In a study published today in the journal Nature Communications, a French-Australian team, coordinated by SYRTE (Observatoire de Paris-PSL, CNRS, SU, LNE), and comprising researchers from SYRTE, the French National Centre for Space Studies (CNES), and the University of Western Australia (ICRAR-UWA), has set a new world record for frequency-stabilized laser transmission by combining phase stabilization technology with advanced self-guided optical terminals. Together, these technologies made it possible to send laser signals from one point to another by correcting fluctuations introduced by atmospheric turbulence. This is the world’s most accurate method for comparing clocks between two distinct locations.

Sketch of the aerial laser link between the roofs of the Auger and Lagrange buildings at CNES/Toulouse. The aerial link is compared to an underground fiber link to measure overall performance. Credit : UWA and Google.

The applications are numerous. In fundamental physics, this method allows to test Einstein’s prediction that clocks located in different places beat at different rates. In more applied sciences, such as geodesy and geophysics, the comparison of clocks located at different locations will allow new measurements of local gravitational potentials. This emerging technique is known as "chronometric geodesy" and takes advantage of today’s best atomic clocks and frequency comparison systems using laser transmissions. There are also applications for optical communications, where the transmission of light in free space to carry information is an emerging field with potential advantages. Indeed, optical communications can securely transmit data at much higher data rates than current radio communications.

The French-Australian demonstration experiment between two buildings on the CNES premises in Toulouse is a first step towards the implementation of longer distance laser links using airborne relays, or links between the ground and satellites in space.

Learn more:

Link to the article in Nature Communication "Point-to-Point Stabilised Optical Frequency Transfer with Active Optics",
Benjamin P. Dix-Matthews, Sascha W. Schediwy, David R. Gozzard, Etienne Savalle, François-Xavier Esnault, Thomas Lévèque, Charles Gravestock, Darlene D’Mello, Skevos Karpathakis, Michael Tobar, Peter Wolf

Contact:
Peter Wolf, peter.wolf@obspm.fr