Special Issue "Extreme UV Lasers: Technologies and Applications"

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

Deadline for manuscript submissions: closed (15 March 2015)

Special Issue Editor

Guest Editor
Dr. Claudio Masciovecchio (Website)

Sincrotrone Trieste, 34012 Basovizza, Trieste, Italy
Interests: uv brillouin scattering; free electron laser; four wave mixing; uv raman spectroscopy; disordered systems; hydration dynamics;

Special Issue Information

Dear Colleagues,

Scientific interest in pushing our knowledge of dynamic phenomena in chemistry, physics and biology towards shorter and shorter times and length-scales goes back more than a century. Generally, the scientific grand 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.

However, the experimental control and understanding of physical, chemical and biochemical processes in complex systems on such microscopic scales is still not fully possible, due to the inadequacy of existing experimental tools.

The emergence and development of high gain harmonic generation and free electron laser in extreme UV and soft X-ray offer unique research prospects for femto-nano-science, and the scientific community interested in using these new experimental tools is exponentially growing. Indeed these novel sources may be employed to shed light on a large array of research fields ranging from chemistry to fundamental physics and from biology to medicine.

This Special Issue is therefore envisioned to encourage scientists to report on their new results in research and development that focus on the most recent advances in extreme UV laser development, optics and research applications.

Dr. Claudio Masciovecchio
Guest Editor

Submission

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. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as 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 refereed through a 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 quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. For the first couple of issues the Article Processing Charge (APC) will be waived for well-prepared manuscripts. English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.


Keywords

  • high gain harmonic generation
  • free electron laser
  • coherent diffraction imaging
  • four wave mixing
  • ultrafast spectroscopy
  • ultrafast demagnetization
  • uv spectroscopies
  • uv optics

Published Papers (13 papers)

