Stopped-light nanolasing in hybrid plasmonic waveguides

We report stopped-light nanolasing in active planar plasmonic waveguides at near-infrared frequencies. Studying its spatial, temporal and spectral signatures we reveal that, in the absence of cavity-induced feedback, the subwavelength lasing mode forms dynamically as a phased-locked superposition of quasi dispersion-free waveguide modes. This mechanism proves remarkably robust against surface roughness and offers a new route towards nanolasing, the experimental realization of thin-film surface lasers and cavity-free quantum electrodynamics.