Special projects between Bavaria and Georgia

Dr. M. Kling

Attosecond Imaging
Max-Planck-Institut für Quantenoptik, Garching

Prof. Dr. M. Stockman

Dep. of Physics & Astronomy
Georgia State University

Ultrafast nanoplasmonics: a key to future ultrahigh-speed communication devices

This collaboration is intended to give experimental and theoretical insight into the interaction of metallic nanostructures with optical radiation on the ultrafast timescale. Plasmonic excitations within such nanostructures tend to create highly localized and enhanced electromagnetic fields, making them interesting for implementation in optoelectronic devices. It will be examined, how the nanostructure's geometry and the waveform of the exciting laser pulse influences the plasmonic response and its propagation. Specially designed nanostructures combined with phase-stabilized few-cycle laser pulses may thus allow for coherent control of  the electromagnetic fields in the vicinity of the nanostructure. During this project, it is planned to establish an experimental tool based on photoemission electron microscopy for mapping the local electric fields with high spatial and temporal resolution for validating theoretical predictions.

Final report

The atomic-scale motion of electrons not only governs the fundamental processes of our everyday lives, but is also of key importance to new technologies in the fields of information and industrial and medical sciences. Ultrafast communications are dominated by laser-based fiber networks, for the development of which Charles Kao was honoured with the 2009 Nobel Prize in physics. Encoding and decoding of information, however, currently relies on the transformation from photon-based communication to electronics and vice-versa. Plasmonic devices can help to remove this bottle-neck and enable purely optical communication and information processing, working at orders of magnitude higher speeds reaching into the Petahertz domain.

Speeds in the Petahertz domain can be reached when electrons are driven by well-controlled optical light waves. Recent developments in attosecond metrology have allowed the generation of such (strong) light fields with spectra spanning more than an octave and near single-cycle pulse durations.

In order to utilize such light fields for the control of electron motion in nanostructured surface systems, we have theoretically explored their response to strong electric fields, in particular we studied the effect of metallization of dielectric nanofilms [1]. The metallization causes optical properties of a dielectric film to become similar to those of a plasmonic metal (strong absorption and negative permittivity at low optical frequencies).The manifestations of the metallization depend on the way the field is induced in the nanostructure. For excitation by an optical or terahertz wave electric field the metallization will cause high values of the permittivity and, consequently, bring about the plasmonic behavior of the system. This will lead, in particular, to screening of the external fields limiting the internal fields to the metallization field strength. In this case, the metallization effect is completely reversible. This will open up the field of nanoplasmonics to a variety of new dielectric and semiconductor nanosystems with a plethora of new phenomena possible. Among potential applications is an ultrafast field-effect transistor where an IR or optical femtosecond pulse controls a dielectric gate.

1. M. Durach, A. Rusina, M. F. Kling, and M. I. Stockman, Metallization of Nanofilms in Strong Adiabatic Electric Fields, Phys. Rev. Lett. 105, 086803-1-4 (2010).



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