- Department Head: C2 "Solid State Light Sources"
- Project Coordinator: 1.2 "Ultrafast Laser Physics and Nonlinear Optics"
In ultrafast optics, it often proves invaluable to exactly know the temporal structure of the few-cycle pulses in the experiments. Compared to transient events in electronics, our means of precisely measuring optical transients on the femtosecond scale appear much more limited. To this end, a number of techniques have emerged that enable simultaneous measurement of the amplitude and phase structures of ultrashort pulses. Among these techniques, interferometric frequency-resolved optical gating has evolved as a particularly powerful technique, which can also be used for spectroscopic experiments on the few-cycle temporal scale.
Experimental setup for filament generation in a controlled noble-gas atmosphere. The characteristic sign for the onset of plasma formation and filamentation is the color change from red (scattered light) to violet (fluorescence) appearing at the 7 cm position on the ruler. After the collapse of the filamention process at 70 cm, a white-light spectrum emerges. Spectral width and the number of filaments inside the cell can be controlled by pressure and gas fill.
A second important aspect is measurement and control of the carrier-envelope phase of an ultrashort optical pulse. This phase plays an important role in attosecond spectroscopy. We have developed the feed-forward technique for stabilization of the carrier-envelope phase. This patented method is now commercially available from a major laser manufacturer. Our research continues and tries to explore the absolute limits of carrier-envelope phase measurements, as they are, e.g., imposed by quantum noise mechanisms.
Further research is devoted to optical filamentation. Loosely focusing an intense laser beam in air, one observes a collapse of the beam profile, and a plasma channel forms that guides the light at nearly constant beam diameter for lengths in the centimeter or meter range. Further increasing the laser power, several such filaments coexist parallel to each other and show highly dynamic behavior. The resulting beam profiles exhibit short-lived extremely bright flashes, which appear in analogy to ocean rogue waves. We carefully studied the statistics of rogue waves in our multifilament scenario and compared them to other rogue-wave supporting systems. This comparison seems to enable some intriguing new insight into the ocean rogue wave mystery, which we are currently exploring in more depth.
10/2017 Fellow, American Physical Society (APS)
09/2017 Full (W3-S) Professor, Department of Physics, Humboldt Universität zu Berlin
03/2017 Fellow, International Union of Radio Science (URSI)
01/2016 Fellow, Optical Society of America (OSA)
01/2015 - 12/2017 Member Editorial Board, Physical Review A
01/2014 Outstanding Referee, American Physical Society (APS)
04/2012 - 03/2018 Topical Editor, Ultrafast Phenomena, Optics Letters
11/2008 - 10/2013 Finland Distinguished Professor Optoelectronics Research Centre, Tampere University of Technology, Finland
07/2002 - present: Senior Staff Scientist and Head of the Department C2, Solid-State Light Sources Max-Born-Institut, Berlin, Germany
09/2002 Habilitation in Experimental Physics Dissertation: New approaches to the Generation and Characterization of Few- Cycle Laser Pulses , Prof. Dr. Ursula Keller
02/1998 - 07/2002 Research Associate Institute of Quantum Electronics,Swiss Federal Institute of Technology, Zürich, Switzerland
11/1995 - 12/1997 Postdoctoral Researcher Research Lab of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
04/1995 - 10/1995 Postdoctoral Researcher Institute of Applied Physics, University of Münster, Germany
02/1995 Ph.D. in Physics (with distinction) Dissertation: Pulse Shaping Processes and Optical Turbulence in a Nonlinear Fiber Ring Resonator , Prof. Dr. Fedor Mitschke
05/1992 - 03/1995 Graduate Student Institute of Quantum Optics, Hannover University, Germany
05/1992 - 03/1995 Teaching Assistant (part time, several appointments) Hannover University and Hannover Medical School, Germany
04/1992 Diploma in Physics Diploma thesis: Construction and Application of a Spectrometer for the VUV/XUV Spectral Range Employing a Laser-Induced Plasma Light Source Prof. Dr. Bernd Wellegehausen
08/1987 - 04/1992 Teaching Assistant (part time, several appointments) Institute of Mathematics, Hannover University, Germany
- Propagation effects in the characterization of 1.5-cycle pulses by XPW dispersion scan IEEE Journal of Selected Topics in Quantum Electronics 25 (2019) 5120407/1-7
- Megafilaments in the mid-infrared Nature Photonics 13 (2019) 7-8
- Active f-to-2f interferometer for record-low jitter carrier-envelope phase locking Optics Letters 44 (2019) 1060-1063
- Strategies for the characterization of partially coherent ultrashort pulses with dispersion scan Journal of the Optical Society of America B-Optical Physics 36 (2019) 2092-2098
- Regularized differential evolution for a blind phase retrieval problem in ultrashort laser pulse characterization Review of Scientific Instruments 90 (2019) 043116/1-13
- Retrieving the coherent artifact in frequency-resolved optical gating Optics Letters 44 (2019) 3142-3145
- High-detectivity optical heterodyne method for wideband carrier-envelope phase noise analysis of laser oscillators Optics Letters 43 (2018) 3108-3111
- Ultrafast optoelectronics Handbook of Optoelectronics, Volume I CRC Press, Taylor & Francis Group (2018) 445-571
- Nonlinear and short pulse effects Handbook of Optoelectronics, Volume I CRC Press, Taylor & Francis Group (2018) 281-301
- Resonant-plasmon-assisted subwavelength ablation by a femtosecond oscillator Physical Review Applied 9 (2018) 024001/1-9