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Temperature dependence of an amorphous organic thin film polariton laser
摘要： Since its first observation, the polariton lasing threshold in organic films has been anomalously high, given that Bosonic condensation should occur at vanishingly small pumping powers. Here, we investigate the temperature dependence of a polariton laser employing an amorphous organic thin film, 2,7-bis[9,9-di(4-methylphenyl)-fluoren-2-yl]-9,9-di(4-methylphenyl)fluorene, in a vertical optical microcavity. An increase in laser threshold is observed at temperatures < 45 K, while the threshold remains unchanged as the temperature increases up to room temperature. In contrast, the energy dispersion characteristic of cavity polaritons is independent of temperature. At low temperature, an energy relaxation bottleneck along the polariton dispersion takes place below threshold. The bottleneck is found to be responsible for the anomalous increase in threshold with decreasing temperature. As the pumping power increases, amplified spontaneous emission (ASE) is observed prior to the onset of lasing. We also study the photoluminescence of the neat organic film versus temperature to explain the origin of the bottleneck in the exciton polariton dispersion.
关键词： exciton,polariton lasing,light-matter interaction,cavity,Strong-coupling
更新于2025-09-23 15:19:57
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New Silica Laser-Optimized Multimode Optical Fibers with Extremely Enlarged 100-??m Core Diameter for Gigabit Onboard and Industrial Networks
摘要： We present new type of silica graded index laser-optimized multimode optical fibers (LOMF) with extremely enlarged core diameter up to 100 μm and “typical” “telecommunication” cladding diameter 125 μm. This optical fiber was designed for harsh environment Gigabit onboard cable systems and industrial networks. It differs by special optimized graded refractive index profile, providing low differential mode delay (DMD) for selected guided modes. We present some results of tests, performed for manufactured pilot 520 m length of described LOMF 100/125, concerned with its geometry properties as well as key transmission parameters—attenuation and DMD map.
关键词： mode coupling,laser-based gigabit data transmission,higher-order modes,large core multimode optical fiber,differential mode delay,short-range optical networks,industrial networks,selected guided modes,on-board cable systems,few-mode regime
更新于2025-09-23 15:19:57
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Coupled-mode-induced transparency and attenuation resulting from cross-polarization coupling
摘要： Induced transparency and attenuation effects are observed in the throughput of a single whispering-gallery microresonator due to mode coupling between two coresonant orthogonally polarized whispering-gallery modes of very different quality factors. Intracavity cross-polarization coupling, occurring when either the transverse electric (TE) mode or the transverse magnetic (TM) mode is driven, results in coupled-mode induced transparency or coupled-mode induced attenuation. Coresonance between the TE and TM modes is obtained by strain tuning, and the cross-polarization coupling is produced by polarization rotation due to optical spin-orbit interaction in a slightly asymmetric resonator. The observed behavior enables slow light and fast light, i.e., the delay or advancement of an incident resonant pulse. Experimental results representative of several different types of behavior are presented here. Induced transparency is seen to be accompanied by pulse delay, whereas induced attenuation can involve pulse advancement or delay. The results are analyzed and explained by analytical modeling and by comparison to the output of a more detailed numerical model describing these effects. Delays of up to 170 ns and advancements of up to 14 ns are found. The observed range of cross-polarization coupling strengths (probability of polarization change per round trip), namely, 10?10–10?7, is in agreement with theory.
关键词： slow light,induced transparency,whispering-gallery microresonator,cross-polarization coupling,attenuation,fast light
更新于2025-09-23 15:19:57
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Size- and Composition-Dependent Exciton Spin Relaxation in Lead Halide Perovskite Quantum Dots
摘要： The strong spin-orbital coupling in lead halide perovskites allows for facile spin injection for spintronics applications, but on the other hand also limits the lifetime of the injected spins. Full-dimensional confinement of the carriers using quantum dots (QDs) has been envisioned as an effective means to prolong the spin relaxation lifetime and has been explored for II-VI and III-V group QDs. Here we applied this idea to colloidal lead halide perovskite QDs and measured the exciton spin dynamics of QDs of varying sizes and compositions using circularly polarized transient absorption spectroscopy at room temperature. Interestingly, the spin lifetimes of CsPbI3 and CsPbBr3 QDs were prolonged and shortened, respectively, as compared to their bulk counterparts. Both CsPbI3 and CsPbBr3 QDs showed decreasing spin lifetime with decreasing QD size. Possible spin relaxation mechanisms, including those that are unique to these quantum-confined systems, were proposed, with important ramifications for the use of these perovskite QDs in spin-related applications.
