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- 2018
- imgae sensor
- internet of things
- drone
- visible light ID
- Signal-to-Noise Ratio (SNR)
- Infinite Gain Multiple Feedback (IGMF)
- Visible Light Communications (VLC)
- LED
- Trans-Impedance Amplifier (TIA)
- Optoelectronic Information Science and Engineering
- Tohoku University
- University of Northumbria
- University of Huddersfield
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Characterization of Si and SiC detectors for laser-generated plasma monitoring in short wavelength range
摘要： Silicon carbide detectors were employed to characterize the plasma produced by laser interaction with a double stream gas-pu? target source. A 10 Hz repetition rate Nd:YAG laser (1064 nm wavelength, 0.69 J pulse energy and 3 ns pulse duration) was employed to irradiate di?erent gas-pu? targets (Argon, Xenon and Sulfur hexa?uoride), at di?erent pressures (1–10 bar), emitting plasma radiation in di?erent wavelength ranges (ultraviolet, extreme ultraviolet and soft X-rays). The emission produced by the laser radiation was properly ?ltered (employing Titanium, Aluminium, Zirconium and Calcium ?uoride ?lters), to narrow down the broad-band emission of the generated plasma. The SiC detectors’ signals were compared with a calibrated traditional silicon detector evaluating their di?erences, i.e. taking into account the plasma stability, the time trace pro?le and the characteristics of the gas-pu? target source. The obtained results, which will be presented and discussed, allow to improve the geometry and con?guration of the SiC detectors avoiding saturation and charge recombination e?ects and getting a better proportionality to the energy and ?uence of the detected radiations.
关键词： X-ray detectors,Radiation monitoring,Detectors for UV, visible and IR photons,Plasma generation (laser-produced, RF, x ray-produced)
更新于2025-09-23 15:21:01
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Integration of 3D Macroscopic Graphene Aerogel with 0D-2D AgVO3-g-C3N4 Heterojunction for Highly Efficient Photocatalytic Oxidation of Nitric Oxide
摘要： The application of three-dimensional (3D) aerogels for immobilizing powder catalysts can greatly enhance the catalyst cycling stability. In this study, we modify two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets with zero-dimensional (0D) silver metavanadate (AgVO3) quantum dots. The resulting 0D-2D heterojunction facilitates the separation of electron-hole pairs, and exhibits high efficiency for removing nitric oxide (NO) at low concentrations (600 ppb) at room temperature. The removal efficiency is much higher than that of pure g-C3N4. The porous network framework of the 3D AgVO3-g-C3N4-graphene hybrid aerogel is formed by bridging of graphene oxide sheets. This results in the heterojunction further enhancing electron-hole separation. The modification of g-C3N4 promotes the separation of photogenerated carriers in a step by step manner, and enhances their oxidation-reduction ability. The AgVO3-g-C3N4-graphene hybrid aerogel exhibits excellent catalytic activity for NO removal (maximum of 65%). Cycling experiments verify the stability and recyclability of the aerogel.
关键词： 0D-2D heterojunction,NO removal,visible light,3D aerogel
更新于2025-09-23 15:21:01
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Mechanism of the Laser Flash Photolysis of Rydimeric e-Tautomers of 4-N,N-Diethylaminoazobenzene in a 2-Propanol Medium
摘要： Difference transit absorption spectra (TASes) obtained via flash photolysis of isopropanol solutions of 4-N,N-diethylaminoazobenzene (DEAB) using 15 ns laser pulses at wavelengths of λex = 265 and 353 nm are analyzed. The inconsistency of constructing the mechanism of trans (t) → cis (c) photisomerization of DEAB based on the concept of this dye having a monomeric structure is shown. Based on the rydimeric concept of aminoazobenzene dyes, which include Rydberg dimers DEAB2, an adequate explanation is given of the nature of TAS signals with structures that change dramatically when in wavelength λex is altered. TAS signals of DEAB2 are compared to ultrahigh-speed (subpico- and pico-second) TAS signals of rydimers of a reference aminoazobenzene (AAB2) dye. It is established that the main difference between the structures of DEAB2 TAS signals generated by pulses with indicated wavelengths λex is due to the excitation of various rydimeric e-tautomers. In addition, a rydimeric e-tautomer that is unstable in the ground state acquires increased stability in propanol and, by absorbing radiation with λex = 353 nm, alters the structure of one of its monomers to quinoid while remaining a rydimer. It is shown that when excited with radiation pulses at λex = 265 nm, a rydimeric e-tautomer (which is more stable in the ground state) dissociates into individual monomers, one of which isomerizes to form cis-DEAB molecules.
