Silica-hafnia-based photonic systems

Silica-hafnia is a reliable and flexible binary system that has proved to be suitable for rare earth doping and fabrication of amorphous and glass-ceramic planar waveguides, as well as for improving thermal stability of spherical microresonators. Here we present a short overview on some rare earth - activated photonic structures fabricated by sol gel route. Fabrication protocols and structural, optical and spectroscopic assessment of the investigated systems are reported. In order to put in evidence the reliability and versatility of the silica-hafnia system for photonics applications, different examples of confined structures are discussed: i) SiO2 amorphous waveguides; ii) glass-ceramic waveguides fabricated by top-down and bottom-up approach; iii) coated spherical microresonators.