451
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Hernández-García C, Picón A, San Román J, Plaja L. Attosecond extreme ultraviolet vortices from high-order harmonic generation. PHYSICAL REVIEW LETTERS 2013; 111:083602. [PMID: 24010438 DOI: 10.1103/physrevlett.111.083602] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Indexed: 06/02/2023]
Abstract
We present a theoretical study of high-order harmonic generation (HHG) and propagation driven by an infrared field carrying orbital angular momentum (OAM). Our calculations unveil the following relevant phenomena: extreme-ultraviolet harmonic vortices are generated and survive to the propagation effects, vortices transport high-OAM multiples of the corresponding OAM of the driving field and, finally, the different harmonic vortices are emitted with similar divergence. We also show the possibility of combining OAM and HHG phase locking to produce attosecond pulses with helical pulse structure.
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Affiliation(s)
- Carlos Hernández-García
- Grupo de Investigación en Óptica Extrema, Universidad de Salamanca, E-37008 Salamanca, Spain and JILA and Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309-0440, USA
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452
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Lai CJ, Cirmi G, Hong KH, Moses J, Huang SW, Granados E, Keathley P, Bhardwaj S, Kärtner FX. Wavelength scaling of high harmonic generation close to the multiphoton ionization regime. PHYSICAL REVIEW LETTERS 2013; 111:073901. [PMID: 23992066 DOI: 10.1103/physrevlett.111.073901] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Indexed: 05/13/2023]
Abstract
We study the wavelength scaling of high harmonic generation efficiency with visible driver wavelengths in the transition between the tunneling and the multiphoton ionization regimes where the Keldysh parameter is around unity. Our experiment shows a less dramatic wavelength scaling of efficiency than the conventional case for near- and mid-IR driver wavelengths, and it is well explained by a generalized three-step model for increased Keldysh parameters that employs complex ionization times in addition to the nonadiabatic ionization. The complex ionization time is critical to avoid the divergence when replacing the quasistatic ionization model by the more general nonadiabatic ionization model. Together, the two modifications present a consistent description of the influence of the atomic potential on the rescattering process in the intermediate Keldysh regime.
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Affiliation(s)
- Chien-Jen Lai
- Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts 02139, USA.
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453
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Hernández-García C, Pérez-Hernández JA, Popmintchev T, Murnane MM, Kapteyn HC, Jaron-Becker A, Becker A, Plaja L. Zeptosecond high harmonic keV x-ray waveforms driven by midinfrared laser pulses. PHYSICAL REVIEW LETTERS 2013; 111:033002. [PMID: 23909315 DOI: 10.1103/physrevlett.111.033002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Indexed: 05/24/2023]
Abstract
We demonstrate theoretically that the temporal structure of high harmonic x-ray pulses generated with midinfrared lasers differs substantially from those generated with near-infrared pulses, especially at high photon energies. In particular, we show that, although the total width of the x-ray bursts spans femtosecond time scales, the pulse exhibits a zeptosecond structure due to the interference of high harmonic emission from multiple reencounters of the electron wave packet with the ion. Properly filtered and without any compensation of the chirp, regular subattosecond keV waveforms can be produced.
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Affiliation(s)
- C Hernández-García
- Grupo de Investigación en Óptica Extrema, Universidad de Salamanca, E-37008 Salamanca, Spain.
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454
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Rudawski P, Heyl CM, Brizuela F, Schwenke J, Persson A, Mansten E, Rakowski R, Rading L, Campi F, Kim B, Johnsson P, L'huillier A. A high-flux high-order harmonic source. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:073103. [PMID: 23902040 DOI: 10.1063/1.4812266] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We develop and implement an experimental strategy for the generation of high-energy high-order harmonics (HHG) in gases for studies of nonlinear processes in the soft x-ray region. We generate high-order harmonics by focusing a high energy Ti:Sapphire laser into a gas cell filled with argon or neon. The energy per pulse is optimized by an automated control of the multiple parameters that influence the generation process. This optimization procedure allows us to obtain energies per pulse and harmonic order as high as 200 nJ in argon and 20 nJ in neon, with good spatial properties, using a loose focusing geometry (f#≈400) and a 20 mm long medium. We also theoretically examine the macroscopic conditions for absorption-limited conversion efficiency and optimization of the HHG pulse energy for high-energy laser systems.
