- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A New Modulation Technique to Improve Received Power Under Turbulence Effects For Free Space Optical Communication
摘要： This paper focus on new modulation technique to improve the performance of the conventional modulation that uses intensity modulation/direct detection (IM/DD) for On-Off Keying (OOK) modulation. This new modulation technique that is Dual Diffuser Modulation (DDM) can create superior modulation with able to reduce scintillation index, enhance power received and threshold signal level. The analysis result shows that the free space optical (FSO) can have good performance of power received under strong turbulence. The DDM are better performance as compare with conventional IM/DD-OOK and IM/DD-OOK with diffuser. This can help FSO system to combat with severe turbulence effect for optimum operation.
关键词： Turbulence Effects,Received Power,Free Space Optical Communication,Modulation Technique
更新于2025-09-23 15:19:57
-
Magnetothermal Microfluidic-Directed Synthesis of Quantum Dots
摘要： A powerful magnetothermal microfluidic technique is demonstrated to fast and continuously prepare quantum dots with good optical performance useful for color conversion materials in wide-color-gamut backlight display.
关键词： color conversion materials,backlight display,magnetothermal microfluidic technique,quantum dots
更新于2025-09-23 15:19:57
-
Nonlinear optical properties of colloidal CdSe/ZnS quantum dots in PMMA
摘要： The colloidal CdSe/ZnS quantum dots (QDs) in the PMMA polymer film with different QDs concentrations were fabricated. The influence of QDs concentration and excitation pump energy on nonlinear optical (NLO) properties of PMMA capped CdSe/ZnS QDs was investigated by the Z-scan technique with nanosecond laser pulses in the near-infrared spectral band. A large effective nonlinear absorption coefficient (βeff～?10?13 esu) due to the saturable absorption was observed. It was found that the appropriate concentration could lead to the reinforcement of NLO effect. In addition, the impact of the excitation energy on the nonlinear refractive index n2, real and imaginary parts of the third-order nonlinear optical susceptibility was also performed. This study involving the light–matter interactions in the colloidal quantum dots will benefit potential NLO-based applications of optoelectronics, optical modulation and photonics.
关键词： nanophotonics,semiconductor colloidal quantum dots,impact behavior,Z-scan technique,nonlinear optical (NLO) properties
更新于2025-09-23 15:19:57
-
[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Spectrally Tunable Germanium-on-silicon Photodetectors: Design and Simulations
摘要： To avoid straightforward volumetric discretization, a discontinuous Galerkin time-domain (DGTD) method integrated with the impedance boundary condition (IBC) is presented in this paper to analyze the scattering from objects with finite conductivity. Two situations are considered. 1) The skin depth is smaller than the thickness of the conductive volume. 2) The skin depth is larger than the thickness of a thin conductive sheet. For the first situation, a surface impedance boundary condition (SIBC) is employed, wherein the surface impedance usually exhibits a complex relation with the frequency. To incorporate the SIBC into DGTD, the surface impedance is first approximated by rational functions in the Laplace domain using the fast relaxation vector-fitting (FRVF) technique. Via inverse Laplace transform, the time-domain DGTD matrix equations can be obtained conveniently in integral form with respect to time t. For the second situation, a transmission IBC (TIBC) is used to include the transparent effects of the fields. In the TIBC, the tangential magnetic field jump is related with the tangential electric field via the surface conductivity. In this work, a specifically designed DGTD algorithm with TIBC is developed to model the graphene up to the terahertz (THz) band. In order to incorporate the TIBC into DGTD without involving the time-domain convolution, an auxiliary surface polarization current governed by a first-order differential equation is introduced over the graphene. For open-region scattering problems, the DGTD algorithm is further hybridized with the time-domain boundary integral (TDBI) method to rigorously truncate the computational domain. To demonstrate the accuracy and applicability of the proposed algorithm, several representative examples are provided.
