Lattice plasmon resonances or surface
lattice resonances (SLRs)
supported in two-dimensional (2D) metal nanoparticle arrays have extremely
narrow line widths and highly localized electric field enhancements,
which are key properties for realizing plasmon lasers and hybrid solid-state
lighting devices. This paper reports lattice plasmons in one-dimensional
(1D) metal nanogratings with broadband tunability (over 400 nm) far
beyond their 2D counterparts at visible wavelengths. The large wavelength
tunabilities of 1D or line-SLRs are from the lower symmetry of the
structures compared to 2D arrays based on nanoparticles. We demonstrate
that line-SLRs exhibit a Fano-like character based on coupling between
an out-of-plane plasmon excitation and 1D Bragg diffraction modes.
We show how the height and periodicity of the grating determine the
spectral properties of the line-SLRs. By adjusting the line height,
we achieved high-quality lattice resonances, even in index-mismatched
environments.
Small lasers can generate coherent light for integrated photonics, in vivo cellular imaging, and solid-state lighting. Unlike conventional lasers, plasmonic lasers can generate coherent light at subwavelength scales, although cavity architectures based on metal films and semiconducting gain exhibit large radiative losses and lack directional emission. In contrast, 2D metal nanoparticle arrays surrounded by organic dyes can support lasing with high directionality at room temperature. However, the relationship between the number of nanoparticles in a finite lattice and their lasing emission characteristics is unknown. Here we show that the number of units in 2D gold nanoparticle lattices is critical to generate robust cavity resonances and lasing emission. Narrower lattice plasmons associated with stronger electromagnetic near fields are observed as the nanoparticle number increases. Experimentally, we demonstrate lasing from a 30 × 30 nanoparticle lattice. Semiquantum modeling indicates lower lasing thresholds and faster population inversion dynamics with higher nanoparticle numbers. These results suggest that finite lattices of nanoparticles integrated with gain can function as independent, coherent light sources for optical multiplexing and lab-on-a-chip applications.
Quantum emitters located in proximity to a metal nanostructure individually transfer their energy via near-field excitation of surface plasmons. The energy transfer process increases the spontaneous emission (SE) rate due to plasmon-enhanced local field. Here, we demonstrate significant acceleration of quantum emitter SE rate in a plasmonic nano-cavity due to cooperative energy transfer (CET) from plasmon-correlated emitters. Using an integrated plasmonic nano-cavity, we realize up to six-fold enhancement in the emission rate of emitters coupled to the same nano-cavity on top of the plasmonic enhancement of the local density of states. The radiated power spectrum retains the plasmon resonance central frequency and lineshape, with the peak amplitude proportional to the number of excited emitters indicating that the observed cooperative SE is distinct from super-radiance.
Plasmon-assisted CET offers unprecedented control over the SE rate and allows to
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