Plasmonic Nanolasers: Pursuing Extreme Lasing Conditions on Nanoscale

Abstract Owing to their ultrahigh optical confinement, plasmonic nanolasers with cavity sizes beyond the diffraction limit of light, are attracting increasing attention for pursuing extreme lasing conditions on nanoscale including ultracompact cavity mode, ultrafast lasing modulation, significantly enhanced light–matter interaction, and Purcell effect. In this review, the recent progress on plasmonic nanolasers from both theoretical and experimental aspects is introduced, with emphases on plasmonic nanolasers with subdiffraction‐limit cavity‐mode confinement. Starting from a theoretical model and key parameters of a plasmonic nanolaser, general concerns of materials for both plasmonic cavities and gain media are summarized. Then, experimental efforts on realization of plasmonic nanolasers with cavity‐mode confinement increased from 1 to 3 dimensions are reviewed, followed by a brief introduction of some novel designs of plasmonic nanolasers and plasmon‐assisted nanolasers. Finally, future prospects and challenges in pursuing extreme lasing conditions of plasmonic nanolasers are discussed, and the identification of lasing threshold in these tiny lasers is revisited.