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End date: 2024 × Start date: 2020 × DDC: 530 × Publisher: Washington, DC : Soc. × WGL Institute: MBI ×

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Now showing 1 - 10 of 31
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    Multi-millijoule, few-cycle 5 µm OPCPA at 1 kHz repetition rate
    (Washington, DC : Soc., 2020) von Grafenstein, Lorenz; Bock, Martin; Ueberschaer, Dennis; Escoto, Esmerando; Koç, Azize; Zawilski, Kevin; Schunemann, Peter; Griebner, Uwe; Elsaesser, Thomas
    A table-top midwave-infrared optical parametric chirped pulse amplification (OPCPA) system generates few-cycle pulses with multi-10 GW peak power at a 1 kHz repetition rate. The all-optically synchronized system utilizes ZnGeP2 nonlinear crystals and a highly stable 2 µm picosecond pump laser based on Ho:YLiF4. An excellent energy extraction is achieved by reusing the pump pulse after the third parametric power amplification stage, resulting in 3.4 mJ idler pulses at a center wavelength of 4.9 µm. Pulses as short as 89.4 fs are achieved, close to only five optical cycles. Taking into account the pulse energy, a record high peak power of 33 GW for high-energy mid-IR OPCPAs beyond 4 µm wavelength is demonstrated. © 2020 OSA - The Optical Society. All rights reserved.
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    8 fs laser pulses from a compact gas-filled multi-pass cell
    (Washington, DC : Soc., 2021) Rueda, P.; Videla, F.; Witting, T.; Torchia, G.A.; Furch, F.J.
    Compression of 42 fs, 0.29 mJ pulses from a Ti:Sapphire amplifier down to 8 fs (approximately 3 optical cycles) is demonstrated by means of spectral broadening in a compact multi-pass cell filled with argon. The efficiency of the nonlinear pulse compression is limited to 45 % mostly by losses in the mirrors of the cell. The experimental results are supported by 3-dimensional numerical simulations of the nonlinear pulse propagation in the cell that allow us to study spatio-spectral properties of the pulses after spectral broadening.
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    High-order parametric generation of coherent XUV radiation
    (Washington, DC : Soc., 2021) Hort, O.; Dubrouil, A.; Khokhlova, M.A.; Descamps, D.; Petit, S.; Burgy, F.; Mével, E.; Constant, E.; Strelkov, V.V.
    Extreme ultraviolet (XUV) radiation finds numerous applications in spectroscopy. When the XUV light is generated via high-order harmonic generation (HHG), it may be produced in the form of attosecond pulses, allowing access to unprecedented ultrafast phenomena. However, the HHG efficiency remains limited. Here we present an observation of a new regime of coherent XUV emission which has a potential to provide higher XUV intensity, vital for applications. We explain the process by high-order parametric generation, involving the combined emission of THz and XUV photons, where the phase matching is very robust against ionization. This introduces a way to use higher-energy driving pulses, thus generating more XUV photons.
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    Sub-100 fs mode-locked Tm:CLTGG laser
    (Washington, DC : Soc., 2021) Wang, Li; Chen, Weidong; Pan, Zhongben; Loiko, Pavel; Bae, Ji Eun; Rotermund, Fabian; Mateos, Xavier; Griebner, Uwe; Petrov, Valentin
    We report on the first sub-100 fs mode-locked laser operation of a Tm3+-doped disordered calcium lithium tantalum gallium garnet (Tm:CLTGG) crystal. Soliton mode-locking was initiated and stabilized by a transmission-type single-walled carbon nanotube saturable absorber. Pulses as short as 69 fs were achieved at a central wavelength of 2010.4 nm with an average power of 28 mW at a pulse repetition rate of ∼87.7 MHz. In the sub-100 fs regime, the maximum average output power amounted to 103 mW.
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    Sub-15-fs X-ray pump and X-ray probe experiment for the study of ultrafast magnetization dynamics in ferromagnetic alloys
    (Washington, DC : Soc., 2021) Liu, Xuan; Merhe, Alaaeldine; Jal, Emmanuelle; Delaunay, Renaud; Jarrier, Romain; Chardonnet, Valentin; Hennes, Marcel; Chiuzbaian, Sorin G.; Légaré, Katherine; Hennecke, Martin; Radu, Ilie; Von Korff Schmising, Clemens; Grunewald, Særen; Kuhlmann, Marion; Lüning, Jan; Vodungbo, Boris
    In this paper, we present a new setup for the measurement of element-specific ultrafast magnetization dynamics in ferromagnetic thin films with a sub-15-fs time resolution. Our experiment relies on a split and delay approach which allows us to fully exploit the shortest X-rays pulses delivered by X-ray Free Electrons Lasers (close to the attosecond range), in an X-ray pump – X-ray probe geometry. The setup performance is demonstrated by measuring the ultrafast elemental response of Ni and Fe during demagnetization of ferromagnetic Ni and Ni80Fe20 (Permalloy) samples upon resonant excitation at the corresponding absorption edges. The transient demagnetization process is measured in both reflection and transmission geometry using, respectively, the transverse magneto-optical Kerr effect (T-MOKE) and the Faraday effect as probing mechanisms.
