| Résumé | Researchers have discovered that pushing the limits of nonlinear optics allows them to produce extreme ultraviolet laser attosecond pulses that are much shorter than the period of the visible or infrared light from which they are generated. The pulses, together with the extreme nonlinear physics that generated them, form a new set of tools that are like the laser. The most intuitive way to understand the extreme nonlinear interaction that leads to attosecond pulses is through the semi-classical re-collision model. A strong infrared light pulse illuminating an atom or molecule creates a free electron wave packet by multiphoton ionization, usually approximated by tunneling. One free from the atom, components of the wave packet respond in a classical-like manner. Photo-ionization of a simple atom produces a photo-electron replica of the attosecond pulse. Every attosecond pulse is perfectly synchronized to the time-dependent field of an infrared pulse. |
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