| 1. |
- Salieres, P, et al.
(author)
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Angular distributions of high-order harmonics generated by a femtosecond laser
- 1996
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 29:20, s. 4771-4786
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Journal article (peer-reviewed)abstract
- We present a systematic study of the angular distributions of high-order harmonics generated with a femtosecond Cr:LiSrAlF6 laser. We investigate the influence of different parameters, namely laser intensity, nonlinear order, nature of the gas and position of the laser focus relative to the generating medium. We show that when the laser is focused before the atomic medium, harmonics with regular spatial profiles can be generated with reasonable conversion efficiency. Their divergence does not depend directly on the nonlinear order, the intensity or even the nature of the generating gas, but rather on the region of the spectrum the considered harmonic belongs to, which is determined by the combination of the three preceding elements. When the focus is drawn closer to the medium, the distributions get increasingly distorted, becoming annular with a significant divergence for a focus right into-or after-the jet. We perform numerical simulations of the angular distributions. The simulated profiles reproduce remarkably well the experimental trends and are thus used to interpret them.
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| 2. |
- Antoine, P, et al.
(author)
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Attosecond pulse trains using high-order harmonics
- 1996
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In: Physical Review Letters. - 1079-7114. ; 77:7, s. 1234-1237
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Journal article (peer-reviewed)abstract
- We demonstrate that high-order harmonics generated by an atom in intense laser field form trains of ultrashort pulses corresponding to different trajectories of electrons that tunnel out of the atom and recombine. Propagation in an atomic jet allows us to select one of these trajectories, leading to a train of pulses of extremely short duration.
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| 3. |
- Antoine, P, et al.
(author)
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Theory of high-order harmonic generation by an elliptically polarized laser field
- 1996
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In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 53:3, s. 1725-1745
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Journal article (peer-reviewed)abstract
- We generalize a recently formulated theory of high-order harmonic generation by low-frequency laser fields [Anne L'Huillier et al., Phys. Rev. A 48, R3433 (1993)] to the case of an elliptically polarized light. Our theoretical description includes both the single-atom response and propagation. Phase matching significantly modifies the results obtained in the single-atom response. The results of our calculations, including propagation for both the intensity and polarization properties of harmonics as a function of laser ellipticity, compare very well with recent experimental observations.
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| 4. |
- Gaarde, Mette, et al.
(author)
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Theory of high-order sum and difference frequency mixing in a strong bichromatic laser field
- 1996
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In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 54:5, s. 4236-4248
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Journal article (peer-reviewed)abstract
- We generalize the recently formulated theory of high-order harmonic generation by low-frequency laser fields to the case of high-order sum and difference frequency mixing in a two-color field of noncommensurate frequencies in the optical-infrared regime. Our theoretical description includes both the single-atom response and propagation. We observe a different behavior of the sum and difference frequency mixing processes, in the single-atom response as well as in the propagation results. The results of our calculations including propagation compare very well with recent experimental observations.
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