We study the collective photon decay of multiple quantum emitters embedded in a thin high-index dielectric layer such as hexagonal boron nitride (hBN), with and without a metal substrate. We first explore the significant role that guided modes including surface plasmon modes play in the collective decay of identical single-photon emitters (super- and subradiance). Surprisingly, on distances relevant for collective emission, the guided or surface-plasmon modes do not always enhance the collective emission. We identify configurations with inhibition, and others with enhancement of the dipole interaction due to the guided modes. We interpret our results in terms of local and cross densities of optical states. In the same structure, we show a remarkably favorable configuration for enhanced Förster resonance energy transfer between a donor and acceptor in the dielectric layer on a metallic substrate. We compare our results to theoretical limits for energy transfer efficiency.
We study the collective photon decay of multiple quantum emitters embedded in a thin high-index dielectric layer such as hexagonal boron nitride (hBN), with and without a metal substrate. We first explore the significant role that guided modes including surface plasmon modes play in the collective decay of identical single-photon emitters (super- and subradiance). Surprisingly, on distances relevant for collective emission, the guided or surface-plasmon modes do not always enhance the collective emission. We identify configurations with inhibition, and others with enhancement of the dipole interaction due to the guided modes. We interpret our results in terms of local and cross densities of optical states. In the same structure, we show a remarkably favorable configuration for enhanced Förster resonance energy transfer between a donor and acceptor in the dielectric layer on a metallic substrate. We compare our results to theoretical limits for energy transfer efficiency.
Collective light emission from many-body quantum systems is a cornerstone of quantum optics, yet its implementation in solid-state platforms operating under ambient conditions remains highly challenging. Large-bandgap van der Waals materials such as hexagonal boron nitride (hBN) host stable room-temperature single-photon emitters with narrow linewidths across a broad spectral range. However, cooperative radiative effects in this system have not been previously explored. Here we demonstrate collective emission from quantum-emitter ensembles in hBN layers when the emitters are nearly indistinguishable and positioned within a sub-wavelength proximity. Using confocal microscopy and a Hanbury Brown-Twiss (HBT) configuration, we identify both isolated emitters and ensembles activated by localized electron-beam irradiation. Time-resolved photoluminescence measurements reveal a superlinear intensity enhancement and a pronounced acceleration of the radiative decay in tightly confined ensembles, with lifetimes approaching the temporal resolution of our experimental system (about 500 ps), compared to approximately 1.85 ns for single emitters or large, spatially extended ensembles. Complementary second-order photon-correlation measurements exhibit sub-Poissonian antidip consistent with emission from a few indistinguishable emitters. The simultaneous observation of lifetime shortening and enhanced emission provides direct evidence of cooperative emission at room temperature, achieved without optical cavities or cryogenic cooling. These results establish optically active defect ensembles in hBN as a scalable solid-state platform for engineered collective quantum optics in two-dimensional materials, opening avenues toward ultrabright superradiant light sources and nonclassical photonic states for quantum technologies.
Surface plasmon polaritons are charge density waves of electrons in a metal, which are coupled to an electromagnetic field at a metal-dielectric interface. The electro- magnetic field associated with surface plasmons is confined, resulting in increased field intensities near the interface. Optical emitters placed near a metal film interact strongly with the surface plasmon modes present, not only modifying the radiation rates, but also the radiation profile. These emitters may be used to store and process information, and understanding their behaviour in the presence of a lossy metal film is important in determining the advantages and limitations of using surface plasmons. In this thesis, we wish to understand how we can optically control atoms by exploring two physical phenomena: first, the influence of surface plasmons on collective effects in an ensemble of emitters. Secondly, the single photon excitation of an emitter near a metal film. In the first case, we analyze the collective radiative behaviour of multiple classical emitters near a metal film that radiatively couple to the far-field through surface plasmon modes. We demonstrate that the contributions of dipolar image charges within the metal film significantly affect the cooperative emission of nearby sources, generating sub- and super-radiant emission that can be controlled with a suitably detuned external driving field. In the second case, we determine the excitation probability of an atom near a metal film by a single photon pulse that is time reversed. Using a quantum electro- dynamic description of absorbing dielectrics, we show that non-radiative decay will limit the excitation probability to about half of the maximum that could be achieved in the absence of losses.
