| 1. |
- Chalupsky, J, et al.
(författare)
-
Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses
- 2009
-
Ingår i: Optics Express. - 1094-4087. ; 17:1, s. 208-217
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first observation of single-shot soft x-ray laser induced desorption occurring below the ablation threshold in a thin layer of poly ( methyl methacrylate) - PMMA. Irradiated by the focused beam from the Free-electron LASer in Hamburg ( FLASH) at 21.7nm, the samples have been investigated by atomic-force microscope (AFM) enabling the visualization of mild surface modifications caused by the desorption. A model describing non-thermal desorption and ablation has been developed and used to analyze single-shot imprints in PMMA. An intermediate regime of materials removal has been found, confirming model predictions. We also report below-threshold multiple-shot desorption of PMMA induced by high-order harmonics (HOH) at 32nm. Short-time exposure imprints provide sufficient information about transverse beam profile in HOH's tight focus whereas long-time exposed PMMA exhibits radiation-initiated surface hardening making the beam profile measurement infeasible. (C) 2008 Optical Society of America
|
|
| 2. |
- Corde, S., et al.
(författare)
-
Betatron emission as a diagnostic for injection and acceleration mechanisms in laser plasma accelerators
- 2012
-
Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 54:12
-
Tidskriftsartikel (refereegranskat)abstract
- Betatron x-ray emission in laser plasma accelerators is a promising compact source that may be an alternative to conventional x-ray sources, based on large scale machines. In addition to its potential as a source, precise measurements of betatron emission can reveal crucial information about relativistic laser-plasma interaction. We show that the emission length and the position of the x-ray emission can be obtained by placing an aperture mask close to the source, and by measuring the beam profile of the betatron x-ray radiation far from the aperture mask. The position of the x-ray emission gives information on plasma wave breaking and hence on the laser non-linear propagation. Moreover, the measurement of the longitudinal extension helps one to determine whether the acceleration is limited by pump depletion or dephasing effects. In the case of multiple injections, it is used to retrieve unambiguously the position in the plasma of each injection. This technique is also used to study how, in a capillary discharge, the variations of the delay between the discharge and the laser pulse affect the interaction. The study reveals that, for a delay appropriate for laser guiding, the x-ray emission only occurs in the second half of the capillary: no electrons are injected and accelerated in the first half.
|
|
| 3. |
- Hort, O., et al.
(författare)
-
High-flux source of coherent XUV pulses for user applications
- 2019
-
Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 27:6, s. 8871-8883
-
Tidskriftsartikel (refereegranskat)abstract
- We present experimental results obtained at a user-oriented XUV beamline implemented at the ELI Beamlines facility. The coherent XUV radiation is produced via high harmonic generation in gases in a loose focusing geometry. The heamline is designed to be driven by 1 kHz, 100 mJ, 20 Is pulses centered at a wavelength of 830 nm. Results such as XUV spectra, beam wavefront and pulse energy obtained during the heamline commissioning with a commercial 1 kHz, 5 mJ, 40 fs laser system are presented. A unique XUV spectrometer for source characterization designed to reach a very high sensitivity is described in detail, and we demonstrate a novel technique for single shot and every shot. XUV pulse energy measurement. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.
|
|
| 4. |
- Balcou, P, et al.
(författare)
-
High-order-harmonic generation: towards laser-induced phase-matching control and relativistic effects
- 2002
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 74:6, s. 509-515
-
Tidskriftsartikel (refereegranskat)abstract
- We present a review of some recent results on high-order-harmonic generation, aiming at optimizing the photon flux to allow for future applications in extreme-ultra-violet non-linear optics. We first present new schemes to control phase matching of high harmonics in gases, by using the effect of the spatially varying atomic phase displayed by the high harmonics. An enhancement by a factor of 50 is observed in neon in conditions for which the gradient of the atomic dispersion balances the electronic dispersion. A new scheme to manipulate the laser field was demonstrated, and shown to improve phase matching. We then turn to high-harmonic generation by solid targets, and show that high harmonics generated by an intense 30-fs laser pulse remain collimated even at the threshold of the relativistic regime.
|
|
