Piezo-spectroscopic assessment of nanoscopic residual stresses in Er3+-doped optical fibres

A quantitative characterization of residual stresses was performed with a nanometric spatial resolution in Er/Ge-doped silica glass fibres. Stresses were assessed by a piezo-spectroscopic technique (i.e., monitoring wavelength shifts), which used the electro-stimulated luminescence of optically active defects in silica glass. Residual stresses of GPa magnitude were found near the core/cladding interface by using a nanometre-sized electron probe. Diffusion of Er/Ge ions from the core towards the cladding area was clearly observed in this optical device and the occurrence of this diffusive phenomenon permitted stress measurement in extended cladding regions beyond the core/cladding interface. A discussion is given of the impact of residual stresses on the optical performance of the fibre device