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Affiliation(s)
- P Rudawski
- Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden.
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455
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Zhao K, Zhong H, Yuan P, Xie G, Wang J, Ma J, Qian L. Generation of 120 GW mid-infrared pulses from a widely tunable noncollinear optical parametric amplifier. OPTICS LETTERS 2013; 38:2159-2161. [PMID: 23811863 DOI: 10.1364/ol.38.002159] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate a noncollinear optical parametric chirped-pulse amplification scheme for generating high-peak-power tunable mid-infrared (IR) pulses. The high-gain LiNbO(3)-based noncollinear parametric amplifier, seeded by a tunable femtosecond optical parametric amplifier, provides a wide wavelength tuning range from 3.3 to 3.95 μm and a large saturated gain of over 4000 in a single-stage amplifier. The compressed mid-IR pulse has a pulse energy of 13.3 mJ and pulse duration of 111 fs, with a peak power as high as 120 GW. To the best of our knowledge, this is the highest peak power ever reported for 3-5 μm tunable mid-IR lasers.
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Affiliation(s)
- Kun Zhao
- Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
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456
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Clerici M, Peccianti M, Schmidt BE, Caspani L, Shalaby M, Giguère M, Lotti A, Couairon A, Légaré F, Ozaki T, Faccio D, Morandotti R. Wavelength scaling of terahertz generation by gas ionization. PHYSICAL REVIEW LETTERS 2013; 110:253901. [PMID: 23829737 DOI: 10.1103/physrevlett.110.253901] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Indexed: 06/02/2023]
Abstract
Low-frequency currents induced by ultrashort laser-driven ionization can emit extremely broadband, single-cycle terahertz pulses. We present a model that predicts a strong wavelength dependence of the THz emission in good agreement with our experimental study. This reveals that the combined effects of plasma currents rising proportionally to the square of the pump wavelength and wavelength-dependent focusing conditions lead to 30 times higher THz emission at 1800 nm compared to an 800 nm wavelength. Unrivaled single-cycle electric field strengths of 4.4 MV/cm are achieved with this compact table-top setup.
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Affiliation(s)
- Matteo Clerici
- INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada.
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457
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Kamor A, Mauger F, Chandre C, Uzer T. How key periodic orbits drive recollisions in a circularly polarized laser field. PHYSICAL REVIEW LETTERS 2013; 110:253002. [PMID: 23829734 DOI: 10.1103/physrevlett.110.253002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Indexed: 06/02/2023]
Abstract
We show that a family of key periodic orbits drives the recollision process in a strong circularly polarized laser field. These orbits, coined recolliding periodic orbits, exist for a wide range of parameters, and their relative influence changes as the laser and atomic parameters are varied. We find the necessary conditions for recollision-driven nonsequential double ionization to occur. The outlined mechanism is universal in that it applies equally well beyond atoms: The internal structure of the target species plays a minor role in the recollision process.
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Affiliation(s)
- A Kamor
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA
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458
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Keskinbora K, Grévent C, Bechtel M, Weigand M, Goering E, Nadzeyka A, Peto L, Rehbein S, Schneider G, Follath R, Vila-Comamala J, Yan H, Schütz G. Ion beam lithography for Fresnel zone plates in X-ray microscopy. OPTICS EXPRESS 2013; 21:11747-11756. [PMID: 23736396 DOI: 10.1364/oe.21.011747] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fresnel Zone Plates (FZP) are to date very successful focusing optics for X-rays. Established methods of fabrication are rather complex and based on electron beam lithography (EBL). Here, we show that ion beam lithography (IBL) may advantageously simplify their preparation. A FZP operable from the extreme UV to the limit of the hard X-ray was prepared and tested from 450 eV to 1500 eV. The trapezoidal profile of the FZP favorably activates its 2nd order focus. The FZP with an outermost zone width of 100 nm allows the visualization of features down to 61, 31 and 21 nm in the 1st, 2nd and 3rd order focus respectively. Measured efficiencies in the 1st and 2nd order of diffraction reach the theoretical predictions.