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Research

Jump to: Review

Open AccessArticle Self Referencing Heterodyne Transient Grating Spectroscopy with Short Wavelength
Photonics 2015, 2(2), 392-401; doi:10.3390/photonics2020392
Received: 16 March 2015 / Revised: 8 April 2015 / Accepted: 8 April 2015 / Published: 15 April 2015
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Abstract
Heterodyning by a phase stable reference electric field is a well known technique to amplify weak nonlinear signals. For short wavelength, the generation of a reference field in front of the sample is challenging because of a lack of suitable beamsplitters. Here, [...] Read more.
Heterodyning by a phase stable reference electric field is a well known technique to amplify weak nonlinear signals. For short wavelength, the generation of a reference field in front of the sample is challenging because of a lack of suitable beamsplitters. Here, we use a permanent grating which matches the line spacing of the transient grating for the creation of a phase stable reference field. The relative phase among the two can be changed by a relative translation of the permanent and transient gratings in direction orthogonal to the grating lines. We demonstrate the technique for a transient grating on a VO2 thin film and observe constructive as well as destructive interference signals. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Towards Realistic Simulations of Macromolecules Irradiated under the Conditions of Coherent Diffraction Imaging with an X-ray Free-Electron Laser
Photonics 2015, 2(1), 256-269; doi:10.3390/photonics2010256
Received: 15 January 2015 / Revised: 10 February 2015 / Accepted: 12 February 2015 / Published: 4 March 2015
Cited by 4 | PDF Full-text (283 KB) | HTML Full-text | XML Full-text
Abstract
Biological samples are highly radiation sensitive. The rapid progress of their radiation damage prevents accurate structure determination of single macromolecular assemblies in standard diffraction experiments. However, computer simulations of the damage formation have shown that the radiation tolerance might be extended at [...] Read more.
Biological samples are highly radiation sensitive. The rapid progress of their radiation damage prevents accurate structure determination of single macromolecular assemblies in standard diffraction experiments. However, computer simulations of the damage formation have shown that the radiation tolerance might be extended at very high intensities with ultrafast imaging such as is possible with the presently developed and operating x-ray free-electron lasers. Recent experiments with free-electron lasers on nanocrystals have demonstrated proof of the imaging principle at resolutions down to 1:6 Angstroms. However, there are still many physical and technical problems to be clarified on the way to imaging of single biomolecules at atomic resolution. In particular, theoretical simulations try to address an important question: How does the radiation damage progressing within an imaged single object limit the structural information about this object recorded in its diffraction image during a 3D imaging experiment? This information is crucial for adjusting pulse parameters during imaging so that high-resolution diffraction patterns can be obtained. Further, dynamics simulations should be used to verify the accuracy of the structure reconstruction performed from the experimental data. This is an important issue as the experimentally recorded diffraction signal is recorded from radiation-damaged samples. It also contains various kinds of background. In contrast, the currently used reconstruction algorithms assume perfectly coherent scattering patterns with shot noise only. In this review paper, we discuss the most important processes and effects relevant for imaging-related simulations that are not yet fully understood, or omitted in the irradiation description. We give estimates for their contribution to the overall radiation damage. In this way we can identify unsolved issues and challenges for simulations of x-ray irradiated single molecules relevant for imaging studies. They should be addressed during further development of these simulation tools. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Extreme Ultraviolet Stokesmeter for Pulsed Magneto-Optics
Photonics 2015, 2(1), 241-255; doi:10.3390/photonics2010241
Received: 9 January 2015 / Revised: 7 February 2015 / Accepted: 9 February 2015 / Published: 16 February 2015
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Abstract
Several applications in material science and magnetic holography using extreme ultraviolet (EUV) radiation require the measurement of the degree and state of polarization. In this work, an instrument to measure simultaneously both parameters from EUV pulses is presented. The instrument determines the [...] Read more.
Several applications in material science and magnetic holography using extreme ultraviolet (EUV) radiation require the measurement of the degree and state of polarization. In this work, an instrument to measure simultaneously both parameters from EUV pulses is presented. The instrument determines the Stokes parameters after a reflection on an array of multilayer mirrors at the Brewster angle. The Stokesmeter was tested at Swiss Light Source at different EUV wavelengths. The experimental Stokes patterns of the source were compared with the simulated pattern. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Optimum Pump Pulse Duration for X-Ray Ar-Plasma Lasing
Photonics 2015, 2(1), 164-183; doi:10.3390/photonics2010164
Received: 22 December 2014 / Accepted: 29 January 2015 / Published: 10 February 2015
Cited by 2 | PDF Full-text (542 KB) | HTML Full-text | XML Full-text
Abstract
In plasma-driven X-ray lasers, it is critical to optimize the duration and time delay between pump pulses. In this study, we have done parametric simulations in order to systematically investigate the optimum time configuration of pump pulses. Here, we are mainly interested [...] Read more.
In plasma-driven X-ray lasers, it is critical to optimize the duration and time delay between pump pulses. In this study, we have done parametric simulations in order to systematically investigate the optimum time configuration of pump pulses. Here, we are mainly interested in soft X-ray lasers created using a Ar target irradiated with laser pulses, which operate at a wavelength \(\lambda=46.9\) nm in the \(2p^5 3p^1(J=0)\rightarrow 2p^5 3s^1(J=1)\) laser transition. It is shown that the optimum time scale required to achieve Ne-like ions, as well as the time required to generate a population inversion depend on the combined effect of the electron temperature and electron density. The electron density and temperature are respectively a factor of \(\approx\)\(2.1\)- and \(\approx\)\(5\)-times higher in the case of a short pulse of \(0.1\) ps in comparison to a long pulse of 1,000 ps (at a constant fluence). The most effective lasing happens with short pulses with a pulse duration comparable to the total relaxation time from the upper level, namely \(\Delta\tau_p\leq35\) ps. Power laws to predict the optimum laser intensity to achieve Ne-like \(Ar^{+8}\) are obtained. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Figures

