Optical parametric chirped pulse amplification (OPCPA) provides an excellent platform to generate ultrashort mid-infrared pulses in the spectral window beyond the scope of traditional mode-locked lasers. This technology has paved the path toward tabletop coherent soft x-ray (SXR) sources in recent years. Commercial availability of high-power Yb:YAG lasers as the pump lasers has enabled OPCPA to generate high-energy femtosecond mid-IR pulses at a high repetition rate. However, it is still difficult to achieve above mJ, high repetition rate OPCPA at 3 μm with less than 100 fs pulsewidth. Here, we present a 10 kHz, few-cycle OPCPA at 3.1 μm generating compressed pulses of 1.1 mJ energy with a record temporal width of 58 fs and an excellent rms stability of 0.8%. Our experimental results are further compared with two different simulation codes for optimization. To increase the amplification efficiency, we utilize a pulse-front tilt matching configuration resulting in 80% more energy in the first power OPCPA stage and expect up to 3 mJ of pulse energy in total with all three power OPCPA stages. These pulses open up the opportunity to access, in particular, the magnetically dichroic L-absorption edges of the 3d metals through the generation of ultrashort SXRs via high harmonic generation beyond the water window (500–900 eV) in a laboratory setup. This provides the prospect of availing femtosecond pump-probe spectroscopy with SXR pulses for studying the electronic structure dynamics of numerous condensed phase systems via resonant transitions from core levels of functionally relevant metals without having to resort to large-scale facilities.

Method development for laboratory-based X-ray microscopes operating in the water-window range invariably involves the development of the X-ray source as well. This paper presents major upgrades to the laboratory soft X-ray microscope (L-TXM) plasma chamber and data analysis protocol. Characterization of the laser-plasma source demonstrates improved performance, while a proof-of-principle tomogram of a diatom showcases a robust data treatment protocol and the system's capabilities for three-dimensional imaging and segmentation. These developments mark significant progress toward making L-TXM a more robust and user-friendly tool for soft X-ray microscopy applications.

We present a 10 kHz repetition rate, few-cycle optical parametric chirped pulse amplification (OPCPA) system at 3.1 mu m central wavelength for high harmonic generation of soft x-rays, accessing L-3,L-2-absorption edges in 3d transition metals. The mid-IR (MIR) system generates pulses of 1.1 mJ energy at a temporal width of 58 fs.

The excitation of atomic clusters and nanodroplets in strong laser fields is an ideal model scenario for studying the ultrafast physical processes underlying the formation and evolution of highly excited matter. Particularly insightful experiments with high temporal and spatial resolution have recently become possible: Via single-particle coherent diffractive imaging (CDI) using the intense femtosecond pulses of X-ray free-electron lasers (X-FELs), a single, isolated cluster can be “snapshot”-imaged in free flight and in parallel, the residuals of this single event (e.g. ions, electrons, fluorescence) can be captured, instead of the usual averaging over ensembles of clusters [1].

We generate circularly-polarized soft X-rays from a laser-driven plasma source by a magnetic thin-film polarizer. This enables first lab-based X-ray magnetic circular dichroism experiments at the Fe L edges with picosecond time resolution.

Multi-electron dynamics in atoms and molecules very often occur on sub- to few-femtosecond timescales. The available intensities of extreme-ultraviolet (XUV) attosecond pulses have previously only allowed the time-resolved investigation of two-photon, two-electron interactions. Here we demonstrate attosecond control over double and triple ionization of argon atoms involving the absorption of up to five XUV photons. In an XUV-pump XUV-probe measurement using a pair of attosecond pulse trains (APTs), the Ar$^{2+}$ ion yield exhibits a weak delay dependence, showing that its generation predominantly results from the sequential emission of two electrons by photoabsorption from the two APTs. In contrast, the Ar$^{3+}$ ion yield exhibits strong modulations as a function of the delay, which is a clear signature of the simultaneous absorption of at least two XUV photons. The experimental results are well reproduced by numerical calculations that provide detailed insights into the ionization dynamics. Our results open up new opportunities for the investigation and control of multi-electron dynamics and complex electron correlation mechanisms on extremely short timescales.