关键词： diethylaminoazobenzene rydimers,rydimer photonics,laser flash photolysis,trans–cis isomerization,visible laser spectroscopy
更新于2025-09-23 15:21:01
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Low-Terahertz Transparent Graphene-Based Absorber
摘要： A new, transparent, metal-free absorber, based on the use of multilayer graphene/dielectric laminates (GLs), is proposed for applications in the low-terahertz frequency range. The designed absorber has a total thickness of around 70 μm and consists of a front matching dielectric layer followed by a GL, a dielectric spacer and a back GL. The laminates are periodic structures constituted of graphene sheets separated by 50-nm-thick polyethylene terephthalate (PET) interlayers, while the matching layer and the spacer are one-quarter-wavelength thick and made of PET. The GLs are modeled as homogeneous-equivalent single layers (ESLs) characterized by their sheet resistances Rs. An innovative analytical method is proposed in order to select Rs values optimizing the electromagnetic wave absorption either in low-gigahertz or low-terahertz frequency range. The frequency spectra of the absorption, reflection and transmission coefficients are computed in the range up to 4 THz by using different values of Rs. Then, realistic Rs values of chemically doped graphene monolayers over PET substrates are considered. The designed absorbers are characterized by an absorption coefficient with a peak value of about 0.8 at the first resonant frequency of 1.1 THz, and a 1.4 THz bandwidth centered at 1.5 THz with reflection coefficient below - 10 dB. Moreover, the optical transmittance of the proposed absorbers are computed by means of the optical matrix theory and it is found to be greater than 86% in all the visible ranges.
关键词： absorption,reflection and transmission performance up to 4 THz,low-terahertz transparent absorber,transmission line approach,graphene-polyethylene terephthalate laminate,laminate effective medium model,optical transmittance in the visible range
更新于2025-09-23 15:21:01
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Nanosheets-assembled Bi2WO6 microspheres with efficient visible-light-driven photocatalytic activities
摘要： The nanosheet-assembled Bi2WO6 microspheres could be successfully synthesized in large quantities by a facile hydrothermal strategy in the presence of surfactant hexadecyl trimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) under mild conditions. The morphology and size of as-prepared Bi2WO6 could be readily controlled by adjusting the synthetic parameters such as hydrothermal time. The probable formation mechanism of nanosheet-assembled Bi2WO6 microspheres was discussed in detail. The hierarchical nanosheet-assembled microspheres could be constructed by orderly arranged nanosheets. The photocatalytic activity of the nanosheet-assembled Bi2WO6 microspheres was evaluated by degrading rhodamine B (RhB) under irradiation of visible light. The brilliant photodegradation e?ciency is about 98% under visible light irradiation for 50 min. The results suggest that the as-prepared Bi2WO6 microspheres have good prospects as the photocatalyst for the removal of organic pollutants.
关键词： Hydrothermal,Bi2WO6,Visible light,Nanosheets,Microspheres,Photocatalysis
更新于2025-09-23 15:21:01
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Fabrication and characterization of graphene quantum dots thin film for reducing cross-sectional heat transfer through smart window
摘要： Graphene and its derivatives have been reported as materials with excellent electrical and thermal conductivity, allowing for various promising applications. In particular, the large-scale surface coating of graphene-based materials can be employed to minimize cross-sectional heat transfer through the glass window. This study introduces a facile and cost-effective method to fabricate graphene quantum dots (GQDs) thin film on Fluorine-doped Tin Oxide (FTO) glass via casting of the GQDs dispersion and stabilizing with poly-vinyl-pyrrolidone (PVP). The thin film possesses excellent optical properties of GQDs and allows more than 80 % of visible transmittance. The presence of the GQDs thin film shows effective reduction in the cross-sectional thermal diffusivity of FTO glass, from 0.55 mm2/s to zero when measured with laser flash over a 4-second period. This low cost and eco-friendly GQDs thin film will be a promising material for heat management in smart window applications.
关键词： Smart window,Cross-Sectional heat transfer,Graphene quantum dots,Poly-Vinyl-Pyrrolidone,Visible transmittance
更新于2025-09-23 15:21:01
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Robust visible-infrared image matching by exploiting dominant edge orientations
摘要： Finding the correspondences between visible and infrared images is a challenging task due to the image spectral inconsistency which leads to large differences of gradient distributions between these images. To alleviate this problem, we propose a novel feature descriptor for visible and infrared image matching based on Log-Gabor filters. The descriptor employs multi-orientation and multi-scale Log-Gabor filters to encode the edge information statistically. Furthermore, the descriptor provides rotation invariance by estimating the dominant orientation which is based on accumulated edge orientations. The experimental results demonstrate the effectiveness of the proposed rotation invariant descriptor and the better performance for matching visible and longwave infrared images as compared with state-of-the-art descriptors.
