Jin-Kyu So, Nikolay I. Zheludev
We report a resonant enhancement of luminescence intensity from an ensemble of CdS/ZnS quantum dots embedded in a nanoscale rectangular photonic waveguide operating at the epsilon-near-zero regime.
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The importance of considering near-field effects on photon recycling and spontaneous emission in a thermophotovoltaic device is investigated. Fluctuational electrodynamics is used to calculate external luminescence from a photovoltaic cell as a function of emitter type, vacuum gap thickness between emitter and cell, and cell thickness. The observed changes in external luminescence suggest strong modifications of photon recycling caused by the presence of the emitter. Photon recycling for propagating modes is affected by reflection at the vacuum-emitter interface and is substantially decreased …
Self-decoupled tetrapodal perylene molecules were designed, synthesized, and deposited on the Au(111) surface through the electrosprayionization technique. Photoluminescence and lifetime measurements show that the chromophore groups of the designed molecules are welldecoupled from the gold substrate. Preliminary scanning tunneling microscopy induced luminescence measurements indicate theobservation of molecule-specific emissions from isolated single tetrapodal perylene molecules adsorbed directly on Au(111). The emergenceof significant emission when the tip is positioned at the molecular cente…
Controlling the emission and interaction properties of quantum emitters (QEs) embedded within an optical cavity is a key technique in engineering light-matter interactions at the nanoscale, as well as in the development of quantum information processing. State-of-the-art optical cavities are based on high Q photonics crystals and dielectric resonators. However, wealthier responses might be attainable with cavities carved in more exotic materials. Here, we theoretically investigate the emission and interaction properties of QEs embedded in open epsilon-near-zero (ENZ) cavities. Using analytical…
We propose a method for engineering thermally excited far field electromagnetic radiation using epsilon-near-zero metamaterials and introduce a new class of artificial media: epsilon-near-pole metamaterials. We also introduce the concept of high temperature plasmonics as conventional metamaterial building blocks have relatively poor thermal stability. Using our approach, the angular nature, spectral position, and width of the thermal emission and optical absorption can be finely tuned for a variety of applications. In particular, we show that these metamaterial emitters near 1500 K can be used…
The key feature of a thermophotovoltaic (TPV) emitter is the enhancement of thermal emission corresponding to energies just above the bandgap of the absorbing photovoltaic cell and simultaneous suppression of thermal emission below the bandgap. We show here that a single layer plasmonic coating can perform this task with high efficiency. Our key design principle involves tuning the epsilon-near-zero frequency (plasma frequency) of the metal acting as a thermal emitter to the electronic bandgap of the semiconducting cell. This approach utilizes the change in reflectivity of a metal near its pla…
Epsilon-near-zero (ENZ) materials have been demonstrated to exhibit unique electromagnetic properties. Here we propose the concept of radiative energy bandgap for an ENZ nanoparticle coupled with a quantum emitter (QE). The radiative emission of the coupled QE-nanoparticle can be significantly suppressed around the ENZ frequency and substantially enhanced otherwise, yielding an effective energy bandgap for radiation. This suppression is effectively invariant with respect to the particle size and is therefore an intrinsic property of the ENZ material. Our concept also heralds an alternative pat…
We report on an experimental technique to quantify the relative importance of electric and magnetic dipole luminescence from a single nanosource in structured environments. By attaching a $Eu^{3+}$-doped nanocrystal to a near-field scanning optical microscope tip, we map the branching ratios associated to two electric dipole and one magnetic dipole transitions in three dimensions on a gold stripe. The relative weight of the electric and magnetic radiative local density of states can be recovered quantitatively, based on a multilevel model. This paves the way towards the full electric and magne…
Single-photon and correlated two-photon sources are important elements for optical information systems. Nonlinear downconversion light sources are robust and stable emitters of single photons and entangled photon pairs. However, the rate of downconverted light emission, dictated by the properties of low-symmetry nonlinear crystals, is typically very small, leading to significant constrains in device design and integration. In this paper, we show that the principles for spontaneous emission control (i.e. Purcell effect) of isolated emitters in nanoscale structures, such as metamaterials, can be…
Metal-halide perovskites are rapidly emerging as solution-processable optical materials for light emitting applications. Here we adopt a plasmonic metamaterial approach to enhance photoluminescence emission and extraction of methylammonium lead iodide (MAPbI3) thin films, based on the Purcell effect. We show that hybridization of the active metal-halide film with resonant nanoscale sized slits carved into a gold film can yield more than one order of magnitude enhancement of luminescence intensity, and nearly threefold reduction of luminescence lifetime. This shows the effectiveness of resonant…
