修车大队一品楼qm论坛51一品茶楼论坛,栖凤楼品茶全国楼凤app软件 ,栖凤阁全国论坛入口,广州百花丛bhc论坛杭州百花坊妃子阁

oe1(光电查) - 科学论文

过滤筛选

出版时间
  • 2018
研究主题
  • GaN HEMTs
  • Power amplifier
  • Broadband power amplifier
  • SC band
  • Power combining
  • concentrated capacitive load
  • distribution of the complex current at the antenna
  • broadband antenna
  • standing wave voltage factor
  • antenna gain factor
应用领域
  • Electronic Science and Technology
机构单位
  • Oles Honchar Dnipro National University
  • University of Tehran
  • Gdansk University of Technology
  • V. N. Karazin Kharkiv National University
  • Reykjavik University
244 条数据
?? 中文（中国） ▾

  • A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene

    摘要： We present a simple design of a broadband tunable metamaterial absorber (MMA) in the terahertz (THz) region, which consists of a single layer complementary gammadion-shaped (CGS) graphene sheet and a polydimethylsiloxane (PDMS) dielectric substrate placed on a continuous metal film. The Fermi energy level (Ef) of the graphene can be modulated dynamically by the applied DC bias voltage, which enables us to electrically control the absorption performance of the proposed MMA flexibly. When Ef = 0.8 eV, the relative bandwidth of the proposed MMA, which represents the frequency region of absorption beyond 90%, can reaches its maximal value of 72.1%. Simulated electric field distributions reveal that the broadband absorption mainly originates from the excitation of surface plasmon polaritons (SPPs) on the CGS graphene sheet. Furthermore, the proposed MMA is polarization-insensitive and has wide angles for both transverse-electric (TE) and transverse-magnetic (TM) waves in the broadband frequency range. The broadband absorption capacity of the designed MMA can be effectively adjusted by varying the Fermi energy level of graphene. Lastly, the absorbance of the MMA can be adjusted from 42% to 99.1% by changing the Ef from 0 eV to 0.8 eV, which is in agreement with the theoretical calculation by using the interference theory. Due to its simple structure and flexible tunability, the proposed MMA has potential application prospects in tunable filtering, modulators, sensing, and other multispectral devices.

    关键词： graphene,surface plasmon polaritons,broadband tunable absorption,terahertz metamaterial absorber

    更新于2025-09-23 15:19:57

  • Transcranial Photobiomodulation (tPBM) With 1,064a??nm Laser to Improve Cerebral Metabolism of the Human Brain In Vivo

    摘要： Background and Objectives: In our previous proof‐of‐principle study, transcranial photobiomodulation (tPBM) with 1,064‐nm laser was reported to significantly increase concentration changes of oxygenated hemoglobin (Δ[HbO]) and oxidized‐state cytochrome c oxidase (Δ[oxi‐CCO]) in the human brain. This paper further investigated (i) its validity in two different subsets of young human subjects at two study sites over a period of 3 years and (ii) age‐related effects of tPBM by comparing sham‐controlled increases of Δ[HbO] and Δ[oxi‐CCO] between young and older adults. Study Design/Materials and Methods: We measured sham‐controlled Δ[HbO] and Δ[oxi‐CCO] using broadband near‐infrared spectroscopy (bb‐NIRS) in 15 young (26.7 ± 2.7 years of age) and 5 older (68.2 ± 4.8 years of age) healthy normal subjects before, during, and after right‐forehead tPBM/sham stimulation with 1,064‐nm laser. Student t tests were used to test statistical differences in tPBM‐induced Δ[HbO] and Δ[oxi‐CCO] (i) between the 15 young subjects and those of 11 reported previously and (ii) between the two age groups measured in this study. Results: Statistical analysis showed that no significant difference existed in Δ[HbO] and Δ[oxi‐CCO] during and post tPBM between the two subsets of young subjects at two study sites over a period of 3 years. Furthermore, the two age groups showed statistically identical net increases in sham‐controlled Δ[HbO] and Δ[oxi‐CCO]. Conclusions: This study provided strong evidence to validate/confirm our previous findings that tPBM with 1,064‐nm laser enables to increase cerebral Δ[HbO] and Δ[oxi‐CCO] in the human brain, as measured by bb‐NIRS. Overall, it demonstrated the robust reproducibility of tPBM being able to improve cerebral hemodynamics and metabolism of the human brain in vivo in both young and older adults.