关键词： lead halide perovskites,spin-orbital coupling,exciton spin dynamics,circularly polarized transient absorption spectroscopy,quantum dots
更新于2025-09-23 15:19:57
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Single-photon superradiance in waveguide-quantum-electrodynamical systems with whispering-gallery-mode resonators
摘要： As a manifestation of cooperative interactions between a single photon and a cluster of atoms, single-photon superradiance has attracted considerable attention recently but has been studied insofar as that only quantum emitters are involved in the superradiance process. Here we expand the scope of investigation to study single-photon superradiance in a waveguide-quantum-electrodynamical system containing whispering-gallery-mode (WGM) resonators which are essential for many nanophotonic devices. It is shown analytically and numerically that single-photon superradiance can also occur when WGM resonators are present. The criteria for the emergence of the superradiant emission peak and the enhanced atom-light coupling strength are derived. Finally, the general case of a cascade of WGM resonators is investigated by a renormalization approach. Single-photon frequency comb generation is demonstrated via a frequency-modulated superradiant effective atom in chiral waveguide-quantum-electrodynamical systems with WGM resonators.
关键词： single-photon superradiance,whispering-gallery-mode resonators,atom-light coupling,waveguide-quantum-electrodynamical systems,frequency comb generation
更新于2025-09-23 15:19:57
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Tuning Plasmonic Coupling from Capacitive to Conductive Regimes via Atomic Control of Dielectric Spacing
摘要： The gap length between plasmonic nanoparticles determines the strength of the optical coupling that results in electromagnetic field enhancement for spectroscopic and other applications. Although gap plasmon resonances have been the focus of increasing research interest, experimental observations have primarily been limited to the coupling of spherical nanoparticles that may not provide clear spectral contrast of the optical response as the interaction evolves from capacitive to charge transfer with the gap size decreasing to subnanometer. Here, by taking advantage of the sharp plasmon resonances of colloidal gold nanorods coupled to gold film, we present the spectral evolution of gap plasmon resonance as the particle-film spacing varies from over 30 nm to the touching limit. We find that, the capacitive gap plasmon resonance of the coupled system red shifts and narrows continuously until it vanishes at the quantum tunneling limit, in contrast to the nonlocal and Landau damping effects that are expected to result in relative blue shifting and spectral broadening. When the spacer thickness is further decreased, high order cavity modes appear, and eventually single peak broad resonances that are characteristic of tunneling and direct contact particle-film interaction emerge. The experimental observations show that nanorods are better suited for creating cavity plasmon resonances with high quality factor, and the spectral contrast at the transition provides clarity to develop improved theoretical modeling of optical coupling at subnanometer gap lengths.
关键词： atomic layer deposition,tunneling,plasmon coupling,Particle on metal film,cavity modes,charge transfer,gold nanorods
更新于2025-09-23 15:19:57
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Determining the sequence and backbone structure of a??semi-statisticala?? copolymers as donora??acceptor polymers in organic solar cells
摘要： Organic photovoltaics (OPVs) are attracting significant attention due to the growing demand for economically viable and renewable energy sources. With efficiencies exceeding 16.5%, single junction bulk heterojunction (BHJ) devices are amongst the most promising and are nearing commercialisation. One recent avenue of research has focused on statistical conjugated copolymers. However, a detailed investigation as to why these materials can achieve higher power conversion efficiencies than their regular alternating counterparts is seldom reported. This work describes an investigation into donor–acceptor polymers demonstrating how differing monomer activities can lead to differing microstructures in a simple batch reaction, which in turn demonstrates promising optoelectronic and morphological properties required for organic photovoltaic devices. A one pot condensation polymerisation reaction with three monomers leads to an ABA triblock structure from differing monomer reactivities. This structure in turn leads to visualised phase separation which is possibly linked to an increase in performance. Further to this we report on the reliability of the Stille coupling for the synthesis of conjugated polymers.
