Seminars Archive

Ultrafast Material Science Using the High Harmonic Generation Process

Abstract
The growing need for coherent and intense pulsed radiation is spread among many research disciplines, raging from biology to nanotechnology. Conventional lasers have been able to provide ultrashort coherent pulses in the infrared and visible region of the electromagnetic spectrum. A greater challenge is to provide the same characteristics in the extreme ultraviolet (XUV) and X-ray regime. Until recently, most X-ray science was conducted at large synchrotron facilities, where the synchrotron light produced by the spontaneous (incoherent) emission of relativistic electrons passing through magnetic devices is partially able to meets these requirements, but with only moderate time resolution. New technological advances in the last decades have made it possible to overcome these limitations and generate coherent XUV and Xray ultrashort pulses (tens of femtoseconds, or shorter). Most notable sources are free-electron lasers (FEL) and devices based on laser high harmonic generation (HHG). While the free-electron laser is an electron accelerator based light source (also referred to as a 4th generation synchrotron), the HHG involves commercially available femtosecond laser systems, making it a table-top setup suitable for a laboratory environment. The availability of such ultrashort X-ray pulses paves the way for a completely new generation of experiments that can capture the coupled dynamics of elementary excitations in materials. Ultrashort XUV and Xray pulses provide access to fundamental interactions between charge, lattice, orbital, and spin dynamics in real time, which eventually determine the intrinsic physical limits at which, for example, the magnetic processes of a material occurs.
In the following talk I will present the experimental work which takes full advantage of the HHG process. This includes the dynamic behavior of a correlated electron material studied via the angle-resolved photoemission spectroscopy experiment, and the demagnetization dynamic of Permalloy investigated via the magneto-optical Kerr effect.