查看更多>>摘要：Plasmonic coupling in both metallic and graphene nanostructures, is of particular interest for fundamental physics and potential applications. Here, we study plasmonic coupling in gold nanorings possessing different vertical thickness, by using three-dimensional finite element method as implemented in COMSOL MULTIPHYSICS. As well known, the coupling between inner and outer edges will result in mode splitting, namely, a symmetric (lower frequency) mode and an antisymmetric (higher frequency) mode; and a larger coupling corresponds to a larger mode shifting, e.g. with a blueshift for the antisymmetric mode and a redshift for the symmetric mode. However, in very thin gold nanorings, we find as increasing the ratio of inner radius to outer radius (equivalently increasing the coupling), the antisymmetric mode exhibits a redshift at first and then a blueshift, which is consistent with that in graphene nanorings of zero thickness. We show this unusual coupling effect depends on the thickness and size of nanorings, and is more significant in nanorings of smaller thickness and size. Our work is a nature extension of recent plasmonic studies, and offers an alternative way to tune in-plane plasmonic resonances by the vertical dimension.
查看更多>>摘要：Energy analyzers are designed specifically to distinguish electrons according to their energies. In these experimental devices, electron beam is focused on the entrance of the detector is vital for the prevention of experimental data loss. In this study, the optimum optical parameters when the electron beam is focused on the detector were obtained by the genetic algorithm, an innovative method. It was used to find the optical parameters of hemispherical deflector analyzers that provide the best focus on the detector. The results of this pilot study indicated that genetic algorithm gave a rapid solution when compared to the traditional methods such as Boundary Element (BEM) and Finite Difference Methods (FDM) for electron energy analyzers. Thanks to the genetic algorithm software prepared in this study, all parameters of the hemispherical deflector analyzer can be calculated simultaneously and in a short time.
Ikhioya, L. ImosobomehNkele, C. AgnesOkoli, N. Donald
8页
查看更多>>摘要：Zinc selenide materials doped with zirconium were successfully synthesized by electrochemical deposition at different temperature and pH variations. The morphology, structure, composition of elements, behavior in light, and electrical characteristics of the synthesized materials were obtained through the use of scanning electron microscope (SEM), X-ray diffractometer (XRD), Energy dispersive X-ray spectroscopy, Ultraviolet-Visible (UV-vis) spectrophotometer, and a fourpoint probe device respectively. The morphology and structure of the films showed nanoclusters and crystalline features. The basic elemental constituents of the synthesized films were revealed. High absorbance and electrically conductive nature of the samples were also observed, alongside reducing band gap energy values at decreasing temperature values and increasing pH values. The synthesized zinc selenide films find potential applications in optical and photovoltaic devices.
查看更多>>摘要：Vanadium carbide (V2C), a newly developed MXene, has been theoretically predicted to be an excellent nonlinear optical materials. Here, few-layer V(2)CT(x )nanosheets were synthesized by liquid phase exfoliation (LPE) method. Z-scan measurement was performed to explore their third order nonlinear optical properties, highlighting the strong nonlinearities of few-layer V2CTx nanosheets. And the effective nonlinear absorption coefficient was determined to be 98.3 cm/MW, corresponding to the imaginary part of the third-order nonlinear effects was obtained to be 1.106 x 10-8 esu. In addition, microfiber-based few-layer V2CTx saturable absorber (SA) was fabricated by optical deposition method and the saturable absorption characteristic was measured by I-scan technique. The Yb-doped and Er-doped fiber lasers (YDFLs and EDFLs) were performed by inserting microfiber-based few-layer V2CTx SA into the ring cavity. And the stable mode-locked operation was realized with super high signal-noise ratio (SNR). Our work systematically reveals that few-layer V2CTx nanosheets should be an excellent SA for ultrafast photonics in the near infrared band.
查看更多>>摘要：In this paper, we report an incoherent space laser beam combiner for rectangular beam combination with 18 fiber-transmitted semiconductor lasers at 972 nm wavelength. The coupled thermo-mechanical properties of all the optical lenses in the combiner were analyzed to evaluate the long-term reliability of the combiner subjected to beyond 10 kW high-power laser irradiation. An experiment-based numerical model was developed on the basis of the multi-beam laser volumetric heat source, and the performance of lenses irradiated by 10 kW combined laser for 1000 s was studied with finite element method (FEM). The maximum temperature among all lenses was 427.27 K which is much lower than the softening point temperature of fused silica material made of lenses. And the 0.1 aperture number corresponding to the maximum thermal deformation of 4.53 mu m is much smaller than the conventional optical lens processing tolerance. The maximal stress of 12.73 MPa is far less than the yield stress of 4.5 GPa for the material. The manufactured laser beam combiner realized a highest output power of 10.641 kW at a power combination efficiency of 98.5%, a combination length of 200 mm and a rectangular focal beam spot of 30 mm x 10 mm. Our method provides a valuable choice for realizing fast and flexible laser surface heat treatment.
