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Headlines 2015

Apr 03, 2015

Les sources d’électrons pulsées représentent une alternative intéressante aux sources de photons X pulsées basées sur des systèmes laser de haute intensité.

Nous décrirons les méthodes actuelles de génération de paquets d’électrons ainsi que les techniques de caractérisation des paquets. Les résolutions temporelles et spatiales ultimes qu’il est possible d’atteindre à ce jour seront discutées. Nous exposerons les résultats obtenus lors de notre dernière campagne de mesure sur le serveur ELYSE de l’Université Paris-Sud en 2014, en collaboration avec une équipe de l’ISMO et la start-up ITEOX. Finalement, quelques applications seront mises en perspective.

Mar 03, 2015

Coherent diffractive imaging is a recent imaging technique that offers spatial resolutions of the order of the wavelength, thanks to the fact that it does not require any potentially aberrating optical elements. We recently demonstrated sub 100-nm resolution using XUV radiation created by infrared laser high order harmonic generation (HHG). However, the resolution is usually limited by the source spectral width. We propose a new lensless holographic imaging scheme that gives the ability to exploit the spectral and temporal properties of HHG emission. Through a clever positioning of the holographic reference, we demonstrate the possibility either to combine the spatial and spectral resolutions in a single laser pulse, or to achieve nanometer spatial or sub-femtosecond temporal resolutions.

Feb 12, 2015

Due to their considerable energy, extreme ultraviolet photons ionize all molecules, regardless of the details of their energy structure. For this reason ultrashort light pulses in this spectral range are second to none to probe photochemical processes. In particular they give access to information on the reaction intermediates, which are ephemeral structures whose spectroscopic properties are usually out of reach. Through a collaboration between the Laboratory interactions, dynamic and lasers - LIDyL (CEA), the intense laser center for applications - CELIA (CNRS / CEA / Univ Bordeaux.), The SOLEIL synchrotron, and the Laboratory collisions, aggregates, reactivity - LCAR (CNRS / Univ. Toulouse 3) we have developed a new laboratory scale source that delivers bright coherent ultrashort and quasi-circularly polarized pulses in the extreme ultraviolet. For this, we used resonant high order harmonic generation in a gas submitted to an intense laser pulse. Today, such a circularly polarized light is produced in this range of radiation by just a few large scale facilities such as synchrotrons and, with the notable exception of a few free electron lasers, only quasi-continuously. Specific polarization properties of this new source presage pump probe studies of processes occurring in chiral molecules, that is to say molecules that are not their own mirror image. The ubiquitous role of these molecules in organic chemistry and biology suggests many applications.

 

http://www.nature.com/nphoton/journal/v9/n2/full/nphoton.2014.314.html

Apr 03, 2015

Following UV absorption, many biomolecular systems are endowed with mechanisms of excited-states deactivation that ensure their photochemical stability. These (ultra)fast processes indeed provide an efficient way to dissipate the electronic energy into vibration, avoiding then structural damages which could affect their biological function. In order to determine and document the basic physical phenomena controlling the lifetime of excited states and to highlight the link between electronic dynamic and structure, we have developed a synergetic theory-experience approach combining Quantum chemistry and Spectroscopies laser. The theoretical challenge is double: i) identify in these complex systems, the critical motions responsible of the electronic relaxation and ii) treat in an accurate and balanced way the different excited states. This challenge is addressed thanks the implementation of an innovative computational multi-step and multi-level strategy. Understanding the fate of the energy absorbed is of fundamental importance and relevant to potential applications in many fields such as photochemistry, biology or material sciences.

Apr 03, 2015

Les sources d’électrons pulsées représentent une alternative intéressante aux sources de photons X pulsées basées sur des systèmes laser de haute intensité.

Nous décrirons les méthodes actuelles de génération de paquets d’électrons ainsi que les techniques de caractérisation des paquets. Les résolutions temporelles et spatiales ultimes qu’il est possible d’atteindre à ce jour seront discutées. Nous exposerons les résultats obtenus lors de notre dernière campagne de mesure sur le serveur ELYSE de l’Université Paris-Sud en 2014, en collaboration avec une équipe de l’ISMO et la start-up ITEOX. Finalement, quelques applications seront mises en perspective.

Mar 03, 2015

Coherent diffractive imaging is a recent imaging technique that offers spatial resolutions of the order of the wavelength, thanks to the fact that it does not require any potentially aberrating optical elements. We recently demonstrated sub 100-nm resolution using XUV radiation created by infrared laser high order harmonic generation (HHG). However, the resolution is usually limited by the source spectral width. We propose a new lensless holographic imaging scheme that gives the ability to exploit the spectral and temporal properties of HHG emission. Through a clever positioning of the holographic reference, we demonstrate the possibility either to combine the spatial and spectral resolutions in a single laser pulse, or to achieve nanometer spatial or sub-femtosecond temporal resolutions.

Feb 12, 2015

Due to their considerable energy, extreme ultraviolet photons ionize all molecules, regardless of the details of their energy structure. For this reason ultrashort light pulses in this spectral range are second to none to probe photochemical processes. In particular they give access to information on the reaction intermediates, which are ephemeral structures whose spectroscopic properties are usually out of reach. Through a collaboration between the Laboratory interactions, dynamic and lasers - LIDyL (CEA), the intense laser center for applications - CELIA (CNRS / CEA / Univ Bordeaux.), The SOLEIL synchrotron, and the Laboratory collisions, aggregates, reactivity - LCAR (CNRS / Univ. Toulouse 3) we have developed a new laboratory scale source that delivers bright coherent ultrashort and quasi-circularly polarized pulses in the extreme ultraviolet. For this, we used resonant high order harmonic generation in a gas submitted to an intense laser pulse. Today, such a circularly polarized light is produced in this range of radiation by just a few large scale facilities such as synchrotrons and, with the notable exception of a few free electron lasers, only quasi-continuously. Specific polarization properties of this new source presage pump probe studies of processes occurring in chiral molecules, that is to say molecules that are not their own mirror image. The ubiquitous role of these molecules in organic chemistry and biology suggests many applications.

 

http://www.nature.com/nphoton/journal/v9/n2/full/nphoton.2014.314.html



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