We utilize a thin-disk laser-driven plasma source to carry out resonant magnetic soft-X-ray scattering experiments to follow ultrafast spin and lattice dynamics in artificial an-tiferromagnets.

We study multiple ionization of Ar using a pair of intense attosecond pulse trains. By controlling the delay with attosecond precision and the spatial overlap with nanometer precision, complex multiphoton ionization pathways can be identified.

We demonstrate attosecond control of the multi-photon multiple ionization of argon. While a weakly oscillating Ar2+ is found in an autocorrelation measurement, the Ar3+ ion yield strongly oscillates due to direct multi-photon absorption.

In this contribution, we discuss the experimental requirements for time-resolved near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in the soft X-ray range between 100 and 1500 eV in the laboratory. This photon energy range covers the so-called water window as well as the L-edges of transition metals and the M-edges of lanthanoids. We present a setup using a laser-produced plasma source and reflection zone plate optics. The setup allows the registration of NEXAFS spectra with a spectral resolution λ/Δλ up to 1000 and time resolution ranging from few nanoseconds to picoseconds.

An XUV beamline based on high-harmonic generation (HHG) is presented. Recent observation of Ar 5+ in XUV ionization experiments indicates high potential for XUV nonlinear optics and coherent diffractive imaging (CDI) with sub-femtosecond resolution.

The latest generation of high-energy-class pulsed laser facilities, under construction or planned, such as EuPRAXIA, require reliable pump sources with high power (many kW), brightness (>1 MW/cm2/sr) and electro-optical conversion efficiency (>50%). These new facilities will be operated at high repetition rates (around 100 Hz) and only diode lasers are capable of delivering the necessary performance. Commercial (quasi-continuous wave, QCW) diode laser pulse-pump sources are, however, constructed as low-cost passively cooled stacked arrays that are limited either in brightness, efficiency or repetition rate. Commercial continuous wave diode laser pumps constructed using microchannel coolers (as used in high-value industrial machine tools) can fulfil all requirements, but are typically not preferred, due to their cost and complexity and the challenges of preventing cooler degradation. A custom solution is shown here to fill this gap, using advanced diode lasers in a novel passive side-cooling geometry to realize 100 … 200 Hz pump modules (10%–20% duty cycle) that emit peak power of 6 kW at wavelength = 940 nm. The latest performance of these modules is summarized and compared to literature. We show that a brightness >1 MW/cm2/sr can be efficiently delivered across a wide range of laser pulse conditions with 10% duty cycle (pulse width: 100 µs … 100 ms … cw, repetition rate up to 1 kHz). Furthermore, we describe how these pumps have been used to construct and reliably operate (>109 pulses without degradation) in high-energy-class regenerative and ring amplifiers at the Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI). We also show first results on 100 Hz pumping of cryogenically cooled solid-state Yb:YAG slab amplifiers, as anticipated for use in the EuPRAXIA laser, and note that peak temperature is disproportionately increased, indicating that improved cooling and more detailed studies are needed.

Coherent diffraction imaging (CDI) at wavelengths in the extreme ultraviolet range has become an important tool for nanoscale investigations. Employing laser-driven high harmonic sources allows for lab-scale applications such as cancer cell classification and phase-resolved surface studies in reflection geometry. The excellent beam properties support a spatial resolution below the wavelength, i.e., close to the Abbe limit. Unfortunately, the usually low photon flux of HHG sources limits their applicability. Recent advances in ultrafast fiber laser development cumulated in sources delivering average powers approaching the milliwatt level in the extreme ultraviolet. In comparison, a tabletop soft X-ray laser driven by moderate pump energies was recently employed for CDI featuring excellent temporal coherence and extraordinary high flux allowing for single-shot imaging.

In this contribution, we report about tomographic nanoscale imaging using a laser-produced plasma-based laboratory transmission X-ray microscope (LTXMLTXM ) in the water window. The soft X-ray radiation of the LTXMLTXM is provided by a high average power laser-produced (1.3 kHz repetition rate, 0.5 ns pulse duration, 140 W average power) plasma source, a multilayer condenser mirror, an objective zone plate, and a back-illuminated CCD camera as a detector. In the second part of the contribution, we will present recent results on holography and coherent diffraction imaging using our high repetition rate X-ray laser. We will discuss advantages of these methods and its potential for nanoscale imaging.

