A Terahertz Ruler for ultra-short XUV Pulses

The advent of ultra-short light pulses has been a revolution for the field of optics and photonics. The availability of well-controlled, precisely timed light pulses, with pulse durations in the femtosecond regime, enabled technological breakthroughs such as the making “molecular” movies of important ultra-fast processes like chemical reactions or the development of a variety of new highly sensitive spectroscopy techniques that have revolutionized the field of laboratory analytics.
A large international collaboration of researchers from the DLR institute of Optical Sensor Systems, the TU Berlin, the FU Berlin, the Helmholtz-Zentrum Dresden-Rossendorf, the European XFEL GmbH, the Johannes Gutenberg University Mainz, the University of Aarhus, the Fritz-Haber-Institute, the Max-Planck-Institute for the Structure and Dynamics of Matter, the University of Hamburg and Elettra-Sincrotrone Trieste has recently demonstrated a novel technique to measure the arrival time, duration and energy of light pulses over a wide range from the near infrared to the extreme ultra-violet spectral range. 
One of the most fascinating and technologically most important assets of ultra-short light pulses is that one can easily transform their wavelength into another over a very broad spectral range from millimeters (terahertz radiation) to the few-10 nm range (extreme ultraviolet) by means of nonlinear optics. A remaining challenge is to characterize the properties of these light pulses, which so far required specific instruments for the different spectral ranges.    
“The beauty of the technique is that it has now been shown to work from the near-infrared to the extreme-ultra violet wavelength, an already extremely broad range” says Michael Gensch, Professor at the TU Berlin and head of department at the DLR Institute of Optical Sensor Systems. 
The underlying mechanism is the quasi instantaneous transformation of the light pulses into a Terahertz light pulse in a specific spintronic metallic multi-nanolayer structure (see Fig. 1). The information on the pulse properties is encoded in the Terahertz waveform and can be detected or if you will, read out, for each individual laser pulse. 
Tom Seifert und Tobias Kampfrath from FU Berlin and founder of the company TeraSpinTec that commercializes the spintronic terahertz emitters, adds: “Our physical understanding of the underlying processes makes us believe that our scheme should also work in the harder X-ray regime”. “This would be of high relevance for the operation of X-ray free electron lasers” comments Robert Carley, scientist at the European XFEL: “We are always on the hunt for robust techniques that allow us to determine properties of individual X-ray pulses and this scheme seems to be particularly promising”.
In the context of space research, the developed scheme has a high potential as a diagnostics tool for pulses from the just emerging space ready femtosecond laser systems. “We are currently working on investigating the space readiness of our `terahertz ruler`.” concludes Gensch.
The experiments were carried out at the EIS-TIMEX beamline of the XUV free-electron laser FERMI.

Figure 1.  Spintronic Terahertz emitter – an ultra-short light pulse is transformed into a Terahertz pulse which contains the information about the arrival time, pulse duration and pulse energy. Credit: TeraSpinTec GmbH (CC BY NC ND), teraspintec.com

 

This research was conducted by the following research team:

Igor Ilyakov¹,Naman Agarwal^2,3,4,5,Jan Christoph Deinert¹, Jia Liu², Alexander Yaroslavtsev^2,6, Laura Foglia⁷, Gabor Kurdi⁷, Riccardo Mincigrucci⁷, Emiliano Principi⁷, Gerhard Jakob^8, Matthias Kläui⁸, Tom Sebastian Seifert^9,10,Tobias Kampfrath^9,10, Sergey Kovalev¹, Robert E. Carley², Andreas O. Scherz² nd Michael Gensch^11,12

¹ Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
² European XFEL, Schenefeld, Germany
³ Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
⁴ Department of Physics, Universität Hamburg, Hamburg, Germany
⁵ Institute of Physics and Astronomy (IFA), Aarhus University, Aarhus C, Denmark
⁶ Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
⁷ Elettra-Sincrotrone Trieste S.C.p.A., Trieste, Italy
⁸ Johannes Gutenberg University Mainz, Institute of Physics, Mainz, Germany
⁹ Department of Physics, Freie Universität Berlin, Berlin, Germany
¹⁰ Fritz Haber Institute of the Max Planck Society, Berlin, Germany
¹¹ Institute of Optical Sensor Systems, DLR (German Aerospace Center), Berlin, Germany
¹² Institute of Optics and Atomic Physics, Technische Universität Berlin, Berlin, Germany

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