LMI Seminar: Extending High Harmonic Generation to the Single Angstrom Level

Prof. James Rosenzweig, UCLA Dept. of Physics and Astronomy

09 August 2017, 13:00 
Auditorium 011, Engineering Class Room Building, Faculty of Engineering 
LMI Seminar

Abstract:

Coherent, ultra-fast X-rays are now an essential tool in science, created at the university lab scale as high harmonic generation (HHG) sources, and at the “big science” scale through free-electron lasers. Accessibility and smaller cost, as well as the natural fs-to-as time scale, make atom-based HHG very attractive, but it is limited to wavelengths approximately > nm.  In atomic physics, HHG enables much ultra-fast science, illuminating questions involving imaging of molecular orbitals in real-time, tunneling, wave function evolution in the continuum, electron rescattering, and delocalization. Atomic HHG is enabled by ionization of electrons, their quasi-free motion in the laser field, and subsequent recombination in the atomic core. The more energy given to the electron in its laser-induced oscillation, the higher harmonic that can be excited. To reach the shorter wavelengths, this aspect of the HHG interaction favors long wavelength l laser excitation. Unfortunately, longer l  also implies that the quasi-free electron wave-function has time to diffuse, making the atomic HHG ineffective above 5 μm. To extend HHG to hard X-rays, a new idea is discussed — to liberate electrons from a metallic surface, in arrays of blades forming a TEM transmission line (permitting solution of the phase matching issue afflicting HHG), and to induce HHG via interaction with the surface potential upon return. This surface interaction mitigates wave-function diffusion by avoiding use of a point-centered potential. HHG in this scenario, through probing the electron’s interactions experienced upon its return trajectory, is thus ideal for exploring the role of localization in laser-electron interactions, and may yield 1 Å coherent light on the table top. We report experimental progress in development of this idea. 

 

Tel Aviv University makes every effort to respect copyright. If you own copyright to the content contained
here and / or the use of such content is in your opinion infringing, Contact us as soon as possible >>