Recent developments in fabrication of van der Waals heterostructures enable new type of devices assembled by stacking atomically thin layers of two-dimensional materials. Using this approach, we fabricate light-emitting devices based on a monolayer WSe$_2$, and also comprising boron nitride tunnelling barriers and graphene electrodes, and observe sharp luminescence spectra from individual defects in WSe$_2$ under both optical and electrical excitation. This paves the way towards the realization of electrically-pumped quantum emitters in atomically thin semiconductors. In addition we demonstrat…
We demonstrate a plasmonic route to control the collective spontaneous emission of two-level quantum emitters. Superradiance and subradiance effects are observed over distances comparable to the operating wavelength inside plasmonic nanochannels. These plasmonic waveguides can provide an effective epsilon-near-zero operation in their cut-off frequency and Fabry-Perot resonances at higher frequencies. The related plasmonic resonant modes are found to efficiently enhance the constructive (superradiance) or destructive (subradiance) interference between different quantum emitters located inside t…
Plasmonic antennas are key elements to control the luminescence of quantum emitters. However, the antenna's influence is often hidden by quenching losses. Here, the luminescence of a quantum dot coupled to a gold dimer antenna is investigated. Detailed analysis of the multiply excited states quantifies the antenna's influence on the excitation intensity and the luminescence quantum yield separately.
Multiqubit entanglement is extremely important to perform truly secure quantum optical communication and computing operations. However, the efficient generation of long-range entanglement over extended time periods between multiple qubits randomly distributed in a photonic system remains an outstanding challenge. This constraint is mainly due to the detrimental effects of decoherence and dephasing. To alleviate this issue, we present engineered epsilon-near-zero (ENZ) nanostructures that can maximize the coherence of light-matter interactions at room temperature. We investigate a practical ENZ…
In this paper, we demonstrate the infrared photoluminescence emission from Ge(Si) quantum dots enhanced with collective Mie modes of silicon nanopillars. We show that the excitation of band edge dipolar modes of a linear nanopillar array results in strong reshaping of the photoluminescence spectra. Among other collective modes, the magnetic dipolar mode with the polarization along the array axis contributes the most to the emission spectrum exhibiting an experimentally measured Q-factor of around 500 for an array of 11 pillars. The results belong to the first experimental evidence of light emi…
Two-dimensional chalcogenide semiconductors have recently emerged as a host material for quantum emitters of single photons. While several reports on defect and strain-induced single photon emission from 2D chalcogenides exist, a bottom-up, lithography-free approach to producing a high density of emitters remains elusive. Further, the physical properties of quantum emission in the case of strained 2D semiconductors are far from being understood. Here, we demonstrate a bottom-up, scalable, and lithography-free approach to creating large areas of localized emitters with high density (~150 emitte…
Leveraging Epsilon Near Zero phenomena for on-chip photonic modulation
本文研究了利用近零epsilon现象实现芯片级光子调制，通过控制材料载流子密度来调节量子发射体的辐射传输，揭示了材料损耗对性能的限制，并为设计近红外波段的光学调制器提供指导。
Plasmonic waveguides are key elements in nanophotonic devices serving as optical interconnects between nanoscale light sources and detectors. Multimode operation in plasmonic two-wire transmission lines promises important degrees of freedom for near-field manipulation and information encoding. However, highly confined plasmon propagation in gold nanostructures is typically limited to the near-infrared region due to ohmic losses, excluding all visible quantum emitters from plasmonic circuitry. Here, we report on top-down fabrication of complex plasmonic nanostructures in single-crystalline silv…
Colour centres in hexagonal boron nitride (hBN) have emerged as intriguing contenders for integrated quantum photonics. In this work, we present detailed photophysical analysis of hBN single emitters emitting at the blue spectral range. The emitters are fabricated by different electron beam irradiation and annealing conditions and exhibit narrow-band luminescence centred at 436 nm. Photon statistics as well as rigorous photodynamics analysis unveils potential level structure of the emitters, which suggests lack of a metastable state, supported by a theoretical analysis. The potential defect ca…
We describe the possibility of drastically boosting the spontaneous emission of a collection of two-level quantum emitters by embedding them in an epsilon-near-zero (ENZ) environment, consisting of a plasmonic waveguide operated at cut-off. This phenomenon relies on the combination of Purcell enhancement and Dicke superradiance effects, exploiting the large and uniform local density of states in ENZ channels, which is shown to significantly extend the spatial extent of these quantum effects. We envision exciting applications in optical sensing, molecular detection and low-threshold lasing.
