A room temperature low-threshold ultraviolet plasmonic nanolaser

Constrained by large ohmic and radiation losses, plasmonic nanolasers operated at visible regime are usually achieved either with a high threshold (10 2 -10 4 â €‰MWâ €‰cm â'2) or at cryogenic temperatures (4-120â €‰K). Particularly, the bending-back effect of surface plasmon (SP) dispersion at high energy makes the SP lasing below 450â €‰nm more challenging. Here we demonstrate the first strong room temperature ultraviolet (∼370â €‰nm) SP polariton laser with an extremely low threshold (∼3.5â €‰MWâ €‰cm â'2). We find that a closed-contact planar semiconductor-insulator-metal interface greatly lessens the scattering loss, and more importantly, efficiently promotes the exciton-SP energy transfer thus furnishes adequate optical gain to compensate the loss. An excitation polarization-dependent lasing action is observed and interpreted with a microscopic energy-transfer process from excitons to SPs. Our work advances the fundamental understanding of hybrid plasmonic waveguide laser and provides a solution of realizing room temperature UV nanolasers for biological applications and information technologies.