关键词： Organic photovoltaics,Donor–acceptor polymers,Bulk heterojunction devices,Statistical conjugated copolymers,Stille coupling
更新于2025-09-23 15:19:57
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Study on coupling optimization model of node enterprises for energy storage-involved photovoltaic value chain in China
摘要： In recent years, with continuous focus on clean energy and environmental protection, the scale of photovoltaic generation industry in China has been gradually expanded, making great achievements. However, it also faces huge challenges and problems such as fierce market competition, serious photovoltaic curtailment, high cost, etc. In order to promote the sustainable development of photovoltaic industry, this paper constructs an energy storage-involved photovoltaic value chain (ES-PVC) consisting of three nodes for upstream, midstream and downstream, in which photovoltaic power suppliers, battery energy storage business and electric vehicle manufacturers locate respectively. The coupling problem for node enterprises in the value chain is studied by multi-objective optimization and G1 method, which is measured eventually via a single value transformed by ideal point method. Considering the particularity of issue, the paper proposes an improved genetic algorithm (IGA) to fit and solve the model. A best value chain is acquired via proposed approach whose feasibility and applicability are verified through comparative analysis with analytic hierarchy process (AHP) and linear assignment method (LAM) and sensitivity analysis. The implications and limitations are presented in the conclusion, aiming to provide theoretical reference for value management of photovoltaic enterprise and to get further research.
关键词： Improved genetic algorithm,Photovoltaic value chain,Node coupling optimization,Energy storage,G1 method,Multi-objective decision-making
更新于2025-09-23 15:19:57
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Collectively induced exceptional points of quantum emitters coupled to nanoparticle surface plasmons
摘要： Exceptional points, resulting from non-Hermitian degeneracies, have the potential to enhance the capabilities of quantum sensing. Thus, finding exceptional points in different quantum systems is vital for developing such future sensing devices. Taking advantage of the enhanced light-matter interactions in a confined volume on a metal nanoparticle surface, here we theoretically demonstrate the existence of exceptional points in a system consisting of quantum emitters coupled to a metal nanoparticle of subwavelength scale. By using an analytical quantum electrodynamics approach, exceptional points are manifested as a result of a strong-coupling effect and observable in a drastic splitting of originally coalescent eigenenergies. Furthermore, we show that exceptional points can also occur when a number of quantum emitters are collectively coupled to the dipole mode of localized surface plasmons. Such a quantum collective effect not only relaxes the strong-coupling requirement for an individual emitter, but also results in a more stable generation of the exceptional points. Furthermore, we point out that the exceptional points can be explicitly revealed in the power spectra. A generalized signal-to-noise ratio, accounting for both the frequency splitting in the power spectrum and the system’s dissipation, shows clearly that a collection of quantum emitters coupled to a nanoparticle provides a better performance of detecting exceptional points, compared to that of a single quantum emitter.
关键词： strong-coupling effect,metal nanoparticle,power spectra,quantum emitters,quantum sensing,signal-to-noise ratio,surface plasmons,Exceptional points
更新于2025-09-23 15:19:57
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Excitonically Coupled Cyclic BF2 Arrays of Calix[8]a?? and Calix[16]phyrin as Neara??IRa?? Chromophores
摘要： A pair of giant calix[n]phyrin derivatives namely calix[8]- (4) and calix[16]phyrin (5), involving two and four BF2 units, respectively, were prepared via the condensation of the bis-naphthobipyrrolylmethene-BF2 complex with pentafluorobenzaldehyde. Both systems and precursor 3 were fully characterized, including via single crystal X-ray diffraction analyses. Calix[n]phyrins 4 and 5 display extremely high extinction coefficients (3.67 and 4.82 105 M-1cm-1, respectively) in the near-IR region. This observation was taken as initial evidence for strong excitonic coupling within these cyclic multi-chromophoric systems. Detailed insights into the effect of excitonic coupling dynamics on the electronic structure and photophysical properties of the macrocycles came from theoretical studies. Taken in concert this combination of theory and experiment served to confirm that the coupling between the excitons depends on the specifics of the calix[n]phyrin structure, not just its size.
关键词： Cyclic BODIPY,Boron,Exciton Coupling,Porphyrinoids,NIR Dye,Calix[n]phyrin
更新于2025-09-23 15:19:57