TU5: High harmonic and attosecond pulse technology and science
TU5.1: Attosecond Science: From Tracing Electrons to Cancer Detection
F. Krausz, Max Planck Institute of Quantum Optics (Germany)
Born around the turn of the new millennium, attosecond metrology has provided real-time insight into atomic-scale electron motions and light field oscillation, previously inaccessible to human observation. Until recently, this capability has relied on attosecond extreme ultraviolet pulses, generated and measured in complex vacuum systems. Next-generation attosecond metrology is now about to change this state of matters profoundly. Sub-femtosecond current injection into wide-gap materials can directly probe ultrafast electron phenomena in condensed matter systems and can also be used for sampling the electric field of light up to ultraviolet frequencies. Petahertz field sampling draws on a robust solid-state circuitry and routine few-cycle laser technology, opening the door for complete characterization of electromagnetic fields all the way from the far infrared to the vacuum ultraviolet. These fields, with accurately measured temporal evolution, serve as a unique probe for the polarization response of matter. Field-resolved spectroscopy will access valence electronic as well as nuclear motions in all forms of matter and constitutes a generalization of pump-probe approaches. Its implementation with a solid-state instrumentation opens the door for real-world applications, such as early cancer detection by measuring miniscule changes of the molecular composition of blood via field-resolved vibrational molecular fingerprinting.
TU5.2: Gating of optical waveforms by attosecond charge control in solids
D. Zimin, Max-Planck-Institut für Quantenoptik (Germany) and Department für Physik, Ludwig-Maximilians-Universität (Germany); S. Sederberg, Max-Planck-Institut für Quantenoptik (Germany); S. Keiber, F. Siegrist, M. Wismer, V. S. Yakovlev, Max-Planck-Institut für Quantenoptik (Germany) and Department für Physik, Ludwig-Maximilians-Universität (Germany); I. Floss, C. Lemell, J. Burgdörfer, Institute for Theoretical Physics, Vienna University of Technology (Austria); M. Schultze, Max-Planck-Institut für Quantenoptik (Germany); F. Krausz, Max-Planck-Institut für Quantenoptik (Germany) and Department für Physik, Ludwig-Maximilians-Universität (Germany); N. Karpowicz, Max-Planck-Institut für Quantenoptik (Germany)
Control of the charge dynamics in solids may circumvent current speed limits of electronics and data processing. We show that such control is achieved by the interaction of solids with strong optical pulses.
Attosecond temporal precision and the sub-cycle injection of charge carriers can be obtained by the high non-linearity of the absorption of sub-bandgap photons. The strong dependence of the probability of the carrier injection on the laser electric field in dielectrics allows to temporally confine the carrier excitation to the vicinity of the strongest peak in the optical pulse.
By exposing the quartz samples, with deposited electrodes, by strong short pulses, we can generate a measurable current proportional to the vector potential of the pulse, from the moment of the carrier injection. The current is dependent on the degree of the waveform asymmetry (CEP dependence). In case of the double pulse interaction (one weak and one strong), the current depends on the delay between pulses.
To benchmark the observation, we have measured the optical pulse waveform with the new technique (NPS) and compared it with the established attosecond streaking technique. By comparing the traces of near-infrared waveform, recorded with electro-optic sampling and with the NPS technique, we could extract the characteristic time of carrier injection to be about 90 as.
To show that the method can be used for attosecond physics we performed the non-linear polarization sampling experiment, results of which previously could have been obtained only with a delicate attosecond streaking beamline.
TU5.3: Formation of attosecond pulses in the “water window” range via optically dressed H-/He-like plasma-based X-ray lasers
V. A. Antonov, Institute of Applied Physics of the Russian Academy of Sciences (Russian Federation) and Prokhorov General Physics Institute of the Russian Academy of Sciences (Russian Federation); I. R. Khairulin, Institute of Applied Physics of the Russian Academy of Sciences (Russian Federation); O. A. Kocharovskaya, Department of Physics and Astronomy, Texas A&M University (United States)
We show the possibility to produce trains of attosecond pulses in the “water window” range via irradiation of active medium of H-like C5+ or He-like C4+ recombination plasma-based X-ray laser by a strong optical laser field. The pulses can be shorter than 200 as, while the peak pulse intensity can exceed 10^12 W/cm^2.