关键词： finite integral technique (FIT),surface/transmission impedance boundary condition (SIBC/TIBC),vector-fitting,time-domain boundary integral (TDBI) algorithm,Auxiliary differential equation (ADE),graphene,discontinuous Galerkin time-domain (DGTD) method
更新于2025-09-23 15:19:57
-
Solar gain mitigation in ventilated tiled roofs by using phase change materials
摘要： Several passive cooling design techniques are known for reducing solar heat gain through building envelope in summer season. These include the use of phase change materials (PCM), which has received an increased attention over the last years, and the strategy of increasing the above-sheathing ventilation (ASV) in ventilated roofs. However, few studies combine both technologies to maximise the building resilience in hot season. The effect of including a PCM layer into a ventilated roof is numerically analysed here in two different configurations: firstly, laid on the roof deck (PCM1 case) and, secondly, suspended in the middle of the ASV channel (PCM2 case). A computational fluid dynamics model was implemented to simulate airflow and heat transfer around and through the building envelope, under 3 days of extreme hot conditions in summer with high temperatures and low wind speed. Results showed slight differences in terms of mean temperatures at the different roof layers, although temperature fluctuations at deck in the PCM1 case were smaller than half of those estimated for the benchmark case. However, PCM2 configuration achieved a daily reduction of about 10 Wh/m2 (18%) in building energy load with respect to the benchmark case, whilst PCM1 got only 4% due to the lower ventilation at night time. Therefore, a suspended PCM layer in the ASV channel would be a better measure in terms of energy performance than laid on the deck surface, although this last option significantly decreases thermal stress of the insulation layer.
关键词： passive cooling technique,ventilated pitched roof,computational fluid dynamics,phase change material
更新于2025-09-23 15:19:57
-
On symmetry of rare-earth scandium borate RESc3(BO3)4 (RE = Ce, Nd) laser crystals
摘要： Symmetry, structural features, and point defects in the Czochralski-grown single crystals with the initial compositions CeSc3(BO3)4 (CSB-1.0) and Nd1.25Sc2.75(BO3)4 (NSB-1.25) are studied by the full-profile Rietveld method on synchrotron X-ray powder data. The space group P321 is first established and confirmed for CSB-1.0 and NSB-1.25 crystals, respectively. The features of synchrotron diffraction patterns that distinguish the space group Р321 from the R32 one are given. The site occupancies in both structures are refined and resulted in the stoichiometric composition for CeSc3(BO3)4, which coincides with the nominal composition, and the composition [Nd0.455(1)Sc0.045(39)(1)]Nd0.500(2)Sc3(BO3)4 ((Nd0.955Sc0.045(39))Sc3(BO3)4), which differs from the initial Nd1.25Sc2.75(BO3)4 one, with partial occurrence of Sc ions in one of the trigonal-prismatic sites. An analysis of literature data on single crystals with the general formula RESc3(BO3)4 (RE ? Ce, Pr, Nd) together with the results of present study of powdered single crystals gives reason to exclude a crystallization of these compounds and solid solutions based on them in the space group R32. The correlation between the refined compositions of RESc3(BO3)4 crystals (RE ? La, Ce, Pr, Nd), having a specific space group, and compositions of initial charge is given.
关键词： Crystal structure,Czochralski technique,Optical materials,Point defects,Synchrotron radiation
更新于2025-09-23 15:19:57
-
A Mode-Matching Solution for the Study of Cylindrical Waveguide Bifurcation via Closed-Form Coupling Integrals
摘要： In this paper, we present a mode-matching technique formulation for the rigorous electromagnetic analysis of a circular waveguide bifurcated into circular and coaxial domains. A generalized scattering matrix is obtained for relating the modal field amplitudes in each of the waveguides, and we were able to obtain closed-form solutions for all the associated coupling integrals. We present a series of validation results showing that the technique introduced in this work can model accurately and efficiently a class of cylindrical waveguide devices.
