Plasmonic green nanolaser based on a metal-oxide-semiconductor structure

Realization of smaller and faster coherent light sources is critically important for the emerging applications in nanophotonics and information technology. Semiconductor lasers are arguably the most suitable candidate for such purposes. However, the minimum size of conventional semiconductor lasers utilizing dielectric optical cavities for sustaining laser oscillation is ultimately governed by the diffraction limit (∼(λ/2n)³ for three-dimensional (3D) cavities, where λ is the free-space wavelength and n is the refractive index). Here, we demonstrate the 3D subdiffraction- limited laser operation in the green spectral region based on a metal-oxide-semiconductor (MOS) structure, comprising a bundle of green-emitting InGaN/GaN nanorods strongly coupled to a gold plate through a SiO₂ dielectric nanogap layer. In this plasmonic nanocavity structure, the analogue of MOS-type "nanocapacitor" in nanoelectronics leads to the confinement of the plasmonic field into a 3D mode volume of 8.0×10 ^-4 μ³ (∼0.14(λ/2n)³).