A nanolaser with extreme dielectric confinement

The interaction between light and matter can be enhanced by spatially concentrating the light field and extending photon dwell time. Plasmonic structures can provide strong light confinement but suffer from ohmic losses. Recent advances in dielectric nanostructures enable strong light localization without metallic losses. However, previous studies primarily focused on minimizing the optical mode volume without adequately addressing light-matter interactions. Here, we demonstrate a nanolaser that colocalizes photons and excited carriers within a dielectric nanobridge. This extreme dielectric confinement of both light and matter yields a subdiffraction-limited mode volume and a subwavelength carrier volume without lateral quantum confinement. We observe a strong correlation between the mode field and carrier distribution, where enhanced mode localization produces stronger carrier confinement. By suppressing carrier surface recombination, this platform not only enables continuous-wave lasing at room temperature but also achieves a substantially reduced lasing threshold. We quantify the intensified interaction with an interaction volume, generalizing mode volume to a broad class of active media.