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Affiliation(s)
- Kahraman Keskinbora
- Max Planck Institute for Intelligent Systems, Heisenbergstr 3, 70569 Stuttgart, Germany
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459
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Ekanayake N, Luo S, Grugan PD, Crosby WB, Camilo AD, McCowan CV, Scalzi R, Tramontozzi A, Howard LE, Wells SJ, Mancuso C, Stanev T, Decamp MF, Walker BC. Electron shell ionization of atoms with classical, relativistic scattering. PHYSICAL REVIEW LETTERS 2013; 110:203003. [PMID: 25167403 DOI: 10.1103/physrevlett.110.203003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Indexed: 06/03/2023]
Abstract
We investigate forward scattering of ionization from neon, argon, and xenon in ultrahigh intensities of 2 × 10(19) W/cm(2). Comparisons between the gases reveal the energy of the outgoing photoelectron determines its momentum, which can be scattered as far forward as 45° from the laser wave vector k(laser) for energies greater than 1 MeV. The shell structure in the atom manifests itself as modulations in the photoelectron yield and the width of the angular distributions. We arrive at an agreement with theory by using an independent electron model for the atom, a dipole approximation for the bound state interaction, and a relativistic, three-dimensional, classical radiation field including the laser magnetic field. The studies provide the atomic physics within plasmas, radiation, and particle acceleration in ultrastrong fields.
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Affiliation(s)
- N Ekanayake
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - S Luo
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - P D Grugan
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - W B Crosby
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - A D Camilo
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - C V McCowan
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - R Scalzi
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - A Tramontozzi
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - L E Howard
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - S J Wells
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - C Mancuso
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - T Stanev
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - M F Decamp
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
| | - B C Walker
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
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460
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Andreasen J, Kolesik M. Midinfrared femtosecond laser pulse filamentation in hollow waveguides: a comparison of simulation methods. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:053303. [PMID: 23767653 DOI: 10.1103/physreve.87.053303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Indexed: 06/02/2023]
Abstract
This work compares computational methods for laser pulse propagation in hollow waveguides filled with rare gases at high pressures, with applications in extreme nonlinear optics in the midinfrared wavelength region. As the wavelength of light λ=2π/k increases with respect to the transverse size R of a leaky waveguide, the loss of light out of the waveguide upon propagation, in general, increases. The now standard numerical approach for studying such structures is based on expansion of the propagating field into approximate leaky waveguide modes. We compare this approach to an improved method that resolves the electric field in real space and correctly captures the energy loss through the waveguide wall. The comparison reveals that the expansion-based approach overestimates losses that occur in nonlinearly reshaped pulsed waveforms. For a modest increase in computational effort, the alternate method offers a physically more accurate model to describe phenomena (e.g., extreme pulse-selfcompression) in waveguides with smaller values of kR.
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Affiliation(s)
- J Andreasen
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
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461
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Dorfman KE, Bennett K, Zhang Y, Mukamel S. Nonlinear light scattering in molecules triggered by an impulsive X-ray Raman process. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 2013; 87:53826. [PMID: 24465122 PMCID: PMC3900012 DOI: 10.1103/physreva.87.053826] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The time-and-frequency resolved nonlinear light scattering (NLS) signals from a time evolving charge distribution of valence electrons prepared by impulsive X-ray pulses are calculated using a superoperator Green's function formalism. The signal consists of a coherent ~ N2-scaling difference frequency generation and an incoherent fluorescence ~ N-scaling component where N is the number of active molecules. The former is given by the classical Larmor formula based on the time-dependent charge density. The latter requires additional information about the electronic structure and may be recast in terms of transition amplitudes representing quantum matter pathways.
