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Spectral and Divergence Characteristics of Plateau High-Order Harmonics Generated by Femtosecond Chirped Laser Pulses in a Semi-Infinite Gas Cell. ATOMS 2022. [DOI: 10.3390/atoms10020053] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The generation of high-order harmonics in a semi-infinite cell by femtosecond laser pulses is a common practice for reliable coherent and low divergence XUV source beams for applications. Despite the relative simplicity of the experimental method, several phenomena coexist that affect the generated spectral and divergence characteristics of the high harmonic XUV frequency comb. The ionisation degree of the medium and the consequent plasma formation length imposes a spatiotemporal evolution of the fundamental EM field and XUV absorption. Varying the laser pulse chirp and the focusing conditions, as well as the gas density, we measured intense harmonic spectral and divergence variations attributed mainly to self-phase modulations of the laser EM field in the partially ionised medium. Additionally, low-divergence high harmonics are observed for certain laser chirp values attributed to the strong phase matching of only the short electron quantum path. Thus, a tunable, low divergent, and coherent XUV source can be realised for spatiotemporal imaging applications in the nanoscale.
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2
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Lu Y, Feng C, Tu L, Li C, Jiang B, Wang D. Generating coherent and ultrashort X-ray pulses via HHG-seeding in storage rings. JOURNAL OF SYNCHROTRON RADIATION 2022; 29:347-354. [PMID: 35254296 PMCID: PMC8900847 DOI: 10.1107/s1600577521013382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 12/16/2021] [Indexed: 06/14/2023]
Abstract
The generation of fully coherent and femtosecond time-scale radiation pulses in the X-ray regime is one of the most common demands of ring-based synchrotron light source users. In this paper, a method that utilizes the recent proposed angular dispersion induced microbunching technique to convert external light from high-harmonic generation (HHG) to coherent light at shorter wavelength is proposed. Numerical simulations using the practical parameters of a diffraction-limited storage ring demonstrate the generation of coherent pulse trains with photon energy as high as 2 keV, pulse duration as short as ∼10 fs and high peak brightness directly from an HHG source at 13 nm.
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Affiliation(s)
- Yujie Lu
- Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, People’s Republic of China
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, People’s Republic of China
| | - Chao Feng
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Lingjun Tu
- Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Changliang Li
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, People’s Republic of China
| | - Bocheng Jiang
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, People’s Republic of China
| | - Dong Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, People’s Republic of China
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
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3
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Liu YL, Wang J, Chu HH. Ion-based high-order harmonic generation from water window to keV region with a transverse disruptive pulse for quasi-phase-matching. OPTICS EXPRESS 2022; 30:1365-1380. [PMID: 35209298 DOI: 10.1364/oe.447796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 12/20/2021] [Indexed: 06/14/2023]
Abstract
A scheme for ion-based high-harmonic generation from water window to keV x-ray is investigated. He1+ ions with 54.42-eV ionization potential extend the harmonic cutoff energy to 1 keV. The transverse selective-zoning method of quasi-phase-matching is utilized to overcome the severe plasma dispersion in a highly ionized medium. The calculated conversion efficiency reaches about 15% of the perfect phase-matching condition. Wavelength tunability is achieved by incorporating a programmable spatial-light modulator to control the quasi-phase-matching pattern.
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4
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Electron quantum path control in high harmonic generation via chirp variation of strong laser pulses. Sci Rep 2021; 11:23882. [PMID: 34903823 PMCID: PMC8668923 DOI: 10.1038/s41598-021-03424-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 11/23/2021] [Indexed: 11/08/2022] Open
Abstract
The quantum phases of the electron paths driven by an ultrafast laser in high harmonic generation in an atomic gas depends linearly on the instantaneous cycle-averaged laser intensity. Using high laser intensities, a complete single ionisation of the atomic gas may occur before the laser pulse peak. Therefore, high harmonic generation could be localised only in a temporal window at the leading edge of laser pulse envelope. Varying the laser frequency chirp of an intense ultrafast laser pulse, the centre, and the width of the temporal window, that the high harmonic generation phenomenon occurs, could be controlled with high accuracy. This way, both the duration and the phase of the electron trajectories, that generate efficiently high harmonics, is fully controlled. A method of spectral control and selection of the high harmonic extreme ultraviolet light from distinct quantum paths is experimentally demonstrated. Furthermore, a phenomenological numerical model enlightens the physical processes that take place. This novel approach of the electron quantum path selection via laser chirp is a simple and versatile way of controlling the time-spectral characteristics of the coherent extreme ultraviolet light with applications in the fields of attosecond pulses and soft x-ray nano-imaging.
