Time-frequency representation of autoionization dynamics in helium Busto, D; Barreau, L; Isinger, M ...
Journal of physics. B, Atomic molecular and optical physics/Journal of physics. B, Atomic, molecular and optical physics,
02/2018, Volume:
51, Issue:
4
Journal Article
Peer reviewed
Open access
Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known ...example of the important role of electron correlation in light-matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the ionized electron wave packet. Using an energy-resolved interferometric technique, we measure the spectral amplitude and phase of autoionized wave packets emitted via the sp2+ and sp3+ resonances in helium. These measurements allow us to reconstruct the corresponding temporal profiles by Fourier transform. In addition, applying various time-frequency representations, we observe the build-up of the wave packets in the continuum, monitor the instantaneous frequencies emitted at any time and disentangle the dynamics of the direct and resonant ionization channels.
Periodic and chaotic solitons in a semiconductor laser with saturable absorber Vahed, H.; Prati, F.; Turconi, M. ...
Philosophical transactions - Royal Society. Mathematical, Physical and engineering sciences/Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences,
10/2014, Volume:
372, Issue:
2027
Journal Article
Peer reviewed
Open access
In a semiconductor laser with saturable absorber, solitons may spontaneously drift and/or oscillate. We study three different regimes characterized by strong intensity oscillations, both periodic and ...chaotic. We show that (i) soliton dynamics may be similar to that of passively Q-switched lasers, (ii) solitons may drift and oscillate simultaneously, and (iii) chaotic solitons may coexist with stationary ones and with the laser off solution.
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Excitable localized states, spatial structures which possess both the features of temporal excitable pulses and of transverse cavity solitons, have been theoretically predicted in model systems as ...single pulses of light localized in space with a finite and deterministic duration. We study experimentally the nucleation of laser localized structures on a device defect and its motion along a spatial gradient. We demonstrate that in the reference frame of the drifting localized structure, the resulting dynamics presents the typical features of excitable systems. In particular, for specific parameter values, we observe that the nucleation of laser localized structures is triggered by noise, while the drift of the localized structure up to a spatial region where it vanishes provides the deterministic orbit which brings the system back to its initial rest state. The control of such structures may open the way to novel applications of localized structures beyond that of simple stationary bits.
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Laser-localized structures have been observed in several experiments based on broad-area semiconductor lasers. They appear as bounded regions of laser light emission which can exist independently of ...each other and are expected to be commuted via external optical perturbations. In this work, we perform a statistical analysis of time-resolved commutation experiments in a system of coupled lasers and show the role of wavelength, polarization and pulse energy in the switching process. Furthermore, we also analyse the response of the system outside of the stability region of laser-localized states in search of an excitable response. We observe not only a threshold separating two types of responses, but also a strong variability in the system's trajectory when returning to the initial stable fixed point.
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Using a spectrally resolved electron interferometry technique, we measure photoionization time delays between the 3s and 3p subshells of argon over a large 34-eV energy range covering the Cooper ...minima in both subshells. The observed strong variations of the 3s − 3p delay difference, including a sign change, are well reproduced by theoretical calculations using the two-photon two-color random-phase approximation with exchange. Strong shake-up channels lead to photoelectrons spectrally overlapping with those emitted from the 3s subshell. These channels need to be included in our analysis to reproduce the experimental data. Our measurements provide a benchmark for multielectronic theoretical models aiming at an accurate description of interchannel correlation.
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Synopsis Photoionization time delays between the 3s and 3p subshells of argon have been measured over a large energy range (35-70eV) covering the Cooper minima in both subshells, providing stringent ...tests for interchannel correlation theories.
In spite of numerous theoretical and experimental reports of excitability in lasers with injected signal based on the locking-unlocking transition, the response of the system to controlled external ...perturbations (which is at the basis of the definition of excitable systems) has not been experimentally studied yet. In the following, we analyze the response of an injection-locked semiconductor laser to different external perturbations. We demonstrate the existence of a perturbation threshold beyond which the response of the system is independent of the strength of the stimulation and, thus, demonstrate its excitable character. We show that optically perturbing such an excitable system via the control of the phase of the injection beam can be useful for optical pulse generation.
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The formation of long stationary filaments resulting in uniform high density plasma strings in air using short pulse UV laser Bessel beams is shown. The length and the electron density of the plasma ...strings can be easily tuned by adjusting the conical Bessel wavefront angle. It is shown that in this regime the length of the plasma string can be extended over meter-long scales without any compromise in the string uniformity or any temporal evolution of the filamented laser pulse.
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Laser solitons are bistable localized laser beams that can be independently addressed by a local optical perturbation in form of a narrow beam. They can form in the transverse section of broad-area ...laser systems when suitable conditions are created. At difference with cavity solitons in driven microresonator, their phase is not fixed by any driving field and therefore no fixed phase relation between laser solitons should be expected. In this paper we analyze experimentally the mutual coherence of single-peak laser solitons and of multi-peaks laser solitons or clusters that coexist in the output beam of a laser system. We show that independent laser solitons are not mutually coherent while the peaks of a cluster have a well established mutual phase relationship.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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