Er3+-activated sol-gel silica derived spherical microresonators

Details of the synthesis, spectroscopic, optical, morphological and structural characterisation of silica microspheres activated by Er3+ ions produced by the sol-gel route are presented. Acetic acid is used to catalyse the hydrolysis and condensation of tetraethyl orthosilicate in the presence of ErCl3. SEM and TEM images are used to determine the dimension of the spheres and demonstrate the high quality of their surfaces. Photoluminescence measurements, both on single spheres and on pressed KBr pellets, containing 5% Er3+-doped silica spheres, confirm the incorporation of Er3+ ions into the silica matrix. The measured lifetime is 13.7 ms, relative to the 4I13/2 metastable state corresponding to a system quantum efficiency of 76%.