Ortiz-Vazquez, EricLujan-Cabrera, I. A.Isaza, CesarRamirez-Gutierrez, C. F....
11页
查看更多>>摘要：This work reports a methodology based on evolutionary search, through genetic algorithms, to design and optimize broadband modulated one-dimensional photonic crystals based on porous silicon in the visible spectral region. The photonic crystal structures consist of chirped layers that form a discrete array of sub-mirrors with different resonance wavelengths. Three modulation functions: exponential, sine, and gaussian, were tested and optimized to maximize the reflectance intensity in a target region. The optical response simulation used the transfer matrix method and effective medium approximation for P, S, and non-polarized light to show the complete optical behavior for several incident angles. It was found that PhC designs with more than 90% reflectively with a total depth less than 6.1 mu m and individual layers higher than 40 nm. Those value ranges can be helpful to improve the structure's mechanical stability.
查看更多>>摘要：This research is to explore the focusing characteristics of chirped phase modulating the BesselGaussian (BG) beam. It can be observed that the focal spot of mixed chirped phase of BG beam will split along the optical axis under different beam parameters beta. Simultaneously, the spot length, the spot position and the peak intensity is tunable by modulating the light distribution factor b and chirped factor c1 and c2. In addition, the evolution of longitudinal field and transverse field is also explored in detail. With the introduction of the special chirped phase, the focusing pattern obtains a series of observable evolution characteristics. These results will be potentially applied to many optical frontier areas, such as optical information transmission, optical capture and modern medical treatment.
查看更多>>摘要：Shadow detection is widely considered as segmentation problem that happens to be time consuming process with lots of duplication of results. The alternative to segmentation can be the applicability of single stage detectors like YOLO (You Only Look Once) that can run on the input image once and perform the detections during single pass. The study proposes a novel deep learning-based architecture namely, Rapid-YOLO which is an extended form of YOLOv3 archi-tecture for detection of shadows. The proposed model is an extension of YOLOv3 architecture with addition of extra YOLO detection layers and convolution layers for aiding detection accu-racy. The model exploits use of spatial pyramid pooling for scaling variations, a novel non -maximum suppression using chaotic whale optimization (CW-NMS) for overpowering false bounding box detections. We further propose tangent loss function for confidence and classifi-cation loss to improve training time and reduce errors. Drop block regularization is also used to reduce over-fitting and optimize results for shadow detection. Further, lack of proper dataset for single shot detectors encouraged us to create a novel dataset for the use of YOLO based detectors to boost further work in this direction. The model has been verified by rich experiments and results prove that the proposed methodology is superior to the state-of-the-art methods in terms of objective quantization and in subjective vision.
查看更多>>摘要：The present study is a theoretical work of the effect of carbon and silicon co-doping on the optoelectronic properties of ZnO, by generalized gradient approximation (GGA) using the Perdew Burke Ernzerhof functional correlations (PBE) exchange. The results confirmed that O atoms acts as a preferential doping site in the crystal lattice. By introducing carbon atoms, the optoelectronic properties of ZnO change and we show a better absorption of visible light compared to other dopants. The co-insertion of C and Si atoms in ZnO matrix, leads to a smaller refractive index and the absorption coefficient increases. Furthermore, C and Si co-doping changes the band gap, the dielectric function and the loss energy. We also report in this paper the achieved results in the effect of co-doping with native defects points on electronic properties of ZnO.
查看更多>>摘要：Generally, images acquired under low-light conditions suffer from contrast loss, blurred scene details and colour distortion, resulting in poor visibility. It conceals certain features helpful to computer vision tasks. Hence, a low-light image enhancement is vital in improving the quality of such images. Inspired by Retinex theory, different low-light image enhancement methods implement light correction and deterioration minimization independently in the illumination and reflectance components produced by decomposing the given low-light image. Besides, ZeroDCE is a recent low-light image enhancement method that utilizes deep light curve estimation with the DCE-Net model. In this paper, we propose a hybrid low-light image enhancement method that combines the Zero-DCE method and Retinex decomposition for better performance. It employs deep light curve estimation of the Zero-DCE method on the illuminance component obtained by the Joint intrinsic-extrinsic prior model for Retinex decomposition. To validate, we conducted experiments on the SICE dataset and compared the results obtained with different methods qualitatively and quantitatively. It is evident from the results that our proposed method performed superior when compared to the state-of-the-art methods.
NSTL
Elsevier