Femtosecond laser tuning of nanoparticles in optical fibers – FESTNOS

The growth of optical fibres has always been supported by the development of new manufacturing processes. FESTNOS is part of this context by developing a new process for optical fibres containing nanoparticles. The potential of this new generation of fibres as lasers and sensors has already been demonstrated. Their development remains limited due to the lack of reliable processes to control the nanoparticles, in particular their size and structure, in the fibres. Based on preliminary results, FESTNOS proposes to develop, over a period of 48 months, an innovative femtosecond laser bench to modify the characteristics of nanoparticles for fibre lengths ranging from µm to km, with possible variations in the characteristics of nanoparticles over micrometric fibre lengths. This control relies on the ability of such a laser to heat at high temperature with very high spatial resolution (µm3) as nanoparticles can be altered though thermodynamic processes.
To achieve this objective, the project gather 3 laboratories and is organised into 4 workpackages, 3 of which are scientific, with WP0 concerning the administration of the project. WP1 aims at preparing the optical fibres containing the nanoparticles to be modified. They will be prepared at INPHYNI, Optical Fibres and Applications team to which the holder belongs. Taking into account the preliminary results, the choice was made to study the fibres whose nanoparticles are formed by doping with lanthanum ions. WP2 concerns the development of the femtosecond laser bench that will be operated within INPHYNI, Waves in Complex Media team. Its development has been sequenced in three stages. The first step will consist in optimising the laser irradiation in the core of the optical fibre, with the help of numerical simulations developed at CEMEF. Then, the set-up will be developed in order to measure the evolution of the NPs in real time during the laser irradiation via the measurement of the backscattered light. Finally, in the last part of the project, a continuous reel-to-reel assembly will be set up in order to be able to modify the fibre continuously over a kilometre-long distance. The effect of laser irradiation on the modifications of the nanoparticles will be the motivation of WP3. Numerical simulations will be developed by CEMEF to study the thermodynamic mechanisms in order to optimise the laser parameters according to the kinetics of the nanoparticle modification. Specific characterisations such as TEM and FIB/SEM for 3D reconstruction of the irradiated volumes will be performed at CP2M. Finally, a last task will be to study the link between the characteristics of the NPs and the light scattering. The results of this task will make it possible to define the characteristics of the NPs according to the targeted applications.
FESTNOS opens up a new manufacturing avenue that has never been explored before and will offer an innovative solution for real control of the characteristics of nanoparticles in optical fibres. This project will make it possible to envisage new applications for this type of optical fibre. More generally, this laser inscription bench can be applied to other components and have spin-offs for the entire photonics community.