operation, the wavelengths in both FELs can be tuned independently over wide ranges of up to a factor of 4 each by undulator gap variation. In addition, two-color operation is also available at reduced repetition rates (e.g., 55.6 MHz of both MIR and FIR pulses), as needed for some applications. This unique two-color mode opens up a wealth of novel user applications, such as MIR-FIR pump-probe experiments.

View figure in article

Physics Subject Headings (PhySH)

Article Text

References (29)

  1. D. A. G. Deacon, L. R. Elias, J. M. J. Madey, G. J. Ramian, H. A. Schwettman, and T. I. Smith, First operation of a free-electron laser, Phys. Rev. Lett. 38, 892 (1977).
  2. H. A. Schwettman and T. I. Smith, Two-color free-electron laser driven by a radio-frequency linear accelerator, J. Opt. Soc. Am. B 6, 973 (1989).
  3. D. D. Dlott and M. D. Fayer, Application of a two-color free-electron laser to condensed-matter molecular dynamics, J. Opt. Soc. Am. B 6, 977 (1989).
  4. W. Schöllkopf, S. Gewinner, H. Junkes, A. Paarmann, G. von Helden, H. Bluem, and A. M. M. Todd, Advances in X-ray Free-Electron Lasers Instrumentation III, in Proceedings of SPIE (SPIE, Prague, Czech Republic, 2015), Vol. 9512.
  5. W. Schöllkopf, S. Gewinner, A. M. M. Todd, W. B. Colson, M. De Pas, D. Dowell, S. C. Gottschalk, H. Junkes, J. W. Rathke, T. J. Schultheiss, L. M. Young, G. v. Helden, and G. Meijer, in Proceedings of the 39th International Free-Electron Laser Conference, edited by W. Decking, H. Sinn, G. Geloni, S. Schreiber, M. Marx, and V. R. W. Schaa (JACoW, Hamburg, Germany, 2019), pp. 52–55.
  6. A. M. M. Todd, W. B. Colson, D. Dowell, S. C. Gottschalk, J. W. Rathke, T. J. Schultheiss, L. M. Young, W. Schöllkopf, M. De Pas, S. Gewinner, H. Junkes, G. von Helden, and G. Meijer, in Proc. 40th International Free Electron Laser Conference, International Free Electron Laser Conference No. 40 (JACoW Publishing, Geneva, Switzerland, 2022), pp. 64–67.
  7. A. M. M. Todd, W. Schöllkopf, S. Gewinner, M. De Pas, H. Junkes, G. von Helden, A. Paarmann, G. Meijer, J. W. Rathke, L. M. Young, S. C. Gottschalk, T. J. Schultheiss, W. B. Colson, and D. H. Dowell, in Proc. IPAC’24, International Particle Accelerator Conference No. 40 (JACoW Publishing, Geneva, Switzerland, 2024), pp. 315–318.
  8. W. Schöllkopf, S. Gewinner, M. De Pas, H. Junkes, G. von Helden, G. Meijer, W. B. Colson, D. Dowell, S. C. Gottschalk, J. W. Rathke, T. J. Schultheiss, A. M. M. Todd, and L. M. Young, in Proc. 41th International Free Electron Laser Conference 2024, Warsaw, Poland (JACoW Publishing, Geneva, Switzerland, 2024).
  9. A. Y. Torres-Boy, A. Ghosh, M. B. T. Osenton, A. C. Behera, S. Gewinner, M. De Pas, H. Junkes, W. Schöllkopf, A. Paarmann, G. von Helden, and G. Meijer, Controlling isomer population using a dual-oscillator infrared free-electron laser, Phys. Rev. Lett. 137, 013001 (2026).
  10. H. Bluem et al., in Proceedings of 32nd International Free Electron Laser Conference, Malmö, Sweden (JACoW Publishing, Geneva, Switzerland, 2010), pp. 45–47.
  11. A. M. M. Todd, H. Bluem, V. Christina, M. D. Cole, J. Ditta, D. Dowell, K. Jordan, R. Lange, J. H. Park, J. Rathke, T. Schultheiss, L. M. Young, W. Schöllkopf, S. Gewinner, W. Erlebach, H. Junkes, A. Liedke, G. v. Helden, W. Zhang, G. Meijer, and S. C. Gottschalk, in Proceedings of IPAC2011, San Sebastián, Spain (JACoW Publishing, Geneva, Switzerland, 2011), pp. 3137–3139.
  12. H. P. Bluem, D. Dowell, H. Loos, J. Park, A. M. M. Todd, L. M. Young, S. Gewinner, and W. Schöllkopf, Proceedings of the 34th International Free-Electron Laser Conference 2012, Nara, Japan (JACoW Publishing, Geneva, Switzerland, 2013), pp. 365–368.