关键词： multifurcated waveguide,Mode-matching technique,generalized scattering matrix
更新于2025-09-23 15:19:57
-
[IEEE 2020 IEEE Latin America Electron Devices Conference (LAEDC) - San Jose, Costa Rica (2020.2.25-2020.2.28)] 2020 IEEE Latin America Electron Devices Conference (LAEDC) - New Deposition Technique for Inverted Polymer Solar Cells Using ZnO-ETL
摘要： In this research work, efficient inverted polymer solar cells (iPSCs) were fabricated for the first time using simple and low cost spray pyrolysis (SP) technique to deposit ZnO thin film as electron transporting layer (ETL) with the structure of ITO/ZnO/PTB7-Th: PC70BM/V2O5/Ag. The effect of the different number of running cycles with the SP technique on the iPSC performance has been investigated. In addition, a state of the art for iPSCs fabricated by spin coating technique has been used as reference. In the spray pyrolysis technique, ZnO thin films were fabricated by spraying the ZnO precursor solution onto the pre-heated ITO substrate. Two different numbers of running cycles of ZnO were performed, namely, 15R and 20R. By increasing the running cycles of the sprayed ZnO film, the fill factor and the power conversion efficiency were enhanced by 20% and 32 %, respectively. This improvement might be attributed to enhancing the roughness with compacted film formation and the matched band gap between the active layer (PTB7-Th: PC70BM) and the ZnO-ETL. Hence, this promising spray pyrolysis technique might facilitate the commercialization of polymer solar cells based on mass production besides the possibility of improving its efficiency.
关键词： Polymer solar cells,Spray pyrolysis technique,Zinc Oxide deposition,Electron transporting layer
更新于2025-09-23 15:19:57
-
A wide dynamic range and high resolution all-fiber-optic turbidity measurement system based on single photon detection technique
摘要： A high-resolution fiber-optic detection system has been developed to measure the wide dynamic range of turbidity. To obtain high-resolution measurement results, a high sensitive single photon detection technique (SPDT) has been used in the system. Based on fiber characteristics, a compact probe structure for fiber-optic integrated transceiver (FITP) is designed to transmitting and collection light signal, which has the capability of detecting turbidity in the narrow workspace. By combining the Beer-Lambert (B-L) law transmission law with single photon counting theory, a novel turbidity measurement theoretical model has been proposed, which shows a good exponential relationship over the whole measurement range from 0.01 to 1000 NTU (Nephelometric Turbidity Units). However, when detecting 0.01–0.1 NTU low turbidity, the experimental results turn into an approximate linear relationship, which good agrees with the proposed theoretical model. Last, some issues about the optimization of light intensity and requiring attention on constructing a practical distributed multi-point water turbidity remote monitoring system in the outdoors are also discussed. It was found that the system can achieve a measurement dynamic range as wide as 50 dB with a resolution better than 0.01 NTU in the range of 0.01–1000 NTU, which is suitable for some specific turbidity measurement in remote and narrow workspace.
关键词： Turbidity measurement,Single photon detection technique,Fiber-optic detection,Wide dynamic range
更新于2025-09-23 15:19:57
-
Direct transfer of the CVD-grown graphene on copper foils on SiO2 substrate under supercritical CO2 assisted-cleaning technique
摘要： The transfer of CVD-grown graphene sheets onto arbitrary substrates is important for the development of practical applications. Unfortunately, designing a low cost and highly efficient graphene transfer technique to achieve defect-free graphene sheets with low contact resistance onto various substrates still remains a challenge. In this paper, a CVD grown monolayer graphene sheet was directly transferred on SiO2/Si substrate. We found that a combination of floating copper with graphene films on ammonium persulfate solution with an original method of supercritical CO2 fluid can effectively produce clean and dry samples without damaging the crystalline quality of graphene. This method does not require any polymeric material to be desposited on the graphene films at any stage. Samples are analyzed by optical microscopy, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. This method is very promising for cleaning graphene samples for electronic device fabrication.
关键词： transfer technique,supercritical CO2,SiO2 substrate,graphene,CVD
更新于2025-09-23 15:19:57