Single photon sources (SPS), especially those based on solid state quantum emitters, are key elements in future quantum technologies. What is required is the development of broadband, high quantum efficiency, room temperature SPS which can also be tunably coupled to optical cavities which could lead to development of all-optical quantum communication platforms. In this regard deterministic coupling of SPS to plasmonic nanocavity arrays has great advantage due to long propagation length and delocalized nature of surface lattice resonances (SLRs). Guided by these considerations, we report experiments on the room temperature tunable coupling of single photon emitting colloidal quantum dots (CQDs) to localised and delocalised modes in plasmonic nanocavity arrays. Using time-resolved photo-luminescence measurement on isolated CQD, we report significant advantage of SLRs in realizing much higher Purcell effect, despite large dephasing of CQDs, with values of ~22 and ~ 6 for coupling to the lattice and localised modes, respectively. We present measurements on the antibunching of CQDs coupled to these modes with g(2)(0) values in quantum domain providing evidence for an effective cooperative behavior. We present a density matrix treatment of the coupling of CQDs to plasmonic and lattice modes enabling us to model the experimental results on Purcell factors as well as on the antibunching. We also provide experimental evidence of indirect excitation of remote CQDs mediated by the lattice modes and propose a model to explain these observations. Our study demonstrates the possibility of developing nanophotonic platforms for single photon operations and communications with broadband quantum emitters and plasmonic nanocavity arrays since these arrays can generate entanglement between to spatially separated quantum emitters.
Experimental approaches to manipulate light-matter interaction at nanoscale have quickly advanced in recent years, leading to the demonstration of spaser (surface plasmon amplification by stimulated emission of radiation) in plasmonic nanocavities. Yet, a well-understood analytical theory to better understand and quantitatively explain the connotation of spaser system is urgently needed. Here we develop an all-analytical semiclassical theory to investigate the energy exchange between active materials and fields and the spaser performance in a plasmonic nanocavity. The theory can be commonly us…
Plasmonic nanolasers have ultrahigh lasing thresholds, especially those devices for which all three dimensions are truly subwavelength. Because of a momentum mismatch between the propagating light and localized optical field of the subwavelength nanocavity, poor optical pumping efficiency is another important reason for the ultrahigh threshold but is normally always ignored. Based on a cavity-embedded nanoantenna array design, we demonstrate a room-temperature low-threshold plasmonic nanolaser that is robust, reproducible, and easy-to-fabricate using chemical-template lithography. The mode vol…
The effect of confinement on surface plasmon polariton in a planar nanocavity was studied. The generalized modes were obtained and studied in detail. It was demonstrated that these modes result from the strong coupling of plasmon-like and photon-like modes.
In the past decade, advances in nanotechnology have led to the development of plasmonic nanocavities which facilitate light-matter strong coupling in ambient conditions. The most robust example is the nanoparticle-on-mirror (NPoM) structure whose geometry is controlled with subnanometer precision. The excited plasmons in such nanocavities are extremely sensitive to the exact morphology of the nanocavity, giving rise to unexpected optical behaviors. So far, most theoretical and experimental studies on such nanocavities have been based solely on their scattering and absorption properties. Howeve…
A novel plasmonic waveguide-coupled nanocavity with a monopole antenna is proposed to localize the optical power from a hybrid plasmonic waveguide and subsequently convert it into electrical current. The nanocavity is designed as a Fabry-Pérot waveguide resonator, while the monopole antenna is made of a metallic nanorod directly mounted onto the metallic part of the waveguide terminal which acts as the conducting ground. The nanocavity coincides with the antenna feed sandwiched in between the antenna and the ground. Maximum power from the waveguide can be coupled into, and absorbed in the nano…
Numerical optimization was performed via COMSOL Multiphysics to maximize the polarization contrast of superconducting nanowire single photon detectors (SNSPDs). SNSPDs were integrated with four different types of one-dimensional periodic plasmonic structures capable of mediating p-polarized photon selectivity to the niobium-nitride superconducting nanowire pattern. Optimization with two different criteria regarding the maximal tilting resulted in wavelength-scaled periodic integrated structures, which have different geometrical parameters, and exhibit different polar angle dependent optical re…