Coherent diffraction imaging (CDI) in the extreme ultraviolet has become an important tool for nanoscale investigations. Laser-driven high harmonic generation (HHG) sources allow for lab scale applications such as cancer cell classification and phase-resolved surface studies. HHG sources exhibit excellent coherence but limited photon flux due poor conversion efficiency. In contrast, table-top soft X-ray lasers (SXRL) feature excellent temporal coherence and extraordinary high flux at limited transverse coherence. Here, the performance of a SXRL pumped at moderate pump energies is evaluated for CDI and compared to a HHG source. For CDI, a lower bound for the required mutual coherence factor of |μ 12| ≥ 0.75 is found by comparing a reconstruction with fixed support to a conventional characterization using double slits. A comparison of the captured diffraction signals suggests that SXRLs have the potential for imaging micron scale objects with sub-20 nm resolution in orders of magnitude shorter integration time compared to a conventional HHG source. Here, the low transverse coherence diameter limits the resolution to approximately 180 nm. The extraordinary high photon flux per laser shot, scalability towards higher repetition rate and capability of seeding with a high harmonic source opens a route for higher performance nanoscale imaging systems based on SXRLs.

Nanoscale imaging of biological samples in the lab as well as mask inspection in extreme ultraviolet lithography near the production line with sub 30 nm resolution require high spectral brightness soft x-ray sources. Laser produced plasma (LPP) sources and plasma based X-ray lasers (XRL) emit soft X-ray radiation in the wavelength region of interest between 2 and 20 nm. Whereas LPP sources easily can be tuned to the so called water window (2.2–4.4 nm) the output of an XRL is restricted to relatively few fixed wavelengths in the extreme ultraviolet range. However due to the relatively high degree of coherence the XRL is well suited also for nanoscale imaging using coherent techniques like coherent diffraction imaging or Fourier transform holography.

X-ray laser simulations based on Ehybrid code have shown that enhanced plasma x-ray laser emission can be achieved mastering the ionization dynamics and plasma temperature using one long and two short pulses (Ursescu and Ionel, J Optoelectron Adv Mat 12:48–51, 2010). In parallel, two simple methods to generate multiple short pulses for pumping x-ray lasers were reported in conjunction with x-ray laser developments. Five to ten fold enhancement in the emission of the silver x-ray laser was demonstrated using the newly developed pump methods, when compared with the traditional one, based on a long pulse followed by one short pump pulse. An overview of these recent experiments will be presented. The possible implementation of these novel x-ray laser pumping methods at Extreme Light Infrastructure—Nuclear Physics facility will be discussed.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text R. Jung, J. Tümmler, T. Nubbemeyer, and I. Will, "Two-Channel Thin-Disk Laser for High Pulse Energy," in Advanced Solid State Lasers, OSA Technical Digest (online) (Optica Publishing Group, 2015), paper AW3A.7. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Thin disk technology has the potential for providing laser pulses with high pulse energy combined with high repetition rate. Large laser projects like ELI or HiPER benefit from this technology as well as stand alone systems like e.g. laser driven x-ray sources.

Laboratory based X-ray lasers (XRL) exhibit a broad application potential in material sciences, imaging, spectroscopy and laser plasma diagnostics if two main issues are solved: a stable, well defined output of the system and a high repetition rate for fast data acquisition. During the last few years using the grazing incidence pumping (GRIP) scheme an pump energy level as low as 1 J was demonstrated for saturated XRL operation. This pump energy could be provided in principle even by commercially available Ti:Sa laser systems. However, the repetition rate of these systems is limited to 10 Hz and the output stability of the XRL follows that of the pumping laser. To overcome this situation a dedicated high repetition rate XRL pumping laser will be introduced here. This concept is based on a fully diode pumped solid state laser using thin Yb:YAG disks as active material. In this paper we report about the first phase of the project aimed at a high average power XRL user station based on the GRIP scheme.