The photoluminescence properties of a silicate glass coactivated with silver and erbium ions were studied. Absorption and photoluminescence spectra allowed to distinguish in the glasses several active species related to the silver, whose ratio depends on heat treatment and silver concentration. The broad emission of silver related species in the visible region of the spectrum has been studied in correlation with the nonresonant excitation of the erbium ions. The comparison of the excitation spectra of silver and erbium shows that the erbium ions are excited through radiative and nonradiative energy transfer from small silver aggregates.

${\mathrm{70SiO}}_2–{\mathrm{30HfO}}_2$ planar waveguides, doped with ${\mathrm{Er}}^{\text{3+}}$ concentrations ranging from 0.3 to 1 mol %, were prepared by sol-gel route, using dip-coating deposition on silica glass substrates. The waveguides show high densification degree, effective intermingling of the two components of the film, and uniform surface morphology. Propagation losses of about 1 dB/cm were measured at 632.8 nm. When pumped with 987 or 514.5 nm continuous-wave laser light, the waveguides show the ${}^4{I}_{\text{13/2}}{\to }^4{I}_{\text{15/2}}$ emission band with a bandwidth of 48 nm. The spectral features are found independent both on erbium content and excitation wavelength. The ${}^4{I}_{\text{13/2}}$ level decay curves presented a single-exponential profile, with a lifetime between 2.9 and 5.0 ms, depending on the erbium concentration.

Low wavenumber Raman scattering of the acoustic vibrational modes of nanoparticles was used for the determination of the size distribution of free dielectric and semiconductor nanoparticles and of nanoparticles embedded in matrices. The theoretical background as well as the experimental results for the free noninteracting nanoparticles and for the nanoparticles in strong interaction with a surrounding matrix is described. The approach is based on a 1/ν dependence of the Raman light‐to‐vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its eigenfrequency ν ∼ 1/D. The model calculation considers the inhomogeneous broadening due to contribution from the particles of different sizes, and homogeneous broadening due to interaction of particles with the matrix. The comparison of the calculated and experimental low wavenumber Raman spectra are presented for SnO₂, TiO₂ and CdS free nanoparticles and TiO₂, CdS_xSe_1−x and HfO₂ nanoparticles embedded in a glass matrix. The particle‐size distributions determined by Raman scattering were compared to those found by TEM measurements. Raman spectroscopy proved to be a simple, fast and reliable method for size‐distribution measurements. By an inverse procedure, starting from the Raman spectra and known particle‐size distribution, a new method for the determination of the mean sound velocities of longitudinal and transverse phonons of nanoparticles is described. Copyright © 2007 John Wiley & Sons, Ltd.