Described in a new paper,* the NIST/JPL array-on-a-chip easily identifies the position of the exact detector in a multi-detector system that absorbs an incoming infrared light particle, or photon.
This NIST device, 1.5 by 3 centimeters in outer dimensions, is a prototype receiver for laser communications enabling much higher data rates than conventional systems. Superconducting detectors in the center of the small square chip register the timing and position of single particles of light.
Credit: Verma and Tomlin/NIST
That's the norm for digital photography cameras, of course, but a significant improvement in these astonishingly sensitive detectors that can register a single photon. The new device also records the signal timing, as these particular single-photon detectors have always done.
The technology could be useful in optical communications in space. Lasers can transmit only very low light levels across vast distances, so signals need to contain as much information as possible.
One solution is "pulse position modulation" in which a photon is transmitted at different times and positions to encode more than the usual one bit of information. If a light source transmitted photons slightly to the left/right and up/down, for instance, then the new NIST/JPL detector array circuit could decipher the two bits of information encoded in the spatial position of the photon. Additional bits of information could be encoded by using the arrival time of the photon.
The same NIST/JPL collaboration recently produced detector arrays for the first demonstration of two-way laser communications outside Earth's orbit using the timing version of pulse position modulation.** The new NIST/JPL paper shows how to make an even larger array of detectors for future communications systems.
The new technology uses superconducting nanowire single-photon detectors. The current design can count tens of millions of photons per second but the researchers say it could be scaled up to a system capable of counting of nearly a billion photons per second with low dark (false) counts. The key innovation enabling the latest device was NIST's 2011 introduction of a new detector material, tungsten-silicide, which boosted efficiency, the ability to generate an electrical signal for each arriving photon.*** Detector efficiency now exceeds 90 percent. Other materials are less efficient and would be more difficult to incorporate into complex circuits.
The detectors superconduct at cryogenic temperatures (about minus 270 °C or minus 454 °F), and cooling needs set a limit on wiring complexity. The NIST/JPL scheme requires only twice as many wires (2N) as the number of detectors on one side of a square array (N x N), greatly reducing cooling loads compared to a one-wire-per-detector approach while maintaining high timing accuracy. NIST researchers demonstrated the scheme for a four-detector array with four wires and are now working on a 64-detector array with 16 wires.
In the circuit, each detector is located in a specific column and row of the square array. Each detector acts like an electrical switch. When the detector is in the superconducting state, the switch is closed and the current is equally distributed among all detectors in that column. When a detector absorbs a photon, the switch opens, temporarily diverting the current to an amplifier for the affected column while reducing the signal through the affected row. As a result, the circuit generates a voltage spike in the column readout and a voltage dip in the row readout. The active detector is at the intersection of the active column and row.
The research was supported by the Defense Advanced Research Projects Agency.
V.B. Verma, R. Horansky, F. Marsili, J.A. Stern, M.D. Shaw, A.E. Lita, R.P. Mirin and S.W. Nam. A four-pixel single-photon pulse position camera fabricated from WSi superconducting nanowire single photon detectors. Applied Physics Letters 104, 051115. DOI: 10.1063/1.4864075. Posted online Feb. 4, 2014.
See Oct. 28, 2013, National Aeronautics and Space Administration news release, "Historic Demonstration Proves Laser Communication Possible," at http://www.nasa.gov/content/goddard/historic-demonstration-proves-laser-communication-possible/#.Um62W3Dkvv2.
See 2011 NIST Tech Beat article, "Key Ingredient: Change in Material Boosts Prospects of Ultrafast Single-photon Detector," at http://www.nist.gov/pml/div686/detector-063011.cfm.
Laura Ost | EurekAlert!
Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center
Tracing aromatic molecules in the early universe
23.03.2017 | University of California - Riverside
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Earth Sciences
24.03.2017 | Health and Medicine
24.03.2017 | Earth Sciences