We measure the dynamics of the thermo-optical nonlinearity of both a mode-gap nanocavity and a delocalized mode in a Ga$_{\mathrm{0.51}}$In$_{\mathrm{0.49}}$P photonic crystal membrane. We model these results in terms of heat transport and thermo-optical response in the material. By step-modulating the optical input power we push the nonlinear resonance to jump between stable branches of its response curve, causing bistable switching. An overshoot of the intensity followed by a relaxation tail is observed upon bistable switching. In this way, the thermal relaxation of both the localized resona…
On chip exciting electric modes in individual plasmonic nanostructures are realized widely; nevertheless, the excitation of their magnetic counterparts is seldom reported. Here, we propose a highly efficient on chip excitation approach of the magnetic dipole mode of an individual split ring resonator (SRR) by integrating it onto a photonic crystal nanocavity (PCNC). A high excitation efficiency of up to 58% is realized through the resonant coupling between the modes of the SRR and PCNC. A further fine adjustment of the excited magnetic dipole mode is demonstrated by tuning the relative positio…
Plasmonic resonators have drawn more attention due to the ability to confine light into subwavelength scale. However, they always suffer from a low quality (Q) factor owing to the intrinsic loss of metal. Here, we numerically propose a plasmonic resonator with ultra-high Q factor based on plasmonic metal-insulator-metal (MIM) waveguide structures. The resonator consists of a disk cavity surrounded by a concentric ring cavity, possessing an ultra-small volume. Arising from the plasmon hybridization between plasmon modes in the disk and ring cavity, the induced bonding hybridized modes have ultr…
Physics-Aligned Deep Learning Enables SERS Resolving and Sequencing of Dynamic Single-Molecule DNA Oligomers in Plasmonic Nanocavity
Research Unit of Health Sciences and Technology, Faculty of Medicine, University of Oulu（奥卢大学医学院健康科学与技术研究部）；Research Unit of Disease Networks, Faculty of Biochemistry and Molecular Medicine, University of Oulu（奥卢大学生物化学与分子医学学院疾病网络研究部）；Biocenter Oulu, University of Oulu（奥卢大学生物中心）；State Key Laboratory of Systems Medicine for Cancer, School of Biomedical Engineering, Shanghai Jiao Tong University（上海交通大学生物医学工程学院癌症系统医学国家重点实验室）；The Biomimetics and Intelligent Systems (BISG) research unit, Faculty of Information Technology and Electronic Engineering, University of Oulu（奥卢大学信息技术与电子工程学院仿生学与智能系统（BISG）研究部）；Institute of Biomedicine, School of Medicine, Faculty of Health Sciences, University of Eastern Finland（芬兰东部大学健康科学学院医学院生物医学研究所）
Graphene plasmons are able to become the fundermental of novel conceptual photonic devices, resulting from their unique characteristics containing excitation at room temperature and tunable spectral selectivity in different frequencies. The pursuit of efficiently exciting and manipulating graphene plasmons is necessary and significant for high-performance devices. Here, we investigate graphene plasmon wave propagating in ferroelectric nanocavity array. We experimentally show that the the periodic ferroelectric polarizations could be used for doping graphene into desired spatial carrier density…
Cascaded optical field enhancement (CFE) can be realized in some specially designed multiscale plasmonic nanostructures, where the generation of extremely strong field at nanoscale volume is crucial for many applications, for example, surface enhanced Raman spectroscopy (SERS). Here, we propose a strategy of realizing a high-quality plasmonic nanoparticle-in-cavity (PIC) nanoantenna array, where strong coupling between a nanoparticle dark mode with a high order nanocavity bright mode can produce Fano resonance at a target wavelength. The Fano resonance can effectively boost the CFE in the PIC,…
Plasmonic nano-antennas can focus light to nanometre length-scales providing intense field enhancements. For the tightest optical confinements (0.5-5 nm) achieved in plasmonic gaps, the gap spacing, refractive index, and facet width play a dominant role in determining the optical properties making tuning through antenna shape challenging. We show here that controlling the surrounding refractive index instead allows both efficient frequency tuning and enhanced in/output-coupling through retardation matching as this allows dark modes to become optically active, improving widespread functionaliti…
We use an all-optical pump-probe method to develop a mass sensing mechanism in a molecular plasmonic system at room temperature. The system consists of a double-clamped graphene nanoribbon that parametrically interacts with two types of isotropic and anisotropic spherical plasmonic cavities in the presence of a strong pump field and a weak probe pulse. Based on the mode-selective quantization scheme and analogy with the canonical model of the cavity optomechanics, we formulate the Hamiltonian of the system in terms of the electromagnetic Greens tensor. In this manner, we derive an explicit for…
