M1: Ultrahigh peak-power laser systems and related technologies
G. Mourou (Ecole Politechnique, France)
M1.2: Ultraintense Ti:sapphire laser with an intensity of 5.5×10^22 W/cm^2
J. Sung, Gwangju Institute of Science and Technology (Korea) and Institute for Basic Science (Korea); J. Yoon, Institute for Basic Science (Korea, Republic of) and Gwangju Institute of Science and Technology (Korea); H. Lee, Institute for Basic Science (Korea); S. Lee, C. Nam, Institute for Basic Science (Korea) and Gwangju Institute of Science and Technology (Korea)
Ultrahigh intensity laser pulses were produced bycorrectingthe wavefront of a multi-PW Ti:sapphire laser and by tightly focusing the laser pulses. The wavefront of the PW laser pulses was corrected using two adaptiveoptics(AO) systems installed before and after the pulse compressor. When a 3-PW laser pulse was focused with an f/1.6 off-axis parabolic mirror (OAP) after the wavefront correction, the measured focal spot size (FWHM) was 1.5 um × 1.8 um, resulting in a peak intensity of 5.5×10^22 W/cm^2.
M1.3: Optimisation of a Petawatt class compressor alignment based on spectrally resolved wave front analysis
C. Le Blanc, L. RANC, J. ZOU, LULI Ecole Polytechnique CNRS (France); X. Levecq, Imagine Optic (France); F. DRUON, Laboratoire Charles Fabry, IOGS (France); D. PAPADOPOULOS, LULI Ecole Polytechnique CNRS (France)
Experiments using highly energetic Ti:Sapphire multi-PW lasers require high overall pulse quality. Delivering ultrashort pulses coupling good temporal and spatial characteristics is one of the crucial parameters leading to achieve multi-PW peak. Focusing a laser pulse with high contrast ratio (>10^10), a large beam size (10’s cm), a broadband spectrum (200nm) and high energy (100’s J) requires numerous precautions and monitoring. This study presents our theoretical and experimental investigations on a grating compressor alignment using a multi-spectral wavefront sensor. We demonstrate that this technique is capable to optimize a compressor alignment and characterize the spatio-temporal coupling of a PW class laser facility.
M2: Generation of ultrashort optical pulses
M2.2: Demystifying Self-Modelocking
G. Steinmeyer, Max-Born-Institute (Germany)
It is commonly believed that synchronization between laser modes can only be achieved in the presence of an effective saturable absorber inside the mode-locked laser cavity. Nevertheless, indications for a threshold-like onset of mode synchronization have been occasionally reported for a number of different lasers and nonlinear optical resonators, yet could not be satisfactorily explained to date. Solving Haus’ master equation in the presence of four-wave mixing, cross and self-phase modulation, we explicitly show that mode-locking can occur in the complete absence of saturable absorption. The resulting phase lock can even serve to overcome a significant amount of dispersion-induced dephasing induced by the cold cavity. However, the resulting lock is only dynamically stable, which explains why, so far, all attempted characterization of self-mode-locking methods ended up in measuring a coherent artifact.
M2.3: TW-Peak-Power Post-Compression of 70-mJ pulses from an YB Amplifier
B. Schmidt, Few-Cycle Inc. (Canada); G. Fan, P. Carpeggiani, TU Wien (Austria); Z. Tao, Fudan University (China); E. Kaksis, TU Wien (Austria); T. Balciunas, GAP-Biophotonics (Switzerland); G. Coccia, TU Wien (Austria); V. Cardin, F. Légaré, Institut National de la Recherche Scientifique (Canada); A. Baltuska, TU Wien (Austria)
High Harmonic Generation has provided an efficient tool for time-resolved investigations in the UV and soft X-ray spectral range. The intrinsically low efficiency of such frequency up-conversion process results in low UV or soft X-ray flux, which can be increased by improving the repetition rate or the energy per pulse of the IR driver. As in high harmonic generation parameters like the cut-off (highest achievable frequency) and efficiency of conversion are related to the peak power rather than to the energy per pulse, post-compression techniques were widely used for the driving pulses, being the spectral broadening in gas-filled hollow core fiber the most diffuse. Post compression techniques have been limited both in energy per pulse and peak power, thus partially limiting the benefits of energy scaling of the drivers. In this work we compress 70mJ, 220fs, 1030nm pulses from an Yb multi-pass amplifier in a 3m long stretched hollow core fiber in a pressure gradient scheme with neon. As a result, we achieve the compression to 25fs of pulses with the record output energy of 40mJ, resulting in a peak power above 1TW.
