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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Design of an Asymmetrical Quadruple-ridge Flared Horn Feed: a Solution to Eliminate Polarization Discrepancy in the Offset Reflecting Systems
摘要： Quadruple-ridge Flared Horns (QRFHs) have been showing qualified performance as the feed antennas for the reflecting systems in the Square Kilometre Array (SKA). However, due to the offset optics of the SKA reflecting system, identical illuminations from dual polarizations of the feed would result in different system performance. This difference would become more severe towards high frequencies and may cause the worse polarization unqualified for the desired specification. In this paper, an asymmetrical QRFH feed working over SKA Band B (covering frequencies 4.6–24 GHz) is proposed and optimized to tackle this problem. The asymmetrical Band-B feed is composed of two different and orthogonal pairs of both ridges and sidewall quad-pieces, so as to provide orthogonal polarizations but different illuminations. Simulated results show that, by this asymmetrical design different illuminations can be provided for two polarizations, and the polarization discrepancy has been eliminated over most of the bandwidth. Benefitting from the elimination, both polarizations of the Band-B feed have now achieved the SKA specification in terms of aperture efficiency.
关键词： polarization discrepancy,offset reflector antenna,quadruple-ridge flared horn
更新于2025-09-23 15:23:52
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Single Polarization Reflectarray Design Based on an Element with Seven Parallel Dipoles to Generate Independent Beams in three frequency bands.
摘要： A single layer reflectarray element based on seven parallel dipoles is proposed for single polarization applications. The dipoles of the reflectarray element make it possible a multi-resonant behavior which provides very large phase range, while keeping low loss and low cross-polarization level. A sequential design process of a reflectarray antenna is proposed where the lengths of the dipoles are adjusted in pairs to provide three independents beams at 20, 25 and 30 GHz. The simulated radiation patterns of the reflectarray antenna exhibit efficiencies of 80%, 62% and 52% at 20, 25 and 30 GHz respectively. The maximum cross-polar radiation obtained is 29.7 dB, 32.9 dB and 39.1 dB below the maximum of the co-polar beam at 20, 25 and 30 GHz respectively. Bandwidths of 14%, 8.2% and 4.3% are achieved at center frequencies of 20, 25 and 30 GHz respectively. These bandwidth results account for a +/-0.5o of deviation in the main beam direction, for 2dB-gain variations in the two first bands, and for a 3dB gain variation in the last band.
关键词： parallel edge-coupled dipoles,single polarization,reflectarrays
更新于2025-09-23 15:23:52
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Optical linear polarization measurements of quasars obtained with the Very Large Telescope at Paranal Observatory
摘要： We report 87 previously unpublished optical linear polarization measurements of 86 quasars obtained in May and October 2008, and from April to July 2015 with the FOcal Reducer and low-dispersion Spectrographs FORS1 and FORS2 attached to the Very Large Telescope at the Paranal Observatory. Of the 86 quasars, 37 have p ≥ 0.6%, 9 have p ≥ 2%, and 1 has p ≥ 10%.
关键词： quasars: general,polarization
更新于2025-09-23 15:23:52
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Highly Sensitive Polarization Photodetection Using a Pseudo-One-Dimensional Nb <sub/> (1– <i>x</i> ) </sub> Ti <sub/><i>x</i> </sub> S <sub/>3</sub> Alloy
摘要： Low-symmetry layered two-dimensional (2D) materials with strong in-plane optical anisotropy can potentially be applied for polarization photodetection. This is especially true for those 2D materials with a direct bandgap, who can efficiently absorb light with specific axial polarization. However, discovering such new anisotropic 2D materials with direct band structure is still extremely challenging. Here, we fabricate a photodetector using a pseudo-one-dimensional (pseudo-1D) Nb(1-x)TixS3 alloy device, and demonstrate that it is highly sensitive to the polarized light due to the strong in-plane optical anisotropy and direct bandgap of the alloy by combining the angle-resolved polarization Raman spectroscopy (ARPRS), azimuth-dependent reflectance difference microscopy (ADRDM), polarization-dependent absorption spectroscopy (PDAS), and hybrid functional theory calculations. As a consequence, the polarization photodetector of the Nb(1-x)TixS3 alloy shows a large photocurrent anisotropic ratio and a high photoresponse. The choice of low-symmetry layered pseudo-1D Nb(1-x)TixS3 alloy in polarization photodetection might open up new functionalities for novel optoelectronic device applications.
关键词： low-symmetry structure,in-plane optical anisotropy,pseudo-one-dimensional materials,Nb(1-x)TixS3 ternary alloy,polarization-sensitive photodetector
更新于2025-09-23 15:23:52
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[IEEE 2018 3rd International Conference for Convergence in Technology (I2CT) - Pune (2018.4.6-2018.4.8)] 2018 3rd International Conference for Convergence in Technology (I2CT) - Implementation of Polarization-Conversion in Ring-Resonator and its Application to Design All-Optical NOT Logic Gate
摘要： All-optical NOT logic gate is theoretically described using the concept of polarization-conversion in ring resonator. Conversion of polarization states occurs at very high speed of 0.2 ps and high Q-factor of about 1500 is obtained. The design may used in intensity based all-optical switching as well as in designing of all-optical logic gates. Low pump power of about 40 nW/m is required for such conversion based all-optical gates. Suitability in pumping, refractive index contrast, height-to-width ratio of waveguide and phase-matching condition is necessary to obtain such results.