TU5.4: 100 gigawatt-class attosecond X-ray laser pulse production and measurement
G. P. Duris, SLAC National Accelerator Lab (United States)
The X-ray Laser-Enhanced Attosecond Pulse generation experiment (XLEAP) at the Linac Coherent Light Source (LCLS) recently demonstrated production and characterization of isolated sub-femtosecond X-ray pulses, creating new opportunities for attosecond-scale science. The project is the first demonstration of the enhanced SASE scheme whereby a wiggler magnet and chicane are used to generate a femtosecond duration, high-current spike on the electron beam which then lases in the LCLS undulator line to produce sub-femtosecond X-ray pulses. We use angular streaking of photo electrons from X-ray induced ionization in a gas jet to reconstruct the pulse temporal profile and use this to measure durations shorter than 400 as with pulse energies six orders of magnitude larger than pulses from HHG. With the addition of 4 new wiggler magnets, we plan to produce pairs of attosecond pulses with 100s of GW peak powers and variable time delay from 0 to tens of femtoseconds for pump probe experiments investigating valence electronic motion in molecules.
TU6: Coherent beam combining and pulse synthesis
TU6.1: 4D-programmable Ultrafast Laser Architectures and their Applications in Accelerator and FEL Physics
S. Carbajo, Stanford University, SLAC National Accelerator Laboratory (United States)
We present a power-scalable laser architecture with programmable control of the polarization vector, transverse and longitudinal intensity, and wavefront in the near and far field as a novel tool to probe and control matter. We will discuss this novel architecture in the context of its applications in accelerator physics and free-electron laser technology.
TU6.2: High-power temporal and spatial coherent pulse combination of ultrafast fiber lasers
L. Stark, M. Müller, J. Buldt, Friedrich-Schiller-University Jena (Germany); A. Klenke, Friedrich-Schiller-University Jena (Germany) and Helmholtz-Institute Jena (Germany); A. Steinkopff, Friedrich-Schiller-University Jena (Germany); A. Tünnermann, J. Limpert, Friedrich-Schiller-University Jena (Germany) and Helmholtz-Institute Jena (Germany) and Fraunhofer Institute for Applied Optics and Precision Engineering (Germany)
Ultrafast high-power laser systems with diffraction-limited beam quality are an indispensable technology in a variety of applications, which usually strongly benefit from higher pulse energies and average powers or inevitably require them. However, the output performance of laser systems is limited. To reach the desired parameters and further scale the output pulse energy and average power of ultrafast lasers, coherent pulse combination is one of the most promising techniques. Basing on this principle, we present two different approaches and most recent experimental results. On the one hand, electro-optically controlled divided-pulse amplification is introduced as a temporal domain coherent pulse combination technique. Here, instead of a single pulse, a pulse burst is amplified and recombined afterwards into a single pulse. The technique is implemented for the first time in a high-energy ytterbiumdoped fiber laser system using additional spatial combination of 12 fiber amplifiers. The result is a combined signal of 674 W average power and 23 mJ pulse energy, while a sample was compressed to 235 fs pulse duration. On the other hand, a turn-key operable ultrafast high-average power system based on coherent beam combination of 4 fiber amplifiers is presented. The combined output has 3.5 kW average power at a pulse repetition rate of 80 MHz and a pulse duration of 430 fs. Both results, the high pulse energy and the high average power, are to the best of our knowledge the highest values achieved with ultrafast fiber-based laser systems so far.
TU6.3: Fully Stabilized and Controlled Sub-Cycle Optical Pulses from Parallel Parametric Waveform Synthesis
R. Mainz, G. Rossi, F. Scheiba, Y. Yang, M. Silva Toledo, G. Cirmi, F. X. Kaertner, Center for Free-Electron Laser Science (Germany)
We present, to the best of our knowledge, the first functional passively CEP-stable parametric waveform synthesizer generating custom-sculptured sub-cycle pulses with millijoule level energy. Our source delivers pulses with 0.65 optical cycles in duration centered at 1.8 μm and 600 μJ in energy. A shot-to-shot stable waveform can be synthesized over hours enabling novel prospects in attosecond pulse generation and attosecond spectroscopy.