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    Propagator operator for pulse propagation in resonant media
    (Washington, DC : Soc., 2021) Morales, Felipe; Richter, Maria; Olvo, Vlad; Husakou, Anton
    We show that, for the case of resonant media, the available models for unidirectional propagation of short pulses can face serious challenges with respect to numerical efficiency, accuracy, or numerical artifacts. We propose an alternative approach based on a propagator operator defined in the time domain. This approach enables precise simulations using short time windows even for resonant media and facilitates coupling of the propagation equation with first-principle methods such as the time-dependent Schödinger equation. Additionally, we develop a numerically efficient recipe to construct and apply such a propagator operator.
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    Terahertz absorption-saturation and emission from electron-doped germanium quantum wells
    (Washington, DC : Soc., 2020) Ciano, Chiara; Virgilio, Michele; Bagolini, Luigi; Baldassarre, Leonetta; Pashkin, Alexej; Helm, Manfred; Montanari, Michele; Persichetti, Luca; Di Gaspare, Luciana; Capellini, Giovanni; Paul, Douglas J.; Scalari, Giacomo; Faist, Jèrome; De Seta, Monica; Ortolani, Michele
    We study radiative relaxation at terahertz frequencies in n-type Ge/SiGe quantum wells, optically pumped with a terahertz free electron laser. Two wells coupled through a tunneling barrier are designed to operate as a three-level laser system with non-equilibrium population generated by optical pumping around the 1→3 intersubband transition at 10 THz. The non-equilibrium subband population dynamics are studied by absorption-saturation measurements and compared to a numerical model. In the emission spectroscopy experiment, we observed a photoluminescence peak at 4 THz, which can be attributed to the 3→2 intersubband transition with possible contribution from the 2→1 intersubband transition. These results represent a step towards silicon-based integrated terahertz emitters.
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    Enabling time-resolved 2D spatial-coherence measurements using the Fourier-analysis method with an integrated curved-grating beam monitor
    (Washington, DC : Soc., 2020) Bagschik, Kai; Schneider, Michael; Wagner, Jochen; Buss, Ralph; Riepp, Matthias; Philippi-Kobs, Andre; Müller, Leonard; Roseker, Wojciech; Trinter, Florian; Hoesch, Moritz; Viefhaus, Jens; Eisebitt, Stefan; Grübel, Gerhard; Oepen, Hans Peter; Frömter, Robert
    Direct 2D spatial-coherence measurements are increasingly gaining importance at synchrotron beamlines, especially due to present and future upgrades of synchrotron facilities to diffraction-limited storage rings. We present a method to determine the 2D spatial coherence of synchrotron radiation in a direct and particularly simple way by using the Fourier-analysis method in conjunction with curved gratings. Direct photon-beam monitoring provided by a curved grating circumvents the otherwise necessary separate determination of the illuminating intensity distribution required for the Fourier-analysis method. Hence, combining these two methods allows for time-resolved spatial-coherence measurements. As a consequence, spatial-coherence degradation effects caused by beamline optics vibrations, which is one of the key issues of state-of-the-art X-ray imaging and scattering beamlines, can be identified and analyzed. © 2020 Optical Society of America.
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    Milliradian precision ultrafast pulse control for spectral phase metrology
    (Washington, DC : Soc., 2021) Stamm, Jacob; Benel, Jorge; Escoto, Esmerando; Steinmeyer, Günter; Dantus, Marcos
    A pulse-shaper-based method for spectral phase measurement and compression with milliradian precision is proposed and tested experimentally. Measurements of chirp and third-order dispersion are performed and compared to theoretical predictions. The single-digit milliradian accuracy is benchmarked by a group velocity dispersion measurement of fused silica.
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    27 W 2.1 µm OPCPA system for coherent soft X-ray generation operating at 10 kHz
    (Washington, DC : Soc., 2020) Feng, Tianli; Heilmann, Anke; Bock, Martin; Ehrentraut, Lutz; Witting, Tobias; Yu, Haohai; Stiel, Holger; Eisebitt, Stefan; Schnürer, Matthias
    We developed a high power optical parametric chirped-pulse amplification (OPCPA) system at 2.1 µm harnessing a 500 W Yb:YAG thin disk laser as the only pump and signal generation source. The OPCPA system operates at 10 kHz with a single pulse energy of up to 2.7 mJ and pulse duration of 30 fs. The maximum average output power of 27 W sets a new record for an OPCPA system in the 2 µm wavelength region. The soft X-ray continuum generated through high harmonic generation with this driver laser can extend to around 0.55 keV, thus covering the entire water window (284 eV - 543 eV). With a repetition rate still enabling pump-probe experiments on solid samples, the system can be used for many applications. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement