Targeted creation and control of photons: This should succeed thanks to a new design for optical antennas developed by Würzburg scientists.
Atoms and molecules can be made to emit light particles (photons). However, without external intervention this process is inefficient and undirected.
If it was possible to influence the process of photon creation fundamentally in terms of efficiency and emission direction, new technical possibilities would be opened up such as tiny, multifunctional light pixels that could be used to build three-dimensional displays or reliable single-photon sources for quantum computers or optical microscopes to map individual molecules.
Nanometre-sized "optical antennas" are a well-known approach. They are capable of sending photons in a specific direction with high efficiency. The idea goes back to Nobel Laureate Richard P. Feynman who envisioned nanoscale antennas during a speech at the California Institute of Technology already in 1959.
Feynman was way ahead of his time, but he triggered a rapid development in nanotechnology which enables building antenna for visible light today. The dimensions and structural details of such antennas can be controlled precisely at a size of around 250 nanometres.
The deficits of existing light antennas
The form of these optical antennas has previously been inspired by established models from radio communication and radio technology. The antennas used there are usually made of specially shaped metal wires and metal rod arrays due to the wavelengths in the centimetre range. It is in fact possible to construct antennas for light waves using metal nanorods to influence the creation and propagation of photons, but the analogy between radio waves and light waves is limited.
While macroscopic radio antennas have a high-frequency generator connected to the antenna via cable, the link at the nanometre scale of a light wave length has to be contactless. But atoms and molecules that act as photon sources do not feature connecting cables to hook them up to an optical antenna.
It is this major difference, combined with a number of other problems that are due to the high frequency of light, that has made it impossible so far to produce and subsequently control photons with optical antennas in a satisfactory manner.
Publication in the journal "Physical Review Letters"
Physicists from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, have now solved this problem and established a set of rules for optimized optical antennas which were published in the prestigious journal "Physical Review Letters".
The new rules could help build antennas for light so that both the photons' birth and their subsequent propagation can be controlled precisely, at least theoretically, according to Thorsten Feichtner, a researcher at JMU’s Institute of Physics in Professor Bert Hecht's team.
The principle behind the new antennas
"The idea behind this is based on the principle of similarity," the Würzburg physicist explains. "What's new in our research is that the currents of the free electrons in the antenna have to fulfil two similarity conditions at the same time. Firstly, the current pattern in the antenna must be similar to the field lines in the direct vicinity of a light-emitting atom or molecule. Secondly, the current pattern must also match the homogeneous electrical field of a plane wave as best as possible so that each photon can reach a distant receiver."
The novel antennas for light built with the help of these new rules extract far more photons from an emitter than previous antenna types derived from radio technology.
Feichtner, T., Christiansen, S., & Hecht, B. (2017). Mode Matching for Optical Antennas. Physical Review Letters, 119(21), 217401, 21 November 2017, DOI: https://doi.org/10.1103/PhysRevLett.119.217401
Thorsten Feichtner, Institute of Physics, JMU, T +49 931 31-85768, email@example.com
Robert Emmerich | Julius-Maximilians-Universität Würzburg
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences