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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Antiresonant Oxide Island as a Measure for Improved Single-Mode Emission in VCSELs
摘要： In this paper, we propose a novel ARROW VCSEL structure with an antiresonant oxide island placed inside the resonant cavity with the use of planar oxidation technique. The oxidized island does not only improve single-mode emission, which is one of the most desired effects in vertical-cavity surface-emitting lasers (VCSELs), but also has a strong impact on modal loss associated with each lateral mode and affects the shape of their profiles. In this work, we investigate the physical basis of this impact and show how the dimensions of oxidized island determine optical properties of the ARROW VCSEL, leading to the strongest modal discrimination.
关键词： optical modeling,oxidation,ARROW,VCSEL,antiresonance,waveguiding
更新于2025-09-23 15:23:52
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Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens
摘要： To determine whether the cellular physiology of the lens actively maintains the optical properties of the lens and whether inhibition of lens transport affects overall visual quality. One lens from a pair of bovine lenses was cultured in artificial aqueous humor (AAH), while the other was cultured in either AAH-High-K+ or AAH + 0.1 mM ouabain for 4 hours. Lens pairs or whole enucleated eyes were then imaged in 4.7 Tesla (T) high-field small animal magnet. Lens surface curvatures, T1 measurements of water content, and T2 measurements of water/protein ratios were extracted from cultured lenses, while the geometrical parameters that define the optical pathway were obtained from whole eyes. Gradients of refractive index (GRIN), calculated from T2 measurements, and the extracted geometric parameters were inputted into optical models of the isolated lens and the whole bovine eye. Inhibiting circulating fluxes by inhibiting the Na/K-ATPase with ouabain or depolarization of the lens potential by High K+ caused changes to lens water content, the water/protein ratio (GRIN) and surface geometry that manifested as an increase in optical power and a decrease in negative spherical aberration in cultured lenses. Changes to optical properties of the lens resulted in a myopic shift that impaired vision quality in the optical model of the bovine eye. The cellular physiology of the lens actively maintains its optical properties and inhibiting the Na/K/ATPase induces a myopic shift in vision similar to that observed clinically in patients who go on to develop cataract.
关键词： physiological optics,optical modeling,cataract,gradient of refractive index,lens physiology,magnetic resonance imaging
更新于2025-09-23 15:21:01
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Analysis of Factors Affecting Optical Performance of GaN-Based Micro-LEDs with Quantum Dots Films
摘要： Optical performance in terms of light efficiency, color crosstalk and ambient contrast ratio were analyzed for blue GaN-based micro-light emitting diodes (micro-LEDs) combined with red/green quantum dots (QDs)-polymethyl methacrylate (PMMA) films. The thickness and mass ratio of QDs films are two critical factors in affecting the performance of micro-LEDs. Firstly, the precise optical modeling of QDs-PMMA films is established based on the double integrating sphere (DIS) testing system and inverse adding doubling algorithm (IADA) theory. Red and green QDs-PMMA films are composed of ZnCdSe/ZnS QDs and green ZnCdSeS/ZnS QDs, respectively. The fundamental optical parameters of QDs-PMMA films, including scattering, absorption and anisotropy coefficients, are obtained successfully. Secondly, based on these optical parameters, the Monte Carlo ray tracing method is applied to analyze the effect of a QDs-PMMA film’s thickness and mass ratio on the optical performance of micro-LEDs. Results reveal that the light efficiency first increases and then decreases with the increase of a QDs film's thickness or mass ratio, owing to the scattering characteristics of QDs. Different from the variation tendencies of light efficiency, the crosstalk between adjacent pixels increases as the QDs-PMMA film's thickness or mass ratio increases, and the ambient contrast ratio is kept stable when the thickness increases. The mass ratio variation of QDs film can change the optical performance of micro-LEDs more effectively than thickness, which demonstrates that mass ratio is a more important factor affecting the optical performance of micro-LEDs.
关键词： micro-LED,quantum dot,optical modeling,light efficiency
更新于2025-09-23 15:19:57
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On the contribution of fullerene to the current of planar heterojunction organic solar cells.
摘要： Recently, significant progress in the field of organic photovoltaic cells was obtained by substituting new electron acceptor molecules to the fullerene, which was attributed to the fact that the fullerene absorption is quite small. Nevertheless, we demonstrate in the present work that, in the case of inverted cells, i.e. when the transparent bottom electrode is used as cathode, the contribution of fullerene to the Jsc short-circuit current of the cells, if not dominant, is not negligible; and that mainly in the short wavelength spectral range. The experimental results are confirmed by an optical simulation. Due to this significant contribution to Jsc, the light transmission of the transparent electrode towards the UV-part of the spectrum is crucial for inverse cell performances. When a transparent conductive electrode based on an alternative dielectric/metal/dielectric structure is substituted to ITO, such as ZnS/Ag/TiO2, the study allows to obtain promising results, although there is a loss of performance due to the decrease of transmission of TiO2 below 400 nm in wavelength.
关键词： Absorption,Optical Modeling,External Quantum Efficiency,Organic solar cells,Planar heterojunction
更新于2025-09-19 17:13:59
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Guideline for Optical Optimization of Planar Perovskite Solar Cells
摘要： Organometallic halide perovskite solar cells have emerged as a versatile photovoltaic technology with soaring efficiencies. Planar configuration, in particular, has been a structure of choice thanks to its lower temperature processing, compatibility with tandem solar cells, and potential in commercialization. Despite all the breakthroughs in the field, the optical mechanisms leading to highly efficient perovskite solar cells lack profound insight. In this paper, a comprehensive guideline is introduced involving semianalytical equations for thickness optimization of the front and rear transport layers, perovskite, and transparent conductive oxides to improve the antireflection and light trapping properties, and therefore to maximize the photocurrent of perovskite solar cells. It is shown that a photocurrent enhancement above 2 mA cm?2 can be achieved by altering—reducing or increasing—the thicknesses of the layers constituting a CH3NH3PbI3 (MAPI) type perovskite solar cell. The proposed guideline is tested against experiments as well as previously published experimental and simulation results for MAPI. Additionally, the provided guideline for various types of perovskites can be extended to other direct bandgap absorber-based solar cells in superstrate configuration.
关键词： perovskite solar cells,light trapping,planar solar cells,antireflection,thickness optimization,optimization guideline,optical modeling
更新于2025-09-11 14:15:04
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Bio-optical Modeling and Remote Sensing of Inland Waters || Bio-optical Modeling of Total Suspended Solids
摘要： Suspended solids play a fundamental role in the aquatic ecosystem as they regulate two major transport routes of materials and contaminants: the dissolved transport in the pelagic water and the particulate benthic sedimentation route (Wetzel, 1983; Ha?kanson, 2006). The presence of total suspended solids (TSS) in water has an impact on primary producers (Zhang et al., 2008), through affecting the amount of light penetrating through the water column that restricts the rate at which benthic algae, phytoplankton, and macrophytes can assimilate energy through photosynthesis.
关键词： Inland Waters,Bio-optical Modeling,Remote Sensing,Total Suspended Solids,Water Quality
更新于2025-09-10 09:29:36