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Tuesday, 12 July 2011

DM extraordinaire: Will & Henry:Talk and Poster presentation for Toulouse and Erice

Will: Poster Erice Summer school: Compression of multi-millijoule pulses using circular polarization with a differentially pumped hollow-fiber

We have compared the performance of a hollow-fiber pulse compression system using both statically filled and differentially pumped configurations. The fibre is seeded using 3mJ, carrier-envelope phase stabilized pulses with either linear or circular polarization. We have found that the most desirable performance of the system is achieved by combining the use of circularly polarized pulses with differential pumping. In this case, a significantly higher energy transmission was measured at 1bar helium pressure, compared with the transmissions for differential pumping with linear polarization, and for both polarization cases under static fill. For a differentially pumped fiber, the broadest spectra were found at 3bar for both polarizations. Linear and circular polarizations both produced spectra supporting sub-4-fs pulse durations, but a higher energy transmission was observed in the circularly polarized case. The performace of the system is improved by differential pumping and circularly polarized pulses as a result of reduced ionization and self-focusing at the fiber entrance. We envisage that our technique will be useful for increasing the energy of few-cycle pulses, for strong field experiments at higher intensities.

Henry: Talk Toulouse FASTQUAST YEP meeting: High-order Harmonic generation from plasma plumes at KHz repetition rate

I am giving my first scientific talk outside of imperial at the YEP meeting in Toulouse in just under a couple of weeks. So I would like to run through the presentation I plan to give and get your feedback. In this talk I will be presenting the some of the resent progress we have with HHG for plasma plumes at KHz repetition rate, including the presence of Quantum path signature and resonant enhancement of certain harmonics from particular tarjets.

Tuesday, 5 July 2011

JC: Felix: Attosecond control of electron-ion recollision in high harmonic generation

We show that high harmonic generation driven by an intense near-infrared (IR) laser can be temporally controlled when an attosecond pulse train (APT) is used to ionize the generation medium, thereby replacing tunnel ionization as the first step in the well-known three-step model. New harmonics are formed when the ionization occurs at a well-defined time within the optical cycle of the IR field. The use of APT-created electron wave packets affords new avenues for the study and application of harmonic generation. In the present experiment, this makes it possible to study harmonic generation at IR intensities where tunnel ionization does not give a measurable signal.