Glass and optical fibers doped with nanoparticles for Photonics

Nanoparticle-containing glasses and optical fibers are materials containing particles smaller than 100 nm in size, with an amorphous or crystalline structure and a composition different from that of the surrounding glass matrix.

Although metallic nanoparticles have been used to color ancient glass such as stained glass, their presence was unknown at the time. It wasn't until the 1950s, with the advent of glass-ceramics, that the presence of heterogeneities (in this case, crystals in a glass matrix) opened up new perspectives. The first applications concerned thermomechanical properties. The presence of nanoparticles induced light scattering, which delayed the development of such glasses for optical applications in terms of transparency. However, by the 1990s, the first transparent glass-ceramics had been prepared, and the concept was extended to optical fibers in the late 90s.

One of the first reasons for using nanoparticles was to provide a different chemical and structural environment for luminescent ions than the glass matrix. The combination of glass + nanoparticles thus makes it possible to combine the advantages of glass (shaping, cost, etc.) with luminescence properties linked to the characteristics of nanoparticles. These applications involve light sources, lasers and amplifiers. Such applications generally require small nanoparticles (< 100 nm) to limit optical losses by light scattering and thus preserve the material's transparency. This criterion is all the more important in the case of optical fibers. However, it has been shown that this light scattering can open up new perspectives, particularly for the realization of sensors.

One of the main obstacles to the development of such optical fibers lies in the difficulty of characterizing nanoparticles. However, the efforts of numerous research teams around the world have led to improvements in knowledge and characterization techniques, pointing to growing interest in this family of optical fibers.

The aim of this article is to review the state of the art in nanoparticle-containing glasses and fibers. It places such materials in the context of other glasses. It also describes the manufacturing processes for these glasses and optical fibers, based both on particle formation by thermodynamic mechanisms (nucleation/growth or phase separation) and by doping the glass matrix with chemically prepared nanoparticles. Last but not least, numerous applications are described, highlighting both the interest in modifying the spectroscopic properties of luminescent ions (such as rare-earth ions or transition metals) and in light scattering, which has been considered undesirable for years.