Surface plasmon (SP) coupling has been successfully applied to nonradiative energy transfer via exciton-plasmon-exciton coupling in conventionally sandwiched donor-metal film-acceptor configurations. However, these structures lack the desired efficiency and suffer poor photoemission due to the high energy loss. Here, we show that the cascaded exciton-plasmon-plasmon-exciton coupling in stratified architecture enables an efficient energy transfer mechanism. The overlaps of the surface plasmon modes at the metal-dielectric and dielectric-metal interfaces allow for strong cross-coupling in comparison with the single metal film configuration. The proposed architecture has been demonstrated through the analytical modeling and numerical simulation of an oscillating dipole near the stratified nanostructure of metal-dielectric-metal-acceptor. Consistent with theoretical and numerical results, experimental measurements confirm at least 50% plasmon resonance energy transfer enhancement in the donor-metal-dielectric-metal-acceptor compared to the donor-metal-acceptor structure. Cascaded plasmon-plasmon coupling enables record high efficiency for exciton transfer through metallic structures.
Nonradiative energy transfer (NRET) has been applied in various applications of Nanosensors, Raman scattering, color tuning, light harvesting and organic light emitting structures. Due to the small range of donor-acceptor separation distance that NRET is effective, the improvement in energy transfer (ET) efficiency for thicker structures seems necessary. The plasmons resonance energy transfer (PRET) has been successfully employed to improve the NRET efficiency. The conventional plasmonic configuration consists of donor-metal nanostructure-acceptor shows remarkable improvement of PRET efficiency from the excited donor dipole to the acceptor molecule in longer separation distance. We report the first successful cascaded plasmons coupling in planar structure of donor/acceptor thin film that significantly gives rise to enhancement of ET efficiency. Moreover, the theoretical analysis shows an enhancement in induced electric field due to stratified metal-dielectric configuration compared to simple metal thin film. We observed ET efficiency increases more than 100% by applying dielectric layer between two metal films in plasmonic structure.
Plasmonic nanostructures have been widely known for their notable capability to enhance spontaneous emission of an electric dipole in their vicinity. Due to the availability of large optical density of states at their metallic surface, the radiative and nonradiative decay channels are dramatically modified. However, enhancement cannot be realized for any desired emissive dipole as the plasmonic resonance frequency is mostly determined intrinsically by the existing plasmonic materials. Although recent studies using metamaterial structures demonstrate a promising approach of tuning the Purcell factor across the emission wavelength, many of the demonstrations lack efficient radiative emission besides the fabrication complexity. Here, we show theoretically and experimentally that a simple metal-dielectric-metal stratified architecture allows for high tunability of the resonance frequency to obtain a maximum radiative decay rate for any desired dipole peak emission wavelength. Owing to the effective cascaded plasmonic mode coupling across the metal-dielectric interfaces, the proposed approach uniquely provides us with the ability to optimize the plasmonic nanostructure for 100% radiative transmission and 3-fold radiative emission enhancement.
Planar plasmonic nanostructures have gained considerable attention due to their crucial role in the theoretical comprehension of surface enhanced fluorescent along with their wide applications in nonradiative energy transfer (NRET), plasmonic wave guided mode, Raman scattering spectroscopy, color filters, light emitting and light harvesting devices. With the availability of large density of states at the metallic surface, the radiative and nonradiative decay channels of an electric dipole in a vicinity of metal would be dramatically modified. However, the radiative enhancement cannot be realized for any desired emissive dipole as the existing plasmonic resonance frequency is limited to the well-known plasmonic materials. Despite the fact that recent studies in metamaterial structures demonstrate a promising approach of tuning Purcell factor across the emission wavelength, the structures still suffer from an inefficient radiative emission. Moreover, in the case of nonradiative energy transfer, the conventionally sandwiched donor-metal film-acceptor configurations lack the desired efficiency and suffer poor photoemission due to the high energy loss. In this dissertation, we propose and demonstrate the nonradiative energy transfer mechanism between the donor and the acceptor through multi-layered metallic nanostructuresstratified configuration, in which an efficient energy transfer can be realized. This novel approach in NRET uniquely provides us with the ability to overcome the drawback of high energy absorption losses in a thick metal film by
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