Nanolasers

Nanolasers are lasers in which the active region and the optical mode are confined to nanometer scales. This extreme confinement allows light to be generated and manipulated in devices with dimensions well below the diffraction limit, making nanolasers of interest for integrated photonics and nanoscale sensing. Nanolasers are typically categorized into plasmonic nanolasers, or spasers, which use metal-dielectric surface plasmon modes to achieve subwavelength confinement, and all-dielectric nanolasers, which employ high-refractive-index dielectric resonators supporting Mie-type resonances with reduced absorption losses.

Operation relies on a gain medium—such as semiconductor quantum dots, colloidal quantum wells, dyes, or III-V semiconductor nanostructures—placed inside or coupled to a nanoscale optical cavity. Optical or electrical pumping provides population inversion, and the resonator feedback selects the lasing mode. The small mode volume, together with the Purcell effect, can lead to a high spontaneous emission coupling factor (beta) and threshold behavior that differs from conventional lasers.

Performance challenges include material losses in metals, heating, and fabrication difficulties at the nanoscale. Metal-based nanolasers typically face higher thresholds and poorer temperature stability, whereas dielectric nanolasers aim to reduce losses but can have weaker confinement or more complex fabrication. Demonstrations of room-temperature lasing have been reported for both plasmonic and dielectric platforms, with ongoing work to improve stability, efficiency, and electrical injection.

Applications envisioned for nanolasers include on-chip optical interconnects, miniaturized sensors, quantum light sources, and integrated photonic circuits. Ongoing research seeks to scale, integrate, and commercially deploy nanolaser technologies.

The field remains interdisciplinary, spanning nanofabrication, materials science, and quantum optics.