Erbium doped silica-titania planar waveguides, co-doped with ytterbium and
aluminum, have been prepared by sol-gel processing, using multilayer spin-c
oating deposition on silicon or silica glass substrates. The Er3+ doping le
vel varied between 0 and 2 at.%, while Yb3+ varied from 0 to 3 at.%. Alumin
um was incorporated up to 15 at.% Al and it was found to have no significan
t effect on the refractive index of the silica-titania (80 : 20 mol%) matri
x. The Er3+ fluorescence emission was flat within +/-0.5 dB, between 1520 a
nd 1560 nm. The corresponding I-4(13/2) metastable level lifetime was found
to decrease from 6.1 to 3.5 ms, as the Er concentration increased from 0.1
to 0.5 at.%, for films co-doped with 0.5 at.% Yb and 10 at.% Al and the fl
uorescence decay was essentially single exponential below a Er quenching co
ncentration of 0.5 at.% (1.1 x 1020 ions/cm(3)). The lifetime appears to be
limited by Er-Er interactions at higher rare-earth ion concentrations and
by residual OH species in the sol-gel derived waveguides. Vacuum heat treat
ment at a temperature near 570 degrees C was somewhat effective in increasi
ng the Er fluorescence lifetime, whereas reactive atmosphere processing in
CCl4 or Cl-2 at a similar temperature appeared to be less effective.