Lasing action in strongly coupled plasmonic nanocavity arrays

Abstract

Periodic dielectric structures are typically integrated with a planar waveguide to create photonic band-edge modes for feedback in one-dimensional distributed feedback lasers and two-dimensional photonic-crystal lasers. Although photonic band-edge lasers are widely used in optics and biological applications, drawbacks include low modulation speeds and diffraction-limited mode confinement. In contrast, plasmonic nanolasers can support ultrafast dynamics and ultrasmall mode volumes. However, because of the large momentum mismatch between their nanolocalized lasing fields and free-space light, they suffer from large radiative losses and lack beam directionality. Here, we report lasing action from band-edge lattice plasmons in arrays of plasmonic nanocavities in a homogeneous dielectric environment. We find that optically pumped, two-dimensional arrays of plasmonic Au or Ag nanoparticles surrounded by an organic gain medium show directional beam emission (divergence angle <1.5° and linewidth <1.3 nm) characteristic of lasing action in the far-field, and behave as arrays of nanoscale light sources in the near-field. Using a semi-quantum electromagnetic approach to simulate the active optical responses, we show that lasing is achieved through stimulated energy transfer from the gain to the band-edge lattice plasmons in the deep subwavelength vicinity of the individual nanoparticles. Using femtosecond-transient absorption spectroscopy, we verified that lattice plasmons in plasmonic nanoparticle arrays could reach a 200-fold enhancement of the spontaneous emission rate of the dye because of their large local density of optical states.

Vivid, full-color aluminum plasmonic pixels

“…For comparison, the individual nanorod spectra were also calculated for these geometries, clearly showing that the spectral peaks and lineshapes obtained are largely controlled by diffractive coupling effects. Whereas the pixel spectra show far narrower lineshapes than the individual nanorods, they are not as narrow as those observed for infinite square arrays of nanospheres or nanodisks (47,48). All simulations were performed using experimental (nonadjustable) structural parameters.…”

Advances in small lasers

“…Furthermore for electrically pumped truly sub-wavelength SPASERs, current densities will have to approach MA/cm 2 , making their practicality dubious 80 . Alternatively, arrays of strongly coupled plasmonic nanocavities can harness some of the advantages of localized surface plasmons, like the dramatically increased spontaneous emission rates, while at the same time reducing the gain required to reach the lasing threshold to a regime that is compatible with the gain available from organic dyes 81,82 . Similar resonant effects were also observed in random ensembles of metallic nanoparticles coated with optical gain media 83 .…”

Defect tolerance and the effect of structural inhomogeneity in plasmonic DNA-nanoparticle superlattices

“…These efficient interactions with visible light are due to localized surface plasmon resonances (LSPRs), the collective oscillation of conduction electrons (1). Hierarchical arrangements of plasmonic nanoparticles have become the basis for colorimetric sensors (2,3), subdiffraction limited waveguides (4), visible light metamaterials (5), and nanoscale lasing devices (6,7), and the ability to adjust architecture in such materials has led to a wide variety of structures with tunable and unusual optical properties (8)(9)(10)(11)(12). Many of these technologies leverage the scalability and modularity of bottom-up assembly techniques, which use chemically synthesized colloidal nanoparticles as building blocks (13,14).…”