| 1. |
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| 2. |
- Fordell, Thomas, et al.
(författare)
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Carrier-envelope phase stabilization of a multi-millijoule, regenerative-amplifier-based chirped-pulse amplifier system
- 2009
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Ingår i: Optics Express. - 1094-4087. ; 17:23, s. 21091-21097
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Tidskriftsartikel (refereegranskat)abstract
- This article reports on the successful stabilization of the carrier-envelope phase of a 1-kHz laser system that includes a large grating stretcher, a regenerative amplifier, a multipass amplifier and a grating compressor. Phase stability for pulse energies up to 6 mJ is demonstrated using electronic feedback to the oscillator locking electronics as well as feedback via an acousto-optic programmable dispersive filter. (C) 2009 Optical Society of America
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| 3. |
- Gaarde, Mette, et al.
(författare)
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High-order tunable sum and difference frequency mixing in the xuv region
- 1996
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 29:5
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of tunable high-order sum and difference frequency mixing in the 7-70 eV range, in xenon, argon and neon. We mix the light from a terawatt, subpicosecond titanium-sapphire laser and that from a tunable optical parametric generator. The radiation generated through mixing processes involves absorption or emission of one or Mo photons from the weak tunable source. The relative strengths of the sum and difference frequency processes depend strongly on the wavelength range of the generated radiation. The sum frequency processes are stronger at low photon energies in xenon, whereas the difference frequency processes dominate at high photon energies, in neon, being almost comparable to harmonic generation.
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| 4. |
- He, Xinkui, et al.
(författare)
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Interference effects in two-color high-order harmonic generation
- 2010
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 82:3
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Tidskriftsartikel (refereegranskat)abstract
- We study high-order harmonic generation in argon driven by an intense 800 nm laser field and a small fraction of its second harmonic. The intensity and divergence of the emitted even and odd harmonics are strongly modulated as a function of the relative delay between the two fields. We provide a detailed analysis of the underlying interference effects. The interference changes drastically when approaching the cutoff region due to a switch of the dominant trajectory responsible for harmonic generation.
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| 5. |
- He, Xinkui, et al.
(författare)
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Spatial and spectral properties of the high-order harmonic emission in argon for seeding applications
- 2009
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 79:6
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Tidskriftsartikel (refereegranskat)abstract
- We characterize and control the harmonic emission in the spectral and spatial domains in order to define in which conditions the harmonic radiation can be a high-quality seed for soft x-ray and x-ray free-electron lasers. The length of the gas cell, where harmonics are generated, was optimized and the energy per pulse was determined in absolute value with a calibrated x-ray photodiode. The beam spatial profile was measured and, in some conditions, a very collimated beam with a half-angle divergence below 1 mrad could be obtained. We also show that increasing the intensity of the fundamental laser field leads to a considerable broadening of the bandwidth of the harmonic radiation, allowing us to cover a large spectral range. This effect is due to fundamental reshaping leading to an efficient phase matching of both short- and long-trajectory contributions.
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| 6. |
- Hunsche, S, et al.
(författare)
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Ionization and fragmentation of C-60 via multiphoton-multiplasmon excitation
- 1996
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Ingår i: Physical Review Letters. - 1079-7114. ; 77:10, s. 1966-1969
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Tidskriftsartikel (refereegranskat)abstract
- We study the intensity dependence of ionization and fragmentation of buckminsterfullerene (C-60) in strong laser fields. Our data provide strong evidence that at intensities less than or similar to 10(14) W/cm(2) these processes occur predominantly via multiphoton excitation of the 20 eV plasmon resonance of C-60 At least two plasmons have to be created to initiate fragmentation or multiple ionization.
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| 7. |
- Kovacev, M, et al.
(författare)
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Extreme ultraviolet fourier-transform spectroscopy with high order harmonics
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 95:22
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a new scheme for extreme ultraviolet (xuv) Fourier-transform spectroscopy based on the generation of two phase-locked high-harmonic beams. It allows us to measure for the first time interferograms at wavelengths as short as 90 nm, and open the perspective of performing high-resolution Fourier-transform absorption spectroscopy in the xuv. Our measurements also demonstrate that a precise control of the relative phase of harmonic pulses can be obtained with an accuracy on an attosecond time scale, of importance for future xuv pump-xuv probe attosecond spectroscopy.
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| 8. |
- Lopez, Rodrigo, et al.
(författare)
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Amplitude and phase control of attosecond light pulses
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 94:3
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Tidskriftsartikel (refereegranskat)abstract
- We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into a gas cell containing argon atoms. The emitted light then goes through a hard aperture and a thin aluminum filter that selects a 30-eV bandwidth around a 30-eV photon energy and synchronizes all of the components, thereby enabling the formation of a train of almost Fourier-transform-limited single-cycle 170 attosecond pulses. Our experiment demonstrates a practical method for synthesizing and controlling attosecond waveforms.
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| 9. |
- Norin, Johan, et al.
(författare)
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Time-frequency characterization of femtosecond extreme ultraviolet pulses.
- 2002
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Ingår i: Physical Review Letters. - 1079-7114. ; 88:19, s. 193901-193901
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Tidskriftsartikel (refereegranskat)abstract
- We present energy-resolved cross-correlation measurements of an extreme ultraviolet (XUV) pulse, generated as the fifth harmonic (15.5 eV) of an intense 80 fs laser pulse centered at 400 nm. Spectrally resolving the cross-correlation signal allows us to characterize the time-dependent frequency of the XUV pulse. We find that the fifth harmonic has a small negative chirp in excess of that predicted by perturbation theory. In addition, by manipulating the chirp of the driving laser we can induce and measure a positive or a negative chirp on the XUV pulse.
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| 10. |
- Rudawski, Piotr, et al.
(författare)
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A high-flux high-order harmonic source.
- 2013
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 84:7
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Tidskriftsartikel (refereegranskat)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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