Glasses may be prepared by sol-gel processing over a wide range of compositions and thick multilayer deposits may be used as waveguides for integrated optics. Doping these layers with rare-earth (RE) ions enables the fabrication of active devices for optical amplifiers; the incorporation of these ions into nanocrystallites offers possibilities for increased dopant concentration without fluorescence quenching, improved spectroscopic performance and high quantum yields. Rare-earth (RE) ions such as erbium (Er3+), ytterbium (Yb3+), neodymium (Nd3+), thulium (Tm3+), holmium (Ho3+) and praseodymium (Pr3+) have been widely used in optical applications and cover a range of wavelengths ranging from UV-visible to the near infrared. This chapter includes basic principles of fluorescence in RE doped glasses, fluorescence lifetimes, quantum yields and Judd-Ofelt analysis. A few information is given about the preparation and characterization of glasses, thin films and glass-ceramics (nanocrystallites embedded in glass matrix) prepared by sol-gel processing. The growth of nanocrystals in glassy sol-gel films through suitable heat treatments can avoid the influence of high phonon energy of silica glasses. The characterization of such materials can be evaluated by optical techniques, namely UV-Visible, FTIR, among other additional techniques that include Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM).
Part of the book: Recent Applications in Sol-Gel Synthesis
This chapter focuses on developing coatings for use as waveguides for integrated optics and photonics. Thin (or thick) films of silica-based inorganic materials and organic-inorganic hybrids can be easily obtained using the sol-gel and spin-coating method, followed by rapid thermal annealing to obtain dense films of good optical quality. The waveguide thermal, structural, and optical properties can be characterized using differential thermal analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. Waveguides can be both doped with semiconductor microcrystallites and rare-earths for the development of optical devices, where light is confined to one or two dimensions (planar, channel or strip loaded).