Plasmonic cavities can confine electromagnetic radiation to deep sub-wavelength regimes. This facilitates strong coupling phenomena to be observed at the limit of individual quantum emitters. Here we report an extensive set of measurements of plasmonic cavities hosting one to a few semiconductor quantum dots. Scattering spectra show Rabi splitting, demonstrating that these devices are close to the strong coupling regime. Using Hanbury Brown and Twiss interferometry, we observe non-classical emission, allowing us to directly determine the number of emitters in each device. Surprising features i…
In order to achieve electrically pumped plasmon nano lasers, several structures, materials and methods, have been proposed recently. However, there is still a long way to find out a reliable appropriate on-chip plasmon source for commercial plasmonic integrated circuits. In this paper, a new waveguide integrated nanocavity plasmon laser is proposed for 1550 nm free-space wavelength. Due to its significant field confinement resulted by the metal strip structure and strong interaction of plasmonic modes with the germanium quantum wells and as a result a considerable Purcell factor about 291, thi…
Strong coupling between light and matter is the foundation of promising quantum photonic devices such as deterministic single photon sources, single atom lasers and photonic quantum gates, which consist of an atom and a photonic cavity. Unlike atom-based systems, a strong coupling unit based on an emitter-plasmonic nanocavity system has the potential to bring these devices to the microchip scale at ambient conditions. However, efficiently and precisely positioning a single or a few emitters into a plasmonic nanocavity is challenging. In addition, placing a strong coupling unit on a designated …
We demonstrate the real-time exciton-manipulation of plexcitonic coupling in monolayer WS2 coupled to a plasmonic nanocavity by immersing into a mixed solution of dichloromethane (DCM) and ethanol. By adjusting the mixture ratio, a continuous tuning of the Rabi splitting energy ranged from 178 meV (in ethanol) to 266 meV (in DCM) is achieved. The results are mainly attributed to the remarkable increase of the proportion of neutral exciton in the monolayer WS2 (from 59% to 100%) as the concentration of DCM is increased. It offers an important stepping stone towards a further study of plexcitoni…
We study the physics of a new type of subwavelength nanocavities. They are based on U-shaped metal-insulator-metal waveguides supporting the excitation of surface plasmon polaritons. The waveguides are simultaneously excited from both sides of the U by incident plane waves. Due to their finite length discrete modes emerge within the nanocavity. We show that the excitation symmetry with respect to the cavity ends permits the observation of even and odd modes. Our investigations include near and far field simulations and predict a strong spectral far field response of the comparable small nanore…
Realizing strong coupling between a single quantum emitter (QE) and an optical cavity is of crucial importance in the context of various quantum optical applications. While Rabi splitting of single quantum emitters coupled to high-Q diffraction limited cavities have been reported in numerous configurations, attaining single emitter Rabi splitting with a plasmonic nanostructure is still elusive. Here, we establish the analytical condition for strong coupling between a single QE and a plasmonic nanocavity and apply it to study various plasmonic arrangements that were shown to enable Rabi splitti…
Fabricating nanocavities in which optically-active single quantum emitters are precisely positioned, is crucial for building nanophotonic devices. Here we show that self-assembly based on robust DNA-origami constructs can precisely position single molecules laterally within sub-5nm gaps between plasmonic substrates that support intense optical confinement. By placing single-molecules at the center of a nanocavity, we show modification of the plasmon cavity resonance before and after bleaching the chromophore, and obtain enhancements of $\geq4\times10^3$ with high quantum yield ($\geq50$%). By …
We have combined atomic layer lithography and template stripping to produce a new class of substrates for surface-enhanced infrared absorption (SEIRA) spectroscopy. Our structure consists of a buried and U-shaped metal-insulator-metal waveguide whose folded vertical arms efficiently couple normally incident light. The insulator is formed by atomic layer deposition (ALD) of Al2O3 and precisely defines the gap size. The buried nanocavities are protected from contamination by a silicon template until ready for use and exposed by template stripping on demand. The exposed nanocavity generates stron…
