41 results found
Krebs M, Hadrich S, Demmler S, et al., 2013, Towards isolated attosecond pulses at megahertz repetition rates., Nature Photonics
The strong-field process of high-harmonic generation is the foundation for generating isolated attosecond pulses1, which are the fastest controllable events ever induced. This coherent extreme-ultraviolet radiation has become an indispensable tool for resolving ultrafast motion in atoms and molecules2, 3. Despite numerous spectacular developments in the new field of attoscience2, 3, 4, the low data-acquisition rates imposed by low-repetition-rate (maximum of 3 kHz) laser systems5 hamper the advancement of these sophisticated experiments. Consequently, the availability of high-repetition-rate sources will overcome a major obstacle in this young field. Here, we present the first megahertz-level source of extreme-ultraviolet continua with evidence of isolated attosecond pulses using a fibre laser-pumped optical parametric amplifier6 for high-harmonic generation at 0.6 MHz. This 200-fold increase in repetition rate will enable and promote a vast variety of new applications, such as attosecond-resolution coincidence and photoelectron spectroscopy7, or even video-rate acquisition for spatially resolved pump–probe measurements.
Driever S, Bigourd D, Fedorov N, et al., 2013, Tunable 1.6–2 μm near infrared few-cycle pulse generation by filamentation, Applied Physics Letters, Vol: 102, Pages: 191119-191119, ISSN: 0003-6951
We present results on tunable few-cycle laser pulses generated in the near infrared region obtained by filamentation in a krypton cell combined with group velocity dispersion compensation in fused silica. We obtain a spectral broadening of a factor ∼2–3 over the entire spectral domain studied. The central wavelength is tuned from 1.6 μm to 2 μm via an optical parametric amplification source. In optimum experimental conditions, where the input central wavelength is set to 1.7 μm, 1.8 μm, and 1.9 μm, the incident power to the gas cell exceeded the critical power of Krypton by a factor of ∼4 and the achieved spectral broadening covered ∼300 nm. Using group velocity compensation in bulk fused silica, we obtain near infrared output pulses as short as 2–3 optical cycles with 200 μJ energy per pulse. This near infrared filamentation tunable few-cycle pulse source is an important achievement for strong field physics applications such as attoscience, where wavelength scaling has an important effect.
Shaaran T, Ciappina MF, Guichard R, et al., 2013, High-order-harmonic generation by enhanced plasmonic near-fields in metal nanoparticles, Physical Review A, Vol: 87, ISSN: 1050-2947
Zair A, Siegel T, Sukiasyan S, et al., 2013, Molecular internal dynamics studied by quantum path interferences in high order harmonic generation, CHEMICAL PHYSICS, Vol: 414, Pages: 184-191, ISSN: 0301-0104
Pérez-Hernández JA, Ciappina MF, Lewenstein M, et al., 2013, Beyond CarbonK-Edge Harmonic Emission Using a Spatial and Temporal Synthesized Laser Field, Physical Review Letters, Vol: 110, ISSN: 0031-9007
Ganeev RA, Hutchison C, Witting T, et al., 2012, High-order harmonic generation in graphite plasma plumes using ultrashort laser pulses: a systematic analysis of harmonic radiation and plasma conditions, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 45, ISSN: 0953-4075
Ganeev RA, Strelkov VV, Hutchison C, et al., 2012, Experimental and theoretical studies of two-color-pump resonance-induced enhancement of odd and even harmonics from a tin plasma, PHYSICAL REVIEW A, Vol: 85, ISSN: 1050-2947
Ganeev RA, Hutchison C, Zair A, et al., 2012, Enhancement of high harmonics from plasmas using two-color pump and chirp variation of 1 kHz Ti:sapphire laser pulses, OPTICS EXPRESS, Vol: 20, Pages: 90-100, ISSN: 1094-4087
Brugnera L, Hoffmann DJ, Siegel T, et al., 2011, Trajectory Selection in High Harmonic Generation by Controlling the Phase between Orthogonal Two-Color Fields, PHYSICAL REVIEW LETTERS, Vol: 107, ISSN: 0031-9007
Perez-Hernandez JA, Roso L, Zair A, et al., 2011, Valley in the efficiency of the high-order harmonic yield at ultra-high laser intensities, OPTICS EXPRESS, Vol: 19, Pages: 19430-19439, ISSN: 1094-4087
Ganeev RA, Hutchison C, Siegel T, et al., 2011, Quantum path signatures in harmonic spectra from metal plasma, PHYSICAL REVIEW A, Vol: 83, ISSN: 1050-2947
Ganeev RA, Hutchison C, Siegel T, et al., 2011, High-order harmonic generation from metal plasmas using 1 kHz laser pulses, JOURNAL OF MODERN OPTICS, Vol: 58, Pages: 819-824, ISSN: 0950-0340
Varela O, Alonso B, Sola IJ, et al., 2010, Self-compression controlled by the chirp of the input pulse, OPTICS LETTERS, Vol: 35, Pages: 3649-3651, ISSN: 0146-9592
Alonso B, Zair A, San Roman J, et al., 2010, Femtosecond multi-filamentation control by mixture of gases: towards synthesised nonlinearity, OPTICS EXPRESS, Vol: 18, Pages: 15467-15474, ISSN: 1094-4087
Skopalova E, El-Taha YC, Zair A, et al., 2010, Pulse-Length Dependence of the Anisotropy of Laser-Driven Cluster Explosions: Transition to the Impulsive Regime for Pulses Approaching the Few-Cycle Limit, PHYSICAL REVIEW LETTERS, Vol: 104, ISSN: 0031-9007
Alonso B, Sola IJ, Varela O, et al., 2010, Spatiotemporal amplitude-and-phase reconstruction by Fourier-transform of interference spectra of high-complex-beams, JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS, Vol: 27, Pages: 933-940, ISSN: 0740-3224
