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Dimer chains in waveguide quantum electrodynamics
摘要： We examine the propagation of single photons in periodic and disordered dimer chains coupled to one-dimensional chiral waveguides. Each dimer is composed of two dipole-coupled atoms. In the disordered setting, we separately treat two types of position disorder, namely in dimer length and in dimer separation. The focus of this study is to understand in what ways the interplay between dipole–dipole interactions and directionality of photon emission can impact the transport of single photons. Cold atoms trapped near optical fibers can serve as an experimentally realizable platform for the models that we consider.
关键词： Chiral quantum optics,Photon localization,Dipole–dipole interactions,Waveguide quantum electrodynamics,Position disorder
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Application of mosaicity induced disorder controlled rare earth nickelate thin films as THz transmission modulator
摘要： Here, we have studied mosaicity induced disorder (a unique type of disorder which is transferred from substrate template to film) controlled properties of rare earth nickelate thin films. While highly oriented film exhibits sharp metal to insulator transition (MIT) and Drude type of terahertz (THz) conductivity behavior, mosaic film exhibit much more subtle and broad transition and Drude-Smith type THz conductivity behavior. On the basis of such contrasting behavior, we propose application of these films as thermally controlled THz transmission modulator: oriented film as digital modulator while mosaic film as analog modulator.
关键词： metal to insulator transition,Drude-Smith model,rare earth nickelate,THz transmission modulator,mosaicity induced disorder
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Tailored Disorder for the Light Management in Photovoltaics
摘要： Light management in photovoltaics continues to be an important ingredient when working towards high efficiency devices. Various approaches have been perceived. Besides spectral modification, e.g. based on up- or down-conversion, the spatial and angular redistribution of light is important. For the latter aspect, on which we concentrate here, various supporting photonic structures were suggested, e.g. photonic crystals, metallic nanostructures, or textured interfaces. From a higher executive perspective we can categorize most structures as being either periodic or random. The emergence of such material classes is explained by the fabrication means. The Fourier spectrum, i.e. the angular distribution with which photonic modes can be excited from such structures beyond specific near-field effects is either discrete and wavelength sensitive or unspecific and spectrally flat. Both combinations are far from optimum when integrating them into photovoltaic devices. In this contribution we elaborate on the notion of a tailored disorder to improve the photon management. With tailored disorder we achieve hyperuniform interfaces. They are characterized by a suppressed variation in the feature density across the interface, like in a periodic structure, but at the same they offer the same properties when viewed from different directions. The hyperuniform interfaces we have in mind combine the benefits of the previously considered categories. Hyperuniform interfaces offer (a) a structured Fourier spectrum, (b) are rather wavelength insensitive, and (c) are subject to a deterministic design process.
关键词： light management,hyperuniform interfaces,photovoltaics,tailored disorder
更新于2025-09-16 10:30:52
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The Efficacy of Light Therapy in the Treatment of Seasonal Affective Disorder: A Meta-Analysis of Randomized Controlled Trials
摘要： Background: Bright light therapy (BLT) has been used as a treatment for seasonal affective disorder (SAD) for over 30 years. This meta-analysis was aimed to assess the efficacy of BLT in the treatment of SAD in adults. Method: We performed a systematic literature search including randomized, single- or double-blind clinical trials investigating BLT (≥400 lx) or sham/low-density negative ion generators as placebo. Only first-period data were used from crossover trials. The primary outcome was the post-treatment depression score measured by validated scales, and the secondary outcome was the rate of response to treatment. Results: A total of 19 studies finally met our predefined inclusion criteria. BLT was superior over placebo with a standardized mean difference of –0.37 (95% CI: –0.63 to –0.12) for depression ratings (18 studies, 610 patients) and a risk ratio of 1.42 (95% CI: 1.08–1.85) for response to active treatment (16 studies, 559 patients). We found no evidence for a publication bias, but moderate heterogeneity of the studies and a moderate-to-high risk of bias. Conclusions: BLT can be regarded as an effective treatment for SAD, but the available evidence stems from methodologically heterogeneous studies with small-to-medium sample sizes, necessitating larger high-quality clinical trials.
关键词： Bright light therapy,Seasonal affective disorder,Winter depression,Meta-analysis
更新于2025-09-16 10:30:52
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Design principles for sensitivity optimization in plasmonic hydrogen sensors
摘要： Palladium nanoparticles have proven to be an exceptionally suitable material for the optical detection of hydrogen gas, due to the dielectric function that changes with the hydrogen concentration. The development of a reliable, low-cost, and widely applicable hydrogen detector requires a simple optical read-out mechanism and an optimization of the lowest detectable hydrogen concentration. So-called ‘perfect absorber’-type structures, consisting of a layer of plasmonic palladium nanoantennas suspended above a metallic mirror layer, are a promising approach to realizing such sensors. The absorption of hydrogen by palladium leads to a shift of the plasmon resonance and thus to a change in the far-?eld re?ectance spectrum. The spectral change can be analyzed in detail using spectroscopic measurements, while the re?ectance change at a speci?c wavelength can be detected with a simple photometric system of a photodiode and a monochromatic light source. Here, we systematically investigate the geometry of cavity-coupled palladium nanostructures as well as the optical system concept, which enables us to formulate a set of design rules for optimizing the hydrogen sensitivity. Employing these principles, we demonstrate the robust detection of hydrogen at concentrations down to 100 ppm. Our results are not limited to hydrogen sensing, but can be applied to any type of plasmonic sensor.
