Photoluminescence and lasing in whispering gallery mode glass microspherical resonators

We report experimental results regarding the development of Er3+-doped glass microspherical cavities for the fabrication of compact sources at 1.55 μm. We investigate several different approaches in order to fabricate the microspheres including direct melting of Er3+-doped glass powders, synthesis of Er3+-doped monolithic microspheres by drawing Er3+-doped glass, and coating of silica microspheres with an Er3+-doped sol-gel layer. 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 have analyzed the photoluminescence spectra of the whispering gallery modes of the microspheres excited using evanescent coupling and we demonstrate tunable laser action in a wide range of wavelengths around 1.55 μm. As much as 90 μW of laser output power was measured in Er3+-doped glass microspheres.