By modifying the density of optical states at the location of an emitter, weak cavity-emitter coupling can enable a host of potential applications in quantum optics, from the development of low- threshold lasers to brighter single-photon sources for quantum cryptography. Although some of the first demonstrations of spontaneous emission modification occurred in metallic structures, it was only after the recent demonstration of cavity quantum electrodynamics effects in dielectric optical cavities that metal-based optical cavities were considered for quantum optics applications. Advantages of met…
Quantum plasmonic systems suffer from significant decoherence due to the intrinsically large dissipative and radiative dampings. Based on our quantum simulations via a quantum tensor network algorithm, we numerically demonstrate the mitigation of this restrictive drawback by hybridizing a plasmonic nanocavity with an emitter ensemble with inhomogeneously-broadened transition frequencies. By burning two narrow spectral holes in the spectral density of the emitter ensemble, the coherent time of Rabi oscillation for the hybrid system is increased tenfold. With the suppressed decoherence, we move …
Nanoparticle-on-mirror plasmonic nanocavities, capable of extreme optical confinement and enhancement, have triggered state-of-the-art progress in nanophotonics and development of applications in enhanced spectroscopies and molecular detection. However, the optical quality factor and thus performance of these nanoconstructs are undermined by the granular polycrystalline metal films used as a mirror. Here, we report an atomically smooth single-crystalline platform for low-loss nanocavities using chemically-synthesized gold microflakes as a mirror. Nanocavities constructed using gold nanorods on…
Plasmonic nanocavities enable the confinement of molecules and electromagnetic fields within nano-metric volumes. As a consequence, the molecules experience a remarkably strong interaction with the electromagnetic field, to such an extent that the quantum states of the system become hybrids between light and matter: polaritons. Here we present a non-perturbative method to simulate the emerging properties of such polaritons: it combines a high-level quantum chemical description of the molecule with a quantized description of the localized surface plasmons in the nanocavity. We apply the method …
Extreme Optical Field Confinement and Enhancement in a Plasmonic Picopatch within a Nanoparticle-on-Mirror Resonator
Pingdingshan University（平顶山大学）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）；University of the Basque Country (UPV/EHU)（巴斯克国立大学）；Zhengzhou University（郑州大学）；Henan Academy of Sciences（河南省科学院）；Ikerbasque, Basque Foundation for Science（伊克尔巴斯科，巴斯克科学基金会）
The Purcell factor $F_p$ is a key quantity in cavity quantum electrodynamics (cQED) that quantifies the coupling rate between a dipolar emitter and a cavity mode. Its simple form $F_p\propto Q/V$ unravels the possible strategies to enhance and control light-matter interaction. Practically, efficient light-matter interaction is achieved thanks to either i) high quality factor $Q$ at the basis of cQED or ii) low modal volume $V$ at the basis of nanophotonics and plasmonics. In the last decade, strong efforts have been done to derive a plasmonic Purcell factor in order to transpose cQED concepts …
We propose a plasmonic ellipse resonator possessing hybrid modes based on metal-insulator-metal (MIM) waveguide system. Specially, this nanocavity has hybrid characteristic of rectangle and disk resonator, therefore supporting both Fabry-Perot modes (FPMs) and whispering-gallery modes (WGMs). Besides, by changing the length of major and minor radius of the ellipse, the resonant wavelengths of FPMs and WGMs can be independently tuned and close to each other, thus constructing a plasmon-induced transparency (PIT) - like spectrum profile. Benefitting from this, a dual-band slow light is achieved …
We illustrate the possibility of light trapping and funneling in periodic arrays of metallic nanoparticles. A controllable minimum in the transmission spectra of such constructs arises from a collective plasmon resonance phenomenon, where an incident plane wave sharply localizes in the vertical direction, remaining delocalized in the direction parallel to the crystal plane. Using hybrid arrays of different structures or different materials, we apply the trapping effect to structure the eigen-mode spectrum, introduce overlapping resonances, and hence direct the light in space in a wavelength-se…
We study spatial coherence properties of a system composed of periodic silver nanoparticle arrays covered with a fluorescent organic molecule (DiD) film. The evolution of spatial coherence of this composite structure from the weak to the strong coupling regime is investigated by systematically varying the coupling strength between the localized DiD excitons and the collective, delocalized modes of the nanoparticle array known as surface lattice resonances. A gradual evolution of coherence from the weak to the strong coupling regime is observed, with the strong coupling features clearly visible…
