Spectrally and spatially configurable superlenses for optoplasmonic nanocircuits

Abstract

Energy transfer between photons and molecules and between neighboring molecules is ubiquitous in living nature, most prominently in photosynthesis. While energy transfer is efficiently utilized by living systems, its adoption to connect individual components in man-made plasmonic nanocircuits has been challenged by low transfer efficiencies that motivate the development of entirely new concepts for energy transfer. We introduce herein optoplasmonic superlenses that combine the capability of optical microcavities to insulate molecule-photon systems from decohering environmental effects with the superior light nanoconcentration properties of nanoantennas. The proposed structures provide significant enhancement of the emitter radiative rate and efficient long-range transfer of emitted photons followed by subsequent refocusing into nanoscale volumes accessible to near-and far-field detection. Optoplasmonic superlenses are versatile building blocks for optoplasmonic nanocircuits and can be used to construct "dark" single-molecule sensors, resonant amplifiers, nanoconcentrators, frequency multiplexers, demultiplexers, energy converters, and dynamical switches.nanophotonics | optical information processing | optical sensing | plasmonics N onradiative energy transfer between nanoobjects is limited to distances of only a few nanometers, making photons the most attractive long-distance signal carriers. However, once the photon is emitted by a donor quantum emitter, the probability of acceptor absorbing its energy becomes negligibly small. Therefore, realizing efficient and controllable on-chip interactions between single photons and single quantum emitters, which are crucial for single-molecule optical sensing and quantum information technology, remains challenging. This problem is mitigated by optical microcavities (OMs), which can significantly boost the probability of a photon reabsorption through acceptor molecules (1) via efficient trapping and recirculating of photons (2). OMs also strongly modify radiative rate of emitters at select frequencies corresponding to cavity modes, which can provide local density of optical states (LDOS) exceeding that of the free space by orders of magnitude (2-5). In turn, noble-metal nanostructures can enhance emission of free-space photons by excited molecules (effectively acting as nano-analogs of radio antennas) (6-12) or facilitate relaxation by coupling to surface plasmons (SPs) (13-15). Consequently, both plasmonic nanostructures and OMs can modify the LDOS (16, 17), but the OM approach suffers from limited accessibility of the intracavity volume by target molecules [which should either be incorporated into the cavity material (3, 4) or interact with photonic modes via their weak evanescent tails (5,(18)(19)(20)], while high dissipative losses in metals create fundamental limitations for long-distance energy and information transfer through surface plasmons (21). Results and DiscussionIn this paper, we develop a previously undescribed approach for photon generation and energy tra...

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