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Affiliation(s)
| | | | - Yu Zhang
- University of California, Irvine, California 92697-2025
| | - Shaul Mukamel
- University of California, Irvine, California 92697-2025
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462
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Hong Z, Zhang Q, Lu P. Compact dual-crystal optical parametric amplification for broadband IR pulse generation using a collinear geometry. OPTICS EXPRESS 2013; 21:9491-9504. [PMID: 23609660 DOI: 10.1364/oe.21.009491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A novel compact dual-crystal optical parametric amplification (DOPA) scheme, collinearly pumped by a Ti:sapphire laser (0.8 μm), is theoretically investigated for efficiently generating broadband IR pulses at non-degenerate wavelengths (1.2 μm~1.4 μm and 1.8 μm~2.1 μm). By inserting a pair of barium fluoride (BaF(2)) wedges between two thin β-barium borate (BBO) crystals, the group velocity mismatch (GVM) between the three interacting pulses can be compensated simultaneously. In this case, the obtained signal spectrum centered at 1.3 μm is nearly 20% broader and the conversion efficiency is increased, but also the pulse contrast and beam quality are improved due to the better temporal overlap. Furthermore, sub-two-cycle idler pulses with carrier-envelope phase (CEP) fluctuation of sub-100-mrad root mean square (RMS) can be generated. Because a tunable few-cycle IR pulse with millijoule energy is attainable in this scheme, it will contribute to ultrafast community and be particularly useful as a driving or controlling field for the generation of ultrafast coherent x-ray supercontinuum.
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Affiliation(s)
- Zuofei Hong
- Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
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463
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Kraus PM, Wörner HJ. Attosecond nuclear dynamics in the ammonia cation: relation between high-harmonic and photoelectron spectroscopies. Chemphyschem 2013; 14:1445-50. [PMID: 23576456 DOI: 10.1002/cphc.201201022] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/16/2013] [Indexed: 11/06/2022]
Abstract
We report measurements of the umbrella motion in the ammonia cation on the attosecond time scale. The motion is prepared by strong-field ionization and probed by photorecombination through the process of high-harmonic generation. Performing such measurements at multiple wavelengths (0.8, 1.44, 1.8 μm) enables us to follow the nuclear dynamics over a broad temporal range (0.8-3.8 fs). The intensity of the driving field is found to have a significant impact on the observed dynamics through the vibrational-state dependence of the strong-field ionization rates. We derive a general model that includes these effects and establishes a new link between high-harmonic spectroscopy and classical photoelectron spectroscopy. Our model reproduces the observed dynamics and their dependence on the intensity of the driving field. Moreover, the model predicts much richer nuclear dynamics on the few-fs timescale than most previous theories. The newly predicted features are shown to reflect the quantized vibronic level structure of the molecular cation.
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Affiliation(s)
- Peter Michael Kraus
- Laboratorium für Physikalische Chemie, ETH Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland
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464
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Dixit G, Santra R. Role of electron-electron interference in ultrafast time-resolved imaging of electronic wavepackets. J Chem Phys 2013; 138:134311. [DOI: 10.1063/1.4798321] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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465
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Dixit G, Slowik JM, Santra R. Proposed imaging of the ultrafast electronic motion in samples using x-ray phase contrast. PHYSICAL REVIEW LETTERS 2013; 110:137403. [PMID: 23581370 DOI: 10.1103/physrevlett.110.137403] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Indexed: 06/02/2023]
Abstract
Tracing the motion of electrons has enormous relevance to understanding ubiquitous phenomena in ultrafast science, such as the dynamical evolution of the electron density during complex chemical and biological processes. Scattering of ultrashort x-ray pulses from an electronic wave packet would appear to be the most obvious approach to image the electronic motion in real time and real space with the notion that such scattering patterns, in the far-field regime, encode the instantaneous electron density of the wave packet. However, recent results by Dixit et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 11636 (2012)] have put this notion into question and have shown that the scattering in the far-field regime probes spatiotemporal density-density correlations. Here, we propose a possible way to image the instantaneous electron density of the wave packet via ultrafast x-ray phase contrast imaging. Moreover, we show that inelastic scattering processes, which plague ultrafast scattering in the far-field regime, do not contribute in ultrafast x-ray phase contrast imaging as a consequence of an interference effect. We illustrate our general findings by means of a wave packet that lies in the time and energy range of the dynamics of valence electrons in complex molecular and biological systems. This present work offers a potential to image not only instantaneous snapshots of nonstationary electron dynamics, but also the laplacian of these snapshots which provide information about the complex bonding and topology of the charge distributions in the systems.
