Subdiffraction Light Concentration by J-Aggregate Nanostructures

Abstract

We show, by accurate scattering calculations, that nanostructures obtained from thin films of J-aggregate dyes, despite their insulating behavior, are able to concentrate the electromagnetic field at optical frequencies like metallic nanoparticles. These results promise to widely enlarge the range of plasmonic materials, thus opening new perspectives in nanophotonics. Specifically we investigate ultrathin nanodisks and nanodisk dimers that can be obtained by standard nanolithography and nanopatterning techniques. These molecular aggregates display highly attractive nonlinear optical properties, which can be exploited for the realization of ultracompact devices for switching by light on the nanoscale without the need of additional nonlinear materials. W hen light interacts with metal nanoparticles and nanostructures, it can excite collective oscillations known as localized surface plasmons (LSPs), which provide the opportunity to confine light to very small dimensions below the diffraction limit. 1−4 This high confinement can lead to a striking near-field enhancement, which can significantly enhance weak nonlinear processes 5 and enables a great variety of applications such as optical sensing, 6,7 higher efficiency solar cells, 8 nanophotonics 1,5,9 including ultracompact lasers and amplifiers, 10 and antennas transmitting and receiving light signals at the nanoscale. 4,11,12 The small mode volume of LSP resonances also increases the photonic local density of states (LDOS) close to a plasmonic nanoparticle, enabling the modification of the optical properties (decay rate and quantum efficiency) of emitters placed in its close proximity (see for example ref 13 and Supporting Information Figure S1). The interaction of quantum emitters, as quantum dots or dye molecules, with individual metallic nanostructures carries significant potential for the quantum control of light at the nanoscale. 1,14−22 As first highlighted by Takahara et al., 23 only materials with a negative real part of the dielectric function and moderate losses are able to excite localized surface plasmons and hence to confine light to very small dimensions below the diffraction limit. These collective and confined excitations are efficiently supported, despite dissipative losses, by noble metals where the effective response of the electrons can be described by a Drude−Lorentz dielectric function whose real part is negative for frequencies below the plasma frequency. 2 Also superconductors or graphene has been proposed as a platform for surface plasmon polaritons. 24,25 Collective oscillations of free electrons are not the only way a negative permittivity may arise. It may also occur in the highenergy tail of a strong absorption resonance. For example, it has been shown that lattice vibrations in polar dielectric materials can also originate negative dielectric permittivity in the far-or mid-infrared spectral range, which can support phononpolaritons confined to the surface. 26,27 It has also been shown

Plasmonic bio-sensing for the Fenna-Matthews-Olson complex

“…Here, the coupling strength g 1(6) between the SPs and site 1 (6) is assumed to be independent of k under the Markovian approximation4345. The strong decay rate into SPs then takes the form24, , and the values we choose for g 1 and g 6 are consistent with a recent analysis of nanowire SPs coupled to J-aggregates181920.…”

Bonding and Antibonding Modes in Metal–Dielectric–Metal Plasmonic Antennas for Dual‐Band Applications

“…Interestingly, apart from the excitonic resonance (approximately repeating the peak of Im(ε j )) the absorption by the j-aggregate ring also shows a broader exciton-polaritonic resonance at higher frequencies, where Re(ε j ) takes negative values. [23,24] The observed significant fingerprint enhancement justifies the use of our dual-band dimer SPP antenna for surface-enhanced spectroscopy. Notice that from the practical point of view, the delivery of the sensed materials in between the gold disks, as well as around the antenna, can potentially be realized via nanofluidics.…”

“…Remarkably, the visibility of the absorption fingerprints exceeds the absorption by the octane disk and j‐aggregate ring by about two orders of magnitude (see orange and violet curves in Figure c). Interestingly, apart from the excitonic resonance (approximately repeating the peak of Im(ε j )) the absorption by the j‐aggregate ring also shows a broader exciton‐polaritonic resonance at higher frequencies, where Re(ε j ) takes negative values . The observed significant fingerprint enhancement justifies the use of our dual‐band dimer SPP antenna for surface‐enhanced spectroscopy.…”

Plasmon-induced light concentration enhanced imaging visibility as observed by a composite-field microscopy imaging system

“…The PILC effect and iCFM system introduces the best visibility enhancement when the energy of the monochromatic vertical beams is matched to the LSPR of the nanoparticles, so iCFM can amplify the degree of the signal change if the LSPR of nanoparticles is regulated in reaction monitoring and analysis. In addition, some new emerging plasmonic nanomaterials, such as heavily-doped colloidal semiconductor, 39 graphene 40 and J-aggregate dyes, 41 are no longer limited to the traditional noble metals and the thin films of J-aggregate dyes has been confirmed to have an excellent PILC effect, 41 suggesting this iCFM system might have wide applications.…”