In this study, we present the superradiance effects of N identical molecular emitters inside Fabry–Pérot (FP) cavity systems in the framework of macroscopic quantum electrodynamics. The proposed theory can estimate the enhancement of spontaneous emission rates, including the effects of cavity geometry and material dielectric properties. Moreover, our study connects the multichromophoric excitation energy transfer theory and the Tavis–Cummings model via identical cooperative decay rates and dipole–dipole shifts. For molecules resonant with the cavity photon mode, we find that the enhancement is not exactly proportional to N even in a perfect FP cavity due to the effects of electrostatic dipole–dipole interactions. Moreover, in a silver FP cavity, our simulation shows that the enhancement saturates for a large N, indicating that the cavity photon mode can lead to only the collective emission of a limited number of molecules. For molecules in the proximity of the silver mirror, we demonstrate that under specific conditions, the subradiance of molecular emitters can occur through surface plasmon polaritons. Our study not only provides new insights into the mechanism of superradiance effects but also demonstrates that collective effects such as superradiance and subradiance can be controlled by manipulating the dielectric environments.
We present results of our theoretical research on collective emission of photons (super- and subradiance) and photon propagation in photonic environments.Just like the single-atom emission, collective emission depends on the photonic environment. For quantum emitters in layered media, we study whether surface plasmons can enhance collective emission, especially for emitters at distances smaller than an optical wavelength.A common approximation in quantum optics is the rotating-wave approximation in the light-matter interaction. We show that in general multi-atom emission rates depend on the approximation, but exceptions exist. Interatomic interactions induced by the electromagnetic field are given by the classical Green tensor, but only when not making the rotating-wave approximation.As a final example of quantum electromagnetics, we describe photons propagating through a layered medium with alternating loss and gain, so-called loss-compensated media. There is no analogous compensation of the quantum noise associated with loss and gain media.
We develop a theory of cooperative emission of light by an ensemble of emitters, such as fluorescing molecules or semiconductor quantum dots, located near a metal nanostructure supporting surface plasmon. The primary mechanism of cooperative emission in such systems is resonant energy transfer between emitters and plasmons rather than the Dicke radiative coupling between emitters. We identify two types of plasmonic coupling between the emitters, (i) plasmon-enhanced radiative coupling and (ii) plasmon-assisted nonradiative energy transfer, the competition between them governing the structure of system eigenstates. Specifically, when emitters are removed by more than several nanometers from the metal surface, the emission is dominated by three superradiant states with the same quantum yield as a single emitter, resulting in a drastic reduction of ensemble radiated energy, while at smaller distances cooperative behavior is destroyed by nonradiative transitions. The crossover between two regimes can be observed in distance dependence of ensemble quantum efficiency. Our numerical calculations incorporating direct and plasmon-assisted interactions between the emitters indicate that they do not destroy the plasmonic Dicke effect.
We theoretically characterize the collective radiative behavior of N classical emitters near an interface between different dielectrics that supports the transfer of surface plasmon modes into the far-field of electromagnetic radiation. The phenomena of superradiance and surface plasmons can be combined to amplify the emitted radiation intensity S as S=AN2S0 compared to a single emitter's intensity S0 in free space. For a practical case study within the article A=240, compared to A=1 in free space. We furthermore demonstrate that there are collective modes for which the intensity of the emitted radiation is suppressed by 2 orders of magnitude despite their supperadiant emission characteristics. A method to control the emission characteristics of the system and to switch from super- to subradiant behavior with a suitably detuned external driving field is devised.