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Affiliation(s)
- Gopal Dixit
- Center for Free-Electron Laser Science, DESY, Notkestrasse 85, D-22607 Hamburg, Germany.
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466
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Dunning DJ, McNeil BWJ, Thompson NR. Few-cycle pulse generation in an x-ray free-electron laser. PHYSICAL REVIEW LETTERS 2013; 110:104801. [PMID: 23521266 DOI: 10.1103/physrevlett.110.104801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Indexed: 06/01/2023]
Abstract
A method is proposed to generate trains of few-cycle x-ray pulses from a free-electron laser (FEL) amplifier via a compact "afterburner" extension consisting of several few-period undulator sections separated by electron chicane delays. Simulations show that in the hard x ray (wavelength ~0.1 nm; photon energy ~10 keV) and with peak powers approaching normal FEL saturation (GW) levels, root mean square pulse durations of 700 zs may be obtained. This is approximately two orders of magnitude shorter than that possible for normal FEL amplifier operation. The spectrum is discretely multichromatic with a bandwidth envelope increased by approximately 2 orders of magnitude over unseeded FEL amplifier operation. Such a source would significantly enhance research opportunity in atomic dynamics and push capability toward nuclear dynamics.
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Affiliation(s)
- D J Dunning
- ASTeC, STFC Daresbury Laboratory and Cockcroft Institute, Warrington WA4 4AD, United Kingdom.
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467
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Generation of Phase-Stable Sub-Cycle Mid-Infrared Pulses from Filamentation in Nitrogen. APPLIED SCIENCES-BASEL 2013. [DOI: 10.3390/app3010122] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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468
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Pérez-Hernández JA, Ciappina MF, Lewenstein M, Roso L, Zaïr A. Beyond carbon K-edge harmonic emission using a spatial and temporal synthesized laser field. PHYSICAL REVIEW LETTERS 2013; 110:053001. [PMID: 23414015 DOI: 10.1103/physrevlett.110.053001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Indexed: 06/01/2023]
Abstract
We present numerical simulations of high-order harmonic generation in helium using a temporally synthesized and spatially nonhomogeneous strong laser field. The combination of temporal and spatial laser field synthesis results in a dramatic cutoff extension far beyond the usual semiclassical limit. Our predictions are based on the convergence of three complementary approaches: resolution of the three dimensional time dependent Schrödinger equation, time-frequency analysis of the resulting dipole moment, and classical trajectory extraction. A laser field synthesized both spatially and temporally has been proven capable of generating coherent extreme ultraviolet photons beyond the carbon K edge, an energy region of high interest as it can be used to initiate inner-shell dynamics and study time-resolved intramolecular attosecond spectroscopy.
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Affiliation(s)
- J A Pérez-Hernández
- Centro de Láseres Pulsados (CLPU), Parque Científico, 37185 Villamayor, Salamanca, Spain.
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469
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Loh ZH, Leone SR. Capturing Ultrafast Quantum Dynamics with Femtosecond and Attosecond X-ray Core-Level Absorption Spectroscopy. J Phys Chem Lett 2013; 4:292-302. [PMID: 26283437 DOI: 10.1021/jz301910n] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Recent technical advances in ultrafast laser sources enable the generation of femtosecond and attosecond soft X-ray pulses in tabletop laser setups as well as accelerator-based synchrotron and free-electron laser sources. These new light sources can be harnessed via pump-probe spectroscopy to elucidate ultrafast quantum dynamics in atoms, molecules, and condensed matter with unprecedented time resolution and chemical sensitivity. Employing such ultrashort pulses in transient X-ray absorption spectroscopy combines the unique advantages of core-level absorption probing of chemical environments and oxidation states with the ability to obtain ultimately freeze-frame snapshots of electronic and nuclear dynamics. In this Perspective, we provide an overview of the progress in applying the recently developed technique of femtosecond to attosecond time-resolved soft X-ray transient absorption spectroscopy to the study of ultrafast phenomena, including some of our own efforts to elucidate the interaction of intense laser pulses with atoms and molecules in the strong-field, nonperturbative limit. Possible avenues for future work are outlined.
