- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Facile synthesis, morphology and tunable photoluminescence properties of BaMgF <sub/>4</sub> :Ce <sup>3+</sup> /Tb <sup>3+</sup> /Eu <sup>3+</sup> phosphors
摘要： A series of BaMgF4:Ce3+/Tb3+/Eu3+ phosphors were successfully prepared via a facile hydrothermal process. X-ray diffraction (XRD), energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), n-UV–UV-vis photoluminescence (PL) and fluorescence decays were employed to investigate the structure, composition, morphology, luminescence properties and energy transfer processes. The as-prepared BaMgF4 phosphors exhibit a rod-like morphology and the size of the product can be effectively regulated by changing the amount of NH4F in the original solution. Under n-UV–UV light excitation, the Ce3+, Tb3+ and Eu3+ singly-doped BaMgF4 phosphors all show good characteristic luminescence; the Ce3+–Tb3+ and Tb3+–Eu3+ co-doped BaMgF4 phosphors both show tunable emission colors from blue (green) to green (orange-red) because of the energy transfer of Ce3+ → Tb3+ and Tb3+ → Eu3+, respectively. Moreover, the efficient energy transfer from Ce3+ (Tb3+) to Tb3+ (Eu3+) ions in the co-doped samples was confirmed by investigating the excitation/emission spectra and decay lifetimes. The results indicate that the phosphors may be potentially used as single-component multi-color phosphors for white light-emitting diodes.
关键词： energy transfer,BaMgF4,white light-emitting diodes,phosphors,hydrothermal process
更新于2025-09-04 15:30:14
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A stage-scanning two-photon microscope equipped with a temporal and a spatial pulse shaper: Enhance fluorescence signal by phase shaping
摘要： Here, we present a stage-scanning two-photon microscope (2PM) equipped with a temporal pulse shaper and a spatial light modulator enabling full control over spectral and spatial phases of the exciting laser pulse. We demonstrate the capability of correcting wavefronts and temporal pulse distortions without cross-dependencies induced by optical elements at the same time enhancing the fluorescence signal. We implemented phase resolved interferometric spectral modulation for temporal pulse shaping and the iterative feedback adaptive compensation technique for spatial pulse modulation as iterative techniques. Sample distortions were simulated by cover glass plates in the optical path and by chirping the exciting laser pulses. Optimization of the spectral and spatial phases results in a signal increase of 30% and nearly complete recovery of the losses. Applying a measured spatial compensation phase within a real leaf sample shows the enhancement in contrast due to wavefront shaping with local fluorescence increase up to 75%. The setup allows full independent control over spatial and spectral phases keeping or improving the spatial resolution of our microscope and provides the optimal tool for sensitive non-linear and coherent control microscopy.
关键词： two-photon microscopy,wavefront shaping,spatial light modulator,fluorescence signal enhancement,temporal pulse shaping
更新于2025-09-04 15:30:14
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Ghost polarimetry: ghost imaging of polarization-sensitive objects
摘要： A new method of polarimetry which we have called ‘ghost polarimetry’ is suggested. The principle underlying the ghost imaging concept is generalized to polarization-sensitive objects which change the polarization state of incident light. Our theoretical model treats an object as a Jones matrix. In this approach, the information on the polarization properties of the object is contained in the elements of this matrix. We show that it is possible to connect the elements of Jones matrix with mutual correlation functions of the currents measured in the object arm and in two reference-arms where the signals in two orthogonal polarizations are registered. We demonstrate that the developed method allows to obtain polarization ghost image and therefore to identify the polarization structure of the object. Also it is shown that in order to implement this method the object should be illuminated by unpolarized incoherent light with Gaussian statistics. We believe that expanding the principle of ghost imaging to polarization sensitive objects will expand the diagnostic capabilities of existing polarimetry and ellipsometry technique.
关键词： ghost imaging,polarimetry,thermal light
更新于2025-09-04 15:30:14
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Asymmetric light transmission effect based on an evolutionary optimized semi-Dirac cone dispersion photonic structure
摘要： In this paper, we present the numerical and experimental demonstration of asymmetric light transmission by a compact photonic crystal (PC) structure, which sustains semi-Dirac cone dispersion. The semi-Dirac point is obtained by exploiting plane-wave expansion method in a rectangular unit cell of a cylindrical dielectric rod, forming a PC structure. The preselected part of the corresponding PC structure is optimized via differential evolution to maximize the transmission efficiency in one direction, and to minimize in the opposite direction. In this regard, finite-difference time-domain method is integrated with the optimization algorithm to numerically design a compact PC structure with asymmetric light transmission effect. The detailed numerical investigation of the optimized PC structure is represented, and the experiments in the microwave regime are performed to verify the numerical results. The experimentally measured transmission efficiency reaches 78% for one direction, whereas in the opposite direction it reduces to 11%. The physical mechanism of asymmetric light transmission is related to differences of the projection of the wave incident from both directions into the eigenmodes of the photonic structure.
关键词： asymmetric light transmission,semi-Dirac cone dispersion,photonic crystal,differential evolution,finite-difference time-domain method
更新于2025-09-04 15:30:14
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Perception of light source distance from shading patterns
摘要： Varying the distance of a light source from an object alters both the intensity and spatial distribution of surface shading patterns. We tested whether observers can use such cues to infer light source distance. Participants viewed stereoscopic renderings of rough objects with diffuse and glossy surfaces, which were illuminated by a point source at a range of distances. In one task, they adjusted the position of a small probe dot in three dimensions to report the apparent location of the light in the scene. In a second task, they adjusted the shading on one object (by moving an invisible light source) until it appeared to be illuminated from the same distance as another object. Participants’ responses increased linearly with the true light source distance, suggesting that they have clear intuitions about how light source distance affects shading patterns for a variety of different surfaces. However, there were also systematic errors: Subjects overestimated light source distance in the probe adjustment task, and in both experiments, roughness and glossiness affected responses. We find the pattern of results is predicted surprisingly well by a simplistic model based only on the area of the image that exceeds a certain intensity threshold. Thus, although subjects can report light source distance, they may rely on simple—sometimes erroneous—heuristics to do so.