  13. S. Gottschalk, T. DeHart, R. Kelly, M. Offenbacker, A. Valla, H. Bluem, D. Dowell, J. Rathke, A. M. Todd, S. Gewinner, H. Junkes, G. Meijer, W. Schöllkopf, W. Zhang, and U. Lehnert, Proceedings of the 34th International Free-Electron Laser Conference 2012, Nara, Japan (JACoW Publishing, Geneva, Switzerland, 2013), pp. 575–578.
  14. R. Kiessling, W. B. Colson, S. Gewinner, W. Schöllkopf, M. Wolf, and A. Paarmann, Femtosecond single-shot timing and direct observation of subpulse formation in an infrared free-electron laser, Phys. Rev. Accel. Beams 21, 080702 (2018).
  15. K. R. Crandall, TRACE 3-D documentation, Los Alamos National Lab., NM (USA), Technical Report, 1987.
  16. W. Colson, J. Blau, R. Armstead, P. Crooker, R. Vigil, T. Voughs, and B. Williams, Short Rayleigh length free electron lasers, Phys. Rev. Accel. Beams 9, 030703 (2006).
  17. R. Prazeres, F. Glotin, and J.-M. Ortega, Analysis of periodic spectral gaps observed in the tuning range of free-electron lasers with a partial waveguide, Phys. Rev. Accel. Beams 12, 010701 (2009).
  18. J.-M. Ortega, J.-P. Berthet, F. Glotin, and R. Prazeres, Evidence for competition modes in a partially guided far-infrared free-electron laser, Phys. Rev. Accel. Beams 17, 100701 (2014).
  19. D. Arslanov, R. T. Jongma, A. F. G. van der Meer, M. A. Vermeulen, M. Fujimoto, V. O. Yatsyna, and V. Zhaunerchyk, in Proceedings of the 36th Free Electron Laser Conference, Basel, Switzerland, edited by J. Chrin, S. Reiche, and V. R. W. Schaa (JACoW Publishing, Geneva, Switzerland, 2015).
  20. R. Prazeres, Laser mode complexity analysis in infrared waveguide free-electron lasers, Phys. Rev. Accel. Beams 19, 060703 (2016).
  21. Y. Zhu, Y. Xu, H. Li, Z. Zhao, and W. Li, Study on spectral gap in FELiChEM infrared free-electron laser, Nucl. Instrum. Methods Phys. Res., Sect. A 1031, 166499 (2022).
  22. M. Xia, Y. Xu, Z. Zhao, and H. Li, Solving the spectral gap problem with a four-mirror bow-tie cavity in waveguide free-electron laser oscillators, Sci. Rep. 13, 22653 (2023).
  23. G. M. H. Knippels, R. F. X. A. M. Mols, A. F. G. van der Meer, D. Oepts, and P. W. van Amersfoort, Intense far-infrared free-electron laser pulses with a length of six optical cycles, Phys. Rev. Lett. 75, 1755 (1995).
  24. J. Blau, K. R. Cohn, and W. B. Colson, Proceedings of the 37th Free Electron Laser Conference, edited by H. S. Kang-D. E. Kim-V. R. W. Schaa (JACoW Publishing, Geneva, Switzerland, 2015), pp. 607–614.
  25. A. Paarmann, I. Razdolski, A. Melnikov, S. Gewinner, W. Schöllkopf, and M. Wolf, Second harmonic generation spectroscopy in the Reststrahl band of SiC using an infrared free-electron laser, Appl. Phys. Lett. 107, 081101 (2015).
  26. W. B. Colson, Laser Handbook, edited by W. B. Colson, C. Pellegrini, and A. Renieri (North-Holland, Amsterdam, 1990), Chap. 5, pp. 115–194.
  27. D. A. Jaroszynski, R. Prazeres, F. Glotin, and J. M. Ortega, Two-color free-electron laser operation, Phys. Rev. Lett. 72, 2387 (1994).
  28. D. A. Jaroszynski, R. Prazeres, F. Glotin, and J. M. Ortega, Two-colour operation of the free-electron laser using a step-tapered undulator, Nucl. Instrum. Methods Phys. Res., Sect. A 358, 224 (1995).
  29. R. Prazeres, F. Glotin, C. Insa, D. A. Jaroszynski, and J. M. Ortega, Two-colour operation of a free-electron laser and applications in the mid-infrared, Eur. Phys. J. D 3, 87 (1998).

Outline

Information

Phys. Rev. Accel. Beams 29, 103403– Published 13 October, 2026
  • Received 16 April 2026
  • Accepted 6 August 2026
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation