Battling absorptive losses by plasmon–exciton coupling in multimeric nanostructures

Abstract

The inherent and strong optical losses present in plasmonic nanostructures, significantly limits their technological applications at optical frequencies. Here, we report about the interplay between plasmons and excitons as a potential approach to selectively reduce ohmic losses. Samples have been prepared by functionalizing plasmonic core-shell nanostructures with excitonic molecules embedded in silica shells and interlocked by silica spacers to investigate the role played by the plasmon-exciton elements separation. Results obtained for different silica spacer thicknesses are evaluated by comparing dispersions of plasmonic multimers with respect to corresponding monomers. We have measured fluorophores emission quenching by means of steady-state fluorescence spectroscopy and as well as significant shortening of the corresponding fluorescence lifetime. These results were accompanied by simultaneous enhancement of Rayleigh scattering and transmittance, revealing an effective absorptive loss mitigation of the multimeric systems. Moreover, upon decreasing the thickness of the intermediate silica layer between gold cores and the external gain functionalized silica shell, the efficiency of excitonplasmon resonant energy transfer (EPRET) was significantly enhanced in both multimeric and monomeric samples. Simulations data along with experimental results confirm that the hybridized plasmon fields of multimers lead to more efficient optical loss compensation with respect to corresponding monomers.

Dynamic Multi-Mode Mie Model for Gain-Assisted Metal Nano-Spheres

“…The idea of coupling metal nanoparticles (mNP) with gain elements [1][2][3][4][5][6] is almost coeval to the very dawn of the stunning scientific interest born around the beginning of the century about the possibility to support localized surface plasmons (LSP) in these nanostructures [7][8][9]. During the last twenty years, the study of hybrid nano-resonators including metal and gain elements (mgNP), rather than remain bound to the role of an exotic sub-topic, constituted an imposingly growing parallel field [10][11][12][13][14][15][16][17][18][19]. Undoubtedly, this was partially due on account of how, while one of the most promising applications of LSPs was to allow the development of visible metamaterials, this very possibility was prevented by the large amount of losses the most viable metals show at these frequencies.…”

Loss compensated extraordinary transmission in hybridized plasmonic nanocavities

“…One of the drawbacks of light confinement is the ohmic loss. Strategies such as synthesizing alternative low-loss plasmonic materials [13] or using gain [14,15] to compensate the loss have been previously developed. These methods have also been implemented in EOT systems to enhance transmission further via plasmonic loss mitigation [16][17][18][19][20].…”

Plasmonics of Opal Surface: A Combined Near- and Far-Field Approach

“…In two-dimensional (2D) structures, high Q factors are obtained in connection to the use of high contrast index materials. − In three-dimensional (3D) structures, photonic crystals are usually fabricated with low-index materials yielding lower Q factors. However, laser-induced lithographic crystals , or self-assembled artificial opals − have permitted the engineering of the density of states, leading to a reinforcement of the light–matter interaction for emitters inserted in these structures. − Despite the limitation in achievable Purcell factors in low-Q cavities, a modification of emission rate has been evidenced. , A major characteristic of low-Q nanostructures is that they are much less demanding in terms of spectral matching. They offer a high versatility in the spectral tuning of the devices, which is a major advantage for applications.…”