关键词： lighting,reflectance,gloss,roughness,light source,illumination,material perception
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Actual Problems of Electron Devices Engineering (APEDE) - Saratov, Russia (2018.9.27-2018.9.28)] 2018 International Conference on Actual Problems of Electron Devices Engineering (APEDE) - Strain-Tuned Multi-Channel Coupler Based on the Lateral Structure
摘要： We observe strain-induced spin-wave routing in the bilateral composite multilayer. By means of Brillouin light scattering, we study the spin-wave transport across three adjacent magnonic stripes, which are strain coupled to a piezoelectric layer. The strain may effectively induce voltage-controlled dipolar spin-wave interactions. We experimentally demonstrate the basic features of the voltage-controlled spin-wave switching. We show that the spin-wave characteristics can be tuned with an electrical field due to piezoelectricity and magnetostriction of the piezolayer and layered composite and mechanical coupling between them.
关键词： spin-wave transport,piezoelectricity,Brillouin light scattering,voltage-controlled spin-wave switching,strain-induced spin-wave routing,magnonic stripes,piezoelectric layer,magnetostriction,voltage-controlled dipolar spin-wave interactions
更新于2025-09-04 15:30:14
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[IEEE 2018 Global Smart Industry Conference (GloSIC) - Chelyabinsk, Russia (2018.11.13-2018.11.15)] 2018 Global Smart Industry Conference (GloSIC) - Numerical Simulation of the Transverse and Longitudinal Shifts of Reflected Beam
摘要： The effects of the spin-orbit interaction of light are observed at the wavelength scale and can be used in nanophotonics. The computer simulation of these effects is a necessary tool for creating devices, based on the spin-orbit interaction of light. We have developed a software package in Python to simulate two known effects, namely, transverse and longitudinal shifts of the center of gravity of beams at the total internal reflection. The package is based on the algorithm for the numerical solution of Maxwell's equations by the finite difference time domain method. We have used the modification of PML – UPML as absorbing boundary conditions. We simulated the refraction and total internal reflection of an electromagnetic wave at the plane interface between two transparent dielectrics and calculated the depth of penetration of a non-uniform electromagnetic wave, occurring at total internal reflection in the optically less dense medium. To test the software package, we have compared the reflection coefficients of the electromagnetic wave for the normal and oblique incidence on the plane interface, calculated by the simulation with the coefficients, obtained by Fresnel formulas for the s-polarization of the wave. We have numerically simulated the shifts of the center of gravity of beams of finite size in the plane of incidence and perpendicular to it, namely, the effects of Goos-H?nchen and Fedorov. The dependence of the direction of the transverse shift on the sign of the circular polarization of the incident beam was demonstrated. The dependence of the longitudinal shift on the direction of linear polarization is also demonstrated. It should be stressed that the developed software package can be applied for simulating of the longitudinal and transverse shifts in anisotropic media, media with optical activity, as well as thin films on the dielectric surface.
关键词： Goos-H?nchen effect,Fedorov-Imbert effect,spin-orbit interaction of light,FDTD,PML
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Emerging Trends and Innovations In Engineering And Technological Research (ICETIETR) - Ernakulam (2018.7.11-2018.7.13)] 2018 International Conference on Emerging Trends and Innovations In Engineering And Technological Research (ICETIETR) - Density Based Traffic Control System Using Image Processing
摘要： In this paper, a novel real-time traffic control system which can easily keep traffic in control using image processing techniques is presented. In this method, a webcam is used in each stage of the traffic light in order to take pictures of the roads where traffic is bound to occur. Count of vehicles in these images is calculated using image processing tools in Matlab and different timings are allocated according to the count along with a green signal for vehicles to pass. In the proposed prototype, the green and red signals are represented using LEDs and the decrementing timer for the green signal is represented by a seven segment display.
关键词： vehicle count,timer,image processing,Traffic light control,foreground detection
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA, USA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - A Patternable, Anti-Reflective Light Blocking Layer using a Nano-Particle Suspension in Photoresist
摘要： This paper presents a method for fabricating a broadband anti-reflective light blocking layer patternable on a micron scale using standard photolithography using a combination of photoresist and Al2O3 nanoparticles over an aluminum layer.
关键词： antireflective,light blocking,lithography
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Nantes (2018.9.24-2018.9.27)] 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Indoor Positioning Using OFDM-Based Visible Light Communication System
摘要： Precise indoor positioning is essential to support emerging applications of location aware mobile computing. Current positioning techniques that use signals transmitted in the Gigahertz region of radio-frequency spectrum do not provide highly accurate position estimates due to multipath propagation of signals. This paper proposes a novel positioning system which uses the entities of visible light communication (VLC) system as anchors and tags. Our technique scales with the number of tags and the VLC network provides both positioning and communication capabilities. The anchor points transmit the OFDM-based VLC signals synchronously, and we estimate the time differences of arrival between anchor points and tags using positioning reference signals embedded into the air-interface of the VLC system. Simulation results show that positioning accuracy of 10 cm or better is possible for over 95% of users if the sampling clock offset is better that 10 ppm, clock jitter is below 1 ps, and a bit resolution of at least 16 bits is available.
关键词： multipath propagation,OFDM,TDOA,visible light communication,indoor positioning
更新于2025-09-04 15:30:14