Anticrossing of a plasmonic nanoresonator mode and a single quantum dot at room temperature
本研究通过光诱导蓝移调谐单个量子点能量，实现室温下与等离激元纳米谐振腔的强耦合，观测到100 meV拉比分裂，证明环境条件下单发射体强耦合，为量子器件发展铺路。
The entanglement and resonance energy transfer between two-level quantum emitters are typically limited to sub-wavelength distances due to the inherently short-range nature of the dipole-dipole interactions. Moreover, the entanglement of quantum systems is hard to preserve for a long time period due to decoherence and dephasing mainly caused by radiative and nonradiative losses. In this work, we outperform the aforementioned limitations by presenting efficient long-range inter-emitter entanglement and large enhancement of resonance energy transfer between two optical qubits mediated by epsilon…
Metallic nanostructures acting as optical nanoantennas can significantly enhance the photoluminescence (PL) of nearby emitters. Albeit luminescence enhancement factors of several orders of magnitude have been reported for quantum dots or molecules, in the case of bulk emitters the magnitude of the plasmonic enhancement is strongly hindered by the weak spatial overlap between the active medium and the electromagnetic modes of the nanoantenna. Here, we propose a solid-state ultraviolet emitter based on a thin film of zinc oxide (ZnO) coupled with an array of aluminum (Al) nanoparticles. The Al n…
Inverse Drexhage effect in Epsilon-Near-Zero Substrates
本研究揭示介电常数近零基底中自发辐射速率对偶极子取向和距离的依赖与金属相反，即逆德雷克萨格效应，并指出实际ENZ超材料因损耗大而表现常规效应，成果可用于量子传感与光电器件。
An optical topological transition is defined as the change in the photonic isofrequency surface around epsilon-near-zero (ENZ) frequencies which can considerably change the spontaneous emission of a quantum emitter placed near a metamaterial slab. Here, we show that due to the strong Kerr nonlinearity at ENZ frequencies, a high power pulse can induce a sudden transition in the topology of the iso-frequency dispersion curve, leading to a significant change in the transmission of propagating as well as evanescent waves through the metamaterial slab. This evanescent wave switch effect allows for …
Room temperature quantum emitters in van der Waals α-MoO3
本研究在经剥离和热退火的范德华α-MoO₃单晶中实现了室温单光子发射，验证了其光子反聚束特性、高亮度与光稳定性，提出氧空位为可能缺陷来源，为二维范德华材料的光子量子信息研究提供了新平台。
Emergence of an Epsilon-Near-Zero Medium from Microscopic Atomic Principles
通过微观原子原理，研究发现离散原子晶格中的集体光散射可产生近零折射率，为宏观电磁学的起源提供了新见解。
Single-photon emitters are essential for enabling several emerging applications in quantum information technology, quantum sensing and quantum communication. Scalable photonic platforms capable of hosting intrinsic or directly embedded sources of single-photon emission are of particular interest for the realization of integrated quantum photonic circuits. Here, we report on the first-time observation of room-temperature single-photon emitters in silicon nitride (SiN) films grown on silicon dioxide substrates. As SiN has recently emerged as one of the most promising materials for integrated qua…
Broadband Fourier transform spectroscopy of quantum emitters photoluminescence with sub-nanosecond temporal resolution
提出基于双折射干涉仪和超导单光子探测器的时域傅里叶变换光谱学方法，实现了量子发射体在近红外至通信波段的宽带光谱表征及亚纳秒级自旋相关光谱变化监测。
The design of single-molecule photoswitchable emitters was the first milestone toward the advent of single-molecule localization microscopy that sets a new paradigm in the field of optical imaging. Several photoswitchable emitters have been developed but they all fluoresce in the visible or far-red ranges, missing the desirable near-infrared window where biological tissues are most transparent. Moreover, photocontrol of individual emitters in the near-infrared would be highly desirable for elementary optical molecular switches or information storage elements since most communication data trans…
