In this review we look at the concepts and state-of-the-art concerning the strong coupling of surface plasmon-polariton modes to states associated with quantum emitters such as excitons in J-aggregates, dye molecules and quantum dots. We explore the phenomenon of strong coupling with reference to a number of examples involving electromagnetic fields and matter. We then provide a concise description of the relevant background physics of surface plasmon polaritons. An extensive overview of the historical background and a detailed discussion of more recent relevant experimental advances concerning strong coupling between surface plasmon polaritons and quantum emitters is then presented. Three conceptual frameworks are then discussed and compared in depth: classical, semi-classical and fully quantum mechanical; these theoretical frameworks will have relevance to strong coupling beyond that involving surface plasmon polaritons. We conclude our review with a perspective on the future of this rapidly emerging field, one we are sure will grow to encompass more intriguing physics and will develop in scope to be of relevance to other areas of science.

https://iopscience.iop.org/article/10.1088/0034-4885/78/1/013901/pdf

Strong coupling between surface plasmon polaritons and emitters: a review

Strong coupling between resonantly matched localized surface plasmons and molecular excitons results in the formation of new hybridized energy states called plexcitons. Understanding the nature and tunability of these hybrid nanostructures is important for both fundamental studies and the development of new applications. We investigate the interactions between J-aggregate excitons and single plasmonic dimers and report for the first time a unique strong coupling regime in individual plexcitonic nanostructures. Dark-field scattering measurements and finite-difference time-domain simulations of the hybrid nanostructures show strong plexcitonic coupling mediated by the near-field inside each dimer gap, which can be actively controlled by rotating the polarization of the optical excitation. The plexciton dispersion curves, obtained from coupled harmonic oscillator models, show anticrossing behavior at the exciton transition energy and giant Rabi splitting ranging between 230 and 400 meV. These energies are, t...

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Near-field Mediated Plexcitonic Coupling and Giant Rabi Splitting in Individual Metallic Dimers

Recent advances and the current status of challenging light-harvesting nanomaterials, such as semiconducting quantum dots (QDs), metal nanoparticles, semiconductor–metal heterostructures, π-conjugated semiconductor nanoparticles, organic–inorganic heterostructures, and porphyrin-based nanostructures, have been highlighted in this review. The significance of size-, shape-, and composition-dependent exciton decay dynamics and photoinduced energy transfer of QDs is addressed. A fundamental knowledge of these photophysical processes is crucial for the development of efficient light-harvesting systems, like photocatalytic and photovoltaic ones. Again, we have pointed out the impact of the metal-nanoparticle-based surface energy transfer process for developing light-harvesting systems. On the other hand, metal–semiconductor hybrid nanostructures are found to be very promising for photonic applications due to their exciton–plasmon interactions. Potential light-harvesting systems based on dye-doped π-conjugated s...

Nanoscale Strategies for Light Harvesting

The advance of modern technology is still driven largely by miniaturization, with optical devices now following electronics in the race towards single-molecule functionality. The combination of different discrete photonic elements to produce 'hybrid' nanophotonic devices could yield a range of useful functions, but it is hard to realize such structures using conventional assembly processes. Oliver Benson reviews the progress being made in this technologically challenging area, and looks forward to the practical benefits that we might ultimately hope to reap.

Assembly of hybrid photonic architectures from nanophotonic constituents

Real-time observations were made of the shape change from pyramids to domes during the growth of germanium-silicon islands on silicon (001). Small islands are pyramidal in shape, whereas larger islands are dome-shaped. During growth, the transition from pyramids to domes occurs through a series of asymmetric transition states with increasing numbers of highly inclined facets. Postgrowth annealing of pyramids results in a similar shape change process. The transition shapes are temperature dependent and transform reversibly to the final dome shape during cooling. These results are consistent with an anomalous coarsening model for island growth.

Transition states between pyramids and domes during Ge/Si island growth

We report measurements of a coherent coupling between surface plasmon polaritons (SPP) and quantum well excitons in a hybrid metal-semiconductor nanostructure. The hybrid structure is designed to optimize the radiative exciton-SPP interaction which is probed by low-temperature, angle-resolved, far-field reflectivity spectroscopy. As a result of the coupling, a significant shift of $\ensuremath{\sim}7\text{ }\text{ }\mathrm{meV}$ and an increase in broadening by $\ensuremath{\sim}4\text{ }\text{ }\mathrm{meV}$ of the quantum well exciton resonance are observed. The experiments are corroborated by a phenomenological coupled-oscillator model predicting coupling strengths as large as 50 meV in structures with optimized detunings between the coupled exciton and SPP resonances. Such a strong interaction can, e.g., be used to enhance the luminescence yield of semiconductor quantum structures or to amplify SPP waves.

Coherent exciton-surface-plasmon-polariton interaction in hybrid metal-semiconductor nanostructures.

Photoluminescence plasmonic enhancement in InAs quantum dots coupled to gold nanoparticles

Selective formation of InAs quantum dots on the sidewalls of mesa strips along both [01−1] and [011] directions of a GaAs(100) surface is demonstrated. This result is in sharp contrast to observations on traditionally deep-patterned substrates, where quantum dots are formed on top mesas and at bottom trenches. This distinction is explained kinetically and energetically. These results may encourage application of organized arrays of quantum dots.

Localized formation of InAs quantum dots on shallow-patterned GaAs(100)

Micro-Hall devices based on modulation-doped Al0.12In0.88Sb∕InSb heterostructures are fabricated and studied in terms of sensitivity and noise. Extremely high supply-current-related magnetic sensitivities of 1800VA−1T−1 at 77K and 1220VA−1T−1 at 300K are reported and observed to be independent of the bias current. The detection limit of the devices studied at low and room temperature are at nanotesla values throughout the broad frequency range from 20Hzto20kHz. The low detection limit of 28nT at 300K and 18nT at 77K were found at high frequencies where the Johnson noise is dominant. A measured detection limit per unit device width of 630pTmmHz−1∕2 is reported indicating the potential for picotesla detectivity.

Highly sensitive micro-Hall devices based on Al0.12In0.88Sb∕InSb heterostructures

Intermediate band solar cells were realized using a GaAs (311)A p-i-n junction with Si as both the p- and n-type dopant, where the intermediate band was realized with a stack of InGaAs quantum wires. This quantum wire photovoltaic device demonstrates a non-trivial increase in solar cell efficiency over a reference p-i-n GaAs (311)A junction resulting from a significant increase in short circuit current and an only slight decrease in open circuit voltage. Presented are optical and electrical characterizations of these devices.

Vas. P. Kunets

Papers

Coherent exciton-surface-plasmon-polariton interaction in hybrid metal-semiconductor nanostructures.

Photoluminescence plasmonic enhancement in InAs quantum dots coupled to gold nanoparticles

Localized formation of InAs quantum dots on shallow-patterned GaAs(100)

Highly sensitive micro-Hall devices based on Al0.12In0.88Sb∕InSb heterostructures

InGaAs quantum wire intermediate band solar cell