25/09/18 Mary: Laser filamentation for atmospheric purposes

Laser filamentation has many applications in remote sensing, air lasing, point-to-point communications and charge conduction. Also of interest are the photochemical reactions which are initiated by laser filamentation in humid air (RH >70%) which lead to nucleation and droplet condensation phenomena in warm conditions and secondary ice crystal growth in cirrus cloud conditions.

I present an overview of recent work and how this can be applied to climate models and atmospheric detection of particulate pollution and organic molecules

08/05/18: Sebastian Jarosch

01/05/18 Bruce Weaver Review on attosecond field synthesizer

10/04/18 Toby Banard: LCLS experiments, what did we do at our two beamtimes at LCLS in February.

20/03/18 Taran Driver: Journal club on his final stage assessment

13/03/18: Gediminas Galinis. LCLS experiments

Gediminas will give an overview of the experiments conducted at LCLS in January and February with participation of the members of the consortium.

06/03/18: [Preliminary] Dougie Garatt

27/02/18: Kaloyan Zlatanov: Optically stimulated second and third harmonic generation

Coherent nonlinear microscopy (CNM) is widely used in three-dimensional imaging of transparent samples, particularly for biological tissues [1]. Examples for parametric and label free CNM processes are second harmonic generation (SHG) and third harmonic generation (THG). However, working under far off-resonant excitation conditions usually leads to low optical conversion efficiencies. Hence, the typically low signals may lead to a bad signal-to-noise ratio and low image contrast. There are several approaches to enhance the signal yield in CNM, e.g. using dispersion to optimize the phase-matching integral [2]. One promising concept is the “Enhancement of Second-Order Nonlinear-Optical Signals by Optical Stimulation” [3]. The basic idea is to stimulate a nonlinear signal by already “seeding” with some  radiation at the harmonic frequency. The previous and first demonstration of the concept for SHG yielded signal enhancements more than 10  in a biologically relevant medium. We present strong enhancements of third harmonic generation by optical stimulation in a microscopy setup. The effect is most pronounced at low laser intensity and weak nonlinear susceptibilities, making it suitable in harmonic microscopy.

[1] S. Yue, M.N. Slipchenko, J.-X. Cheng, “Multimodal nonlinear optical microscopy”, Laser Photon. Rev. 5, 496–512 (2011).
[2] Christian Stock, Kaloyan Zlatanov, and Thomas Halfmann, “Dispersion-enhanced third-harmonic microscopy”, Optics Communications Vol. 393, 289-293 (2017).
[3] A. J. Goodman and W. A. Tisdale, “Enhancement of Second-Order Nonlinear-Optical Signals by Optical Stimulation”,  Phys. Rev. Lett. 114, 183902 (2015).

20/02/18: Timur Avni: Journal club on photoionization timedelays in neon

In particular will he cover the famous 2s-2p paper from MPQ using streaking, as well as a recent paper from Lund measuring time delays using the Rabbit technique. 

06/02/18: Daniel Greening. Attosecond surface science a topical review

Daniel will give a journal club as part of his 18-24 month review.

15/01/2018 Bruce: Diffraction and microscopy with attosecond electron pulse trains

Bruce will give  a journal club over the following paper from MPQ carching :

Diffraction and microscopy with attosecond electron pulse trains

https://www.nature.com/articles/s41567-017-0007-6