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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
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Optical Scheme of Obtaining Highest Transmission Factor in Case of KDP Based Electro-Optic Crystal by the Adjustment of Suitable Biasing Voltage and Number of Feedback Passing
摘要： The electro-optic effect becomes prominent when an electric field is applied across the optic axis of a dielectric material inducing the changes in refractive indices of the medium. Kerr and Pockels cells are massively used as optical switches because of their nonlinear electro-optic character. Potassium di-hydrogen Phosphate (KDP) crystal is a very good electro-optic Pockels material as well as has a good switching behavior in optical and opto-electronic domain. The principle of this electro optic effect can be successfully used to develop optical switch based information processing devices. Transmission co- efficient of the polarized light beam have been modulated in a new way by introducing a multi passing scheme across a electro-optic material. Here transmission co-efficient plays a vital role to examine how much output intensity changes for developing feedback one by one in ascending order. In this paper a novel study for the sizable increase of transmission co-efficient of a KDP crystal for a fixed biasing voltage is reported adopting proper feedback mechanism of light. This paper we also observe an theoretical basis for achieving unit transmission coefficient which minimum amount of voltage require for adopting comparatively many large number of feedback.
关键词： electro-optic effect,amplitude modulation,KDP crystal,transmission co-efficient
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Evaluation of dissolved oxygen concentration in silicon wafers by measuring infrared attenuated total reflection
摘要： Dissolved oxygen concentration of silicon wafers were evaluated by measuring infrared absorption of dissolved oxygen in attenuated total reflection (ATR) spectra of silicon wafers and compared with transmission-based evaluation. ATR peak height and the correlation between ATR and transmission was significantly stronger after chemical-mechanical polishing of both sides of wafers to 450 ± 10 μm. The results also indicate that the quantitative evaluation of the oxygen concentration of thin silicon wafers can be done by ATR measurements with appropriate preprocessing.
关键词： dissolved oxygen,infrared attenuated total reflection,ATR,silicon wafers,transmission-based evaluation
更新于2025-09-11 14:15:04
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[IEEE 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Xi'an, China (2019.6.19-2019.6.21)] 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Signature-Based Morse Code Encoding for a LED-Based optical Layer 2 data communication
摘要： With the rapid improvements in engineering technology, underwater communications have gained major interests from researchers with application areas from commercial to military water based communication systems. However, underwater wireless communication is challenging and difficult compared to wireless terrestrial as it can be easily interrupted due to interference from harsh underwater operation conditions, noise, limited bandwidth and power resources. Various researches in underwater acoustic, optical, and RF communications for secured and reliable underwater wireless network have been carried out. In this paper, an LED based optical wireless communications is proposed using a layered 2 Morse-code based encoding protocol for short distance underwater communication. The proposed system converts the data into a serial of dots and spaces before it is transmitted using the LED as a light source. At the receiver end, the system decodes sequences of on-off light sensed by the photo-diode into the data. The main contribution of this work is the design of a layer 2 signature-based encoding and decoding systems for short range wireless underwater optical communication protocol that can provide a higher data rates compared to traditional acoustic systems with significant lower power consumption and simpler computational complexity. The transmission protocol is evaluated in a dark room and in a water medium. The results have shown above 90% transmission success rate. The result also showed that different colors of the LED emission can affect the reliability of data transmission.
关键词： LED,Transmission Protocol,Optical Communication,Morse Code,Underwater Communication
更新于2025-09-11 14:15:04
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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Comparison between ps- and μs-laser radiation for drilling holes for force transmission elements in CFRP-preforms
摘要： Current lightweight strategies in automobile, aerospace and wind energy applications include composite structures consisting of metal and fiber reinforced plastics for minimum weight, maximum force transmission and high material efficiency. Therefore, economic and technological beneficial material processing for the integration of force transmission elements such as inserts are crucial for these high performance materials. Current state of the art of machining carbon fiber reinforced material is to drill or mill the work piece after the consolidation process. Conventional mechanical and water jet processes lead to high tool wear and often non-repairable defects in the work piece such as delamination, fiber pullout, cracks in matrix and fibers, and deformation. Laser processing of the consolidated material can prevent force induced defects but leads to degradation of the matrix and leaves freestanding fibers inside the drilling hole which can damage the protective surface of subsequently inserted force transmission elements. This is especially critical for lifetime and performance during operation of the structural part. One solution is to drill the so called preform, prior to the infusion process, insert force transmission elements and subsequently infuse the preform with resin. Ultra sonic excited cutting knifes are not applicable for cutting hole diameters of a few millimeters with high aspect ratios. Punching as well as water jet cutting drop out due to force induced interaction with the textile or necessity of a subsequent drying process. Laser material processing could be an adequate solution to circumvent the above mentioned issues. Within this work, non-crimp carbon fiber (NCF) layers are investigated regarding laser processing via ultra-short pulsed and microsecond (fiber laser) radiation. The influence of different process parameters such as scanning speed, repetition rate and laser power are being evaluated regarding geometrical and materialographical quality such as conicity, textile swelling and heat affected zone (HAZ). The temperature distribution during laser processing is important for the estimation of when and where the knitting yarn, which keeps the carbon fiber plies together, disintegrates. Without the knitting yarn swelling occurs which is not desired for subsequent process steps.