TU6.4: A parametric waveform synthesizer for attosecond science
Y. Yang, G. Rossi, R. E. Mainz, F. Scheiba, M. A. Silva-Toledo, DESY (Germany) and Universität Hamburg (Germany); P. Keathley, Massachusetts Institute of Technology (United States); G. Cirmi, F. X. Kärtner, DESY (Germany) and Universität Hamburg (Germany)
We present HHG driven with a sub-cycle, mJ-level parametric waveform synthesizer. The variation of the HHG spectral shape and yield as a function of the relative phase between the synthesizer channels is shown. Photoelectron streaking measurements demonstrate attosecond pulse generation with a duration of ~112 attoseconds.
TU6.5: Broadband interferometric subtraction of ultrashort pulses
T. Buberl, Max-Planck-Insitute of Quantum Optics (Germany)
We present a simple, cost-effective method to optically subtract ultrashort pulses spanning a super-octave spectrum (950 – 2100 nm). Achromatic extinction is achieved in a Mach-Zehnder-like interferometer with an intensity extinction of 6.2×10^-4 by unbalancing the number of Fresnel reflections off optically denser media in the two interferometer arms. By introducing a methane gas sample in one interferometer arm, we isolate the coherent molecular vibrational emission from the broadband, impulsive excitation. We predict a potential improvement in detectable concentration compared to direct transmission geometry by more than one order of magnitude. The presented concept will benefit sensing applications requiring high detection sensitivity and dynamic range, including time-domain and frequency-domain spectroscopy and affords the potential of separating the nonlinear polarization response of a sample from the linear one, upon excitation with intense laser pulses.
TU7: FEL technology and applications
TU7.1: Realization of Ultra-stable Hard X-ray Free Electron Laser
H. Kang, Pohang Accelerator Lab (Korea)
The use of electron-beam-based alignment incorporating undulator radiation spectrum analysis, state-of-the-art design of the linac RF and timing system, and the three-chicane bunch-compressor lattice allows reliable operation of PAL-XFEL with unprecedented stability in terms of arrival timing, beam pointing, and intensity jitter. An electron beam arrival timing jitter of smaller than 15 fs, a transverse position jitter of smaller than 10% of the photon beam size, and an FEL intensity jitter of smaller than 5% are consistently achieved. The measured central wavelength jitter is as small as 2.9 E-4, much smaller than the FEL parameter of 5.0E-4, which is attributed to the small e-beam energy jitter of 0.013%. A distinguishing feature of PAL-XFEL is the unprecedented temporal stability, with the rms timing jitter of ~18 fs between X-ray pulses and optical pulses from a synchronized laser system. This low timing jitter of the electron beam makes it possible to observe Bi(111) phonon dynamics without the need for timing-jitter correction, indicating that PAL-XFEL is an extremely useful tool for hard X-ray time-resolved experiments.
TU7.2: Towards Free Electron Laser based on Laser Plasma Accelerators
M. Couprie,Synchrotron SOLEIL (France)
The laser invention led to the development of free electrons lasers (FEL), that are ultra-short coherent high brightness sources from the infra-red to the X-ray, range, providing a unique tool for matter investigation and to laser plasma acceleration (LPA), that can provide large acceleration gradient in extremely short distances. Combining both of them for developing a laser plasma based free electron laser would provide the qualification of the new acceleration concept, and open the path towards compact FELs. Since the LPA electron beam characteristics do not yet reached these currently achieved on conventional accelerators, especially in terms of energy spread and divergence, strategies of beam manipulation have to be developed. A panorama of major progresses is then drawn.
