Whispering gallery mode resonators for microlasers and microsensors

In dielectric spheres light can be guided through high-Q whispering-gallery-modes (WGMs) with an unique combination of strong temporal and spatial confinement of light. Glass microspheres are then of interest for a large number of applications including compact lasers sources and biological sensing. Here we first review some basics of spherical resonators and we then focus our attention on these two applications. We describe the fabrication of both the microspheres and the tapered fibers and we demonstrate efficient coupling of light from the tapered fiber to the microspheres. We report some results on WGM microlasers in different types of erbium-doped glasses and finally a brief overview of the state of the art of microspherical biological sensors is presented.