Half-wave nanolasers and intracellular plasmonic lasing particles.

The ultimate limit for laser miniaturization would be achieving lasing action in the lowest-order cavity mode within a device volume of ≤(λ/2n)(3), where λ is the free-space wavelength and n is the refractive index. Here we highlight the equivalence of localized surface plasmons and surface plasmon polaritons within resonant systems, introducing nanolasers that oscillate in the lowest-order localized surface plasmon or, equivalently, half-cycle surface plasmon polariton. These diffraction-limited single-mode emitters, ranging in size from 170 to 280 nm, harness strong coupling between gold and In(x)Ga(1-x)As(1-y)P(y) in the near-infrared (λ = 1,000-1,460 nm), away from the surface plasmon frequency. This configuration supports only the lowest-order dipolar mode within the semiconductor's broad gain bandwidth. A quasi-continuous-level semiconductor laser model explains the lasing dynamics under optical pumping. In addition, we fabricate isolated gold-coated semiconductor discs and demonstrate higher-order lasing within live biological cells. These plasmonic nanolasers hold promise for multi-colour imaging and optical barcoding in cellular applications.