TU7.3: High-sensitivity Femtosecond X-ray Optical Cross-Correlator for Next Generation Free-Electron Lasers
S. Droste, L. Shen, V. White, E. Diaz-Jacobo, R. Coffee, S. Zohar, A. Reid, F. Tavella, M. Minitti, J. Turner, K. Gumerlock, J. Robinson, A. Fry, G. Coslovich, SLAC National Accelerator Lab (United States)
We designed a novel X-ray arrival time monitor that cross-correlates X-ray and 1550 nm optical pulses used in stateof- the-art femtosecond timing distribution systems. We exploit an interferometric detection scheme and etalon effects in thin-film Germanium to achieve unprecedented high sensitivity to soft X-rays. The resolution of the timing measurement is 2.8 fs (rms). The detection scheme is compatible with various wavelengths with the choice of appropriate sample materials.
TU7.4: Timing stabilization of synchronized femtosecond laser system for pump-probe experiments in SACLA
T. Togashi, Japan Synchrotron Radiation Research Institute (Japan) and RIKEN SPring-8 Center (Japan); A. Kon, Japan Synchrotron Radiation Research Institute (Japan); K. Sueda, RIKEN SPring-8 Center (Japan); T. Yabuuchi, S. Owada, T. Katayama, Japan Synchrotron Radiation Research Institute (Japan) and RIKEN SPring-8 Center (Japan); K. Nakajima, RIKEN SPring-8 Center (Japan); S. Matsubara, Japan Synchrotron Radiation Research Institute (Japan); H. Tomizawa, K. Tono, M. Yabashi, Japan Synchrotron Radiation Research Institute (Japan) and RIKEN SPring-8 Center (Japan)
A synchronization system of a femtosecond laser has been developed for pump-probe experiments using X-ray free electron laser (XFEL) and optical laser pulses in a Japanese XFEL facility: SPring-8 Angstrom Compact free-electron LAser (SACLA). This system controls the mode-locked oscillator with a balanced optical-microwave phase detector (BOM-PD) using the 5.7-GHz RF signal from the accelerator of SACLA as a reference. We have evaluated relative timing fluctuation between these pulses using an arrival-timing monitor based on spatial encoding technique with X-ray induced change in optical transmittance of gallium arsenide (GaAs). The timing fluctuation was estimated as 20 fs r.m.s. in a short period (3 minutes).
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TU8: High average power ultrafast lasers
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TU8.2: Frontiers in high power ultrafast thin-disk lasers operating in the sub-100-fs regime
T. Südmeyer, N. Modsching, J. Drs, J. Fischer, C. Paradis, F. Labaye, M. Gaponenko, Univ de Neuchâtel (Switzerland); C. Kränkel, Center for Laser Materials, Leibniz-Institut für Kristallzüchtung (Germany); V. J. Wittwer, Univ de Neuchâtel (Switzerland)
The thin-disk laser (TDL) concept is highly beneficial for ultrafast oscillators operating in the sub-100-fs regime: excessive nonlinearities from the gain material are suppressed by the thin gain geometry, and the TDL pumping scheme circumvents the need for dichroic mirrors with high pump transmission in the laser cavity. In this way, Kerr lens mode-locked (KLM) TDLs can operate with nearly transform-limited soliton pulses in a strongly self-phase modulation (SPM) broadened regime, featuring an optical bandwidth that can be several times larger than the bandwidth of the employed gain material, reaching so far down to 30-fs pulses. We discuss the current state-of-the-art and present in detail the design and optimization of an Yb:Lu2O3 oscillator, which generates pulses with a duration of 95 fs at 21.1 W average power and 47.9 MHz repetition rate. Unlike to usual KLM TDL oscillators, an operation at the edge of the stability zone in continuous-wave operation is not required. The average power is nearly twice as high as previous sub-100-fs laser oscillators. We expect that further power scaling towards power levels in excess of hundred Watt will be soon be achieved.
