Colloidal quantum dot (CQD) assemblies exhibit interesting optoelectronic properties when coupled to optical resonators ranging from Purcell-enhanced emission to the emergence of hybrid electronic and photonic polariton states in the weak and strong coupling limits, respectively. Here, experiments exploring the weak-to-strong coupling transition in CQD–plasmonic lattice hybrid devices at room temperature are presented for varying CQD concentrations. To interpret these results, generalized retarded Fano–Anderson and effective medium models are developed. Individual CQDs are found to interact locally with the lattice yielding Purcell-enhanced emission. At high CQD densities, polariton states emerge as two-peak structures in the photoluminescence, with a third polariton peak, due to collective CQD emission, appearing at still higher CQD concentrations. Our results demonstrate that CQD–lattice plasmon devices represent a highly flexible platform for the manipulation of collective spontaneous emission using lattice plasmons, which could find applications in optoelectronics, ultrafast optical switches, and quantum information science.
A plasmonic nanolaser architecture that can produce white‐light emission is reported. A laser device is designed based on a mixed dye solution used as gain material sandwiched between two aluminum nanoparticle (NP) square lattices of different periodicities. The (±1, 0) and (±1, ±1) band‐edge surface lattice resonance (SLR) modes of one NP lattice and the (±1, 0) band‐edge mode of the other NP lattice function as nanocavity modes for red, blue, and green lasing respectively. From a single aluminum NP lattice, simultaneous red and blue lasing is realized from a binary dye solution, and the relative intensities of the two colors are controlled by the volume ratio of the dyes. Also, a laser device is constructed by sandwiching dye solutions between two Al NP lattices with different periodicities, which enables red–green and blue–green lasing. With a combination of three dyes as liquid gain, red, green, and blue lasing for a white‐light emission profile is realized.
Spontaneous emission of quantum emitters can be enhanced by increasing the local density of optical states, whereas engineering dipole–dipole interactions requires modifying the two-point spectral density function. Here, we experimentally demonstrate long-range dipole–dipole interactions (DDIs) mediated by surface lattice resonances in a plasmonic nanoparticle lattice. Using angle-resolved spectral measurements and fluorescence lifetime studies, we show that unique nanophotonic modes mediate long-range DDI between donor and acceptor molecules. We observe significant and persistent DDI strengths for a range of densities that map to ∼800 nm mean nearest-neighbor separation distance between donor and acceptor dipoles, a factor of ∼100 larger than free space. Our results pave the way to engineer and control long-range DDIs between an ensemble of emitters at room temperature.
This paper reports the observation of band-edge states at the high-symmetry M-point in the first Brillouin zone of hexagonal and honeycomb plasmonic nanoparticle (NP) lattices. The surface lattice resonance at the M-point (SLR M ) of a hexagonal lattice results from asymmetric out-of-plane dipole coupling between NPs. In contrast to the hexagonal lattice, honeycomb lattices support two SLR modes at the M-point because of their non-Bravais nature: (1) a blue-shifted SLR M1 from the coupling of two distinct out-of-plane dipole LSP resonances, and (2) a redshifted SLR M2 from in-plane dipole−dipole coupling. By incorporating organic dye solutions as gain media with Ag NP lattices, we achieved M-point lasing from both hexagonal and honeycomb lattices. Understanding coupling mechanisms at high-symmetry points in NP lattices with the same geometry but different unit cells is important to assess the prospects of topological states in plasmonic systems.
longitudinal beam profiles, [1,2] and because of their increased rotational symmetry, 2D cavities enable multimode lasing, [3,4] vortex polarization, and annular-shaped beams. [2,5] Most lasing work on 2D photonic crystals exploits band edges at high symmetry points (e.g., Γ, X, and M points of a square lattice) in reciprocal space for optical feedback. [6][7][8][9] Since standing waves at these points are biaxially confined, solutions to their wave equation are critically constrained, which limits lasing action to discrete wavelengths and directions. [10] However, 2D photonic crystals can also be considered as lines of 1D arrays, where in-plane scattered waves are decomposed along two orthogonal directions. [2,10,11] In this picture, quasi-propagating photonic modes are slow traveling waves and can be interpreted as uniaxially confined standing waves that propagate along high-symmetry directions (e.g., Γ-M, Γ-X, and M-X). The additional degree of freedom from propagation enables the band edge states to span a continuum of energies and wavevectors. [10,12,13] Although quasi-propagating modes are predicted to support optical feedback, [10,13,14] lasing action via 2D cavities remains primarily focused on that from high symmetry points.Strongly scattering 2D plasmonic nanoparticle (NP) lattices that can trap light in-plane support hybrid photonic-plasmonic modes known as surface lattice resonances (SLRs). [15,16] Feedback from SLRs has enabled nanoscale lasing from NP lattice cavities integrated with index-matched emitter gain materials such as organic dyes in solvents and upconversion NP thin films. [17][18][19][20] NP lattices integrated with high-refractiveindex emissive materials such as colloidal quantum dot films have also demonstrated lasing from transverse electric (TE) and transverse magnetic (TM) waveguide-hybridized SLRs (W TE -SLRs and W TM -SLRs). [21][22][23] Because of the mode structure of the waveguide component, W-SLRs can excite large volumes of active material for lasing. [22,24] For either SLR or W-SLR modes, however, feedback for lasing is from biaxially confined standing waves [21,23,[25][26][27] since their losses are lower than quasipropagating modes. [2,28,29] Lasing from quasi-propagating modes should be possible; we hypothesize that they have been elusive due to insufficient gain coefficients (≈10-200 cm −1 ). [30,31] Although engineered gain materials such as gradient-shell quantum dots [32] or dyes with minimized triplet states [33] may offer higher gain, their syntheses are challenging. In contrast, lead halide perovskite nanocrystals (NCs) can be readily Band edges at the high symmetry points in reciprocal space of periodic structures hold special interest in materials engineering for their high density of states. In optical metamaterials, standing waves found at these points have facilitated lasing, bound-states-in-the-continuum, and Bose-Einstein condensation. However, because high symmetry points by definition are localized, properties associated with them are limited to specific e...
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