Collective Blinking of Upconversion Emission in Lanthanide-doped Nanocrystals
本研究发现单个镧系掺杂纳米晶体内数千个镧系离子的上转换发光存在可调控的集体闪烁，阐明其机制并实现1.2纳米分辨率的超分辨成像，为相关领域提供新策略。
Quench, Glow, or Stay Silent: Distance-Controlled Up-Conversion Emission near Metallic Nanowires
研究通过控制NaYF4:Er3+/Yb3+纳米晶体与金属纳米线间距，去除纳米线残留聚合物层并换用聚合物间隔层，实现三种不同相互作用机制转换，为设计功能性纳米光子和传感结构提供基础。
In the world of epsilon-near-zero (ENZ) materials, the plasma is unique for its natural ENZ properties at the plasma frequency (wp). However, for the air plasma during femtosecond laser filamentation with wp in terahertz (THz) band, which is also known as a broadband THz emitter, the possible ENZ effect has long been neglected. In this work, interactions between the laser plasma in air and the radiated THz waves were investigated, and the THz resonance absorption at the ENZ point, which gave rise to the generation of surface plasmon waves, has been theoretically and experimentally demonstrated…
Photoneutralization of charges in GaAs quantum dot based entangled photon emitters
本文研究GaAs/AlGaAs量子点在双光子共振激发下的中性激子发射间歇性，发现通过控制量子点附近自由电子和空穴的平衡可主动抑制由Coulomb阻塞引起的闪烁，将量子效率显著提高30%。
The radiation dynamics of optical emitters can be manipulated by properly designed material structures providing high local density of photonic states, a phenomenon often referred to as the Purcell effect. Plasmonic nanorod metamaterials with hyperbolic dispersion of electromagnetic modes are believed to deliver a significant Purcell enhancement with both broadband and non-resonant nature. Here, we have investigated finite-size cavities formed by nanorod metamaterials and shown that the main mechanism of the Purcell effect in these hyperbolic resonators originates from the cavity hyperbolic mo…
Engineering band selective absorption with epsilon-near-zero media in the infrared
本研究提出一种基于ENZ材料ITO纳米光栅的三层涂层，实现红外波段广角高吸收，为热管理和能量收集提供新途径。
Attaining near-ideal Dicke superradiance in expanded spatial domains
本文研究等离激元波导和介电光子晶体等ENZ结构在扩展空间域中实现近理想Dicke超辐射的潜力，提出一种基于退相干矩阵的通用评估方法，并通过数值分析揭示了全互连相互作用下量子相干性的作用及最大光子爆发率的判定意义。
Recently, near-field radiative heat transfer enhancement across nanometer vacuum gaps has been intensively studied between two hyperbolic metamaterials (HMMs) due to unlimited wavevectors and high photonic density of state. In this work, we theoretically analyze the energy conversion performance of a thermophotovoltaic (TPV) cell made of In0.2Ga0.8Sb when paired with a HMM emitter composed of tungsten nanowire arrays embedded in Al2O3 host at nanometer vacuum gaps. Fluctuational electrodynamics integrated with effective medium theory and anisotropic thin-film optics is used to calculate the ne…
Voltage-Induced Oxidation for Enhanced Purity and Reproducibility of Quantum Emission in Monolayer 2D Materials
研究提出一种利用导电原子力显微镜的电压诱导氧化技术，通过局部抑制缺陷发光，显著提升了单层WSe2中量子发射体的单光子纯度与稳定性，为二维量子光源的集成应用提供了可扩展路径。
Colour centres of hexagonal boron nitride (h-BN) have been discovered as promising and practical single photon sources due to their high brightness and narrow spectral linewidth at room-temperature. In order to realize h-BN based photonic quantum communications, the ability to electrically activate the single photon fluorescence using an external electric field is crucial. In this work, we show the electrical switching of the photoluminescence from h-BN quantum emitters, enabled by the controllable electron transfer from the nearby charge reservoir. By tuning the Fermi level of graphene next t…