M2.4: 1-D energy scaling of multi-plate pulse compression to 6 mJ in a compact setup
G. Fan, TU Wien (Austria); Z. Tao, Fudan University (China); P. Carpeggiani, G. Coccia, TU Wien (Austria); S. Zhang, Z. Fu, Fudan University (China); M. Chen, S. Liu, A. Kung, National Tsing Hua University (China); E. Kaksis, A. Pugzlys, A. Baltuska, TU Wien (Austria).
Spectral broadening via Self-Phase Modulation for pulse post compression has been successfully demonstrated both in gases and solids reaching higher and higher peak powers. The most diffused technique is hollow core fiber compression, which can grant the best performances in terms of pulse duration and energy content, but at the price of a coupling mechanism very sensitive to beam pointing and related instabilities. Alternative systems with non guided focusing geometries into gases or bulk have been successfully demonstrated. The common issue of all these techniques though is the limitation in pulse energy. Given the limits of intensity, for the damage in solids or ionization in gases, and of peak power, causing detrimental self-focusing and filamentation, the handling of higher energies requires looser focusing conditions and hence, to inconveniently large setups. In this work we present a route for energy scaling in external pulse compression based on layered Kerr media combined with 1D focusing geometry, which permits to extend the operation into a multi-mJ energy range within a 1-m-long setup. As a proof of concept, a highly stable 92%- efficient 4-fold compression of 1030-nm pulses is demonstrated.
M2.5: Strong and weak seeded four-wave mixing in stretched gas-filled hollow capillary fibers
F. Belli, A. Lekosiotis, J. C. Travers, Heriot-Watt University (United Kingdom)
We report a remarkably efficient experimental scheme for the generation of high energy ultra-short pulses by means of four-wave mixing in long stretched hollow capillary fibers filled with helium. We thoroughly investigate the role of strong and weak seeding fields in a degenerate up-conversion scheme to the deep ultraviolet. In the weak seed regime we demonstrate the tunable emission of up to 30 μJ in ultrashort pulses (~8 fs) in the 250-300 nm range, corresponding to pump energy conversion of up to 30%, from pump pulses with energies readily available from high-average power lasers. In the strong seed regime, we obtain higher pump conversion efficiencies, up to 42%, together with a spectral bandwidth supporting few femtosecond pulses and a record high deepultraviolet pulse energy exceeding 70 μJ. The energy can be further scaled by using stretched hollow-core fibers with larger core diameters.
M3: Other applications
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M3.3: Laser micromachining of gratings for X-ray interferometry imaging and sub-micron hole patterns
R. Carreto, B. Lüscher, B. Resan, R. Holtz, FHNW (Switzerland)
We compare micromachining with an F-Theta and axicon lenses using an UV picosecond laser system to obtain a tungsten grating for X-ray interferometry medical imaging and sub-micrometer hole patterns.
M3.4: Optical wavefront control for filament-induced breakdown signal enhancement
L.A. Finney, J. Lin, P. J. Skrodzki, M. Burger, J. Nees, K. Krushelnick, I. Jovanovic, University of Michigan (United States)
We demonstrate that laser wavefront control with a deformable mirror can enhance the signal intensity generated through filament-induced breakdown of a solid metallic copper (Cu) target. In our experiment, we find that the signal optimization through a genetic algorithm is reached after 150 iterations, during which the wavefront is primarily corrected for horizontal coma and the signal from the Cu I 521.8 nm atomic spectral line is nearly doubled. The ability to increase the intensity of spectroscopic signals generated in filament-induced breakdown spectroscopy is an essential component of the effort to extend the detection distance in remote sensing applications.
