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Ultrahigh brightening of infrared PbS quantum dots via collective energy transfer induced by a metal-oxide plasmonic metastructure
摘要： We demonstrate a solution-processed heterojunction interface formed via addition of a thin buffer layer of CdSe/ZnS quantum dots to a functional metal oxide plasmonic metastructure (FMOP) can set up a collective inter-quantum dot energy transport process, significantly enhancing the emission of infrared PbS quantum dots. The FMOP includes a Schottky junction, formed via deposition of a Si layer on arrays of Au nanoantennas, and a Si/Al oxide charge barrier. We show when these two junctions are separated from each other by about 15 nm and the CdSe/ZnS quantum dot buffer layer is placed in touch with the Si/Al oxide junction, the quantum efficiency of an upper layer of PbS quantum dots can increase by about one order of magnitude. These results highlight a unique energy circuit formed via collective coupling of the CdSe/ZnS quantum dots with the hybridized states of plasmons and diffraction modes of the arrays (surface lattice resonances) and coupling between such resonances with PbS QDs via lattice-induced photonic modes.
关键词： exciton-plasmon coupling,plasmons,collective,PbS quantum dots,metallic nanoantennas,surface lattice resonances,energy transfer
更新于2025-09-23 15:19:57
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The challenge in realizing an exchange coupled BiFeO3- double perovskite bilayer
摘要： In this work we propose a device design for efficient voltage control of magnetism. The magnetization of a ferrimagnetic double perovskite may be manipulated by an exchange coupled layer of multiferroic BiFeO3. Bilayers of Barium doped BiFeO3 and ferrimagnetic double perovskite Sr2FeMoO6 have been prepared by pulsed laser deposition motivated by the possibility of strong interlayer exchange coupling. While single layers of each material show high quality we observe that in both stacking orders the first layer decomposes during the deposition of the second layer. The reason for the decomposition are strongly differing growth conditions for BiFeO3 and Sr2FeMoO6. This means that the generation of artificial multiferroic stacks requires careful choice of the constituent materials to ensure the bilayer stability.
关键词： BiFeO3,Exchange Bias,Double Perovskite,Perovskite,Sr2FeMoO6,Exchange coupling
更新于2025-09-23 15:19:57
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Second-Harmonic Generation from a Quantum Emitter Coupled to a Metallic Nanoantenna
摘要： We use time-dependent density functional theory and a semiclassical model to study second-harmonic generation in a system comprising a quantum emitter and a spherical metallic nanoparticle, where the transition frequency of the quantum emitter is set resonant with the second harmonic of the incident frequency. The quantum emitter is shown to enable strong second-harmonic generation, which is otherwise forbidden because of symmetry constraints. The time-dependent density functional theory calculations allow to identify the main mechanism driving this nonlinear effect, where the quantum emitter plays the role of an optical resonator that experiences the nonlinear near fields generated by the metallic nanoantenna located nearby. The influence of the intrinsic properties of the quantum emitter and the nanoantenna, together with the relative position of both in the coupled system allows for a high degree of control of the nonlinear light emission. The main effects and contributions to this nonlinear process can be correctly captured by a semiclassical description developed in this work.
关键词： quantum emitter,plasmonics,nonlinear optical response,Second-harmonic generation,electromagnetic coupling
更新于2025-09-23 15:19:57
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Active control of narrowband total absorption based on terahertz hybrid Dirac semimetal-graphene metamaterials
摘要： A narrowband total absorber consists of a single layer of graphene, Photoactive Silicon and bulk Dirac semimetal (BDS) and has been studied in three different ways for light absorption control without changing the geometry of the structure. Numerical simulation results show that the total absorption is achieved in the narrow spectral range by the critical coupling achieved by the guided resonance, and the results are in good agreement with the coupled mode theory (CMT). Interestingly, this device exhibits exceptional polarization insensitivity and excellent absorption stability over a range of incident angles. In addition, the extremely remarkable sensing performance is more conducive to the application of bio-chemical sensors. In this article, we propose that this work achieves a significant enhancement of the interaction of light and matter in single-layer graphene without graphene plasmon response. This simple and easily fabricated narrowband total absorption structure has outstanding potential applications in the design of modulators, filters and photodetectors.
关键词： metamaterials,narrowband,absorption,critical coupling
更新于2025-09-23 15:19:57
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-matrix based master equation for Coulomb drag in double quantum dots
摘要： Recently, novel Coulomb drag mechanisms in capacitively coupled double quantum dots were uncovered by the T -matrix based master equation (TME). The TME is so far the primary approach to studying Coulomb drag in the weak-coupling regime; however, its accuracy and reliability remain unexplored. Here, we evaluate the performance of the TME for Coulomb drag via a comparison with numerically exact results obtained by the hierarchical equation-of-motion approach. We ?nd that the TME can capture qualitative current evolutions versus dot levels, temperature, and effective coupling strengths but only partially succeeds at the quantitative level. Speci?cally, the TME gives highly inaccurate drag currents when large charge ?uctuations on dots exist and the fourth-order tunneling processes make a leading-order contribution. This failure of the TME is attributed to the combined effect of the unique drag mechanisms and its overlook of the fourth-order single-electron tunnelings. We identify the reliable regions to facilitate further quantitative studies on Coulomb drag by the TME.