Quantum dots emission enhancement via coupling with an epsilon-near-zero sublayer
本研究通过将PbS/CdS量子点耦合至ITO基底上的epsilon-near-zero光谱区域，实现寿命缩短54倍、饱和强度提升7.5倍及发射锥角收窄，展示了TCO材料在量子光子器件中的潜力。
Nanophotonics achieves accurate control over the luminescence properties of a single quantum emitter by tailoring the light-matter interaction at the nanoscale and modifying the local density of optical states (LDOS). This paradigm could also benefit to Förster resonance energy transfer (FRET) by enhancing the near-field electromagnetic interaction between two fluorescent emitters. Despite the wide applications of FRET in nanosciences, using nanophotonics to enhance FRET remains a debated and complex challenge. Here, we demonstrate enhanced energy transfer within single donor-acceptor fluoroph…
The coupling between multiple nanocavities in close vicinity leads to hybridization of their modes. Stacked Metal/Insulator/Metal (MIM) nanocavities constitute a highly versatile and very interesting model system to study and engineer such mode coupling, since they can be realized by lithography-free fabrication methods with fine control on the optical and geometrical parameters. The resonant modes of such MIM cavities are epsilon-near-zero (ENZ) resonances, which are appealing for non-linear photophysics and a variety of applications. Here we study the hybridization of ENZ resonances in MIMIM…
In recent years, the concept of metamaterials has offered platforms for unconventional tailoring and manipulation of the light-matter interaction. Here, we explore the notion of "static optics", in which the electricity and magnetism are decoupled and their fields are statically distributed, while being temporally dynamic. This occurs when both the relative effective permittivity and permeability attain near-zero values at an operating frequency. We theoretically investigate some of the unprecedented wave features, such as unusual radiation characteristics of an emitter embedded in such epsilo…
Nonreciprocal thermal radiation in ultrathin magnetized epsilon-near-zero semiconductors
首次实验验证超薄磁化InAs半导体在ENZ频率下打破基尔霍夫热辐射定律，实现大于0.6的吸收与发射差异，并灵活调控单频、双频及宽带非互易热辐射，为革新下一代非互易能量器件奠定基础。
Purcell enhancement of silicon W centers in circular Bragg grating cavities
本研究针对硅基量子光子芯片的单光子生成需求，在圆形布拉格光栅腔中实现硅W色心的Purcell增强，实验观测到零声子线强度20倍提升与弛豫时间减半，为硅基按需单光子源开发提供了可行路径。
In this work we investigate the nonperturbative decay dynamics of a quantum emitter coupled to a composite right/left handed transmission line (CRLH-TL). Our theory captures the contributions from the different spectral features of the waveguide, providing an accurate prediction beyond the weak coupling regime, and illustrating the multiple possibilities offered by the nontrivial dispersion of metamaterial waveguides. We show that the waveguide is characterized by a band-gap with two asymmetric edges: (i) a mu-near-zero (MNZ) band edge, where spontaneous emission is inhibited and an unstable p…
Nanoscale positioning and in-situ enhancement of single G center in silicon using a fluorescence-localization technique
本文提出荧光定位技术将硅中单个G色心精确嵌入圆形布拉格光栅腔中心，使成功概率提高240倍，实现发光增强30倍和Purcell因子超11，为量子光源大规模集成奠定基础。
Engineering Perovskite Emissions via Optical Quasi-Bound-States-in-the-Continuum
提出具有偏振控制q-BIC共振的光学纳米天线阵列，在环境条件下非侵入性地将FAPbI3钙钛矿量子点的光致发光波长位移约39 nm并实现21倍发射增强，为先进光电器件提供新途径。
Long-range quantum entanglement in dielectric mu-near-zero metamaterials
提出兼容NV金刚石色心技术的全介电mu-near-zero超材料平台，实现超17个自由空间波长的长程量子纠缠，concurrence提升一个数量级并展现反聚束特征。
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