    关键词： transcranial photobiomodulation,cytochrome c oxidase,reproducibility,broadband near‐infrared spectroscopy,tPBM

    更新于2025-09-23 15:19:57

  • Silicon quantum dot/black silicon hybrid nanostructure for broadband reflection reduction

    摘要： The incorporation of silicon quantum dots (Si QDs) onto black silicon (b-Si) as a hybrid nanostructure has resulted in reflectance reduction over a wide spectral range (300–1000 nm). Si QDs were derived from porous Si (P–Si) by anodic electrochemical etching and ultrasonication whereas b-Si was fabricated by the two-step metal assisted chemical etching (MACE) technique. Si QDs with average diameter of 1.8 ?1.1 nm are suitable for photon down-conversion of UV light (365 nm) into the visible (665 and 740 nm). As a hybrid nanostructure, smaller sized Si QDs exhibited better surface coverage on the b-Si nanopillar sidewalls resulting in enhanced broadband reflection reduction, particularly at 600 nm and beyond. At wavelength of 600 nm, the Si QD/b-Si nanostructure exhibited a reflectance reduction from 9.9% to 6.5% with a more pronounced reduction towards the longer wavelengths, attributed to refractive index matching and optical confinement within the Si nanostructure. Photocurrent enhancement in the UV-blue excitation region is attributed to photon down-conversion (UV to visible) by Si QDs to the underlying b-Si.

    关键词： Photon down-conversion,Broadband reflection reduction,Black silicon,Quantum dot

    更新于2025-09-23 15:19:57

  • Highly sensitive, broadband, fast response organic photodetectors based on semi-tandem structure

    摘要： Solution-processed organic photodetectors (OPDs) simultaneously integrating high performance by solution-processability. The semi-tandem structure directly superimposes two active layers with complementary absorption spectra, achieving a broad spectral response of 300-1000 nm. It provides a detection covering from ultraviolet to near-infrared range, while the external quantum efficiency in the spectral range of 550 nm to 950 nm retains 70 %. The high electron and hole injection barriers enable a dark current density as low as 6.51×10-5 mA cm-2 at -0.1 V, resulting in a noise current of 3.91×10-13 A Hz-1/2 at 70 Hz, which is nearly three times lower than single-junction photodetectors. Encouragingly, the device response speed is improved by suppressing the resistance-capacitance time constant of the device employing semi-tandem structure induced capacitance decreasing. The state-of-the-art OPDs contribute to the response time of 26.27 ns, which is the fastest one in OPDs to the best of our knowledge. We believe that the semi-tandem structures provide a new approach to achieving high-performance photodetectors integrating fast, sensitive and broadband response.

    关键词： broadband,ultra-fast response,Organic photodetectors,semi-tandem structure

    更新于2025-09-23 15:19:57

  • Solutiona??Processed Flexible Broadband Photodetectors with Solutiona??Processed Transparent Polymeric Electrode

    摘要： Room-temperature solution-processed flexible photodetectors with spectral response from 300 to 2600 nm are reported. Solution-processed polymeric thin film with transparency ranging from 300 to 7000 nm and superior electrical conductivity as the transparent electrode is reported. Solution-processed flexible broadband photodetectors with a 'vertical' device structure incorporating a perovskite/PbSe quantum dot bilayer thin film based on the above solution-processed transparent polymeric electrode are demonstrated. The utilization of perovskite/PbSe quantum dot bilayer thin film as the photoactive layer extends spectral response to infrared region and boosts photocurrent densities in both visible and infrared regions through the trap-assisted photomultiplication effect. Operated at room temperature and under an external bias of -1 V, the solution-processed flexible photodetectors exhibit over 230 mA W-1 responsivity, over 1011 cm Hz1/2/W photodetectivity from 300 to 2600 nm and ≈70 dB linear dynamic ranges. It is also found that the solution-processed flexible broadband photodetectors exhibit fast response time and excellent flexibility. All these results demonstrate that this work develop a facile approach to realize room-temperature operated ultrasensitive solution-processed flexible broadband photodetectors with 'vertical' device structure through solution-processed transparent polymeric electrode.

    关键词： perovskite photodetectors,broadband photodetectors,PbSe quantum dots,flexible electronics

    更新于2025-09-23 15:19:57

  • Unsymmetrical Small Molecules for Broadband Photoresponse and Efficient Charge Transport in Organic Phototransistors

    摘要： Organic photosensitizers have been investigated as effective light sensing elements that can promote strong absorption with high field-effect mobility in organic phototransistors (OPTs). In this study, a novel organic photosensitizer is synthesized to demonstrate broadband photoresponse with enhanced electrical performance. An unsymmetrical small molecule of a solubilizing donor(Dsol)-acceptor(A)-dye donor(Ddye) type connected with twisted conjugation system is designed for broadband detection (ranging from 250 nm to 700 nm). This molecule has high solubility, thereby facilitating the formation of uniformly dispersed nanoparticles in an insulating polymer matrix, which is deposited on top of OPT semiconductors by a simple solution process. The broadband photodetection shown by the organic photosensitizer is realized with improved mobility by close to an order of magnitude and high on/off current ratio (~105) of the organic semiconductor. Furthermore, p-type charge transport behavior in the channel of the OPT is enhanced through the intrinsic electron-accepting ability of the organic photosensitizer, caused by the unique molecular configuration. These structural properties of organic photosensitizers contribute to an improvement in broadband photosensing systems with new optoelectronic properties and functionalities.

