We report experimental results obtained in our laboratories in the development of Er3+-
doped glass microspherical cavities for the fabrication of compact and low threshold laser sources
at 1.55 μm. We investigate three different approaches in order to fabricate the microspheres
including direct melting of Er3+-doped glass powders, coating of silica microspheres with an Er3+-
doped sol-gel layer, and synthesis of Er3+-doped monolithic microspheres using the sol-gel route in
acid catalysis. Details of the different fabrication processes are presented together with the
photoluminescence characterization in free space configuration of the microspheres and of the glass
precursor. We analyse the photoluminescence spectra of the whispering gallery modes of the
microspheres exited using evanescent coupling and we demonstrate laser action in a wide range of
wavelengths around 1.55 μm.
All-polymer whispering gallery mode resonators for gas sensing