关键词： Hydrogen detection,Palladium,Tailored disorder,Plasmonic sensing,Microspectroscopy,Metasurface,Perfect absorber,Fourier-plane spectroscopy
更新于2025-09-16 10:30:52
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Disorder vs Delocalization: Which Is More Advantageous for High-Efficiency Organic Solar Cells?
摘要： We investigate the combined influence of energetic disorder and delocalization on electron-hole charge-transfer state separation efficiency in donor-acceptor organic photovoltaic systems using an analytical hopping model and Monte Carlo calculations, coupled with an effective mass model. Whereas energetic disorder increases the separation yield at intermediate and low electric fields for low efficiency blends with strongly localized carriers, we find that it reduces dramatically the fill factors and power conversion efficiencies in high efficiency solar cells that require high carrier delocalization within the conjugated segment and high mobility-lifetime product. We further demonstrate that the initial electron-hole distance and thermalization processes play only a minor role in the separation dynamics.
关键词： Charge separation,delocalization,organic photovoltaics,disorder,Monte Carlo simulations
更新于2025-09-12 10:27:22
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Nonequilibrium site distribution governs charge-transfer electroluminescence at disordered organic heterointerfaces
摘要： The interface between electron-donating (D) and electron-accepting (A) materials in organic photovoltaic (OPV) devices is commonly probed by charge-transfer (CT) electroluminescence (EL) measurements to estimate the CT energy, which critically relates to device open-circuit voltage. It is generally assumed that during CT-EL injected charges recombine at close-to-equilibrium energies in their respective density of states (DOS). Here, we explicitly quantify that CT-EL instead originates from higher-energy DOS site distributions significantly above DOS equilibrium energies. To demonstrate this, we have developed a quantitative and experimentally calibrated model for CT-EL at organic D/A heterointerfaces, which simultaneously accounts for the charge transport physics in an energetically disordered DOS and the Franck–Condon broadening. The 0–0 CT-EL transition lineshape is numerically calculated using measured energetic disorder values as input to 3-dimensional kinetic Monte Carlo simulations. We account for vibrational CT-EL overtones by selectively measuring the dominant vibrational phonon-mode energy governing CT luminescence at the D/A interface using fluorescence line-narrowing spectroscopy. Our model numerically reproduces the measured CT-EL spectra and their bias dependence and reveals the higher-lying manifold of DOS sites responsible for CT-EL. Lowest-energy CT states are situated ～180 to 570 meV below the 0–0 CT-EL transition, enabling photogenerated carrier thermalization to these low-lying DOS sites when the OPV device is operated as a solar cell rather than as a light-emitting diode. Nonequilibrium site distribution rationalizes the experimentally observed weak current-density dependence of CT-EL and poses fundamental questions on reciprocity relations relating light emission to photovoltaic action and regarding minimal attainable photovoltaic energy conversion losses in OPV devices.
关键词： organic electronics,Franck–Condon vibronic progression,energetic disorder,electroluminescence at organic interfaces,3D kinetic Monte Carlo model
更新于2025-09-12 10:27:22
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Laser Controlled 65 Micrometer Long Microrobot Made of Ni‐Ti Shape Memory Alloy
摘要： Background: Although previous research provides insight into the role of neuroinflammation in idiopathic REM sleep behavior disorder, the association of this disorder with peripheral blood inflammatory markers remains unclear. Objective: To investigate inflammatory cytokines in plasma samples in patients with idiopathic rapid eye movement sleep behavior disorder and to explore whether these markers are associated with prodromal symptoms of α-synucleinopathies. Methods: We collected plasma from patients with polysomnographically confirmed idiopathic rapid eye movement sleep behavior disorder without parkinsonism or dementia (n = 54) and from healthy controls (n = 56). The interleukin-1β, interleukin-2, interleukin-6, interleukin-10, and tumor necrosis factor-α were measured. The idiopathic REM sleep behavior disorder patients underwent sleep, motor, cognitive, olfactory, and autonomic testing. Results: The anti-inflammatory cytokine, interleukin-10, levels in the idiopathic rapid eye movement sleep behavior disorder group were significantly upregulated compared to the control group (P = 0.022), but this difference did not withstand Bonferroni correction. The other proinflammatory cytokine levels did not differ between the groups. No correlation was found between the cytokine levels and any clinical variable. Conclusions: Our data do not provide evidence supporting the role of peripheral inflammation in idiopathic rapid eye movement sleep behavior disorder. However, considering the limited statistical power because of the small sample size, further large-scale longitudinal studies with a broader spectrum of cytokines are needed to clarify this issue.
