Silica-Hafnia: a viable photonic system
Résumé
Silica-based glasses take up a consolidated place as materials for photonic. The fruitful exploitation of silicate glasses is not restricted only to the area of Information and Communication Technology. Many other photonic devices, with a large spectrum of application covering Health and Biology, Structural Engineering, and Environment Monitoring Systems, have been developed during the last years. Even if several of these devices are actually available on the market, at the state of the art the strength of the research on silica-based glasses is focused on optimizing chemical composition and developing innovative fabrication processes, in order to reduce the costs and increase the performances of the devices so obtained. In this context a significant role is played by the silica-hafnia system. HfO2 has a wide bandgap of about 5.5 eV allowing transparency from the ultraviolet to the mid-infrared spectral region, exhibits high refractive index, and a phonon energy cutoff lower than that of SiO2 (700 vs. 1100 cm−1). In this lecture we discuss the most significant results obtained by our research unit for the rare earth-activated SiO2-HfO2 system, in order to put in evidence its reliability and versatility for photonics application. In particular we demonstrate that this binary system is suitable for fabrication of amorphous and glass-ceramic planar waveguides, down-converters, and spherical microresonators.