关键词： weak-coupling regime,Coulomb drag,double quantum dots,T-matrix based master equation,hierarchical equation-of-motion approach
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 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 fluorescence, time-correlated single-photon counting (TCSPC) and transient absorption (TA) measurements. Support for the experimental findings 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
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Coupling characteristics of the spun optical fiber with multiple stress elements
摘要： Possible coupling between fundamental modes and higher order modes in a spun optical ?ber with multiple stress elements is analyzed. It shows that only the higher order HEmn mode with the opposite circular polarization state can be coupled with the fundamental HE11 mode. The coupling between the fundamental HE11 mode and the TE, TM or EH modes can never be occurred. In the possible coupling between HEmn mode and HE11 mode, m should be equal to N-1, where N is the number of the stress elements. As a comparison, the coupling property in a spun optical ?ber with single stress element is also demonstrated. In this case, the fundamental HE11 mode can not only be coupled with the higher orderHE2n mode but also can be coupled with the higher order TE mode.
关键词： Coupling characteristics,Polarization,Stress elements,Spun optical fiber,Optical fiber
更新于2025-09-23 15:19:57
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Radiation of a Resonant Medium Excited by a Periodically Phase-Modulated Laser in the Regime of Strong Coupling between the Field and the Matter
摘要： The radiation of a two-level resonant medium that is placed into a cavity and is excited by a periodically phase modulated laser pulse is studied theoretically. The radiation is analyzed based on the analytical and numerical solutions of the system of Maxwell–Bloch equations under conditions of a strong coupling between the field and the matter. Under these conditions, this system is similar to a polariton laser. The excitation efficiency of a polariton laser by a phase-modulated radiation pulse is shown to be high compared to a pulse without phase modulation of the carrier frequency. It is shown that the main reason for the efficient excitation of polariton modes in the medium is the appearance of difference combination parametric resonance. The obtained results open up new possibilities for the excitation of radiation of polariton lasers by low-power frequency-modulated pump laser radiation.
关键词： phase modulation,Rabi vacuum splitting,strong coupling,polariton laser
更新于2025-09-23 15:19:57
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Plasmonic Coupling of AgNPs near Graphene Edges: A Cross-Section Strategy for High-Performance SERS Sensing
摘要： Fully exploiting plasmonic coupling of nanostructured metals is an effective method to promote surface-enhanced Raman scattering (SERS) performance for trace detection of molecules. Herein, we propose a cross-section strategy to maximize plasmonic coupling of silver nanoparticles (AgNPs) in graphene-based membrane. Specifically, AgNPs are isolated by water-dispersible graphene (W-Gr) and enriched in the vicinity of W-Gr edges when assembling into a macroscopic membrane, thus affording AgNPs on the cross section with uniform and proper gaps in the vertical plane to generate maximal plasmon coupling. Moreover, the superior sensitivity (5×10-13 M for R6G) to most reported graphene-metal structures and the long-term stability against aerobic oxidation jointly make the cross-section of AgNPs/W-Gr membrane a potential SERS substrate for trace-molecule detection. The revealed mechanism for AgNPs enrichment near edges highlights the importance of flow-directed assembly process of W-Gr. This work provides new insight into the interpretation and utilization of two-dimensional materials as building blocks in high-performance SERS sensing.
关键词： Cross-section strategy,AgNPs,SERS sensing,Plasmonic coupling,Graphene edges
更新于2025-09-23 15:19:57
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Improvement in light out-coupling efficiency of OLED by using high fill factor parabola curve microlens arrays
摘要： Aspheric microlens arrays (MLAs) are introduced on glass substrate to improve the light out-coupling efficiency (LOCE) of organic light-emitting diode (OLED). Geometric ray tracing was employed to simulate the improved effects and optimize the structure parameters of the MLAs pattern. The simulation results show that when the parameters of MLAs as follows, the curved profile is parabola, the base shape is hexagon, the fill factor is 1, the aspect ratio is 0.6, and the material refractive index should be match to that of the substrate of the OLED, which can improve LOCE maximum. Poly-dimethyl-siloxane (PDMS) parabola curve MLAs films ware fabricated by maskless lithography technique and template replication. The experimental results show that the MLAs can improve the LOCE and the trends of the experimental results agree with the simulation results. A maximum increase of 49% in the coupling efficiency was achieved.
关键词： light out-coupling efficiency,aspheric microlens arrays,OLED,parabola curve
更新于2025-09-23 15:19:57