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Extreme UV Lasers: Technologies and Applications

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A special issue of Photonics (ISSN 2304-6732).

Deadline for manuscript submissions: closed (1 February 2017) | Viewed by 72457

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Special Issue Editor

Prof. Dr. Giovanni De Ninno

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Elettra-Synchrotron Trieste, 34149 Basovizza TS, Italy
Interests: nonlinear optics; dynamics of nonlinear systems; condensed matter physics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Innovative light sources, generating fully coherent, femtosecond pulses, tunable in the XUV spectral range, are among the most powerful instruments for carrying out cutting-edge experiments, in both fundamental and applied science. The scientific opportunities created by these devices have a strong impact on many disciplines, ranging from material science to nano-technologies, and from molecular and cluster femto- and nano-physics to chemistry, with strong connections to life, environmental, astrophysical, and Earth sciences.

In these fileds, the challenge is to reach the frontier of ultrafast timescales of electron motion around an atom, the spatial scale of the interatomic distance, and the energy scale of the chemical bonds. Once these borders are crossed, one can get the very essence of chemistry and condensed matter physics, which will undoubtedly impact the development of future technologies.

Presently, only two types of sources can help scienstists to take up the challenge: Those based on the generation of laser high-order harmonics in gas (HHG) and free-electron lasers (FELs). Such sources are highly complementary: HHG sources are quite compact (almost table-top), easily accessible and generate relatively powerful radiation (i.e., tens of nanojoules per pulse) down to a few tens of nanometers; seeded FELs are large in scale, and have expensive facilities, producing very powerful radiation (tens of microjoules per pulse), at wavelengths as short as few nanometers.

This Special Issue is intended to encourage researchers worldwide to contribute original research articles, as well as review articles, that explore the properties and the possible applicaions of of HHG and FEL sources.

Prof. Dr. Giovanni De Ninno
Guest Editor

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

high gain harmonic generation
free electron laser
ultrafast dynamics
ultrafast spectroscopy
UV spectroscopies
UV optics

Published Papers (12 papers)

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Research

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2711 KiB

Open AccessArticle

High Harmonics with Controllable Polarization by a Burst of Linearly-Polarized Driver Pulses

by Ofer Neufeld, Eliyahu Bordo, Avner Fleischer and Oren Cohen

Photonics 2017, 4(2), 31; https://doi.org/10.3390/photonics4020031 - 17 Apr 2017

Cited by 3 | Viewed by 5043

Abstract

We theoretically explore a scheme for generation of bright circularly and elliptically polarized high-order harmonics by bursts of linearly polarized pulses with a rotating polarization axis. Circularly polarized harmonics are formed if the bursts are comprised of N pulses that uphold an N-fold rotational symmetry, for N > 2. Rotating the polarization axes of the comprising pulses can generate elliptical harmonics with a collectively tunable ellipticity, from circular through elliptic to linear. The method preserves the single-cycle, single-atom and macroscopic physics of ‘standard’ linearly polarized high harmonic generation, with a high yield and cutoff energy. We investigate the method from a time-domain perspective, as well as a photonic perspective, and formulate the energy and spin-angular momentum conservation laws for this scheme. We find that the case of N = 4 is optimal for this method, resulting with the highest conversion efficiency of elliptical photons. The new features of this source offer new applications to helical ultrafast spectroscopy and ellipsometry. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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1506 KiB

Open AccessArticle

Polarization Characterization of Soft X-Ray Radiation at FERMI FEL-2

by Eléonore Roussel, Enrico Allaria, Carlo Callegari, Marcello Coreno, Riccardo Cucini, Simone Di Mitri, Bruno Diviacco, Eugenio Ferrari, Paola Finetti, David Gauthier, Giuseppe Penco, Lorenzo Raimondi, Cristian Svetina, Marco Zangrando, Andreas Beckmann, Leif Glaser, Gregor Hartmann, Frank Scholz, Joern Seltmann, Ivan Shevchuk, Jens Viefhaus and Luca Giannessi Show full author list Hide full author list