Open AccessArticle Transverse Electromagnetic Mode Conversion for High-Harmonic Self-Probing Spectroscopy
Photonics 2015, 2(1), 184-199; doi:10.3390/photonics2010184
Received: 25 December 2014 / Accepted: 30 January 2015 / Published: 10 February 2015
Cited by 2 | PDF Full-text (6834 KB) | HTML Full-text | XML Full-text
Abstract
We report on high-order harmonic (HHG) two-source interferometry (TSI) in molecular gases. We used a 0-\(\pi\) phase plate to create two bright spots at the focus of a lens by converting a Gaussian laser beam into a TEM please define \(_{01}\) Transverse [...] Read more.
We report on high-order harmonic (HHG) two-source interferometry (TSI) in molecular gases. We used a 0-\(\pi\) phase plate to create two bright spots at the focus of a lens by converting a Gaussian laser beam into a TEM please define \(_{01}\) Transverse Electromagnetic Mode. The two bright foci produce two synchronized HHG sources. One of them is used to probe on-going dynamics in the generating medium, while the other serves to heterodyne the signal. The interference of the emissions in the far–field gives access to the phase difference between the two sources. In self–probing HHG phase spectroscopy, one of the two sources is used as a reference while the other one probes some on goin dynamics in the generating medium. We first compute overlap integrals to investigate the mode conversion efficiency. We then establish a clear relation between the laser phase-front curvature and the far-field overlap of the two HHG beams. Both Fresnel diffraction calculations and an experimental lens position scan are used to reveal variations of the phase front inclination in each source. We show that this arrangement offers \(\frac{\lambda_{XUV}}{100}\) precision, enabling extremely sensitive phase measurements. Finally, we use this compact setup for TSI and measure phase variations across the molecular alignment revival of nitrogen and in vibrating sulfur hexafluoride. In both gases, the phase variations change sign around the ionization threshold of the investigated molecule. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Quantum Path Interference and Multiple Electron Scattering in Soft X-Ray High-Order Harmonic Generation
Photonics 2015, 2(1), 104-123; doi:10.3390/photonics2010104
Received: 10 December 2014 / Accepted: 13 January 2015 / Published: 23 January 2015
Cited by 1 | PDF Full-text (976 KB) | HTML Full-text | XML Full-text
Abstract
High-order harmonic generation is an important mechanism to generate coherent radiation in the few–100-eV spectral range with ultrashort laser pulses. Moreover, a closer inspection of the measured spectra provides unique information about the underlying physics and allows deriving guidelines for improvements. The [...] Read more.
High-order harmonic generation is an important mechanism to generate coherent radiation in the few–100-eV spectral range with ultrashort laser pulses. Moreover, a closer inspection of the measured spectra provides unique information about the underlying physics and allows deriving guidelines for improvements. The long-range modulation of the spectral envelope is linked to phase matching, and we will show how to improve it with a double-pulse excitation scheme. Additionally, the spectrum contains only every fourth harmonic, which can be well explained by the quantum interference of multiple scattered electrons, and two dominant electron trajectories were selected by X-ray parametric interaction. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Photo-Ionization of Noble Gases: A Demonstration of Hybrid Coupled Channels Approach
Photonics 2015, 2(1), 93-103; doi:10.3390/photonics2010093
Received: 15 December 2014 / Accepted: 14 January 2015 / Published: 16 January 2015
Cited by 2 | PDF Full-text (826 KB) | HTML Full-text | XML Full-text
Abstract
We present here an application of the recently developed hybrid coupled channels approach to study photo-ionization of noble gas atoms: Neon and Argon. We first compute multi-photon ionization rates and cross-sections for these inert gas atoms with our approach and compare them [...] Read more.
We present here an application of the recently developed hybrid coupled channels approach to study photo-ionization of noble gas atoms: Neon and Argon. We first compute multi-photon ionization rates and cross-sections for these inert gas atoms with our approach and compare them with reliable data available from R-matrix Floquet theory. The good agreement between coupled channels and R-matrix Floquet theory show that our method treats multi-electron systems on par with the well established R-matrix theory. We then apply the time dependent surface flux (tSURFF) method with our approach to compute total and angle resolved photo-electron spectra from Argon with linearly and circularly polarized 12 nm wavelength laser fields, a typical wavelength available from Free Electron Lasers (FELs). Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Toward the Extreme Ultra Violet Four Wave Mixing Experiments: From Table Top Lasers to Fourth Generation Light Sources
Photonics 2015, 2(1), 57-70; doi:10.3390/photonics2010057
Received: 13 December 2014 / Accepted: 8 January 2015 / Published: 12 January 2015
Cited by 1 | PDF Full-text (642 KB) | HTML Full-text | XML Full-text
Abstract
Three different Transient Grating setups are presented, with pulsed and continuous wave probe at different wavelengths, ranging from infrared to the extreme ultra violet region. Both heterodyne and homodyne detections are considered. Each scheme introduces variations with respect to the previous one, [...] Read more.
Three different Transient Grating setups are presented, with pulsed and continuous wave probe at different wavelengths, ranging from infrared to the extreme ultra violet region. Both heterodyne and homodyne detections are considered. Each scheme introduces variations with respect to the previous one, allowing moving from classical table top laser experiments towards a new four wave mixing scheme based on free electron laser radiation. A comparison between the various setups and the first results from extreme ultra violet transient grating experiments is also discussed. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Liquid Carbon Reflectivity at 19 nm
Photonics 2015, 2(1), 50-56; doi:10.3390/photonics2010050
Received: 15 December 2014 / Accepted: 5 January 2015 / Published: 9 January 2015
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Abstract
We hereby report on a pump-probe reflectivity experiment conducted on amorphous carbon, using a 780 nm laser as a pump and a 19 nm FEL emission as probe. Measurements were performed at 50 degrees with respect to the surface normal to have [...] Read more.
We hereby report on a pump-probe reflectivity experiment conducted on amorphous carbon, using a 780 nm laser as a pump and a 19 nm FEL emission as probe. Measurements were performed at 50 degrees with respect to the surface normal to have an un-pumped reflectivity higher than 0.5%. A sub-10 fs time synchronization error could be obtained exploiting the nearly jitter-free capabilities of FERMI. EUV FEL-based experiments open the way to study the behaviour of a liquid carbon phase being unaffected by plasma screening. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessArticle Grating Configurations for the Spectral Selection of Coherent Ultrashort Pulses in the Extreme-Ultraviolet
Photonics 2014, 1(4), 442-454; doi:10.3390/photonics1040442
Received: 4 November 2014 / Revised: 21 November 2014 / Accepted: 21 November 2014 / Published: 26 November 2014
Cited by 2 | PDF Full-text (359 KB) | HTML Full-text | XML Full-text
Abstract
The design and realization of grating instruments to handle and condition coherent ultrafast pulses in the extreme ultraviolet spectral region are discussed. The main application of such instruments is the spectral selection of high-order laser harmonics and free-electron-laser pulses in the femtosecond [...] Read more.
The design and realization of grating instruments to handle and condition coherent ultrafast pulses in the extreme ultraviolet spectral region are discussed. The main application of such instruments is the spectral selection 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. Here, we discuss two configurations useful for the realization of grating monochromator with ultrafast response: the single-grating design, applied to high-order laser harmonics, and the time-delay-compensated configuration with two gratings, applied to free-electron lasers. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

