Direct evidence for stationary light

Summary form only given. In recent years there have been several reports of pulsed laser action in random media, including powdered semi-conductors, polymers, rare earth and transition-metal-doped powders. These results were ascribed in a few cases to strong Anderson localization, despite the fact that distance scales of the virtual cavities associated with these lasers were much greater than a wavelength and output spectra exhibited angular and frequency selectivity, contrary to expectations for sub-wavelength feedback structures. Here we describe the results of experiments in which rather different properties are observed for a continuous-wave, electrically-pumped nanopowder laser. Our results provide the first direct evidence of three-dimensional confinement of light in a structureless random medium.