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Crystal Fibers

Due to their perfectly ordered atoms, single crystals have properties much sought after in high technology: hardness, scintillation, laser effect, light transmission, resistance to high temperatures, etc. Their applications–of which many are already in existence–are likely to see further development with the complex manufacturing process developed by Fibercryst. The company, set up in 2003 by Kheirredine Lebbou and Olivier Tillement, at LPCML1 in Lyon, is the first to produce and market on an industrial scale oxide single crystals in the form of flexible fibers. Available in diameters ranging from 300 micrometers to 2 millimeters, the fibers can be up to 1 meter long. The company, which is currently headed by Jean-Marie Fourmigué, is located on the premises of LPCML where it successfully works on applications of the research in growing crystal fibers carried out by the Crystals Growth group at the lab. “We no longer have to go through the tedious process of machining single-crystal balls weighing several kilograms to give them the right shape and polish them on six faces,” explains Lebbou, the research engineer at LPCML behind the crystal 'pulling' process. “All we have to do now is cut a section of fiber to the desired length and then polish the two ends.” All this leads to major improvements in both time and efficiency. Furthermore, it also ensures very high stability and near-perfect crystal purity. Such assets make it possible to produce high-powered lasers–up to 20 watts–as compared to a previous maximum of 300 milliwatts. These lasers are in high demand, especially for the defense industry. The laser generation is performed in collaboration with Francois Ballembois and Patrick Georges from the LCFIO.2
“In the future,” predicts Lebbou, “single-crystal fibers will compete with silica optical fibers, because they're much better transmitters of light.” Indeed, Fibercryst and the LPCML lab are working on the production of a medical imaging prototype that uses crystal fibers. These fibers, with their high thermal conductivity and hardness, can also be used in the most hostile environments–like the cores of nuclear reactors.
Long term, the aim is to widen their scope of applications by producing longer, thinner single-crystal fibers designed for telecommunications and photonics. Yet a method for sealing together two single crystal fibers at their extremities without altering their quality still remains to be found. In order to achieve this, Fibercryst expects a lot from the competitiveness cluster currently being set up, which will bring together all those working in the field of crystal research in the Rhône-Alpes region.

Emmanuel Thévenon

Notes :

1. Laboratoire de physico-chimie des matériaux luminescents (CNRS / Université Lyon-I).
2. Laboratoire Charles Fabry Institut d'optique (CNRS /Université Paris XI / Institut d'optique–graduate school).

Contacts :

Kheirredine Lebbou
LPCML, Lyon.


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