Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Asymmetric plasmonic antennas deliver femtosecond pulses for fast optoelectronics

26.06.2018

A team headed by the TUM physicists Alexander Holleitner and Reinhard Kienberger has succeeded for the first time in generating ultrashort electric pulses on a chip using metal antennas only a few nanometers in size, then running the signals a few millimeters above the surface and reading them in again a controlled manner. The technology enables the development of new, powerful terahertz components.

Classical electronics allows frequencies up to around 100 gigahertz. Optoelectronics uses electromagnetic phenomena starting at 10 terahertz. This range in between is referred to as the terahertz gap, since components for signal generation, conversion and detection have been extremely difficult to implement.


Pulses of femtosecond length from the pump laser (left) generate on-chip electric pulses in the terahertz frequency range. With the right laser, the information is read out again.

Image: Christoph Hohmann / NIM, Alexander Holleitner / TUM


Electronmicroscopic image of the chip with asymmetric plasmonic antennas made from gold on sapphire.

Image: Alexander Holleitner / TUM

The TUM physicists Alexander Holleitner and Reinhard Kienberger succeeded in generating electric pulses in the frequency range up to 10 terahertz using tiny, so-called plasmonic antennas and run them over a chip. Researchers call antennas plasmonic if, because of their shape, they amplify the light intensity at the metal surfaces.

Asymmetric antennas

The shape of the antennas is important. They are asymmetrical: One side of the nanometer-sized metal structures is more pointed than the other. When a lens-focused laser pulse excites the antennas, they emit more electrons on their pointed side than on the opposite flat ones. An electric current flows between the contacts – but only as long as the antennas are excited with the laser light.

"In photoemission, the light pulse causes electrons to be emitted from the metal into the vacuum," explains Christoph Karnetzky, lead author of the Nature work. "All the lighting effects are stronger on the sharp side, including the photoemission that we use to generate a small amount of current."

Ultrashort terahertz signals

The light pulses lasted only a few femtoseconds. Correspondingly short were the electrical pulses in the antennas. Technically, the structure is particularly interesting because the nano-antennas can be integrated into terahertz circuits a mere several millimeters across.

In this way, a femtosecond laser pulse with a frequency of 200 terahertz could generate an ultra-short terahertz signal with a frequency of up to 10 terahertz in the circuits on the chip, according to Karnetzky.

The researchers used sapphire as the chip material because it cannot be stimulated optically and, thus, causes no interference. With an eye on future applications, they used 1.5-micron wavelength lasers deployed in traditional internet fiber-optic cables.

An amazing discovery

Holleitner and his colleagues made yet another amazing discovery: Both the electrical and the terahertz pulses were non-linearly dependent on the excitation power of the laser used. This indicates that the photoemission in the antennas is triggered by the absorption of multiple photons per light pulse.

"Such fast, nonlinear on-chip pulses did not exist hitherto," says Alexander Holleitner. Utilizing this effect he hopes to discover even faster tunnel emission effects in the antennas and to use them for chip applications.

Publication:

Towards femtosecond on-chip electronics based on plasmonic hot electron nano-emitters.
C. Karnetzky, P. Zimmermann, C. Trummer, C. Duque-Sierra, M. Wörle, R. Kienberger, A. Holleitner; Nature Communications June 25, 2018 – DOI: 10.1038/s41467-018-04666-y
https://www.nature.com/articles/s41467-018-04666-y

More information:

The experiments were funded by the European Research Council (ERC) as part of the "NanoREAL" project and the DFG Cluster of Excellence "Nanosystems Initiative Munich" (NIM).

Contact:

Prof. Dr. Alexander Holleitner
Walter Schottky Institute / Department of Physics
Center for Nanotechnology and Nanomaterials
Technical University of Munich
Am Coulombwall 4a, 85748 Garching, Germany
Tel: +49 89 289 11575
E-Mail: holleitner@wsi.tum.de
Web: https://www.wsi.tum.de/groups.php?group=holleitner

Prof. Dr. Reinhard Kienberger
Physik-Department E11
Technical University of Munich
James-Franck-Str. 1, 85748 Garching, Germany
Tel: +49 89 289 12840
E-Mail: reinhard.kienberger@tum.de
Web: http://www.groups.ph.tum.de/e11

Weitere Informationen:

https://www.tum.de/nc/en/about-tum/news/press-releases/detail/article/34767/ Link to the press release

Dr. Ulrich Marsch | Technische Universität München

More articles from Power and Electrical Engineering:

nachricht Researchers produce synthetic Hall Effect to achieve one-way radio transmission
13.09.2019 | University of Illinois College of Engineering

nachricht Penn engineers' new topological insulator reroutes photonic 'traffic' on the fly
13.09.2019 | University of Pennsylvania

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Happy hour for time-resolved crystallography

Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.

The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.

Im Focus: Modular OLED light strips

At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.

Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...

Im Focus: Tomorrow´s coolants of choice

Scientists assess the potential of magnetic-cooling materials

Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....

Im Focus: The working of a molecular string phone

Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Potsdam (both in Germany) and the University of Toronto (Canada) have pieced together a detailed time-lapse movie revealing all the major steps during the catalytic cycle of an enzyme. Surprisingly, the communication between the protein units is accomplished via a water-network akin to a string telephone. This communication is aligned with a ‘breathing’ motion, that is the expansion and contraction of the protein.

This time-lapse sequence of structures reveals dynamic motions as a fundamental element in the molecular foundations of biology.

Im Focus: Milestones on the Way to the Nuclear Clock

Two research teams have succeeded simultaneously in measuring the long-sought Thorium nuclear transition, which enables extremely precise nuclear clocks. TU Wien (Vienna) is part of both teams.

If you want to build the most accurate clock in the world, you need something that "ticks" very fast and extremely precise. In an atomic clock, electrons are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Society 5.0: putting humans at the heart of digitalisation

10.09.2019 | Event News

Interspeech 2019 conference: Alexa and Siri in Graz

04.09.2019 | Event News

AI for Laser Technology Conference: optimizing the use of lasers with artificial intelligence

29.08.2019 | Event News

 
Latest News

Stroke patients relearning how to walk with peculiar shoe

18.09.2019 | Innovative Products

Statistical inference to mimic the operating manner of highly-experienced crystallographer

18.09.2019 | Physics and Astronomy

Scientists' design discovery doubles conductivity of indium oxide transparent coatings

18.09.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>