19 August 2020
To meet the needs of many space projects requiring ultrastable optical frequency links, inter-satellite or ground-side, for space geodesy (GRICE), the measurement of the Earth’s gravitational field (GRACE FO, NGGM), or the detection of gravitational waves (LISA->https://www.elisascience.org/]), stabilized laser sources of known frequency are required. More industrial applications are also envisaged, such as underwater WIFI!
SYRTE has also been developing for several years, frequency-stabilized infrared laser devices on iodine vapor in cells, with compact and all-fibered designs, in order to facilitate their use outside the laboratory. One challenge is to link the Telecom C & L bands (1530 nm - 1600 nm) to the very strong absorption band of molecular iodine in the green range of the electromagnetic spectrum, where many hyperfine transitions have quality factors Q > 109.
The frequency connection between the IR and the green range of the electromagnetic spectrum is achieved by an original frequency tripling process developed in the laboratory. It is based on the use of fully fibrillated Lithium Niobate crystals and has resulted in a conversion efficiency P3ω/Pω > 36%, a world record to our knowledge for a laser emitting in continuous mode. The power consumption required to achieve this harmonic process is < 20 W.
Syrte is conducting a specific study for the space mission Laser Interferometer Space Antenna (LISA), that aims to set up a fully fibered device, including the frequency tripling process and a monolithic iodine molecular vapor interrogation optical bench. The total volume of the assembly will not exceed 10 litres. This new project is being carried out in partnership with a Paris Region and the SME (KYLIA). The transfer of frequency stability from the Telecom domain to 1064 nm (nominal wavelength of LISA) involves - in a simple way - a frequency doubling operation and a phase locked loop (PLL), already demonstrated in the laboratory.
The frequency stability conferred to the infrared laser, via servo-control on the hyperfine transitions of iodine is 3 x10-14 τ-1/2 and 4 x10-15 at 200 s. This level of performance already meets the specifications of the LISA space mission dedicated to the detection of gravitational waves in space. This space mission has been classified by ESA as an L3 mission, with a launch target of 2034. The SYRTE laboratory is in charge of supplying a frequency-stabilized laser device for the ground tests of the LISA payload (AIVT), conducted by CNES, as part of the French participation in this ESA/NASA space mission.
For more information: This presentation
given in a SYRTE seminar gives an account of the techniques, characterizations, results and perspectives resulting from this development.
The webpage dedicated to the experience of stabilized lasers on molecular iodine ->https://syrte.obspm.fr/spip/science/fop/experiences/article/lasers-stabilises-sur-l-iode-moleculaire-62] also extends this description.
Contact: Ouali Acef
Phone: +33 (0) 1 40 51 20 50