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Tuesday, 26 February 2013

Davide: VUV double whammy

Extreme-ultraviolet pump–probe studies of one-femtosecond-scale electron dynamics

Observation of Ultrafast Charge Migration in an Amino Acid

and maybe a discussion of some first results?

Tuesday, 19 February 2013

Thomas: Manipulation of quantum paths for space–time characterization of attosecond pulses

Attosecond extreme-ultraviolet pulses1 have a complex space–time structure2. However, at present, there is no method to observe this intricate detail; all measurements of the duration of attosecond pulses are, to some extent, spatially averaged1, 3, 4, 5. A technique for determining the full space–time structure would enable a detailed study of the highly nonlinear processes that generate these pulses as a function of intensity without averaging6, 7. Here, we introduce and demonstrate an all-optical method to measure the space–time characteristics of an isolated attosecond pulse. Our measurements show that intensity-dependent phase and quantum-path interference both play a key role in determining the pulse structure. In the generating medium, the attosecond pulse is strongly modulated in space and time. Propagation modifies but does not erase this modulation. Quantum-path interference of the single-atom response, previously obscured by spatial and temporal averaging, may enable measuring the laser-field-driven ion dynamics with sub-cycle resolution.

Tuesday, 12 February 2013

Han: Generation of EUV radiation by plasmonic field enhancement using nano-structured bowties and funnel-waveguides

Generation of EUV radiation by plasmonic field enhancement using nano-structured bowties and funnel-waveguides

Recent experimental data of high-order harmonic generation (HHG), obtained by use of the plasmonic field enhancement of nanostructure bowties and funnel-waveguides, are presented. Emphasis is laid on reproduction of previous experimental results and also elucidation of the fundamental limitations associated with the nanostructure thermal damage, small laser-gas interaction volume, and atomic line emission in the plasmon-driven HHG process. In addition, the dominance of coherent harmonics is quantitatively verified by implementing a two-beam interference experiment using a pair of funnel-waveguides. This study proves that funnel-waveguides are a superior plasmonic device capable of providing not only high thermal immunity but also sufficient atom emitters to produce practically usable extreme-ultraviolet (EUV) radiation in a reproducible manner.

Tuesday, 5 February 2013

Yusuke: HHG in aligned molecules with CEP-controlled pulses

High-order harmonics generated aligned molecules with CEP-controlled pulses are investigated. With short duration pulses harmonics are spectrally broadened due to non-adiabatic effect, which give rise to interferences between adjacent odd harmonics. The overlapped harmonics create interferences that become visible by locking the CEP. The interference contains the information of the phase of harmonics. We compare spectra generated with 25 fs pulses and spectra generated with 10 fs pulses. We have found some characteristics of the interference observing order dependence and molecular alignment dependence of the interference.