by Staff Writers
Helsinki, Finland (SPX) Feb 10, 2016
Research results recently presented in the distinguished Nature Photonics journal open up new outlooks on ghost imaging in the time domain.
The conventional approach to decode information carried by ultrafast optical signals that propagate in optical fibers employs fast detectors that convert the temporal intensity variations of a light beam into an RF electrical signal. This technique is at the core of ultrafast optical communications, enabling the transmission of information at speeds exceeding several billion bits per second.
A team led by Professor Goery Genty from the Optics Laboratory at the Tampere University of Technology in collaboration with Professor Ari T. Friberg from the University of Eastern Finland now demonstrates how ultrafast pulses that carry information over durations shorter than 1 billionth of a second can be detected without actually 'seeing' those pulses directly.
The results were obtained within the framework of the 'Temporal correlation imaging' project funded by the Academy of Finland.
"Ghost imaging is an all-new physical imaging method that enables us to image a target by correlating two beams of light, neither of which contains image information. One beam sees the object and measures the overall output, while the other is in no contact with the object although its space distribution is measured. When these measured intensities are correlated, the image of the target magically appears, 'like a ghost'," Friberg explains.
In their experiments, the team transposed the concept of ghost imaging into the time domain to produce the 'image' of an ultrafast signal in the form of short optical pulses by correlating in time the intensity of two light beams, neither of which independently carries information about the signal.
The key element was to use a laser source with random intensity fluctuations at a time scale of a picosecond, a feature which is generally highly detrimental for the standard transmission of information. By correlating these fluctuations with the total power of the modulated signal, it was possible to reconstruct a perfect copy of the ultrafast signal.
"Even more fascinating", says Professor Genty, "is the fact that the technique is completely insensitive to distortion that the signal may experience due to dispersion, nonlinearity, or attenuation, for example."
To demonstrate this inherent property associated with ghost imaging, the researchers have scrambled the information carried by the optical pulses using a multi-mode fiber whose large dispersion spreads the individual pulses in time to the extent that they start overlapping and thus prevent the information from being faithfully retrieved with a conventional fast detector. When the ghost imaging approach was used, the team showed that a perfect replica of the original signal could be obtained and the information could be recovered.
The method is scalable, it can be integrated on-chip, and it offers great promise for the dynamic imaging of ultrafast waveforms with applications in communications, remote sensing and ultrafast spectroscopy.
Academy of Finland
Understanding Time and Space
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|