Review

Jump to: Research

Open AccessReview On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers
Photonics 2015, 2(2), 317-341; doi:10.3390/photonics2020317
Received: 4 March 2015 / Revised: 23 March 2015 / Accepted: 24 March 2015 / Published: 27 March 2015
Cited by 1 | PDF Full-text (1414 KB) | HTML Full-text | XML Full-text
Abstract
Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain free-electron lasers (FELs). The FEL radiation output efficiency is often parametrized through the power gain length that relates FEL performance to electron beam quality at the undulator. [...] Read more.
Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain free-electron lasers (FELs). The FEL radiation output efficiency is often parametrized through the power gain length that relates FEL performance to electron beam quality at the undulator. In this review article we illustrate some approaches to the preliminary design of FEL linac-drivers, and analyze the relationship between the output FEL wavelength, exponential gain length and electron beam brightness. We extend the discussion to include FEL three-dimensional effects and electron beam projected emittances. Although mostly concentrating on FELs based upon self-amplified spontaneous emission (SASE), our findings are in some cases highly relevant to externally seeded FELs. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessReview Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization
Photonics 2015, 2(1), 71-92; doi:10.3390/photonics2010071
Received: 3 December 2014 / Accepted: 8 January 2015 / Published: 12 January 2015
Cited by 1 | PDF Full-text (1527 KB) | HTML Full-text | XML Full-text
Abstract
Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\(_2^+\) and nonsymmetric HHe\(^{2+}\) one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions [...] Read more.
Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\(_2^+\) and nonsymmetric HHe\(^{2+}\) one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima) in molecular attosecond photoelectron energy spectra (MAPES) at critical angles \(\vartheta_c\) between the molecular \(\textbf{R}\) axis and the photoelectron momentum \(\textbf{p}\). The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)
Open AccessReview Recent Developments in UV Optics for Ultra-Short, Ultra-Intense Coherent Light Sources
Photonics 2015, 2(1), 40-49; doi:10.3390/photonics2010040
Received: 19 December 2014 / Accepted: 4 January 2015 / Published: 8 January 2015
Cited by 1 | PDF Full-text (552 KB) | HTML Full-text | XML Full-text
Abstract
With the advent of Free Electron Lasers and general UV ultra-short, ultra-intense sources, optics needed to transport such radiation have evolved significantly to standard UV optics. Problems like surface damage, wavefront preservation, beam splitting, beam shaping, beam elongation (temporal stretching) pose new [...] Read more.
With the advent of Free Electron Lasers and general UV ultra-short, ultra-intense sources, optics needed to transport such radiation have evolved significantly to standard UV optics. Problems like surface damage, wavefront preservation, beam splitting, beam shaping, beam elongation (temporal stretching) pose new challenges for the design of beam transport systems. These problems lead to a new way to specify optics, a new way to use diffraction gratings, a search for new optical coatings, to tighter and tighter polishing requirements for mirrors, and to an increased use of adaptive optics. All these topics will be described in this review article, to show how optics could really be the limiting factor for future development of these new light sources. Full article
(This article belongs to the Special Issue Extreme UV Lasers: Technologies and Applications)

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