Attosecond Science with Long Wavelength Laser Sources: Soft X-ray Attosecond Pulses and High Harmonic Spectroscopy
September 13th, 2017 ALLAN JOHNSON Imperial College London

The driving technology for attosecond measurements and attosecond science has so far been the 800 nm wavelength titanium-sapphire laser. The use of longer wavelength driving sources (1.5 to 3 microns) has numerous advantages for the generation of attosecond pulses, allowing harmonics to be generated in the soft X-ray, as well as for self-referenced (re-collision based) attosecond measurements, where longer wavelengths increase the time window and enable the study of larger molecules. Here I’ll present some recent results using longer wavelength sources for attosecond science. Using a few-cycle driving field at 1.8 microns, we have generated carrier-envelope phase dependent harmonics beyond the oxygen K-edge (540 eV) with a flux in the important water window spectral region (284-540 eV) that is ten times higher than previously demonstrated. With advanced diagnostics and modelling, we show that the plasma response of the medium strongly spatio-temporally re-shapes the driving field and leads to transient buildup of the harmonic radiation in space and time. Additionally, I will present some new results in high harmonic spectroscopy of benzenes with 1.8 micron laser fields, where we precisely control the macroscopic response and demonstrate a new method of extracting meaningful dynamical information from harmonic spectra of un-aligned complex molecules.

Seminar, September 13, 2017, 12:00. ICFO Seminar Room

Hosted by Simon Wall