Brian T. Cunningham | Searcharxiv

arXiv2019

Enhanced Plasmonic Photocatalysis through Cooperative Plasmonic--Photonic Hybridization

Plasmonic nanoparticles (NPs) hold tremendous promise for catalyzing light-driven chemical reactions. The conventionally assumed detrimental absorption loss from plasmon damping can now be harvested to drive chemical transformations of the NP adsorbent, through the excitation and transfer of energetic "hot" carriers. The rate and selectivity of plasmonic photocatalysis are dependent on the characteristics of the incident light. By engineering the strength and wavelength of the light harvesting of a NP, it is possible to achieve more efficient and predictive photocatalysts. We report a plasmonic--photonic resonance hybridization strategy to substantially enhance hot electron generation at tunable, narrow-band wavelengths. By coupling the plasmon resonance of silver NPs to the guided mode resonance in a photonic crystal (PC) slab, the reaction rate of a hot-electron-driven reduction conversion is greatly accelerated. The mechanism is broadly compatible with NPs with manifold materials and shapes optimized for the targeted chemistry. The novel enhancement platform sheds light on rational design of high-performance plasmonic photocatalysts.

physics.optics↗

arXiv2018

Nanoantenna-Microcavity Hybrids with Highly Cooperative Plasmonic-Photonic Coupling

Nanoantennas offer the ultimate spatial control over light by concentrating optical energy well below the diffraction limit, whereas their quality factor (Q) is constrained by large radiative and dissipative losses. Dielectric microcavities, on the other hand, are capable of generating a high Q-factor through an extended photon storage time but have a diffraction-limited optical mode volume. Here we bridge the two worlds, by studying an exemplary hybrid system integrating plasmonic gold nanorods acting as nanoantennas with an on-resonance dielectric photonic crystal (PC) slab acting as a low-loss microcavity and, more importantly, by synergistically combining their advantages to produce a much stronger local field enhancement than that of the separate entities. To achieve this synergy between the two polar opposite types of nanophotonic resonant elements, we show that it is crucial to coordinate both the dissipative loss of the nanoantenna and the Q-factor of the low-loss cavity. In comparison to the antenna-cavity coupling approach using a Fabry-Perot resonator, which has proved successful for resonant amplification of the antenna's local field intensity, we theoretically and experimentally show that coupling to a modest-Q PC guided resonance can produce a greater amplification by at least an order of magnitude. The synergistic nanoantenna-microcavity hybrid strategy opens new opportunities for further enhancing nanoscale light-matter interactions to benefit numerous areas such as nonlinear optics, nanolasers, plasmonic hot carrier technology, and surface-enhanced Raman and infrared absorption spectroscopies.

physics.optics↗