Er3+-doped silica-hafnia films for optical waveguides and spherical resonators

The silica-hafnia glass system has proved to be highly suitable for photonic applications. The refractive index can be tailored in a wide range by appropriate composition, due to the high refractive index of HfO2. Moreover, its transparency is optimal in both visible and NIR range. Here we report on fabrication, morphological and spectroscopic assessment of Er3+-activated planar waveguides and glass ceramic waveguides. Results concerning silica microspheres coated by silica-hafnia film are presented as well. In the case of planar waveguides comparison with other binary systems, in particular SiO2-TiO2, is considered, and concentration quenching and energy transfer processes are discussed. Two examples of silicahafnia-derived waveguiding glass ceramics, prepared by top-down and bottom-up techniques are reported, and the main optical properties are discussed. Finally, some properties of activated microspherical resonators, having a silica core, obtained by melting the end of a telecom fiber, coated with an Er3+-doped 70SiO2-30HfO2 film, are presented