Photonics 2017, 4(2), 29; https://doi.org/10.3390/photonics4020029 - 10 Apr 2017

Cited by 12 | Viewed by 4826

Abstract

The control of polarization state in soft and hard X-ray light is of crucial interest to probe structural and symmetry properties of matter. Thanks to their Apple-II type undulators, the FERMI-Free Electron Lasers are able to provide elliptical, circular or linearly polarized light within the extreme ultraviolet and soft X-ray range. In this paper, we report the characterization of the polarization state of FERMI FEL-2 down to 5 nm. The results show a high degree of polarization of the FEL pulses, typically above 95%. The campaign of measurements was performed at the Low Density Matter beamline using an electron Time-Of-Flight based polarimeter. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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1280 KiB

Open AccessArticle

Optimization and Characterization of High-Harmonic Generation for Probing Solid Density Plasmas

by Jayanath C. P. Koliyadu, Swen Künzel, Thomas Wodzinski, Barbara Keitel, Joana Duarte, Gareth O. Williams, Celso P. João, Hugo Pires, Victor Hariton, Mario Galletti, Nuno Gomes, Gonçalo Figueira, João Mendanha Dias, Nelson Lopes, Philippe Zeitoun, Elke Plönjes and Marta Fajardo

Photonics 2017, 4(2), 25; https://doi.org/10.3390/photonics4020025 - 30 Mar 2017

Cited by 6 | Viewed by 4994

Abstract

The creation of high energy density plasma states produced during laser–solid interaction on a sub-picosecond timescale opens a way to create astrophysical plasmas in the lab to investigate their properties, such as the frequency-dependent refractive index. Available probes to measure absorption and phase-changes given by the complex refractive index of the plasma state are extreme-UV (EUV) and soft X-ray (XUV) ultra-short pulses from high harmonic generation (HHG). For demanding imaging applications such as single-shot measurements of solid density plasmas, the HHG probe has to be optimized in photon number and characterized in intensity and wavefront stability from shot-to-shot. In an experiment, a coherent EUV source based on HHG driven by a compact diode-pumped laser is optimized in photons per pulse for argon and xenon, and the shot-to-shot intensity stability and wavefront changes are characterized. The experimental results are compared to an analytical model estimating the HHG yield, showing good agreement. The obtained values are compared to available data for solid density plasmas to confirm the feasibility of HHG as a probe. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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1883 KiB

Open AccessArticle

Transient EUV Reflectivity Measurements of Carbon upon Ultrafast Laser Heating

by Riccardo Mincigrucci, Emiliano Principi, Filippo Bencivenga, Laura Foglia, Alessandro Gessini, Gabor Kurdi, Alberto Simoncig and Claudio Masciovecchio

Photonics 2017, 4(2), 23; https://doi.org/10.3390/photonics4020023 - 23 Mar 2017

Cited by 6 | Viewed by 4178

Abstract

Time resolved extreme ultraviolet (EUV) transient reflectivity measurements on non-equilibrium amorphous carbon (a-C) have been carried out by combining optical and free electron laser (FEL) sources. The EUV probing was specifically sensitive to lattice dynamics, since the EUV reflectivity is essentially unaffected by the photo-excited surface plasma. Data have been interpreted in terms of the dynamics of an expanding surface, i.e., a density gradient rapidly forming along the normal surface. This allowed us to determine the characteristic time (

τ ≲

1 ps) for hydrodynamic expansion in photo-excited a-C. This finding suggests an extremely narrow time window during which the system can be assumed to be in the isochoric regime, a situation that may complicate the study of photo-induced metastable phases of carbon. Data also showed a weak dependence on the probing EUV wavelength, which was used to estimate the electronic temperature (

T_{e} \approx

0.8 eV) of the excited sample. This experimental finding compares fairly well with the results of calculations, while a comparison of our data and calculations with previous transient optical reflectivity measurements highlights the complementarities between optical and EUV probing. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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Open AccessArticle

