- 标题
- 摘要
- 关键词
- 实验方案
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Optically reconfigurable planar monopole antenna for cognitive radio application
摘要： Frequency reconfigurable antenna is one of the important elements needed for cognitive radio application. Such antenna can be designed using highly resistive (HR) silicon (Si) operating as an optical switch. This letter presents a novel frequency reconfigurable planar monopole antenna suitable for cognitive radio application. The antenna is designed using HR Si working as an optical switch. The main idea behind the design of antenna is the redistribution of surface current on the antenna while changing the state of Si switches optically from high resistance to low resistance. The antenna is highly compact and uses only two switches for multiband reconfiguration. It is switchable on 1.9 GHz, 2.75 GHz, 3.7 GHz, 4.1 GHz, 4.6 GHz, 4.8 GHz, and 7.6 to 11 GHz frequency bands. Simulated and measured results are presented for the antenna. To the best of authors knowledge, this is the first multiband optically reconfigurable planar monopole antenna.
关键词： high-resistive (HR) silicon,optical excitation,low-resistive (LR) silicon,planar monopole antenna,cognitive radio,reconfigurable,multiband
更新于2025-09-23 15:22:29
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Laser Optoacoustic Method for Measurement of Light Extinction Coefficient and Investigation of Its Spatial Distribution in Colloidal Media
摘要： In the present work, the method which allows investigating the spatial distribution of light extinction coefficient in colloidal media is experimentally realized. The proposed method is based on the dependence of temporal profiles of excited OA-signals on the absorption and extinction coefficients of the studied medium. Water-based and kerosene-based magnetic fluids with volume content of magnetite particles in the range 0.35–3.5 % were studied as an example of the medium with spatially non-uniform optical properties. The capability of the reconstruction of the one-dimensional spatial distribution for the light extinction coefficient in the investigated media is demonstrated. It was shown that the relative change of the extinction coefficient with depth depends on volume concentration of magnetite particles, type of acoustical boundary and properties of carrier liquids. In the case of acoustical rigid boundary of magnetic fluid, an additional induced anisotropy occurs, which leads to increasing of the light extinction coefficient with depth in comparison with acoustical free boundary of fluid.
关键词： Laser optoacoustic method,Concentration,Magnetite particles,Thermo-optical excitation,Magnetic fluids,Structural inhomogeneities,Light extinction,Colloidal medium
更新于2025-09-23 15:21:01
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Polarization Properties and Polarization Depth Profiles of (Cd:Zn)S/P(VDF-TrFE) Composite Films in Dependence of Optical Excitation
摘要： The influence of optical excitation intensity on the electrical, ferroelectric and pyroelectric properties of ferroelectric-semiconductor-composites was investigated. For this purpose, composite thin films consisting of poly(vinylidene fluoride-co-trifluoroethylene) and 10 vol % (Cd:Zn)S particles with a thickness of 34 μm were fabricated. The samples were used to measure the absolute pyrocoefficient and to determine the relative pyroelectric depth profile using Laser Intensity Modulated Method. It was shown that a polarization of the samples without an optical excitation at the utilized relatively small peak-to-peak voltages could not be verified by the Sawyer–Tower circuit and the measurement setup of the pyroelectric coefficient, respectively. Both remanent polarization and pyroelectric coefficients increased with increasing optical excitation intensity during poling as well as increasing peak-to-peak voltage. The pyrocoefficient shows a temporal decay in the first hours after poling. The specific heat and thermal conductivity or the thermal diffusivity are required for the calibration of the pyroelectric depth profile. Rule of mixture and photo-acoustic investigations proved that the thermal properties of the utilized composites do not differ significantly from those of the pristine polymer. Based on the pyroelectric depth profile which is proportional to the polarization profile, the existing “three phase model” has been extended to generate a replacement circuit diagram, explaining the local polarization due to the optical excitation dependency for both local resistivity and local field strength.
关键词： composite,optical excitation,ferroelectric polymer,semiconductor
更新于2025-09-19 17:15:36
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Optical remote control of a single charge qubit
摘要： Both the electron transport-based qubits, implemented through double quantum dots, and the sources of indistinguishable single photons like self-assembled quantum dots are strong candidates for the implementation of quantum technologies, such as quantum computers and quantum repeaters. Here, we demonstrate a reliable way of coupling these two types of qubits, uncovering the possibility of controlling and reading out the population of the double quantum dot via optical excitation. It is also shown that, in spite of the decoherence mechanisms affecting the qubits, the entanglement between them is achievable and, consequently, the implementation of the suggested system in quantum technologies is feasible.
关键词： quantum technologies,quantum dots,entanglement,optical excitation,qubits
更新于2025-09-11 14:15:04
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Optical characterization of high and low resistive silicon samples suitable for reconfigurable antenna design
摘要： Highly resistive (HR) silicon (Si) can behave as a switch when illuminated by optical source of suitable wavelength. Different reconfigurable passive structures, such as filters, waveguides, and antennas, can be constructed using such silicon switches. This letter presents experimental characterization of high and low resistive (HR & LR) silicon for switching application. In the experiment, HR Si is modeled on a switched transmission line by halogen lamp and a laser source. The experiment of utilizing halogen lamp for Si switch characterization is cost-effective and can assist engineers in designing reconfigurable antennas. In future, this experiment could be utilized in designing novel reconfigurable antennas.
关键词： reconfigurable antenna,low resistive (LR) silicon,meandered transmission line,high resistive (HR) silicon,optical excitation,halogen lamp
更新于2025-09-04 15:30:14
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Polariton-enhanced exciton transport
摘要： The transport distance of excitons in exciton-polariton systems has previously been assumed to be very small ((cid:2)1 μm). The sharp spatial pro?les observed when generating polaritons by nonresonant optical excitation show that this assumption is generally true. In this paper, however, we show that the transport distances of excitons in two-dimensional planar cavity structures with even a slightly polaritonic character are much longer than expected (≈20 μm). Although this population of slightly polaritonic excitons is normally small compared to the total population of excitons, they can substantially outnumber the population of the polaritons at lower energies, leading to important implications for the tailoring of potential landscapes and the measurement of interactions between polaritons.
关键词： interactions,exciton-polariton,transport distance,potential landscapes,nonresonant optical excitation
更新于2025-09-04 15:30:14