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Application of Quasi-Phase Matching Concept for Enhancement of High-Order Harmonics of Ultrashort Laser Pulses in Plasmas. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9081701] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Novel methods of coherent short-wavelength sources generation require thorough analysis for their further amendments and practical implementations. In this work, we report on the quasi-phase matching (QPM) of high-order harmonics generation during the propagation of single- and two-color femtosecond pulses through multi-jet plasmas, which allows the enhancement of groups of harmonics in different ranges of extreme ultraviolet. The role of the number of coherent zones; sizes of plasma jets and the distance between them; plasma formation conditions, and the characteristics of the fundamental radiation on the harmonic efficiency at quasi-phase matching (QPM) conditions are analyzed. We demonstrate the ~40× enhancement factor of the maximally-enhanced harmonic with respect to the one generated at ordinary conditions in the imperforated plasma.
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6
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Wöstmann M, Splitthoff L, Zacharias H. Control of quasi-phase-matching of high-harmonics in a spatially structured plasma. OPTICS EXPRESS 2018; 26:14524-14537. [PMID: 29877488 DOI: 10.1364/oe.26.014524] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 05/09/2018] [Indexed: 06/08/2023]
Abstract
High-harmonic generation is widely used for providing extreme ultraviolet radiation in attosecond science. Such experiments include photoelectron spectroscopy, diffractive imaging, or the investigation of spin dynamics. Many applications are restricted by a low photon flux which originates from the low efficiency of the generation process. In this article an effective method based on the quasi-phase-matched generation of high harmonics in spatially structured, laser ablated plasma is demonstrated. Through a proper dimensioning of the plasma structure, the harmonic yield is optimized for a controllable range of harmonic orders. By using four coherent zones, the intensity of a single harmonic is increased to a maximal possible value of 16 compared to using a single zone. The Gouy phase shift of the fundamental field is identified as the primary effect responsible for constructive interference of the harmonic fields generated in the individual plasma jets of the plasma structure.
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7
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Lerner G, Diskin T, Neufeld O, Kfir O, Cohen O. Selective suppression of high-order harmonics within phase-matched spectral regions. OPTICS LETTERS 2017; 42:1349-1352. [PMID: 28362766 DOI: 10.1364/ol.42.001349] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Phase matching in high-harmonic generation leads to enhancement of multiple harmonics. It is sometimes desired to control the spectral structure within the phase-matched spectral region. We propose a scheme for selective suppression of high-order harmonics within the phase-matched spectral region while weakly influencing the other harmonics. The method is based on addition of phase-mismatched segments within a phase-matched medium. We demonstrate the method numerically in two examples. First, we show that one phase-mismatched segment can significantly suppress harmonic orders 9, 15, and 21. Second, we show that two phase-mismatched segments can efficiently suppress circularly polarized harmonics with one helicity over the other when driven by a bi-circular field. The new method may be useful for various applications, including the generation of highly helical bright attosecond pulses.
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8
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Tao Y, Goh SJ, Bastiaens HMJ, van der Slot PJM, Biedron SG, Milton SV, Boller KJ. Temporal model for quasi-phase matching in high-order harmonic generation. OPTICS EXPRESS 2017; 25:3621-3638. [PMID: 28241575 DOI: 10.1364/oe.25.003621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a model for quasi-phase matching (QPM) in high-order harmonic generation (HHG). Using a one-dimensional description, we analyze the time-dependent, ultrafast wave-vector balance to calculate the on-axis harmonic output versus time, from which we obtain the output pulse energy. Considering, as an example, periodically patterned argon gas, as may be provided with a grid in a cluster jet, we calculate the harmonic output during different time intervals within the drive laser pulse duration. We find that identifying a suitable single spatial period is not straightforward due to the complex and ultrafast plasma dynamics that underlies HHG at increased intensities. The maximum on-axis harmonic pulse energy is obtained when choosing the QPM period to phase match HHG at the leading edge of the drive laser pulse.
