Dressing Plasmons in Particle-in-Cavity Architectures

Abstract

Placing metallic nanoparticles inside cavities, rather than in dimers, greatly improves their plasmonic response. Such particle-in-cavity (PIC) hybrid architectures are shown to produce extremely strong field enhancement at the particle-cavity junctions, arising from the cascaded focusing of large optical cross sections into small gaps. These simply constructed PIC structures produce the strongest field enhancement for coupled nanoparticles, up to 90% stronger than for a dimer. The coupling is found to follow a universal power law with particle-surface separation, both for field enhancements and resonant wavelength shifts. Significantly enhanced Raman signals are experimentally observed for molecules adsorbed in such PIC structures, in quantitive agreement with theoretical calculations. PIC architectures may have important implications in many applications, such as reliable single molecule sensing and light harvesting in plasmonic photovoltaic devices.

Synergetic Light-Harvesting and Near-Field Enhancement in Multiscale Patterned Gold Substrates

“…23 Recently, the incorporation of Au nanoparticles into the voids of SSV arrays has been explored, showing also an important increase in field enhancement at the particle-cavity junction. [24][25][26] These results reinforce the idea that electromagnetic fields in SSV arrays may be further confined by smaller metallic features at the nanometric scale.…”

“…26 In our case, we have not detected new plasmon modes arising from the coupling with nanoscale features (see Fig. 6b), presumably because the surface roughness is an integral part of the surface of the cavity, without air gaps.…”

“…While a full model for such a complex system is beyond present day computation capabilities, part of the involved physics can be grasped by a model considering a single void cavity coupled by a 1 nm gap with a single gold nanoparticle, as described by Huang and coworkers. 26 As it has been…”

“…This is in full agreement with the simulations from Huang et. al, 26 that indicate that more charge accumulates at the junctions in nanoparticle-cavity systems than in nanoparticle-nanoparticle ones. The enhanced charge accumulation is attributed to the large optical cross section of the resonant cavity.…”

Rapid Ultrasensitive Single Particle Surface-Enhanced Raman Spectroscopy Using Metallic Nanopores

“…In this arrangement, the enhancement is generated after the nanoparticle has translocated through the nanopore. Simulations and experimentation has shown a strong coupling exists between NPs and metallic nanovoids 44,45 . This interaction will no longer be governed by the NPs position in relation to the nanopore allowing NP stabilization methods, such as silica encapsulation, to be used.…”