Thermal evaporation of rare-earth chlorides: application to vapor phase deposition of rare earth-doped fluoride glass waveguides

A systematic study of the evaporation rate for single and binary mixtures of rare earth (RE) chlorides (NdCl3,ErCl3,TmCl3,PrCl3,YbCl3) has been performed. Single RE chlorides follow the physical evaporation law except NdCl3 that could be explained by a possible dimerisation in the vapor state. Erbium- and neodymium-doped planar and channel waveguides have been prepared by dual evaporation of RE chloride and PbF2–ZnF2–GaF3 fluoride glass. Also, planar waveguides are attacked by atmospheric moisture whereas, channel waveguides are stable, suggesting that the deposited glass is more compact in the latter case. The low optical loss (0.4 dB/cm at 633 nm for 1.5 mol% Er-doped channel waveguide) outlines the good quality of these devices.