HOLIGRALE

Fiber Lasers are nowadays changing the idea people have regarding laser systems by allowing reaching high powers, higher compactness and easy use (compared to classical laser systems). In particular, fiber lasers are expected to occupy 30 to 40% of the laser market. The main interests of the optical fiber devices remain in their unique geometry which provides their adaptability to be used in various environments and allows minimizing the thermal effects induced by the laser emission. Even though the advantages of the fibers are obvious, important issues remain to be solved and it appears clearly that the silica based materials are definitely not, for several applications, the best candidates to meet the challenge. Tellurite glasses and glass-ceramics will offer new opportunities to extend the operational wavelength range in the near infrared (above 1µm up to 5-6 µm) and will allow accessing high second order and third order optical nonlinearities. Glass-ceramics have been considered in the past as very attractive materials for photonics but their use has led so far only to limited applications, mainly due to technological difficulties in relation with the complex nature of the materials in fiber form. However, the benefit of achieving glass-ceramics fibers would be considerable and real, justifying completely this project. Several issues, specific to glass-ceramics, will have to be addressed. In particular, the size of nanocrystals disseminated within the glassy matrix will have to be carefully controlled to avoid their excessive growth. As well, a small refractive index difference between the crystallites and the glassy matrix will constitute a key focus to maintain optical scattering losses at a low level. In addition, the low phonon energy intrinsic to the tellurite glass matrix, combined to that of selected crystals, will be essential parameters to reach important laser efficiency for the targeted applications above 1µm and up to 5-6 µm. Finally, glass-ceramics should present higher laser damage thresholds, in comparison to the “equivalent” glass compositions, due to their improved mechanical properties. Thus, in order to guaranty the success of the HOLIGRALE project, the strategy will be to select the most adapted materials for the fabrication of fibers for Gain and fibers for Non-Linear Optics, to develop the drawing technique, to test and adopt innovative geometries for fibers and to establish some correlation between fiber architectures, materials chemistry and optical properties. This unique project will rely on the excellence of the French expertise in the aforementioned fields of research, and on the quality of the consortium created by the gathering of the laboratories implied.