关键词： Log-Gabor filters,rotation invariant descriptor,edge orientations,visible-infrared image matching
更新于2025-09-23 15:21:01
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Efficient N, Fe Co-Doped TiO2 Active under Cost-Effective Visible LED Light: From Powders to Films
摘要： An eco-friendly photocatalytic coating, active under a cost-effective near-visible LED system, was synthesized without any calcination step for the removal of organic pollutants. Three types of doping (Fe, N and Fe + N), with different dopant/Ti molar ratios, were investigated and compared with undoped TiO2 and the commercial P25 photocatalyst. Nano-crystalline anatase-brookite particles were successfully produced with the aqueous sol-gel process, also at a larger scale. All samples displayed a higher visible absorption and specific surface area than P25. Photoactivity of the catalyst powders was evaluated through the degradation of p-nitrophenol in water under visible light (>400 nm). As intended, all samples were more performant than P25. The N-doping, the Fe-doping and their combination promoted the activity under visible light. Films, coated on three different substrates, were then compared. Finally, the photoactivity of a film, produced from the optimal N-Fe co-doped colloid, was evaluated on the degradation of (i) p-nitrophenol under UV-A light (365 nm) and (ii) rhodamine B under LED visible light (395 nm), and compared to undoped TiO2 film. The higher enhancement is obtained under the longer wavelength (395 nm). The possibility of producing photocatalytic films without any calcination step and active under low-energy LED light constitutes a step forward for an industrial development.
关键词： aqueous sol-gel process,Fe/N doping,LED visible light,titania,photocatalysis
更新于2025-09-23 15:21:01
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New approach to raising the resolution of position sensitive detector with moving current-voltage characteristic
摘要： Position sensitive detectors (PSD) are widely applied for determining the coordinate of an optical signal and continuously tracking it. Currently, studies concerned with the possibility of further raising the spatial resolution of PSDs remain topical. In this paper, we present the results obtained in reaching an ultrahigh resolution for a device based on the PSD Multiscan with an integral operation principle which fundamentally differs from that of the lateral PSD. The PSD Multiscan design is based on an array of back-to-back photodiodes. Its optical signal coordinate read-out is formed via the moving current-voltage characteristic of the sensor directly on the PSD as an output potential proportional to the coordinate of the optical spot median. This measurement principle provides a continuous comparison of near-equal photocurrents, which maintains a high signal-to-noise ratio over the whole sensing area. The absence of computational operations in electronic circuits of the PSD Multiscan makes it possible to introduce a nonlinear amplifier element, which substantially improves the resolution of the device based on the sensor developed in the study (as good as 0.05 μm). It has been shown that the resolution remains high for detectors with different lengths and is independent of the position of the optical spot on the sensing area.
关键词： Analogue electronic circuits,Photon detectors for UV, visible and IR photons (solid-state) (PIN diodes, APDs, Si-PMTs, G-APDs, CCDs, EBCCDs, EMCCDs etc),Optical detector readout concepts
更新于2025-09-23 15:21:01
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Surface characteristics of nitrogen ion implanted CR-39 polymer: RBS studies
摘要： This paper investigates the surface characteristics of nitrogen ion implanted CR- 39 polymer. The specimens were implanted with 100 keV N+ beam to various ?uences of 1 × 1015, 1 × 1016 and 2 × 1016 ions cm?2. The ion implantation induced modi?cations in these specimens were analyzed by Rutherford Backscattering Spectrometry (RBS) and UV- Visible spectroscopy. RBS studies reveal that the structure of the virgin CR-39 specimen has been modi?ed completely after N+ implantation. The spatial distribution in the form of carbonization, projected range, retained dose and atomic concentration of implanted nitrogen have been estimated using RBS spectra. RUMP analysis revealed that for the implanted specimen at ?uence 2 × 1016 N+ cm?2, the carbon concentration increases from 32 at.% to 43 at.% and oxygen concentration from 19 at.% to 26 at.% respectively near the surface. This increase in the concentration of carbon points towards the carbonization in the implanted layers. Furthermore, UV–Visible transmission spectra demonstrate that for higher ?uences, almost complete UV region is blocked; making CR-39 a viable functional material for UV blocking devices.
关键词： RBS,Ion implantation,UV–Visible spectroscopy,CR-39
更新于2025-09-23 15:21:01