    关键词： Photosensitizer,Surface doping,Broadband detection,Phototransistor,Charge trap

    更新于2025-09-23 15:19:57

  • Broadband infrared circular dichroism in chiral metasurface absorbers

    摘要： Chirality is ubiquitous in nature and it is essential in many fields, but natural materials possess weak and narrow-band chiroptical effects. Here, chiral plasmonic metasurface absorbers are designed and demonstrated to achieve large broadband infrared circular dichroism (CD). The broadband chiral absorber is made of multiple double-rectangle resonators with different sizes, showing strong absorption of left-handed or right-handed circularly polarized (LCP or RCP) light above 0.7 and large CD in absorption more than 0.5 covering the wavelength range from 1.35 μm to 1.85 μm. High broadband polarization-dependent local temperature increase is also obtained. The switchable infrared reflective chiral images are further presented by changing the wavelength and polarization of incident light. The broadband chiral metasurface absorbers promise future applications in many areas such as polarization detection, thermophotovoltaics, and chiral imaging.

    关键词： chiral image,broadband,Chiral metasurface,circular dichroism

    更新于2025-09-23 15:19:57

  • Enhanced Performances of p-Si/n-ZnO Self-powered Photodetector by Interface State Modification and Pyro-phototronic Effect

    摘要： ZnO based self-powered photodetector (PD) has great application potential in distributing sensor networks and internet of things. However, a large number of surface or interface states within ZnO limit its performance improvement. Here, the surface and interface states of ZnO is greatly eliminated by ultraviolet irradiation as an interfacial modification engineering. Reduction of interface states reduces ohmic resistance, also enhances the tuning role of pyro-phototronic effect. And the transient response currents of the self-powered PD are thus significantly improved with a maximal enhancement factor of more than 5900% for the 325-785 nm broadband stimulating beams. The corresponding response time is decreased to few milliseconds or sub-milliseconds. The results indicate that surface-state reduction of ZnO can effectively enhance the modifying role of pyro-phototronic effect and greatly improve the response performances of the self-powered broadband PDs with great application demands in Internet of things, broad spectral detecting and imaging, and smart optoelectronic devices.

    关键词： Self-powered,ultraviolet irradiation,interface states,pyro-phototronic effect,broadband photodetectors

    更新于2025-09-23 15:19:57

  • Defect mediated transport in self-powered, broadband and ultrafast photoresponse of MoS <sub/>2</sub> /AlN/Si based photodetector

    摘要： By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized. Here we report a self-powered and ultrafast photodetector based on hybrid MoS2/AlN/Si heterostructure. The heterojunction is formed by depositing MoS2 thin film by pulsed laser deposition on AlN/Si(111) template. The vertical transport properties of the device under dark and light illumination conditions, exhibit an excellent photoresponse in a broad range of wavelengths (300–1100 nm) at 0 V. The maximum responsivity of this photodetector is found to be 9.93 A/W at wavelength of 900 nm. The device shows an ultrafast temporal response with response/recovery times of 12.5/14.9 μs. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy reveal presence of native oxygen impurities in AlN, throughout the bulk of the film. These oxygen defects form a deep donor level in AlN and play a crucial role in the transport of the photogenerated carriers, resulting in enhanced device performance.

    关键词： broadband and ultrafast photoresponse,deep defects,MoS2,AlN,pulsed laser deposition

    更新于2025-09-23 15:19:57

  • Self-powered ultra-broadband and flexible photodetectors based on the bismuth films by vapor deposition

    摘要： Bismuth (Bi), as a topological semi-metallic material, has received widespread attention on account of its fascinating properties. Here, Bi films were successfully grown through a direct and facile vapor deposition method on 300 nm SiO2/Si (SiO2) and polyimide (PI) substrates. The Bi films were utilized further to fabricate rigid and flexible photodetectors. The rigid photodetector based on Bi/SiO2 show fast, highly stable, self-powered, and ultra-broadband photoresponses. The flexible Bi/PI photodetector exhibits durability and reproducibility in photoresponse behaviors under bending with various curvature radius and after hundreds of bending cycles. Our results demonstrated that the Bi films by vapor deposition have great application potentials in next generation of optoelectronic devices.

    关键词： flexible,vapor deposition,ultra-broadband,self-powered,photodetector,Bi films

    更新于2025-09-23 15:19:57