Laser action in strongly scattering rare-earth-metal-doped dielectric nanophosphors

We report continuous-wave laser action in two oxide nanopowders doped with Ce and Pr ions. To our knowledge, these are the first observations of stimulated emission from electrically pumped random media in which scattering and distributed feedback scale lengths are much shorter than a wavelength. The continuous nature of the laser emission in small volumes ~on the order of a cubic wavelength! of these low gain systems, and the absence of coherent speckle, provide compelling evidence that these results are mediated by strong Anderson localization of light.