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Affiliation(s)
- Zhi-Heng Loh
- †Division of Chemistry and Biological Chemistry, and Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Stephen R Leone
- ‡Departments of Chemistry and Physics, University of California, Berkeley, California 94720, United States
- §Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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470
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Yuan KJ, Bandrauk AD. Single circularly polarized attosecond pulse generation by intense few cycle elliptically polarized laser pulses and terahertz fields from molecular media. PHYSICAL REVIEW LETTERS 2013; 110:023003. [PMID: 23383902 DOI: 10.1103/physrevlett.110.023003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Indexed: 05/23/2023]
Abstract
We present a method for producing a single circularly polarized attosecond pulse by an intense few cycle elliptically polarized laser pulse combined with a terahertz field from numerical solutions of the time-dependent Schrödinger equation for the molecular ion H2(+). It is found that in the presence of a 62.5 THz (λ=4800 nm) field at an intensity of ∼10(14) W/cm2, a single circularly polarized 114 as pulse can be generated by an elliptical polarized laser pulse at a wavelength of 400 nm with an ellipticity of ϵ=0.59. The efficiency of circular polarization attosecond pulse generation is interpreted based on a classical model of single electron recollision with the parent ion.
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Affiliation(s)
- Kai-Jun Yuan
- Laboratoire de Chimie Théorique, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
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471
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Mills MS, Kolesik M, Christodoulides DN. Dressed optical filaments. OPTICS LETTERS 2013; 38:25-27. [PMID: 23282826 DOI: 10.1364/ol.38.000025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In this Letter we show that by appropriately providing an auxiliary "dress" beam one can extend the longevity of an optical filament by almost one order of magnitude. These optical dressed filaments can propagate substantially further by judiciously harnessing energy from their secondary beam reservoir. This possibility is theoretically investigated in air when the filament is dressed with a conically convergent annular Gaussian beam.
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Affiliation(s)
- M S Mills
- CREOL, College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816-2700, USA
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472
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Mukamel S, Healion D, Zhang Y, Biggs JD. Multidimensional attosecond resonant X-ray spectroscopy of molecules: lessons from the optical regime. Annu Rev Phys Chem 2012; 64:101-27. [PMID: 23245522 PMCID: PMC3721744 DOI: 10.1146/annurev-physchem-040412-110021] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
New free-electron laser and high-harmonic generation X-ray light sources are capable of supplying pulses short and intense enough to perform resonant nonlinear time-resolved experiments in molecules. Valence-electron motions can be triggered impulsively by core excitations and monitored with high temporal and spatial resolution. We discuss possible experiments that employ attosecond X-ray pulses to probe the quantum coherence and correlations of valence electrons and holes, rather than the charge density alone, building on the analogy with existing studies of vibrational motions using femtosecond techniques in the visible regime.
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Affiliation(s)
- Shaul Mukamel
- Department of Chemistry, University of California, Irvine, California 92697, USA.
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473
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Relativistic frequency upshift to the extreme ultraviolet regime using self-induced oscillatory flying mirrors. Nat Commun 2012. [PMID: 23187631 PMCID: PMC3514503 DOI: 10.1038/ncomms2245] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Coherent short-wavelength radiation from laser–plasma interactions is of increasing interest in disciplines including ultrafast biomolecular imaging and attosecond physics. Using solid targets instead of atomic gases could enable the generation of coherent extreme ultraviolet radiation with higher energy and more energetic photons. Here we present the generation of extreme ultraviolet radiation through coherent high-harmonic generation from self-induced oscillatory flying mirrors—a new-generation mechanism established in a long underdense plasma on a solid target. Using a 30-fs, 100-TW Ti:sapphire laser, we obtain wavelengths as short as 4.9 nm for an optimized level of amplified spontaneous emission. Particle-in-cell simulations show that oscillatory flying electron nanosheets form in a long underdense plasma, and suggest that the high-harmonic generation is caused by reflection of the laser pulse from electron nanosheets. We expect this extreme ultraviolet radiation to be valuable in realizing a compact X-ray instrument for research in biomolecular imaging and attosecond physics. Generation of ultrafast X-rays using lab-based laser sources is promising for numerous spectroscopic and imaging techniques. By generating a long underdense plasma in a solid, Kim et al. show relativistic frequency upshift of a laser pulse to 4.9 nm, caused by reflection from electron nanosheets.