关键词： REM sleep behavior disorder,immune markers,peripheral inflammation,cytokine,interleukin
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Disorder-Induced Acceleration of Condensation in Multimode Fibers
摘要： Recent studies on wave turbulence revealed that a purely classical system of random waves can exhibit a process of condensation, whose thermodynamic properties are analogous to those of Bose-Einstein condensation [1-3]. Classical wave condensation finds its origin in the natural thermalization toward the Rayleigh-Jeans equilibrium distribution, whose divergence is responsible for the macroscopic occupation of the fundamental mode of the system. The experimental study of condensation in a conservative (cavity-less) configuration constitutes a major challenge, because of the prohibitive large propagation lengths required to achieve thermalization. In contrast with this commonly accepted opinion, a remarkable phenomenon of spatial beam self-cleaning has been recently discovered in graded-index multimode optical fibers (MMFs) [4-7]. This phenomenon is due to a purely conservative Kerr nonlinearity [7] and its underlying mechanism still remains debated. Light propagation in MMFs is known to be affected by a structural disorder of the material due to inherent imperfections and external perturbations. On the basis of the wave turbulence theory, we formulate a nonequilibrium kinetic description of the random waves that accounts for the impact of disorder. The theory reveals that a structural disorder is responsible for a dramatic acceleration of the process of condensation by several orders of magnitudes. This counterintuitive mechanism of condensation acceleration provides a natural explanation for the effect of spatial beam self-cleaning: As a consequence of the fast condensation process, the beam power rapidly flows toward the fundamental mode of the MMF, which becomes macroscopically populated to the detriment of the other modes that exhibit energy equipartition, as predicted by the Rayleigh-Jeans distribution [1]. The simulations of the nonlinear Schrodinger equation (NLSE) are in quantitative agreement with those of the derived kinetic equation, and thus confirm the validity of the theory and the effect of acceleration of condensation mediated by disorder (see Fig. 1). Furthermore, the derived kinetic equation also explains why spatial beam self-cleaning has not been observed in step-index MMFs. We performed experiments in a MMF to evidence the transition to light condensation by varying the coherence of the input beam (as described in Fig. 1c). When a large number of modes are excited, the output intensity distribution tends to relax toward the thermal Rayleigh-Jeans distribution, i.e., the 'temperature' is above the critical value for condensation (E > Ecrit in Fig. 1c) and spatial beam self-cleaning is not observed. By reducing the excitation of modes (E < Ecrit in Fig. 1c), the power gradually condenses into the fundamental mode of the MMF, leading to a cleaned beam with a measured condensate fraction as large as ～60%.
关键词： multimode fibers,spatial beam self-cleaning,condensation,wave turbulence,disorder
更新于2025-09-11 14:15:04
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Orientational Disorder in Epitaxially Connected Quantum Dot Solids
摘要： Periodic arrays of strongly coupled colloidal quantum dots (QDs) may enable unprecedented control of electronic bandstructure through manipulation of QD size, shape, composition, spacing, and assembly geometry. This includes the possibilities of precisely engineered bandgaps and charge carrier mobilities, as well as remarkable behaviors such as metal-insulator transitions, massless carriers, and topological states. However, experimental realization of these theoretically predicted electronic structures is presently limited by structural disorder. Here, we use aberration-corrected scanning transmission electron microscopy to precisely quantify the orientational disorder of epitaxially connected QD films. In spite of coherent atomic connectivity between nearest neighbor QDs, we find misalignment persists with a standard deviation of 1.9 degrees, resulting in significant bending strain localized to the adjoining necks. We observe and quantify a range of out-of-plane particle orientations over thousands of QDs, and correlate the in-plane and out-of-plane misalignments, finding QDs misoriented out-of-plane display a statistically greater misalignment with respect to their in-plane neighbors as well. Using the bond orientational order metric ψ4, we characterize both the fourfold symmetry and introduce a quantification of the local superlattice (SL) orientation. This enables direct comparison between local orientational order in the SL and atomic lattice (AL). We find significantly larger variations in the SL orientation, and a statistically robust but locally highly variable correlation between the orientations of the two differently scaled lattices. Distinct AL and SL behaviors are observed about a grain boundary, with a sharp boundary in the AL orientations, but a more smooth transition in the SL, facilitated by lattice deformation between the neighboring grains. Coupling between the AL and SL is a fundamental driver of film growth, and these results suggest nontrivial underlying mechanics, implying that simplified models of epitaxial attachment may be insufficient to understand QDs growth and disorder when oriented attachment and superlattice growth occur in concert.
关键词： orientational disorder,quantum dot solids,self-assembly,scanning transmission electron microscopy,nanocrystals,PbSe
更新于2025-09-11 14:15:04