Recollision processes – from measurement to control
Date | Di, 28.10.2014 | |
Time | 9.00 - 12.00 | |
Speaker | Nirit Dudovich | |
Location | ETH Zurich, Hönggerberg Campus, HPF G6 | |
Program | Attosecond techniques have opened up opportunities for time-resolved measurements of multi-electron dynamics on their natural time-scale in atoms, molecules, nano-structures, surfaces, and dielectrics, with attosecond pulses used to initiate or probe fast-evolving processes. Applying these pulses for measurement or control is based on the ability to manipulate their basic optical properties – the temporal shape, phase, and polarization. Can we extend the basic schemes of “pulse shaping” into the attosecond regime? In the lecture I will describe two approaches that enable us to manipulate the the basic properties of the harmonics via manipulating their generation mechanism. In the first study we import the tool box catastrophe theory into attosecond science. Many intriguing phenomena in nature—ranging from phase transitions to black holes—occur at singularities. A unique type of singularity common in wave phenomena, known as caustics, links processes observed in many different branches of physics. I will describe the role of caustics in the attosecond generation mechanism. I will show how caustics provide a deeper understanding of the basic mechanism underlying HHG production, in a regime where the simple semi-classical model describing the production diverges. Such an analysis provides us with a method to accurately ‘engineer’ the harmonic spectrum, leading to a tunable dramatic enhancement of a narrow spectral band. In the second study we explore the ability to “shape” the 2D trajectory of the recolliding electron. Inducing HHG by a two-color field in an orthogonal configuration enables us to accurately control and decouple the angle of ionization and the angle of recollision -- increasing the dimensionality of high harmonics experiments. As an example I will focus on an experiment where the 2D shaping resolves the symmetry of the atomic wavefunction with notably high contrast. Such accurate spatio-temporal control of the harmonics generation’s mechanism holds the potential of revealing and manipulating new phenomena that were previously inaccessible in many experimental observations. |
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Link | Nirit Dudovich |