Dynamics of the MnAs α/β-Striped Microstructure and of the Fe Magnetization Reversal in Fe/MnAs/GaAs(001): An Optical-Laser Pump–Free-Electron-Laser Probe Scattering Experiment

by Franck Vidal, Lounès Lounis, Carlo Spezzani, Eugenio Ferrari, Renaud Delaunay, Alessandra Ciavardini, Horia Popescu, Mahmoud Eddrief, Yunlin Zheng, Flavio Capotondi, Emanuele Pedersoli, Cristian Svetina, Lorenzo Raimondi, Marco Zangrando, Rosen Ivanov, Ivaylo Nikolov, Alexander Demidovich, Miltcho B. Danailov, Giovanni De Ninno, Enrico Allaria, Maya Kiskinova and Maurizio Sacchi Show full author list Hide full author list

Photonics 2017, 4(2), 21; https://doi.org/10.3390/photonics4020021 - 23 Mar 2017

Cited by 4 | Viewed by 4678

Abstract

It was shown recently that the Fe magnetization reversal in the Fe/MnAs/GaAs(001) epitaxial system, attained by temperature control of the regular stripe pattern of the MnAs α- and β-phases, can also be driven by an ultrashort optical laser pulse. In the present time-resolved scattering experiment, we address the dynamics of the MnAs α-β self-organized stripe pattern induced by a 100 fs optical laser pulse, using as a probe the XUV radiation from the FERMI free-electron laser. We observe a loss in the diffraction intensity from the ordered α-β stripes that occurs at two characteristic timescales in the range of ~10⁻¹² and ~10⁻¹⁰ s. We associate the first intensity drop with ultrafast electron-lattice energy exchange processes within the laser-MnAs interaction volume and the second with thermal diffusion towards the MnAs/GaAs interface. With the support of model calculations, the observed dynamics are interpreted in terms of the formation of a laterally homogeneous MnAs overlayer, the thickness of which evolves in time, correlating the MnAs microstructure dynamics with the Fe magnetization response. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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2094 KiB

Open AccessArticle

Echo-Enabled Harmonic Generation Studies for the FERMI Free-Electron Laser

by Primož Rebernik Ribič, Eléonore Roussel, Gregory Penn, Giovanni De Ninno, Luca Giannessi, Giuseppe Penco and Enrico Allaria

Photonics 2017, 4(1), 19; https://doi.org/10.3390/photonics4010019 - 14 Mar 2017

Cited by 23 | Viewed by 5906

Abstract

Studying ultrafast processes on the nanoscale with element specificity requires a powerful femtosecond source of tunable extreme-ultraviolet (XUV) or x-ray radiation, such as a free-electron laser (FEL). Current efforts in FEL development are aimed at improving the wavelength tunability and multicolor operation, which will potentially lead to the development of new characterization techniques offering a higher chemical sensitivity and improved spatial resolution. One of the most promising approaches is the echo-enabled harmonic generation (EEHG), where two external seed lasers are used to precisely control the spectro-temporal properties of the FEL pulse. Here, we study the expected performance of EEHG at the FERMI FEL, using numerical simulations. We show that, by employing the existing FERMI layout with minor modifications, the EEHG scheme will be able to produce gigawatt peak-power pulses at wavelengths as short as 5 nm. We discuss some possible detrimental effects that may affect the performance of EEHG and compare the results to the existing double-stage FEL cascade, currently in operation at FERMI. Finally, our simulations show that, after substantial machine upgrades, EEHG has the potential to deliver coherent multicolor pulses reaching wavelengths as short as 3 nm, enabling x-ray pump–x-ray probe experiments in the water window. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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2302 KiB

Open AccessArticle

XUV Transient Absorption Spectroscopy: Probing Laser-Perturbed Dipole Polarization in Single Atom, Macroscopic, and Molecular Regimes