TU8.3: 100 µJ, 100 kHz, CEP-stable high-power few-cycle fiber laser
E. Shestaev, Friedrich-Schiller-University Jena, Institute of Applied Physics (Germany); D. Hoff, A. M. Sayler, Institut für Optik und Quantenelektronik (Germany); S. Hädrich, F. Just, T. Eidam, Active Fiber Systems GmbH (Germany); P. Jójárt, Á. Szabó, Z. Várallyay, K. Osvay, ELI-ALPS, ELI-HU Non-Profit Ltd. (Hungary); G. G. Paulus, Institut für Optik und Quantenelektronik (Germany); A. Tünnermann, Friedrich-Schiller-University Jena, Institute of Applied Physics (Germany) and Fraunhofer Institute for Applied Optics and Precision Engineering IOF (Germany); J. Limpert, Friedrich-Schiller-University Jena, Institute of Applied Physics (Germany) and Active Fiber Systems GmbH (Germany) and Helmholtz-Institute Jena (Germany)
We present a CEP-stable Yb:fiber-based laser system delivering 100 μJ few-cycle pulses at the repetition rate of 100 kHz. The CEP stability of a free-running system amounts to 340 mrad (10 Hz … 50 kHz) measured on a pulse-to-pulse basis with a Stereo-ATI phase meter. A slow loop from the ATI to the AOM acting as a pulse picking device has been implemented, allowing for suppression of CEP fluctuations below 300 Hz. To the best of our knowledge, this is the highest performance in terms of CEP stability achieved from a fiber-based high-power few-cycle laser to date.
TU8.4: Yb-doped fiber laser system with 1kW, 10mJ and <300fs pulse for the generation of TW class few-cycle pulses
S. Breitkopf, S. Hädrich, M. Kienel, Active Fiber Systems GmbH (Germany); P. Jojart, ELI-ALPS, ELI-HU Non-Profit Ltd. (Hungary); Z. Varallyay, K. Osvay, ELI-ALPS (Hungary); P. Simon, Laser-Laboratorium Göttingen e.V. (Germany); T. Nagy, Max- Born- Institute for Nonlinear Optics and Short Pulse Spectroscopy (Germany); A. Blumenstein, Laser-Laboratorium Göttingen e.V. (Germany); R. Klas, Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena (Germany) and Helmholtz-Institute Jena (Germany); J. Buldt, H. Stark, E. Shestaev, Institute of Applied Physics (Germany); T. Eidam, Active Fiber Systems GmbH (Germany); J. Limpert, Institute of Applied Physics (Germany) and Helmholtz-Institute Jena (Germany) and Fraunhofer Institute for Applied Optics and Precision Engineering, (Germany)
We present a 10-mJ and 1-kW, sub 300-fs CPA system with excellent beam quality (M2=1.1). To achieve such parameter-set, the output of 16 main-amplifier channels is coherently combined using a polarization-based filled-aperture scheme. The system exhibits excellent long-term stability of 0.3% RMS power fluctutations over >9hours and is a major part of the ELI-ALPS HR2 laser system. It will be combined with a nonlinear pulse compression unit that aims to achieve 5 mJ pulse energy at 100 kHz pulse repetition rate (i.e. 500 W of average power) and with pulse durations of 6 fs, i.e. a terawatt class laser. In addition to the CPA system we present first promising experimental results on compression of high energy pulses with high average power in a long stretched capillary setup. In a first proof-of-principle experiments, 5 mJ pulses at 100 kHz (500 W average power) are spectrally broadened in a 4 m long capillary to a bandwidth supporting <17 fs pulses. Further experimental results towards the achievement of the HR2 pulse parameters will be presented at the conference.
TH8.5: Table-top high energy 7µm OPCPA for strong field physics
U. Elu, D. Sanchez, T. Steinle, L. Maidment, ICFO – The Institute of Photonic Sciences (Spain); K. Zawilski, P. Schunemann, BAE Systems (United States); G. Matras, C. Simon-Boisson, THALES Optronique S.A.S. (France); J. Biegert, ICFO –The Institute of Photonic Sciences (Spain) and ICREA (Spain)
We present the development of a 0.75 mJ pulse energy, 7 μm OPCPA at 100 Hz with an intermediate chirp inversion stage permitting compression with 93.5% efficiency in bulk BaF2 to 188 fs duration (8 optical-cycles). The output is used to generate high harmonics in ZnSe spanning the near infrared into the visible spectral region, reaching harmonic order 13. The high intensity, passively carrier-to-envelope phase stable mid-infrared pulses make this table-top source a key enabling tool for strong field physics and keV-level coherent x-ray sources.