We have recently initiated a project involving the ultrahigh resolution electron microscopy of ytterbium-doped optical fibres. Doped fibres represent a very important domain in terms of state-of-the-art laser and optical amplifier technology. One of the key motivations for initiating the work was to gain further insights into photodarkening mechanisms in doped optical fibres. Photodarkening refers to the degradation of signal beam transmission due to optical pumping of the fibres. There are various models for photodarkening mechanisms, but there is no general agreement on the details amongst researchers world wide.

The ultrahigh resolution electron microscopy of Yb atoms in glass, conducted with the facilities of the Canadian Centre for Electron Microscopy, is extremely challenging experimentally. We aim to detect single Yb atoms in glass which can reveal effects of ion clustering. The tour-de-force experiments push the techniques of sample preparation and analysis to the limit. Beyond possible insights into photodarkening, our experiments could also lead to new knowledge into fabrication mechanisms of various specialty optical fibres.