by Chen-Ting Liao and Arvinder Sandhu

Photonics 2017, 4(1), 17; https://doi.org/10.3390/photonics4010017 - 08 Mar 2017

Cited by 4 | Viewed by 8409

Abstract

We employ an extreme ultraviolet (XUV) pulse to impulsively excite dipole polarization in atoms or molecules, which corresponds to coherently prepared superposition of excited states. A delayed near infrared (NIR) pulse then perturbs the fast evolving polarization, and the resultant absorbance change is monitored in dilute helium, dense helium, and sulfur hexaﬂuoride (SF6) molecules. We observe and quantify the time-dependence of various transient phenomena in helium atoms,includinglaser-inducedphase(LIP),time-varying(AC)Starkshift,quantumpathinterference, and laser-induced continuum structure. In the case of dense helium targets, we discuss nonlinear macroscopic propagation effects pertaining to LIP and resonant pulse propagation, which accoun tfor the appearance of new spectral features in transient lineshapes. We then use tunable NIR photons to demonstrate the wavelength dependence of the transient laser induced effects. In the case of molecular polarization experiment in SF6, we show suppression of XUV photoabsorption corresponding to inter-valence transitions in the presence of a strong NIR ﬁeld. In each case, the temporal evolution of transient absorption spectra allows us to observe and understand the transient laser induced modiﬁcations of the electronic structure of atoms and molecules. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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911 KiB

Open AccessArticle

Optical Klystron Enhancement to Self Ampliﬁed Spontaneous Emission at FERMI

by Giuseppe Penco, Enrico Allaria, Giovanni De Ninno, Eugenio Ferrari, Luca Giannessi, Eléonore Roussel and Simone Spampinati

Photonics 2017, 4(1), 15; https://doi.org/10.3390/photonics4010015 - 01 Mar 2017

Cited by 14 | Viewed by 4226

Abstract

The optical klystron enhancement to a self-ampliﬁed spontaneous emission free electron laser has been studied in theory and in simulations and has been experimentally demonstrated on a single-pass high-gain free electron laser, the FERMI FEL-1, in 2014. The main concept consists of two undulators separated by a dispersive section that converts the energy modulation induced in the ﬁrst undulator in density modulation, enhancing the coherent harmonic generation in the ﬁrst part of the second undulator. This scheme could be replicated in a multi-stage: the bunching is enhanced after each dispersive section, consistently reducing the saturation length. We have applied the multi-stage optical klystron (OK) scheme on the FEL-2 line at FERMI, whose layout includes three dispersive sections. Optimizing the strength of the dispersions allowed a signiﬁcant increase of the self-ampliﬁed spontaneous emission (SASE) intensity in comparison to a single-stage OK and extending to the soft-X rays the OK enhanced SASE previously demonstrated on FEL-1. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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1906 KiB

Open AccessArticle

Design Study of Time-Preserving Grating Monochromators for Ultrashort Pulses in the Extreme-Ultraviolet and Soft X-Rays

by Fabio Frassetto, Nicola Fabris, Paolo Miotti and Luca Poletto

Photonics 2017, 4(1), 14; https://doi.org/10.3390/photonics4010014 - 01 Mar 2017

Cited by 10 | Viewed by 4426

Abstract

The design of grating-based instruments to handle and condition coherent ultrafast pulses in the extreme-ultraviolet is discussed. The main application of such instruments is the monochromatization of high-order laser harmonics and free-electron-laser pulses in the femtosecond time scale. Broad-band monochromators require the use of diffraction gratings at grazing incidence. A grating can be used for the spectral selection of ultrashort pulses without altering the pulse duration in a significant way, provided that the number of illuminated grooves is equal to the resolution. We discuss here the design conditions to be fulfilled by a grating monochromator that does not increase the pulse duration significantly longer than the Fourier limit. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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3034 KiB

Open AccessArticle

Element Selective Probe of the Ultra-Fast Magnetic Response to an Element Selective Excitation in Fe-Ni Compounds Using a Two-Color FEL Source

by Eugenio Ferrari, Carlo Spezzani, Franck Fortuna, Renaud Delaunay, Franck Vidal, Ivaylo Nikolov, Paolo Cinquegrana, Bruno Diviacco, David Gauthier, Giuseppe Penco, Primož Rebernik Ribič, Eléonore Roussel, Mauro Trovò, Jean-Baptiste Moussy, Tommaso Pincelli, Lounès Lounis, Cristian Svetina, Marco Zangrando, Nicola Mahne, Lorenzo Raimondi, Michele Manfredda, Emanuele Pedersoli, Flavio Capotondi, Alexander Demidovich, Luca Giannessi, Maya Kiskinova, Giovanni De Ninno, Miltcho Boyanov Danailov, Enrico Allaria and Maurizio Sacchi Show full author list Hide full author list