M3.5: Centre for advanced laser techniques (CALT)
D . Aumiler, Institute of Physics (Croatia)
Centre for Advanced Laser Techniques (CALT) is a strategic research infrastructure project of the Republic of Croatia, funded by the European Regional Development Fund (ERDF). The main goal of the CALT project is to establish a fully equipped, modern scientific research centre specialized in advanced laser and optical techniques. CALT will be located at the Institute of Physics in Zagreb (IPZg), the only research institution in Croatia to have several larger laser/optical systems and relevant expertise, which are the basis for laser-matter interaction studies. CALT will be set as a collection of state-of-the-art laboratories that will be open to users, where both the infrastructure and the expertise will be at service to Croatian, as well as regional RDI community. A total of over 1200 m2 of fully equipped laboratory space will be available by reconstructing one of the IPZg buildings. CALT’s activities; which comprise research, education, and providing access to laser facilities; will address socially important issues through planned research activities in the four domains: Quantum Technology, Plasma Technology, Nano and Bio Systems, and Ultrafast Dynamics.
M4: Science and technology of ultrashort pulse amplification
M4.1: Optical parametric chirped pulse amplification with PPLN: high average power sub-two-cycle 2.5 µm pulses
C. R. Phillips, J. Pupeikis, N. Bigler, P. Chevreuil, S. Hrisafov, L. Gallmann, U. Keller, ETH Zurich (Switzerland)
We present a mid-infrared optical parametric chirped-pulse amplifier (OPCPA) delivering 12.6 W at 100 kHz centered at 2.5 μm. Through a time-gated pulse shaping scheme, the pulses were compressed to 14.4 fs (1.7 cycles). The peak power corresponds to 6.3 GW. The OPCPA system utilizes periodically poled lithium niobate (PPLN) as the amplification medium, due to its capacity to support ultra-broad bandwidths. Some of the challenges to power scaling in this material are discussed. Our on-going efforts towards further power scaling will be presented at the conference.
M4.2: Near-fully efficient, back-conversion suppressed optical parametric amplification via a secondary nonlinear wave-mixing channel
N. Flemens, N. Swenson, J. Moses, Cornell University (United States)
Back-conversion in parametric amplification can be suppressed over the full spatiotemporal pump profile by means of a simultaneously phase-matched wave-mixing process, a general concept allowing nearly full conversion efficiency. A device for ultrafast chirped pulse amplification based on simultaneous parametric amplification and second harmonic generation is presented, and is based on a novel quasi-phase matching scheme for simultaneous phase matching of multiple three-wave mixing processes. A full spatiotemporal analysis predicts pump energy conversion up to 65% for femtosecond pulses and as high as 80% for picosecond pulses.
M4.3: High power, 100 kHz repetition rate OPCPA operating at 800 nm and 1.5 – 2.0 µm
M. K. Windeler,SLAC National Accelerator Laboratory (United States) and Department of Physics, Engineering Physics & Astronomy, Queen’s University (Canada); K. Mecseki, F. Tavella, J. S. Robinson, A. R. Fry, SLAC National Accelerator Laboratory (United States); J. M. Fraser, Department of Physics, Engineering Physics & Astronomy, Queen’s University (Canada)
Optical parametric chirped pulse amplification (OPCPA) enables high repetition rate amplification due to low thermal absorption in the amplifier medium. Wavelength conversion and extension processes are available to access wavelengths from the XUV to THz at high repetition rates offsetting the conversion efficiency losses. These technologies are used at next generation free electron laser (FEL) facilities, such as the Linac Coherent Light Source (LCLS). Additionally, the higher repetition rate of the system benefits pump-probe experiments for weakly scattering samples and serves a variety of experiments which require attenuation to avoid perturbation and damage of the sample by the X-ray probe. An R&D laser amplifier is demonstrated operating 24 hours a day, 7 days a week with mJ pulse energy to test experimental conditions for optical laser beam delivery at LCLS-II. The laser can be operated in two distinct wavelength ranges. At 800 nm center wavelength we use the second harmonic of an Yb:YAG amplifier system to pump an 88 W OPCPA in BBO crystals. A second tunable version operates between 1.5 – 2.0 μm center wavelength using the fundamental Yb:YAG beam to pump a KTA OPCPA with average output powers in excess of 100 W.