关键词： force transmission elements,CFRP-preforms,microsecond laser,ultra-short pulsed laser,laser drilling
更新于2025-09-11 14:15:04
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Digital-Preprocessed Analog-Multiplexed DAC for High-Speed Optical Communications
摘要： Ultra-wideband super-DAC technologies based on analog electronic bandwidth-extension schemes are reviewed. These technologies enable high-speed optical transmissions with signal bandwidths exceeding the capability of CMOS DACs.
关键词： Transmission Subsystems,Advanced modulation and demodulation,Photonics-Electronics integration
更新于2025-09-11 14:15:04
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Multiple LOD-FDTD Method for Inhomogeneous Coupled Transmission Lines and Stability Analyses
摘要： A multiple locally one-dimensional (MLOD) finite-difference time-domain (FDTD) method for inhomogeneous coupled transmission lines and stability analyses are presented. The method is aptly called the MLOD coupled line (CL)-FDTD method. Various split matrices are proposed, and the corresponding update equations are formulated and discussed. All the proposed split matrices yield implicit electric field update equations with tridiagonal or block tridiagonal matrices on the left-hand sides. For more efficiency, the block tridiagonal matrices for implicit electric field may be reformulated and replaced by tridiagonal matrices for implicit magnetic field. The stability analysis is first performed using the von Neumann method in the Fourier domain. It is shown that the von Neumann method alone may not be sufficient to ascertain stability for inhomogeneous media. To include media inhomogeneity, the two-media reduced-matrix stability analysis is proposed. It allows us to analyze efficiently the key stability characteristics in inhomogeneous media, and is useful for quick detection of any potential instability that is not apparent via the von Neumann method. The stability characteristics with variation of media parameters are also investigated and discussed. Numerical results are provided to validate the stability and accuracy of the proposed MLOD CL-FDTD method with various split matrices.
关键词： Multiple LOD FDTD method,stability,split matrices,coupled transmission lines
更新于2025-09-11 14:15:04
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - GAWBS Noise Characteristics in Digital Coherent Transmission in Various Optical Fibers
摘要： We investigated in detail the phase noise caused by guided acoustic wave Brillouin scattering (GAWBS) in digital coherent transmissions in various fibers. Small Aeff fiber is disadvantageous because of a large overlap between electric field and acoustic mode.
关键词： Transmission impairments and their mitigations
更新于2025-09-11 14:15:04
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Distributed Fiber Sensing and Dynamic Rating of Power Cables || Optical Fibers, Connectors, and Cables
摘要： This chapter introduces the types of fibers available in the industry for DTS applications, the types of optical connectors, and their relevance in the context of distributed sensing applications. It also discusses how they may be incorporated into power cable transmission land and submarine corridors as well as the potential challenges that one may encounter during installation, particularly when fibers are embedded in the power cable itself.
关键词： Installation challenges,Connectors,Submarine corridors,DTS applications,Distributed sensing,Optical Fibers,Power cable transmission,Cables
更新于2025-09-11 14:15:04
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Effects of graphene on light transmission spectra in Dodecanacci photonic quasicrystals
摘要： We make a theoretical study of light waves, for both TE and TM polarization with oblique incidence. The light waves propagate on SiO2/TiO2 multilayers, organized by Dodecanacci sequence, where we consider a graphene monolayer at the interfaces between distinct layers. We also calculate numerically the optical transmissivity spectrum, by using the transfer matrix method, for the cases with a graphene sheet and without a graphene sheet at the interfaces. Our results indicate that the whole optical spectrum becomes affected by the presence of graphene in the interfaces. Among these effects, we can highlight the shift of bandgaps to high-frequency regions, the emergence of a graphene induced bandgap at low-frequency regions, and the decreasing of transmittance in the whole frequency range considered here. The self-similarity, which is a property that indicates a fractal spectrum, keeps essentially unchanged when we consider graphene sheets between the layers. Our studies can be applied to electromagnetic filters, where an input gate voltage, applied on the graphene sheets, can control the bandgaps which arise on these structures.
关键词： Light transmission,Photonic quasicrystals,Graphene,Dodecanacci
更新于2025-09-11 14:15:04