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9
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Wachulak PW. Contributed Review: The novel gas puff targets for laser-matter interaction experiments. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:091501. [PMID: 27782609 DOI: 10.1063/1.4962012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Various types of targetry are used nowadays in laser matter interaction experiments. Such targets are characterized using different methods capable of acquiring information about the targets such as density, spatial distribution, and temporal behavior. In this mini-review paper, a particular type of target will be presented. The targets under consideration are gas puff targets of various and novel geometries. Those targets were investigated using extreme ultraviolet (EUV) and soft X-ray (SXR) imaging techniques, such as shadowgraphy, tomography, and pinhole camera imaging. Details about characterization of those targets in the EUV and SXR spectral regions will be presented.
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Affiliation(s)
- Przemyslaw W Wachulak
- Institute of Optoelectronics, Military University of Technology, Ul. Gen. S. Kaliskiego 2, 00-908 Warsaw, Poland
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10
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Hadas I, Bahabad A. Periodic density modulation for quasi-phase-matching of optical frequency conversion is inefficient under shallow focusing and constant ambient pressure. OPTICS LETTERS 2016; 41:4000-4003. [PMID: 27607957 DOI: 10.1364/ol.41.004000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The two main mechanisms of a periodic density modulation relevant to nonlinear optical conversion in a gas medium are spatial modulations of the index of refraction and of the number of emitters. For a one-dimensional model neglecting focusing and using a constant ambient pressure, it is shown theoretically and demonstrated numerically that the effects of these two mechanisms during frequency conversion cancel each other exactly. Under the considered conditions, this makes density modulation inefficient for quasi-phase-matching an optical frequency conversion process. This result is particularly relevant for high-order harmonic generation.
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11
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Ganeev RA, Husakou A, Suzuki M, Kuroda H. Application of mid-infrared pulses for quasi-phase-matching of high-order harmonics in silver plasma. OPTICS EXPRESS 2016; 24:3414-3423. [PMID: 26907000 DOI: 10.1364/oe.24.003414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate the quasi-phase-matching of a group of harmonics generated in Ag multi-jet plasma using tunable pulses in the region of 1160 - 1540 nm and their second harmonic emission. The numerical treatment of this effect includes microscopic description of the harmonic generation, propagation of the pump pulse, and the propagation of the generated harmonics. We obtained more than 30-fold growth of harmonics at the conditions of quasi-phase-matching in the region of 35 nm using eight-jet plasma compared with the case of imperforated plasma.
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12
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Hadas I, Bahabad A. Macroscopic manipulation of high-order-harmonic generation through bound-state coherent control. PHYSICAL REVIEW LETTERS 2014; 113:253902. [PMID: 25554882 DOI: 10.1103/physrevlett.113.253902] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Indexed: 06/04/2023]
Abstract
We propose a paradigm for macroscopic control of high-order harmonic generation by modulating the bound-state population of the medium atoms. A unique result of this scheme is that apart from regular spatial quasi-phase-matching (QPM), also purely temporal QPM of the emitted radiation can be established. Our simulations demonstrate temporal QPM by inducing homogenous Rabi oscillations in the medium and also spatial QPM by creating a grating of population inversion using the process of rapid adiabatic passage. In the simulations a scaled version of high-order harmonic generation is used: a far off-resonance 2.6 μm source generates UV-visible high-order harmonics from alkali-metal-atom vapor, while a resonant near IR source is used to coherently control the medium.
