Reducing Effective System Dimensionality with Long-Range Collective Dipole-Dipole Interactions.

Dimensionality plays a crucial role in long-range dipole-dipole interactions (DDIs). We demonstrate that a resonant nanophotonic structure modifies the apparent dimensionality in an interacting ensemble of emitters, as revealed by population decay dynamics. Our measurements on a dense ensemble of interacting quantum emitters in a resonant nanophotonic structure with long-range DDIs reveal an effective dimensionality reduction to d[over ¯]=2.20(12), despite the emitters being distributed in 3D. This contrasts with the homogeneous environment, where the apparent dimension is d[over ¯]=3.00. Our work presents a promising avenue to manipulate dimensionality in an ensemble of interacting emitters.

Plasmonic Nanoparticle Lattice Devices for White-Light Lasing.

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.

Lasing Action from Quasi-Propagating Modes.

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 energies and wavevectors. Conversely, quasi-propagating modes along the high symmetry directions are predicted to enable similar phenomena over a continuum of energies and wavevectors. Here, quasi-propagating modes in 2D nanoparticle lattices are shown to support lasing action over a continuous range of wavelengths and symmetry-determined directions from a single device. Using lead halide perovskite nanocrystal films as gain materials, lasing is achieved from waveguide-surface lattice resonance (W-SLR) modes that can be decomposed into propagating waves along high symmetry directions, and standing waves in the orthogonal direction that provide optical feedback. The characteristics of the lasing beams are analyzed using an analytical 3D model that describes diffracted light in 2D lattices. Demonstrations of lasing across different wavelengths and lattice designs highlight how quasi-propagating modes offer possibilities to engineer chromatic multibeam emission important in hyperspectral 3D sensing, high-bandwidth Li-Fi communication, and laser projection displays.

Room Temperature Weak-to-Strong Coupling and the Emergence of Collective Emission from Quantum Dots Coupled to Plasmonic Arrays.

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.