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474
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High-resolution, low-dose phase contrast X-ray tomography for 3D diagnosis of human breast cancers. Proc Natl Acad Sci U S A 2012; 109:18290-4. [PMID: 23091003 DOI: 10.1073/pnas.1204460109] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ~10-20% of palpable tumors are not detectable on mammograms and only about 40% of biopsied lesions are malignant. Here we report a high-resolution, low-dose phase contrast X-ray tomographic method for 3D diagnosis of human breast cancers. By combining phase contrast X-ray imaging with an image reconstruction method known as equally sloped tomography, we imaged a human breast in three dimensions and identified a malignant cancer with a pixel size of 92 μm and a radiation dose less than that of dual-view mammography. According to a blind evaluation by five independent radiologists, our method can reduce the radiation dose and acquisition time by ~74% relative to conventional phase contrast X-ray tomography, while maintaining high image resolution and image contrast. These results demonstrate that high-resolution 3D diagnostic imaging of human breast cancers can, in principle, be performed at clinical compatible doses.
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475
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Picón A, Jaroń-Becker A, Becker A. Enhancement of vibrational excitation and dissociation of H2(+) in infrared laser pulses. PHYSICAL REVIEW LETTERS 2012; 109:163002. [PMID: 23215074 DOI: 10.1103/physrevlett.109.163002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Indexed: 06/01/2023]
Abstract
We study vibrational excitations, dissociation, and ionization of H(2)(+) in few-cycle laser pulses over a broad wavelength regime. Our results of numerical simulations supported by model calculations show a many orders-of-magnitude enhancement of vibrational excitation and dissociation (over ionization) of the molecular ion at infrared wavelengths. The enhancement occurs without any chirping of the pulse, which was previously applied to take account of the anharmonicity of the molecular vibrations. The effect is related to strong-field two- and higher-order photon transitions between different vibrational states.
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Affiliation(s)
- A Picón
- JILA and Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309-0440, USA
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476
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Pomfret MB, Walker RA, Owrutsky JC. High-Temperature Chemistry in Solid Oxide Fuel Cells: In Situ Optical Studies. J Phys Chem Lett 2012; 3:3053-3064. [PMID: 26292249 DOI: 10.1021/jz3012047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Solid oxide fuels cells (SOFCs) are promising devices for versatile and efficient power generation with fuel flexibility, but their viability is contingent upon understanding chemical and material processes to improve their performance and durability. Newly developed in situ optical methods provide new insight into how carbon deposition varies with different hydrocarbon and alcohol fuels and depends on operating conditions. Some findings, such as heavier hydrocarbon fuels forming more carbon than lighter fuels, are expected, but other discoveries are surprising. For example, methanol shows a greater tendency to form carbon deposits than methane at temperatures below 800 °C, and kinetically controlled steam reforming with ethanol at high temperatures (∼800 °C) is less detrimental to SOFC performance than operating the device with dry methanol as the fuel. In situ optical techniques will continue to provide the chemical information and mechanistic insight that is critical for SOFCs to become a viable energy conversion technology.
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Affiliation(s)
- Michael B Pomfret
- †Chemistry Division, Naval Research Laboratory, Washington, DC 20375, United States
| | - Robert A Walker
- ‡Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Jeffrey C Owrutsky
- †Chemistry Division, Naval Research Laboratory, Washington, DC 20375, United States
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477
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Ishii N, Kaneshima K, Kitano K, Kanai T, Watanabe S, Itatani J. Sub-two-cycle, carrier-envelope phase-stable, intense optical pulses at 1.6 μm from a BiB3O6 optical parametric chirped-pulse amplifier. OPTICS LETTERS 2012; 37:4182-4. [PMID: 23073404 DOI: 10.1364/ol.37.004182] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We report on the generation of 9.0 fs, 550 μJ, carrier-envelope phase (CEP)-stabilized optical pulses around 1.6 μm at 1 kHz. Few-cycle IR pulses are obtained from a BiB(3)O(6) optical parametric chirped-pulse amplifier. The amplification of nearly octave-spanning ultrabroad pulses without spectral broadening results in good stability in output energy (0.85% rms) and CEP (160 mrad rms). We observed high harmonics in the water window from a neon cell that corresponds to a laser intensity of 4.1×10(14) W/cm(2).
