This Letter describes strong coupling of densely packed molecular emitters in metal−organic frameworks (MOFs) and plasmonic nanoparticle (NP) lattices. Porphyrin-derived ligands with small transition dipole moments in an ordered MOF film were grown on Ag NP arrays. Angle-resolved optical measurements of the MOF-NP lattice system showed the formation of a polariton that is lower in energy and does not cross the uncoupled MOF Q 1 band. Modeling predicted the upper polariton energy and a calculated Rabi splitting of 110 meV. The coupling strength was systematically controlled by detuning the plasmon energy by changing the refractive index of the solvents infiltrating the MOF pores. Through transient absorption spectroscopy, we found that the lower polariton decays quickly at shorter time scales (<500 ps) and slowly at longer times because of energy transfer from the upper polariton. This hybrid system demonstrates how MOFs can function as an accessible excitonic material for polariton chemistry.
Nanostructured surfaces with quasi-random geometries can manipulate light over broadband wavelengths and wide ranges of angles. Optimization and realization of stochastic patterns have typically relied on serial, direct-write fabrication methods combined with real-space design. However, this approach is not suitable for customizable features or scalable nanomanufacturing. Moreover, trial-and-error processing cannot guarantee fabrication feasibility because processing-structure relations are not included in conventional designs. Here, we report wrinkle lithography integrated with concurrent design to produce quasi-random nanostructures in amorphous silicon at wafer scales that achieved over 160% light absorption enhancement from 800 to 1,200 nm. The quasi-periodicity of patterns, materials filling ratio, and feature depths could be independently controlled. We statistically represented the quasi-random patterns by Fourier spectral density functions (SDFs) that could bridge the processing-structure and structure-performance relations. Iterative search of the optimal structure via the SDF representation enabled concurrent design of nanostructures and processing.wrinkles | light trapping | silicon photonics | spectral density function | pattern transfer Q uasi-random structures with neither periodic nor fully disordered geometries are useful in the design of superhydrophobic substrates (1, 2), stretchable electronics (3-6), and sensors (7,8). In particular, these nanostructured systems support rich Fourier spectra that enable light manipulation over broadband wavelengths and over wide collection angles (9, 10). Independent control over the relative degree of order vs. disorder, materials filling ratio, and feature size is critical to generate patterns with a diverse range of optical responses (11). For example, quasi-random nanostructures in photonic materials such as amorphous silicon (a-Si) are being increasingly used in photovoltaics and light-emitting diodes (9, 12-18). To enhance device performance from the patterns, optimization of nanoscale structure is crucial. However, most efforts to control quasirandom patterns have relied on serial processes such as electron-beam lithography (9,12,16,18,19). Although such approaches enable precise pattern placement and maximum control over the nanostructured features, the tools are not scalable and are cost prohibitive for large-area fabrication (>1 cm 2 ). Furthermore, most work has focused on the traditional, sequential strategy for pattern generation: (i) design nanostructures in real space for a target performance and then (ii) fabricate structures by trial-and-error processing optimization (9, 20). Without considering the fabrication conditions as part of the overall design strategy, however, conventional methods cannot ensure manufacturing feasibility of the optimized nanostructures. Trial-and-error experiments to achieve optimal designs are usually time-consuming. Hence, development of a concurrent design approach can establish the phase space of target quasi-rand...
This paper describes the design and prototyping of single-crystalline TiN plasmonic metasurfaces based on subwavelength hole arrays. An evolutionary algorithm with a multiobjective fitness function was developed to produce a variety of threedimensional (3D) light profiles with balanced intensities at the light spots. We also demonstrated a simple, efficient technique to prototype these lattice designs in large-area TiN films by combining focused ion beam milling and wet chemical etching. Multilevel phase control was achieved by tuning nanohole size, and multipoint focusing with arbitrary light spot patterns was realized. Using anisotropic nanohole shapes, the TiN lattice lenses could exhibit dynamic tuning of the focal profiles by changing the polarization of incident light.
This paper describes a computational imaging platform to determine the orientation of anisotropic optical probes under differential interference contrast (DIC) microscopy. We established a deep-learning model based on data sets of DIC images collected from metal nanoparticle optical probes at different orientations. This model predicted the in-plane angle of gold nanorods with an error below 20°, the inherent limit of the DIC method. Using low-symmetry gold nanostars as optical probes, we demonstrated the detection of in-plane particle orientation in the full 0–360° range. We also showed that orientation predictions of the same particle were consistent even with variations in the imaging background. Finally, the deep-learning model was extended to enable simultaneous prediction of in-plane and out-of-plane rotation angles for a multibranched nanostar by concurrent analysis of DIC images measured at multiple wavelengths.
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.
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