关键词： ring-resonator,polarization conversion,all-optical switch,FDTD simulation,logic gates
更新于2025-09-23 15:23:52
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Polarization attack on continuous-variable quantum key distribution
摘要： The shot-noise unit (SNU) is a crucial factor for the practical security of a continuous-variable quantum key distribution system. In the most widely used experimental scheme, the SNU should be calibrated first and acts as a constant during the key distribution. However, the SNU of a practical system is dependent on the various parameters of the local oscillator (LO), which can be controlled by the eavesdropper in the open channel. In this paper, we report a quantum hacking method to control the practical SNU by using the limited compensation rate of the polarization compensation. Since the compensation is only based on of the polarization measurement results of part of LO pulses, the polarization of other unmeasured pulses may not be compensated correctly, which can be utilized by the eavesdropper to control the practical SNU. The simulation and experiment results indicate that the practical SNU can be controlled by the eavesdropper. Thus, the eavesdropper can use the fact that the practical SNU is no longer equals to the calibrated one to control the excess noise and final key rate.
关键词： shot noise unit,polarization compensation,continuous-variable quantum key distribution,quantum hacking
更新于2025-09-23 15:23:52
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Design and implementation of a low profile polarization-reconfigurable transmitarray with linear polarized feed
摘要： A novel polarization-reconfigurable transmitarray with linear polarized feed is presented in this letter. Each element in the proposed transmitarray consists of two cascaded cross dipoles to achieve more than 310° of linear phase with transmission magnitude equal to or better than 0.8 dB. The proposed unit cell has a thickness of 0.22λ0, which leads to a low profile transmitarray compared with those conventional designs. The element behavior of low transmission loss has resulted in higher antenna efficiency. By properly rotating the feed antenna around the center and selecting the x- and y-dimension of each element, the proposed transmitarray can generate radiation patterns with different polarization states, including left-handed circular polarization (LHCP), right-handed circular polarization (RHCP), and linear polarization(LP). For the purpose of validation, a double-layer center-fed 11 × 11-element transmitarray prototype is manufactured and tested at X-band. Measurement results demonstrate the designed transmitarray realize both high gain performance and multiple polarization operation.
关键词： cross dipole,polarization reconfigurable,low profile,transmitarray
更新于2025-09-23 15:23:52
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Design of a C-band polarization rotator-splitter based on a mode-evolution structure and an asymmetric directional coupler
摘要： A C-band polarization rotator-splitter based on a mode-evolution structure and an asymmetric directional coupler is proposed. The mode-evolution structure is designed in a bi-level taper through which the TM0 mode can evolve into the TE1 mode. Then the TE1 mode is coupled to the TE0 mode at the cross port using the asymmetric directional coupler. The input TE0 mode propagates along the waveguide without mode conversion and output at the through port. From the experimental results, the extinction ratio is lower than 30 dB and the excess loss is less than 1 dB for input TE0 mode at the whole C-band. For input TM0 mode, the ER and the EL are, respectively, lower than ?10 and 1.5 dB.
关键词： silicon photonics,integrated optic devices,polarization rotator splitters
更新于2025-09-23 15:23:52
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Theoretical demonstration of Single polarization single mode hollow core anti-resonance fiber using surface plasmon resonance
摘要： We designed a hollow core anti-resonance fiber based on surface plasmon resonance and optimized its characteristics by using the finite element method with perfectly matched layer boundary condition. A single mode single polarization bandwidth, up to 200 nm, is obtained by employing surface plasmon resonance which is produced by two embedded gold wires. Only the x-polarized fundamental mode of the fiber suffers a high loss because of the surface plasmon resonance. In addition, single mode guidance is obtained by adjusting the size of cladding tubes. Simulation results show that the designed fiber has an effective single polarization single mode guidance in the wavelength range from 1.3 to 1.5μm. In this range, both the higher order mode extinction ratio and the polarization mode extinction ratio are more than 100. The structure is shown to have a good fabrication tolerance with respect to variations in the position and size of the gold wires. The proposed fiber has many potential applications in polarization splitters, fiber-optic gyroscopes and polarization-dependent fiber systems.
关键词： Anti-resonance hollow core fiber,Surface plasmon resonance,Single polarization single mode.
更新于2025-09-23 15:23:52
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Axion-modified photon propagator, Coulomb potential, and Lamb shift
摘要： A consistent renormalization of a quantum theory of axion-electrodynamics requires terms beyond the minimal coupling of two photons to a neutral pseudoscalar field. This procedure is used to determine the self-energy operators of the electromagnetic and the axion fields with an accuracy of second-order in the axion-diphoton coupling. The resulting polarization tensor is utilized for establishing the axion-modified Coulomb potential of a static pointlike charge. In connection, the plausible distortion of the Lamb-shift in hydrogenlike atoms is established and the scopes for searching axionlike particles in high-precision atomic spectroscopy and in experiments of Cavendish-type are investigated. Particularly, we show that these hypothetical degrees of freedom are ruled out as plausible candidates for explaining the proton radius anomaly in muonic hydrogen. A certain loophole remains, though, which is linked to the nonrenormalizable nature of axion-electrodynamics.
关键词： axion-electrodynamics,axionlike particles,proton radius anomaly,polarization tensor,renormalization,Lamb-shift,Coulomb potential
更新于2025-09-23 15:23:52