Siegel T, Torres R, Hoffmann DJ, et al., 2010, High harmonic emission from a superposition of multiple unrelated frequency fields, OPTICS EXPRESS, Vol: 18, Pages: 6853-6862, ISSN: 1094-4087
Sansone G, Benedetti E, Caumes JP, et al., 2009, Shaping of attosecond pulses by phase-stabilized polarization gating, PHYSICAL REVIEW A, Vol: 80, ISSN: 1050-2947
Auguste T, Salieres P, Wyatt AS, et al., 2009, Theoretical and experimental analysis of quantum path interferences in high-order harmonic generation, PHYSICAL REVIEW A, Vol: 80, ISSN: 1050-2947
Cormier E, Zair A, Holler M, et al., 2009, Direct observation of quantum-path interferences in high order harmonic generation, EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, Vol: 175, Pages: 191-194, ISSN: 1951-6355
Perez-Hernandez JAPH, Hoffmann DJH, Zair AZ, et al., 2009, Extension of the cut-off in high-harmonic generation using two delayed pulses of the same colour, Pages: 1-9, ISSN: 0953-4075
We demonstrate a novel technique for an extension of the cut-off frequency in high-harmonic generation using a shaped field, consisting of two delayed pulses, identical in all parameters except a carrier envelope phase shift of pi. We obtain high harmonics up to an energy of 5.5U(p) + I(p), surpassing the conventional limit of 3.17U(p) + I(p). For high intensities approaching the threshold for barrier suppression ionization, beyond which no harmonics are generated, this mechanism acquires practical importance as a means to overcome the limit imposed by saturation. We analyse the underlying mechanism using both classical and quantum approaches, and highlight the role of the shaped field in modifying the electron trajectories in the continuum to enhance the collection of kinetic energy from the driving field. Of greatest importance are the trajectories describing electrons ionized across the first peak of the laser field which receive the enhanced kinetic energies responsible for the cut-off extension above the conventional limit. Interestingly, the most energetic trajectories do not contribute to the harmonic cut-off in the single pulse case. We conclude with a discussion of the sub-cycle structure of the emitted harmonic radiation and possible applications of the technique.
Holler MH, Zair AZ, Schapper FS, et al., 2009, Ionization effects on spectral signatures of quantum-path interference in high-harmonic generation, Optics Express, Vol: 17, Pages: 5716-5722, ISSN: 1094-4087
The interference between the emission originating from the short and long electron quantum paths is intrinsic to the high harmonic generation process. We investigate the universal properties of these quantum-path interferences in various generation media and discuss how ionization effects influence the observed interference structures. Our comparison of quantum-path interferences observed in xenon, argon, and neon demonstrates that our experimental tools are generally applicable and should also allow investigating more complex systems such as molecules or clusters.
Varela OV, Zair AZ, San Roman JSR, et al., 2009, Above-millijoule super-continuum generation using polarisation dependent filamentation in atoms and molecules, Optics Express, Vol: 17, Pages: 3630-3639, ISSN: 1094-4087
We demonstrate for the first time that input polarisation control inducing one single filamentation is a very robust technique to accurately control the filamentation dynamics enhancing throughput energy of the supercontinuum generation up to 1.2 millijoule. Reaching the above-millijoule regime opens the way to post-compression of multi-terawatt laser pulses.
Varela O, Zair A, San Roman J, et al., 2009, Above-millijoule continuum generation using polarisation dependent filamentation in atoms and molecules, Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference (CLEO/QELS 2009), Publisher: IEEE, Pages: 720-721
Zair AZ, Holler MH, Guandalini AG, et al., 2008, Quantum path interferences in high-order harmonic generation, Physical Review Letters, Vol: 100, Pages: 143902-1-143902-4, ISSN: 0031-9007
We have investigated the intensity dependence of high-order harmonic generation in argon when the two shortest quantum paths contribute to the harmonic emission. For the first time to our knowledge, experimental conditions were found to clearly observe interference between these two quantum paths that are in excellent agreement with theoretical predictions. This result is a first step towards the direct experimental characterization of the full single-atom dipole moment and demonstrates an unprecedented accuracy of quantum path control on an attosecond time scale.
ZAIR A, Holler M, Schapper F, et al., 2007, Observation electronic trajectories interference in high-order harmonicgeneration process, ICPEAC, Freiburg, Germany 2007
Zaïr A, Guandalini A, Schapper F, et al., 2007, Spatio-temporal characterization of few-cycle pulses obtained by filamentation, Optics Express, Vol: 15, Pages: 5394-5394
ZAIR A, 2006, Generation and characterisation of attosecond pulses via high order harmonics generation
Sola IJ, Zair A, Lopez-Martens R, et al., 2006, Temporal and spectral studies of high-order harmonics generated by polarization-modulated infrared fields, PHYSICAL REVIEW A, Vol: 74, ISSN: 1050-2947
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