M4.4: Conceptual study of a 1 kHz 10 mJ-class mid-IR OPCPA system with thermal aspects
S. Tóth, R. Nagymihály, ELI-ALPS Ltd (Hungary) and University of Szeged (Hungary); A. Andrianov, Institute of Applied Physics of the Russian Academy of Sciences (Russian Federation); B. Kiss, ELI-ALPS Ltd (Hungary); R. Flender, ELI-ALPS Ltd (Hungary) and University of Szeged (Hungary); M. Kurucz, L. Haizer, ELI-ALPS Ltd (Hungary); E. Cormier, CELIA, Université de Bordeaux – CNRS – CEA (France); K. Osvay, ELI-ALPS Ltd (Hungary)
In this work a conceptual study is presented about a 1 kHz, dual-channel OPCPA system which produces passively CEP-stabilized, sub-30 fs, 10 mJ mid-IR pulses and sub-30 fs, 40 mJ near-IR pulses. The modelled mid-IR laser system consists of eight KTA-based OPCPA stages. Amplification was simulated with an advanced 3D numerical code for OPCPA modelling. It was revealed that the gain curve of KTA, when pumped at 1 μm, can support the amplification of 25 fs pulses in the absence of gain narrowing, which was exploited in the presented conceptual study. This advantageous property of KTA however, comes with the cost of increased heat load on the crystal as the idler spectrum extends to 4.5 μm where the absorption of KTA gets significant. In order to analyze the thermal performance and limitations in the amplifier stages, heat-transfer numerical simulations were carried out in 3D.
M4.5: Design study of two-cycle bandwidth, single-color pumped OPCPA chain
S. Tóth, ELI-ALPS Ltd (Hungary) and University of Szeged (Hungary); T. Stanislauskas, I. Balčiunas, Light Conversion Ltd. (Lithuania); A. Andrianov, Institute of Applied Physics of the Russian Academy of Sciences, (Russian Federation); R. Budriūnas, G. Veitas, Light Conversion Ltd. (Lithuania); J. Csontos, ELI-ALPS Ltd (Hungary); Á. Börzsönyi, ELI-ALPS Ltd (Hungary) and University of Szeged (Hungary); L. Tóth, T. Somoskői, K. Osvay, ELI-ALPS Ltd (Hungary)
ELI-ALPS 1kHz SYLOS laser aims to deliver 15TW, two-cycle pulses for attosecond pulse generation and electron acceleration. One of the main challenges during development of such a laser system is the amplification of two-cycle bandwidth pulses in OPCPA. In this study, broadband NOPCPA schemes were examined using LBO crystal and the technique of spectral multiplexing in BBO crystal sandwich. This examination involved a through investigation of phase-matching properties of the aforementioned schemes and a very accurate, 3D numerical modelling using and advanced OPCPA code. Spectral gain curves calculated from the undepleted pump approximation and numerical results provided by the numerical code show that single LBO crystal and BBO crystal sandwich can support sub-2 cycle Fourier-limited pulse duration. The compressibility of such pulses was also examined numerically and it was shown that the pulses are compressible down to 2.2 cycles. The numerically calculated and experimentally measured spectrum and peak power values were compared and it was found that they are in well agreement.