Plasmonic photonic crystals realized through DNA-programmable assembly

Abstract

Three-dimensional dielectric photonic crystals have well-established enhanced light-matter interactions via high Q factors. Their plasmonic counterparts based on arrays of nanoparticles, however, have not been experimentally well explored owing to a lack of available synthetic routes for preparing them. However, such structures should facilitate these interactions based on the small mode volumes associated with plasmonic polarization. Herein we report strong lightplasmon interactions within 3D plasmonic photonic crystals that have lattice constants and nanoparticle diameters that can be independently controlled in the deep subwavelength size regime by using a DNA-programmable assembly technique. The strong coupling within such crystals is probed with backscattering spectra, and the mode splitting (0.10 and 0.24 eV) is defined based on dispersion diagrams. Numerical simulations predict that the crystal photonic modes (Fabry-Perot modes) can be enhanced by coating the crystals with a silver layer, achieving moderate Q factors (∼10 2 ) over the visible and near-infrared spectrum.DNA-programmable assembly | 3D photonic crystals | plasmonics | deep subwavelength scale | strong coupling E nhancing light-matter interactions is essential in photonics, including areas such as nonlinear optics (1), quantum optics (2, 3), and high-Q lasing (4). In general, there are two ways of achieving this in optical cavities: (i) with long cavity lifetimes (high Q factors) and (ii) with strong photonic confinement (small mode volume, V) (2, 3). In particular, 3D dielectric photonic crystals, with symmetry-induced photonic band gaps (Bragg gaps), enhance light-matter interactions via high Q factors (4-6). However, the coupling strength between photons and electronic transitions within such systems is intrinsically weak owing to diffraction-limited photonic confinement (3, 7). Recently, it was suggested that a plasmonic counterpart of photonic crystals can prohibit light propagation and open a photonic band gap by strong coupling between surface plasmons and photonic modes (a polariton gap) if the crystal is in deep subwavelength size regime (8); these crystals have been referred to as polaritonic photonic crystals (PPCs) (9-12). This opens up the exciting possibility of combining plasmonics with 3D photonics in the strong coupling regime and optimizing the photonic crystals as small-mode-volume devices owing to the strong plasmonic mode confinement (13). However, such systems require control over the positioning of the plasmonic elements in the crystal on the nano-or deep subwavelength scale (8), and owing to this synthetic challenge such 3D PPCs have largely remained unexplored in the visible wavelength range.The recent discovery that DNA can be used to program the assembly of high-quality single crystals with well-defined crystal habits consisting of nanoparticles occupying sites in a preconceived lattice (14) opens up possibilities for fine tuning the interaction between light and highly organized collections of particles as a functi...

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

“…This suggests that the interparticle plasmonic interactions here are primarily coherent and in-phase; small displacements (relative to their radii) in nanoparticle position do not meaningfully change the weak plasmonic coupling between particles. In turn, many of the emergent plasmonic and photonic effects that we have identified in similar systems (29,34,39) are likely robust to the presence of defects and forgiving to minor variations to the crystalline environment.…”

“…We have previously implemented volume-fraction-based methods with predictable and consistent agreement between experiment and simulation in the far field (28,29,32,34,39). Many of the unique and exciting plasmonic materials that we have explored using programmable DNA assembly depend solely on dipolar interparticle interactions (at low volume fraction) and are fairly insensitive and defect-tolerant.…”

Directional emission from dye-functionalized plasmonic DNA superlattice microcavities

“…Such superstructures behave as 3D plasmonic microcavities (passive cavities) that exhibit both guided modes and plasmonic near-field effects throughout the cavity medium. Therefore, upon incorporating excitonic materials into these superlattices, the nature of such 3D plasmonic microcavities (active cavities) can be explored systematically through an analysis of excitonic emission properties.In this work, we synthesize dye-functionalized plasmonic superlattices via DNA programmable assembly (10,14), and study their emission properties both experimentally and theoretically. …”

“…Therefore, these methods provide exciting possibilities for controlling the interaction between photonic modes of microcavity structures and plasmonic modes of the highly polarizable nanoparticles for nano-/micrometer-scale optical applications. Indeed, it was recently demonstrated that one can control the strength of coupling between Fabry-Perot modes and localized surface plasmons in a body-centered cubic (bcc) crystal composed of gold nanoparticles with a rhombic dodecahedron (RD) crystal habit (14). Such superstructures behave as 3D plasmonic microcavities (passive cavities) that exhibit both guided modes and plasmonic near-field effects throughout the cavity medium.…”

“…In this work, we synthesize dye-functionalized plasmonic superlattices via DNA programmable assembly (10,14), and study their emission properties both experimentally and theoretically.…”