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Affiliation(s)
- Itai Hadas
- Department of Physical Electronics, School of Electrical Engineering, Iby and Aladar Fleischman Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Alon Bahabad
- Department of Physical Electronics, School of Electrical Engineering, Iby and Aladar Fleischman Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel
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13
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Hage A, Landgraf B, Taylor M, Wünsche M, Gangolf T, Höppner H, Prandolini MJ, Riedel R, Schulz M, Tavella F, Willner A, Yeung M, Paulus GG, Spielmann C, Dromey B, Zepf M. New design of a multi-jet target for quasi phase matching. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:103105. [PMID: 25362369 DOI: 10.1063/1.4897269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
An improved dual-gas quasi-phase matching (QPM) foil target for high harmonic generation (HHG) is presented. The target can be setup with 12 individual gas inlets each feeding multiple nozzles separated by a minimum distance of 10 μm. Three-dimensional gas density profiles of these jets were measured using a Mach-Zehnder Interferometer. These measurements reveal how the jets influence the density of gas in adjacent jets and how this leads to increased local gas densities. The analysis shows that the gas profiles of the jets are well defined up to a distance of about 300 μm from the orifice. This target design offers experimental flexibility, not only for HHG/QPM investigations, but also for a wide range of experiments due to the large number of possible jet configurations. We demonstrate the application to controlled phase tuning in the extreme ultraviolet using a 1 kHz-10 mJ-30 fs-laser system where interference between two jets in the spectral range from 17 to 30 nm was observed.
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Affiliation(s)
- A Hage
- Deutsches Elektronensynchrotron (DESY), Notkestrasse 85, 22607 Hamburg, Germany
| | - B Landgraf
- Institute of Optics and Quantum Electronics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
| | - M Taylor
- School of Mathematics and Physics, Queen's University, University Road, Belfast BT7 1NN, United Kingdom
| | - M Wünsche
- Institute of Optics and Quantum Electronics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
| | - T Gangolf
- Institute of Optics and Quantum Electronics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
| | - H Höppner
- Deutsches Elektronensynchrotron (DESY), Notkestrasse 85, 22607 Hamburg, Germany
| | - M J Prandolini
- Helmholtzinstitut Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - R Riedel
- Helmholtzinstitut Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - M Schulz
- Deutsches Elektronensynchrotron (DESY), Notkestrasse 85, 22607 Hamburg, Germany
| | - F Tavella
- Helmholtzinstitut Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - A Willner
- Deutsches Elektronensynchrotron (DESY), Notkestrasse 85, 22607 Hamburg, Germany
| | - M Yeung
- School of Mathematics and Physics, Queen's University, University Road, Belfast BT7 1NN, United Kingdom
| | - G G Paulus
- Institute of Optics and Quantum Electronics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
| | - C Spielmann
- Helmholtzinstitut Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - B Dromey
- School of Mathematics and Physics, Queen's University, University Road, Belfast BT7 1NN, United Kingdom
| | - M Zepf
- School of Mathematics and Physics, Queen's University, University Road, Belfast BT7 1NN, United Kingdom
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14
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Pullen MG, Gaffney NS, Hall CR, Davis JA, Dubrouil A, Le HV, Buividas R, Day D, Quiney HM, Dao LV. High-order harmonic generation from a dual-gas, multi-jet array with individual gas jet control. OPTICS LETTERS 2013; 38:4204-4207. [PMID: 24321960 DOI: 10.1364/ol.38.004204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present a gas jet array for use in high-order harmonic generation experiments. Precise control of the pressure in each individual gas jet has allowed a thorough investigation into mechanisms contributing to the selective enhancement observed in the harmonic spectra produced by dual-gas, multi-jet arrays. Our results reveal that in our case, the dominant enhancement mechanism is the result of a compression of the harmonic-producing gas jet due to the presence of other gas jets in the array. The individual control of the gas jets in the array also provides a promising method for enhancing the harmonic yield by precise tailoring of the length and pressure gradient of the interaction region.
