Leader : Dussardier Bernard
Collaborators within the LPMC : Blanc Wilfried, Benabdesselam Mourad, Mady Franck, Doya Valérie, Aschiéri Pierre, Michel Claire
External Collaborators : Peterka P. et Kasik I. (IPEE, Prague), Rastogi V. (IIT Roorkee, India), Farahi S. (EPFL, Switzerland)
PhD students/Post-doctoral fellows : Lupi Jean-François, Mebrouk Yasmine, Duchez Jean-Bernard
Financial supports : CNRS, UNS, EPFL, ANR, EADS Foundation
Technological platforms : Specialty optical fibres manufacture
There is a very strong growth in the variety of application areas of specialty optical fibres as passive or active components in optical devices. These components offer ever more original functions, and ever better technical and/or performances efficiency. It is also frequently necessary to integrate several of these functions in a single optical fibre.
Currently, several paradigms of fibre optic systems are revisited in order to meet future needs. One can cite several examplary sectors :
- High power fibre lasers or passive transport of intense beams by fibres require to increase the appearance threshold of detrimental non-linear effects. Many strategies are planned to integrate the functions of amplification (when present), modal filtering (for diffraction limited beam) and stability (low non-linearities). The now complex geometry of a fibre laser must take into account both the opto-geometrical and compositional characteristics of the different portions of the active fibre.
- One needs to extend the spectral coverage by lasers and amplifiers to fill large gaps in the visible and near-infrared ranges, that prevent the development of a large number of applications. Again it si essential to implement original compositions, or even nanoscale structures, in the amplifying core of fibres within a reliable glass such as silica.
- It is increasingly common to expose lasers, amplifiers and sensors to extreme conditions (temperature, pressure, radiation, optical power) that require the development of specially designed optical fibres, and their integration in special devices, for space and nuclear security applications.
- The field of optical fibre telecommunications must now meet the ever growing demand for speed and data rate, which is currently attracting an extraordinary R&D effort. The latest technologies (dense wave division multiplexing, coherent coding, digital processing,…) must now be intergrated into a new technology : the Spatial Division Multiplexing (SDM) : it is to encode information in several spatially separated spatial channels, either in few-mode (single-core) fibres or multicore fibres (each core being singlemode), and eventually in both. All line-fibres, components (couplers, filters, pump - signal combiners, routers, pump diodes,etc. ) and devices (amplifiers) are being revisited.
In this area, the Optical Fibre team is involved in several projects on designing, fabrication and characterization of specialty optical fibres based on original concepts, and upstream of applications. These projects implement results from the more fundamental projects of the team, with clearly identified potential applications. They include :
- optical amplification and shaping of gain curve of rare earth-doped fibres ( applied to lasers and telecommunications),
- transition metal ions doped fibres as saturable absorbers (for passively Q–switched fibre lasers ),
- chromatic dispersion management (for high-speed telecommunications) or inter-modal dispersion management (for SDM)
- modal filtering and large mode area fibres carrying radiative modes (for power lasers )
- non-symmetrical fibre geometries, applied to linear and non-linear chaos in guided wave optics
- laser operation at original wavelengths (for laser pumping, medical, metrology).
The team maintains numerous collaborations and a rich network of external collaborators. Its core work is based on the LPMC technological platform Specialty optical fibres manufacture.
Details of the ongoing projects :
Currently available fibre lasers operate on a limited number of narrow bands in the near infrared spectral range : 1 µm (Yb3+), 1.5 µm (Er3+) and 1.9 µm (Tm3+). A transversally single-mode fibre laser operting near 0.8 µm can be achieved through an "improved" Tm3+-doped optical fibre amplifier. We hence contribute to the extension of the spectral range coverage by optical fibre devices, for medical applications, metrology and telecommunications.
- Amplifiers and concepts for optical telecommunications
Under the current development of SDM (Spatial Division Multiplexing ), the explored solutions are today limited to few-mode fibres ( 8-12 modes ) or multicore fibres (12 to 19). Our team has embarked on this effort, with an original proposal for the erbium-doped amplifiers. Further upstream of these considerations, a more significant increase in the number of modes (tens or hundreds) could be obtained by fallout from MOSAIQ activity devoted to mesoscopic physics, particularly on chaos in guided-wave optics.
- Lasers, amplifiers and sensors in extreme environments
Several ongoing studies in the laboratory or in collaboration deal with the interactions of ionizing radiation with active optical fibres. The expected benefits firstly concern radiation resistant amplifying fibres (ANR/PARADYSIO et EADS/HAPOLO projects, see online Optical fibres and radiations (OFR)), and secondly distributed and real-time dosimeters (ANR / DROÏD project).