Erbium doped materials are of great interest in optical telecommunications
due to the Er3+ intra-4f emission at 1.54 ?m. Erbium doped fibre amplifiers
(EDFA) were developed in silica glass because of the low losses at this
wavelength and the reliability of this glass. Developments of new rare earth
doped fibre amplifiers aim to control their spectroscopic properties including
shape and width of the gain curve and optical quantum efficiency. Standard
silica glass modifiers, such as aluminium, result in very good properties in
current EDFA. However, for more drastic spectroscopic changes, more important
modifications of the rare earth ions local environment are required. To address
this aim, we present a fibre fabrication route creating rare earth doped
calcia?silica or calcia?phosphosilica nanoparticles embedded in silica glass.
By adding alkaline earth elements such as calcium, in low concentration, one
can obtain a glass with an immisci- bility gap so that phase separation occurs
with an appropriate heat treatment. We investigated the role of two elements:
calcium and phosphorus (a standard silica modifier). Scanning electron
microscopy shows that nanoparticles are only observed when calcium is
incorporated. The size of the particles is determined to be around 50 nm in
preform samples. The nature of these particles depends on phosphorus content:
without P, electron diffraction shows that the particles are amorphous whilst
they are partially crystalline when phosphorus is added. In addition through
use of energy dispersive x-ray techniques, we have shown that erbium ions are
located in the nanoparticles