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15
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Antonov VA, Radeonychev YV, Kocharovskaya O. Formation of a single attosecond pulse via interaction of resonant radiation with a strongly perturbed atomic transition. PHYSICAL REVIEW LETTERS 2013; 110:213903. [PMID: 23745878 DOI: 10.1103/physrevlett.110.213903] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Indexed: 06/02/2023]
Abstract
We propose a technique to form a single few-cycle attosecond pulse from vacuum ultraviolet or extreme ultraviolet radiation via resonant interaction with hydrogenlike atoms, irradiated by a high-intensity far-off-resonant laser field. The laser field strongly perturbs excited atomic energy levels via the Stark effect and ionizes atoms from the excited states. We show that an isolated attosecond pulse can be formed using either a short incident femtosecond pulse of the resonant radiation or a steep front edge of the laser field. We propose an experimental realization of a single subfemtosecond pulse formation at 121.6 nm in atomic hydrogen and a single sub-100 as pulse formation at 13.5 nm in Li(2+) plasma.
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Affiliation(s)
- V A Antonov
- Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov Street, Nizhny Novgorod, 603950, Russia.
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16
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Laban DE, Palmer AJ, Wallace WC, Gaffney NS, Notermans RPMJW, Clevis TTJ, Pullen MG, Jiang D, Quiney HM, Litvinyuk IV, Kielpinski D, Sang RT. Extreme ultraviolet interferometer using high-order harmonic generation from successive sources. PHYSICAL REVIEW LETTERS 2012; 109:263902. [PMID: 23368563 DOI: 10.1103/physrevlett.109.263902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Indexed: 06/01/2023]
Abstract
We present a new interferometer technique whereby multiple extreme ultraviolet light pulses are generated at different positions within a single laser focus (i.e., from successive sources) with a highly controllable time delay. The interferometer technique is tested with two generating media to create two extreme ultraviolet light pulses with a time delay between them. The delay is found to be a consequence of the Gouy phase shift. Ultimately the apparatus is capable of accessing unprecedented time scales by allowing stable and repeatable delays as small as 100 zs.
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Affiliation(s)
- D E Laban
- ARC Centre of Excellence for Coherent X-Ray Science, Griffith University, Brisbane, Queensland 4111, Australia
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17
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Willner A, Hage A, Riedel R, Grguraš I, Simoncig A, Schulz M, Dzelzainis T, Höppner H, Huber S, Prandolini MJ, Dromey B, Zepf M, Cavalieri AL, Tavella F. Coherent spectral enhancement of carrier-envelope-phase stable continua with dual-gas high harmonic generation. OPTICS LETTERS 2012; 37:3672-3674. [PMID: 22940986 DOI: 10.1364/ol.37.003672] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Attosecond science is enabled by the ability to convert femtosecond near-infrared laser light into coherent harmonics in the extreme ultraviolet spectral range. While attosecond sources have been utilized in experiments that have not demanded high intensities, substantially higher photon flux would provide a natural link to the next significant experimental breakthrough. Numerical simulations of dual-gas high harmonic generation indicate that the output in the cutoff spectral region can be selectively enhanced without disturbing the single-atom gating mechanism. Here, we summarize the results of these simulations and present first experimental findings to support these predictions.
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Affiliation(s)
- A Willner
- Deutsches Elektronensynchrotron (DESY), Hamburg, Germany.
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18
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O'Keeffe K, Robinson T, Hooker SM. Quasi-phase-matching high harmonic generation using trains of pulses produced using an array of birefringent plates. OPTICS EXPRESS 2012; 20:6236-6247. [PMID: 22418507 DOI: 10.1364/oe.20.006236] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Quasi-phase-matched high harmonic generation using trains of up to 8 counter-propagating pulses is explored. For trains of up to 4 pulses the measured enhancement of the harmonic signal scales with the number of pulses N as (N + 1)², as expected. However, for trains with N > 4, no further enhancement of the harmonic signal is observed. This effect is ascribed to changes of the coherence length Lc within the generating medium. Techniques for overcoming the variation of Lc are discussed. The pressure dependence of quasi-phase-matching is investigated and the switch from true-phase-matching to quasi-phase-matching is observed.
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Affiliation(s)
- Kevin O'Keeffe
- Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK.
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