idw – Informationsdienst Wissenschaft
Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
Abstract The spatial confinement of light using metallic nanostructures enables the enhancement of a multitude of different nonlinear optical phenomena, including harmonic generation, atomic ionization [1, 2], and nonlinear photoemission. This talk will discuss the nonlinear and field-driven interaction of electrons with localized optical near-fields at nanostructures over a broad range of physical parameters, with an emphasis on several examples of our recent [1-7] and ongoing work. Specifically, the characteristics of ultrafast photoelectron emission from nanoscopic cathodes is studied [3,4], alongside strategies to control this photoemission [5] and utilize it in time-resolved electron imaging and diffraction applications [6,7].
In one set of measurements, photoemission spectra from electrochemically etched metal nanotips are investigated using intense near- and mid-infrared laser pulses with wavelengths ranging from 400 nm to 10 μm [3-4]. The results demonstrate localized electron emission and ponderomotive acceleration up to energies of hundreds of eV. The measurements lead to the identification of a sub-cycle fielddriven regime, in which the near-field decay length plays a crucial role in the electron dynamics [4]. In a related geometry, we employ single-cycle terahertz (THz) transients to further control the nanotip photoemission [5]. Based on large enhancements of the THz field at the tip apex, gating and spectral streaking of the photoemission process is demonstrated. In this way, both the THz amplitude and its spatio-temporal decay can be characterized. The approach allows for a spectral tuning, i.e. stretching or compression, of the photoemission spectrum, features only attainable from the electron propagation within confined fields.
In an application of nanotip photoemission, the enhanced brightness of these electron sources [6, 7] can be used to implement Ultrafast Low-Energy Electron Diffraction (ULEED) and Ultrafast Transmission Electron Microscopy (UTEM). While ULEED allows for the study of structural dynamics.
Information on participating / attending:
Organisation: Prof. H. Fehske und Prof. L. Schweikhard
Kontakt: Institut für Physik
Felix-Hausdorff-Straße 6, 17489 Greifswald
Tel. 03834 86-4700, http://www.physik.uni-greifswald.de
Date:
11/13/2014 17:00 - 11/13/2014 18:00
Event venue:
Hörsaal, Institut für Physik
Felix-Hausdorff-Straße 6
17489 Greifswald
Mecklenburg-Vorpommern
Germany
Target group:
Scientists and scholars, Students
Relevance:
transregional, national
Subject areas:
Physics / astronomy
Types of events:
Presentation / colloquium / lecture
Entry:
11/07/2014
Sender/author:
Sabine Köditz
Department:
Presse- und Informationsstelle
Event is free:
no
Language of the text:
German
URL of this event: http://idw-online.de/en/event49089
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