  Whispering gallery mode resonators (WGMRs) take advantage of strong light
confinement and long photon lifetime for applications in sensing,
optomechanics, microlasers and quantum optics. However, their rotational
symmetry and low radiation loss impede energy exchange between WGMs and the
surrounding. As a result, free-space coupling of light into and from WGMRs is
very challenging. In previous schemes, resonators are intentionally deformed to
break circular symmetry to enable free-space coupling of carefully aligned
focused light, which comes with bulky size and alignment issue that hinder the
realization of compact WGMR applications. Here, we report a new class of
nanocouplers based on cavity enhanced Rayleigh scattering from
nano-scatterer(s) on resonator surface, and demonstrate whispering gallery
microlaser by free-space optical pumping of an Ytterbium doped silica
microtoroid via the scatterers. This new scheme will not only expand the range
of applications enabled by WGMRs, but also provide a possible route to
integrate them into solar powered green photonics.