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Affiliation(s)
- N Ishii
- Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581, Japan. ‑tokyo.ac.jp
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478
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Lee SK, Suits AG, Schlegel HB, Li W. A Reaction Accelerator: Mid-infrared Strong Field Dissociation Yields Mode-Selective Chemistry. J Phys Chem Lett 2012; 3:2541-2547. [PMID: 26295872 DOI: 10.1021/jz301038b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Mode-selective chemistry has been a dream of chemists since the advent of the laser in the 1970s. Despite intense effort, this goal has remained elusive due to efficient energy randomization in polyatomic molecules. Using ab initio molecular dynamics calculations, we show that the interaction of molecules with intense, ultrashort mid-infrared laser pulses can accelerate and promote reactions that are energetically and entropically disfavored, owing to efficient kinetic energy pumping into the corresponding vibrational mode(s) by the laser field. In a test case of formyl chloride ion photodissociation, the reactions are ultimately complete under field-free conditions within 500 fs after the laser pulse, which effectively overcomes competition from intramolecular vibrational energy redistribution (IVR). The approach is quite general and experimentally accessible using currently available technology.
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Affiliation(s)
- Suk Kyoung Lee
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Arthur G Suits
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - H Bernhard Schlegel
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Wen Li
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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479
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Andreasen J, Kolesik M. Nonlinear propagation of light in structured media: Generalized unidirectional pulse propagation equations. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:036706. [PMID: 23031052 DOI: 10.1103/physreve.86.036706] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 09/11/2012] [Indexed: 06/01/2023]
Abstract
Unidirectional pulse propagation equations [UPPE, Phys. Rev. E 70, 036604 (2004)] have provided a theoretical underpinning for computer-aided investigations into dynamics of high-power ultrashort laser pulses and have been successfully utilized for almost a decade. Unfortunately, they are restricted to applications in bulk media or, with additional approximations, to simple waveguide geometries in which only a few guided modes can approximate the propagating waveform. The purpose of this work is to generalize the directional pulse propagation equations to structures characterized by strong refractive index differences and material interfaces. We also outline a numerical solution framework that draws on the combination of the bulk-media UPPE method with single-frequency beam-propagation techniques.
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Affiliation(s)
- J Andreasen
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
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480
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Gardner DF, Zhang B, Seaberg MD, Martin LS, Adams DE, Salmassi F, Gullikson E, Kapteyn H, Murnane M. High numerical aperture reflection mode coherent diffraction microscopy using off-axis apertured illumination. OPTICS EXPRESS 2012; 20:19050-19059. [PMID: 23038545 DOI: 10.1364/oe.20.019050] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We extend coherent diffraction imaging (CDI) to a high numerical aperture reflection mode geometry for the first time. We derive a coordinate transform that allows us to rewrite the recorded far-field scatter pattern from a tilted object as a uniformly spaced Fourier transform. Using this approach, FFTs in standard iterative phase retrieval algorithms can be used to significantly speed up the image reconstruction times. Moreover, we avoid the isolated sample requirement by imaging a pinhole onto the specimen, in a technique termed apertured illumination CDI. By combining the new coordinate transformation with apertured illumination CDI, we demonstrate rapid high numerical aperture imaging of samples illuminated by visible laser light. Finally, we demonstrate future promise for this technique by using high harmonic beams for high numerical aperture reflection mode imaging.
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Affiliation(s)
- Dennis F Gardner
- JILA, University of Colorado, 440 UCB, Boulder, Colorado 80309-0440, USA.
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