Glass photonic structures fabricated by sol-gel route

To emphasize the scientific and technological interest in the silica-based glassy systems and the versatility of the sol-gel route, nano and micrometer scale structures are discussed focusing the attention mainly on the rare-earth-activated materials and their spectroscopic characterization. We have demonstrated that various SiO 2 -based binary systems can be successfully employed for the fabrication of amorphous planar waveguides, glass–ceramic waveguides, and tapered rib waveguide laser. Different technological processes allowed to realize Er 3+ -activated microspheres that can be exploited as microresonator and it has been evidenced that through specific coating it is possible to modify modal free spectral range and/or modal dispersion of the microresonator and achieve laser action. In the case of rare-earth-doped 3-D colloidal crystals in different configurations (direct and inverse one), it has been shown that the relaxation dynamics of the electronic states can be engineered.