Daniel: DM: Third harmonic enhancement of VUV generation

I will report on simulations that suggest sub-femtosecond VUV pulse generation can be enhanced by mixing the driving IR field with its third harmonic. Previous experimental work has shown that below threshold harmonics can boost HHG from longer pulses.

Tobi: JC: Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses

In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub–4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems.

http://www.sciencemag.org/content/346/6207/336.abstract

Alvaro: X-ray pulse characterization at LCLS using XTCAV

X-ray free electron lasers rely on an accelerated electron bunch passing through an undulator to create and amplify x-ray pulses. This generation/amplification process leaves a signature on the electron bunch than is dependent on the temporal profile of the generated x-rays. By streaking the electron bunch after the generation and looking at the electron spectrum as a function of time it is possible to characterize the generated x-ray pulses on a shot to shot basis.

I am not going to present the paper itself, but if you want to include the link it could be useful to the curious attendee:
http://journals.aps.org/prstab/abstract/10.1103/PhysRevSTAB.14.120701

Will: JC: Attosecond Photoscopy of Plasmonic Excitations

We propose an experimental arrangement to image, with attosecond resolution, transient surface plasmonic excitations. The required modifications to state-of-the-art setups used for attosecond streaking experiments from solid surfaces only involve available technology. Buildup and lifetimes of surface plasmon polaritons can be extracted and local modulations of the exciting optical pulse can be diagnosed in situ.

DOI: http://dx.doi.org/10.1103/PhysRevLett.113.113903

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• Published 12 September 2014
• Received 20 January 2014

© 2014 American Physical Society

Jon: LCLS briefing + Zara: JC: Quasi-phase-matching-induced enhancement of high-order harmonics during two-colour pump of multi-jet plasmas

Jon: LCLS: probing hole dynamics in glycine 



Zara: Quasi-phase-matching-induced enhancement of high-order harmonics during two-colour pump of multi-jet plasmas

The first demonstration of quasi-phase-matching during high-order harmonic generation (HHG) of laser radiation in multi-jet plasmas produced on the silver and chromium targets under the conditions of two-colour pump (804 and 402 nm) is presented. We analyse the enhancement of the groups of odd and even harmonics along the plateau range and compare the harmonic yields using a different number of plasma jets. The comparison of extended line plasma and multi-jet plasma shows the advanced properties of the latter formation for the efficient HHG using the two-colour pump. The 25× and 13× enhancement factors of quasi-phase-matched harmonics were obtained in the cases of the two-colour and single-colour pumps of multi-jet plasmas.

http://iopscience.iop.org/0953-4075/47/10/105401

http://iopscience.iop.org/0953-4075/47/10/105401/pdf/0953-4075_47_10_105401.pdf

Davide: JC: Coherent phase-matched VUV generation by field-controlled bound states

The generation of high-order harmonics1 and attosecond pulses2 at ultrahigh repetition rates (>1 MHz) promises to revolutionize ultrafast spectroscopy. Such vacuum ultraviolet (VUV) and soft X-ray sources could potentially be driven directly by plasmonic enhancement of laser pulses from a femtosecond oscillator3, 4, but recent experiments suggest that the VUV signal is actually dominated by incoherent atomic line emission5, 6. Here, we demonstrate a new regime of phase-matched below-threshold harmonic generation, for which the generation and phase matching is enabled only near resonance structures of the atomic target. The coherent VUV line emission exhibits low divergence and quadratic growth with increasing target density up to nearly 1,000 torr mm and can be controlled by the sub-cycle field of a few-cycle driving laser with an intensity of only ~1 × 1013 W cm−2, which is achievable directly from few-cycle femtosecond oscillators with nanojoule energy7.

http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2014.83.html

Nick: JC: Frequency domain optical parametric amplification

Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43?mJ two-cycle pulses at 1.8?µm wavelength.

http://www.nature.com/ncomms/2014/140507/ncomms4643/full/ncomms4643.html#ref-link-38