Strong coupling between a single quantum emitter and an electromagnetic mode is one of the key effects in quantum optics. In the cavity QED approach to plasmonics, strongly coupled systems are usually understood as single-transition emitters resonantly coupled to a single radiative plasmonic mode. However, plasmonic cavities also support non-radiative (or "dark") modes, which offer much higher coupling strengths. On the other hand, realistic quantum emitters often support multiple electronic transitions of various symmetry, which could overlap with higher order plasmonic transitions -- in the …
Metal-insulator-metal (MIM) nanogaps in canonical nanoparticle-on-mirror geometry (NPoM) provide deep-subwavelength confinement of light with mode volumes smaller than $V/V_0$ $<$ $10^{-6}$. However, access to these hotspots is limited by the impendence mismatch between the high in-plane $k_{//}$ of trapped light and free-space plane-waves, making the in- and out-coupling of light difficult. Here, by constructing a nanoparticle-on-foil (NPoF) system with thin metal films, we show the mixing of insulator-metal-insulator (IMI) modes and MIM gap modes resulting in MIMI modes. This mixing provides…
A scanning tunneling microscope (STM) can do more than atomic imaging and manipulation. Its tunneling current can also be used for the excitation of light, converting electron energy to photon energy. STM based single-molecule electroluminescence can be realized by adopting a combined strategy of both efficient electronic decoupling and nanocavity plasmonic enhancement. The emission intensity, upon optimized material combination for the molecule, spacer, tip, and substrate, can be strong and stable enough for performing second-order photon correlation measurements. The observation of an eviden…
Integrated photonic circuits are an integral part of all-optical and on-chip quantum information processing and quantum computer. Deterministically integrated single-photon sources in nanoplasmonic circuits lead to densely packed scalable quantum logic circuits operating beyond the diffraction limit. Here, we report the coupling efficiency of single-photon sources to the plasmonic waveguide, characteristic transmission spectrum, propagation length, decay length, and plasmonic Purcell factor. We simulated the transmission spectrum to find the appropriate wavelength for various width of the diel…
Disorder-Engineered Hybrid Plasmonic Cavities for Emission Control of Defects in hBN
Middle East Technical University（中东技术大学）；Izmir Institute of Technology（伊兹密尔理工大学）；Tampere University（坦佩雷大学）；Eindhoven University of Technology（埃因霍温理工大学）；Sabancı University（萨班哲大学）
Plexcitonic strong coupling has ushered in an era of room-temperature quantum electrodynamics that is achievable at the nanoscale, with potential applications ranging from high-precision single-molecule spectroscopy to quantum technologies functional under ambient conditions. Realizing these applications on an industrial scale requires scalable and mass-producible plasmonic cavities that provide ease of access and control for quantum emitters. Via a rational selection of substrates and the canonical gold bowtie nanoantenna, we propose a novel design strategy for multidimensional engineering of…
The strong spatial confinement of a nanocavity plasmonic field has made it possible to visualize the inner structure of a single molecule and even to distinguish its vibrational modes in real space. With such ever-improved spatial resolution, it is anticipated that full vibrational imaging of a molecule could be achieved to reveal molecular structural details. Here we demonstrate full Raman images of individual vibrational modes on the Ångström level for a single Mg-porphine molecule, revealing distinct characteristics of each vibrational mode in real space. Furthermore, by exploiting the unde…
Giant Purcell broadening and Lamb shift for DNA-assembled near-infrared quantum emitters
Ecole Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；University of Fribourg（弗里堡大学）；Materials Physics Center CSIC-UPV/EHU（CSIC-巴斯克国立自治大学材料物理中心）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）；Ikerbasque, Basque Foundation for Science（伊克拉巴斯科，巴斯克科学基金会）；University of the Basque Country (UPV/EHU)（巴斯克国立自治大学）
We investigate the quantum-optical properties of the light emitted by a nanoparticle-on-mirror cavity filled with a single quantum emitter. Inspired by recent experiments, we model a dark-field set-up and explore the photon statistics of the scattered light under grazing laser illumination. Exploiting analytical solutions to Maxwell's equations, we quantize the nanophotonic cavity fields and describe the formation of plasmon exciton polaritons (or plexcitons) in the system. This way, we reveal that the rich plasmonic spectrum of the nanocavity offers unexplored mechanisms for nonclassical ligh…
Electron-beam Writing of Spectrally Uniform Green Single-photon Emitters in Hexagonal Boron Nitride
Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences（中国科学院大学杭州高等研究院）；Zhejiang University（浙江大学）；University of Science and Technology of China（中国科学技术大学）；Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences（中国科学院上海光学精密机械研究所）