Photonics 2017, 4(1), 6; https://doi.org/10.3390/photonics4010006 - 26 Jan 2017

Cited by 8 | Viewed by 4866

Abstract

The potential of the two-color mode implemented at the FERMI free-electron laser (FEL) source for pumping and probing selectively different atomic species has been demonstrated by time-resolved scattering experiments with permalloy (FeNi alloy) and NiFe₂O₄ samples. We monitored the ultra-fast demagnetization of Ni induced by the pump FEL pulse, by tuning the linearly-polarized FEL probe pulse to the Ni-3p resonance and measuring the scattered intensity in the transverse magneto-optical Kerr effect geometry. The measurements were performed by varying the intensity of the FEL pump pulse, tuning its wavelength to and off of the Fe-3p resonance, and by spanning the FEL probe pulse delays across the 300–900 fs range. The obtained results have evidenced that for the case of NiFe₂O₄, there is a sensible difference in the magnetic response at the Ni site when the pump pulse causes electronic excitations at the Fe site. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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Review

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13608 KiB

Open AccessReview

Generation and Applications of Extreme-Ultraviolet Vortices

by Carlos Hernández-García, Jorge Vieira, Jose T. Mendonça, Laura Rego, Julio San Román, Luis Plaja, Primoz R. Ribic, David Gauthier and Antonio Picón

Photonics 2017, 4(2), 28; https://doi.org/10.3390/photonics4020028 - 07 Apr 2017

Cited by 48 | Viewed by 9512

Abstract

Vortex light beams are structures of the electromagnetic field with a spiral phase ramp around a point-phase singularity. These vortices have many applications in the optical regime, ranging from optical trapping and quantum information to spectroscopy and microscopy. The extension of vortices into the extreme-ultraviolet (XUV)/X-ray regime constitutes a significant step forward to bring those applications to the nanometer or even atomic scale. The recent development of a new generation of X-ray sources, and the refinement of other techniques, such as harmonic generation, have boosted the interest of producing vortex beams at short wavelengths. In this manuscript, we review the recent studies in the subject, and we collect the major prospects of this emerging field. We also focus on the unique and promising applications of ultrashort XUV/X-ray vortex pulses. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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7180 KiB

Open AccessFeature PaperReview

Generation of Attosecond Light Pulses from Gas and Solid State Media

by Stefanos Chatziathanasiou, Subhendu Kahaly, Emmanouil Skantzakis, Giuseppe Sansone, Rodrigo Lopez-Martens, Stefan Haessler, Katalin Varju, George D. Tsakiris, Dimitris Charalambidis and Paraskevas Tzallas

Photonics 2017, 4(2), 26; https://doi.org/10.3390/photonics4020026 - 31 Mar 2017

Cited by 48 | Viewed by 10487

Abstract

Real-time observation of ultrafast dynamics in the microcosm is a fundamental approach for understanding the internal evolution of physical, chemical and biological systems. Tools for tracing such dynamics are flashes of light with duration comparable to or shorter than the characteristic evolution times of the system under investigation. While femtosecond (fs) pulses are successfully used to investigate vibrational dynamics in molecular systems, real time observation of electron motion in all states of matter requires temporal resolution in the attosecond (1 attosecond (asec) = 10⁻¹⁸ s) time scale. During the last decades, continuous efforts in ultra-short pulse engineering led to the development of table-top sources which can produce asec pulses. These pulses have been synthesized by using broadband coherent radiation in the extreme ultraviolet (XUV) spectral region generated by the interaction of matter with intense fs pulses. Here, we will review asec pulses generated by the interaction of gas phase media and solid surfaces with intense fs IR laser fields. After a brief overview of the fundamental process underlying the XUV emission form these media, we will review the current technology, specifications and the ongoing developments of such asec sources. Full article

(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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