Improved telecommunication thanks to superconducting detectors
Meer informatie
Contactperso(o)n(en): Ans Hekkenberg
Weblocatie: http://www.fom.nl/live/nieuws/archief_persberichten/persberichten2015/artikel.pag?objectnumber=303393
printerversie
9 juli 2015
Improved telecommunication thanks to superconducting detectors
A team of Dutch and Swiss researchers have succeeded in very accurately exploring the surface of a superconducting light detector. This new technique makes it possible to improve the design of such detectors. A few applications of superconducting light detectors are communication with space
satellites, monitoring of cancer therapies and encrypted communication. The research was published on 8 July 2015 in the journal Nano Letters, and it was carried out by scientists from FOM, Leiden University, Eindhoven University of Technology and the University of Zurich.
Light detectors can detect individual light particles (photons). Superconducting detectors are particularly suitable for this purpose because they respond quickly and reliably to incoming light. These detectors have therefore become very popular in recent years in both scientific research and
technological applications. The problem is, however, that the detectors do not actually detect every photon that comes in. Why that is the case was not clear up until now.
Researchers have now established what causes this limitation: certain parts of the detector are less good in detecting light particles than other parts. If a photon touches one of these less sensitive areas there is a chance that the detector will not detect the particle.
Nanowire
In the light detector there is a flat nanowire which is about 5 billionths of a metre thick and 100 billionths of a metre wide. This wire is very precisely folded up so that it forms a tightly packed, winding pattern. If a photon touches the wire, a small voltage peak rises locally that the
detector rapidly notices. The researchers discovered that the edges of the wire detected a photon more easily than the middle of the wire. That is because a small vortex of electrical current must form at the edge of the wire before detection is possible. If the photon falls directly on the
point where this must occur then the process is more efficient than if the photon falls elsewhere.
Illumination technique
The research team came to this conclusion by scanning the surface of the detector with an illumination technique developed especially for this research. They Illuminated the detector with two different types of light (polarisations). They subsequently deducted the results of these two
measurements from each other. This gave rise to an image of a far higher contrast than usual, which allowed the researchers to observe details that could not previously be seen.
The research was carried out as part of the FOM programme 'Nanoscale Quantum Optics'.
Contact
Jelmer Renema, +31 71 527 5932
Reference
Position-Dependent Local Detection Efficiency in a Nanowire Superconducting Single-Photon Detector, Nano Letters . DOI: 10.1021/acs.nanolett.5b01103.