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Coherence and interference effects in high harmonics generation and Above - Threshold Ionisation

Ziel

The project is dealing with the interaction of atoms with intense ultrashort light pulses and specifically with High-Harmonic Generation (HHG) and Above-Threshold Ionisation (ATI).
First, it explores novel approaches to the theory of HHG with the goal of improving the understanding of this process and achieving higher conversion efficiencies. Second it investigates the ionisation process in the tunnelling limit.

The objectives include:
To validate the concept of amplification of a high harmonic wave propagating through an atomic medium simultaneously irradiated by an intense infrared beam, to make quantitative predictions and to calculate and measure the gain;
To investigate HHG by two coherent laser beams with equal frequencies propagating in slightly different directions. The goal is to establish the new phase-matching condition and to optimise and control the harmonic intensity by varying the angle between the incident waves with fundamental frequency;
To calculate the duration of a high harmonic radiation pulse by using the quantum radiation theory approach. The goal is to compare results and interpretations following from the new approach and existing theories;
To obtain analytic expressions for the quantum distributions in the tunnelling limit of high-order ATI and HHG by individual atoms in an elliptically polarized laser field;
To investigate the influence of the detailed shape of the atomic binding potential on HHG and ATI.

The project involves experimental and theoretical research. The novel physical ideas stated in objectives 1, 2 will be investigated both experimentally and theoretically. Experiments related to these objectives will be carried out in Saclay while the MBI team and the NIS teams provide the relevant theory. These teams will, as well, be involved in theoretical investigations on the quantum theory of the HHG by individual atoms and on the quantum interference effects in the high energy ATI.
The expected results
The quantum theory of HHG and a quantitative prediction of the gain.
Experimental set-up allowing to amplify a harmonic wave travelling through the interaction volume pumped by a laser with the fundamental frequency.
A measured value of the gain of a harmonic wave.

The phase-matching condition in the case of two non-collinear pump waves.
A practical method allowing to optimise and control the harmonic intensity by varying the angle between the incident waves with fundamental frequency.

The relationship between the quantum and semi-classical approaches to HHG.

A set of approximate analytic formulas describing HHG by individual atoms and the high -energy part of the photoelectron distribution in elliptically polarized field taking into account quantum interference effects.

Established properties of high harmonic generation and above-threshold ionisation which essentially depend on the particular shape of the atomic potential and criteria of that influence.

Aufforderung zur Vorschlagseinreichung

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Finanzierungsplan

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Koordinator

Commissariat à l'Energie Atomique
EU-Beitrag
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Adresse
Centre d'Etudes de Saclay
91191 Gif-sur-Yvette
Frankreich

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Gesamtkosten
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Beteiligte (3)