Showing papers on "Circular polarization published in 2013"
TL;DR: Huang et al. as mentioned in this paper developed ultrathin plasmonic metasurfaces to provide 3D optical holographic image reconstruction in the visible and near-infrared regions for circularly polarized light.
Abstract: Holographic techniques allow for the construction of 3D images by controlling the wave front of light beams. Huang et al. develop ultrathin plasmonic metasurfaces to provide 3D optical holographic image reconstruction in the visible and near-infrared regions for circularly polarized light.
1,129 citations
TL;DR: A strong photonic SHE resulting in a measured large splitting of polarized light at metasurfaces is reported, which may provide a route for exploiting the spin and orbit angular momentum of light for information processing and communication.
Abstract: The spin Hall effect (SHE) of light is very weak because of the extremely small photon momentum and spin-orbit interaction. Here, we report a strong photonic SHE resulting in a measured large splitting of polarized light at metasurfaces. The rapidly varying phase discontinuities along a metasurface, breaking the axial symmetry of the system, enable the direct observation of large transverse motion of circularly polarized light, even at normal incidence. The strong spin-orbit interaction deviates the polarized light from the trajectory prescribed by the ordinary Fermat principle. Such a strong and broadband photonic SHE may provide a route for exploiting the spin and orbit angular momentum of light for information processing and communication.
1,042 citations
TL;DR: An organic field effect transistor featuring the chiral molecule helicene acts as a photodetector that is able to distinguish between left and right-handed circularly polarized light.
Abstract: An organic field effect transistor featuring the chiral molecule helicene acts as a photodetector that is able to distinguish between left- and right-handed circularly polarized light.
642 citations
TL;DR: Huang et al. as mentioned in this paper demonstrated a reconfigurable, unidirectional coupling scheme for excitation of collective oscillations of the electrons at a metal surface, the so-called surface plasmon-polaritons.
Abstract: Researchers have now demonstrated a reconfigurable, unidirectional coupling scheme for excitation of collective oscillations of the electrons at a metal surface, the so-called surface plasmon-polaritons. Lingling Huang and co-workers achieved an efficient and controllable coupling of photons in free space to these surface states on a metal film — a task important for the future development of nanoscale optoelectronic circuitry — by employing a nanostructured thin metal film on a glass substrate. The nanostructured metal film features an array of rectangular nano-apertures arranged in a carefully designed orientation and pattern. Such a ‘plasmonic metasurface’ couples photons to surface plasmon-polaritons while depending crucially on the circular polarization state of the incident light. As a result, when circularly polarized light strikes the surface, the handedness of the light dictates the propagation direction of the resulting surface plasmon-polaritons.
451 citations
TL;DR: In this paper, the authors designed and fabricated two separate transmit arrays that operate at 77 GHz, one as a quarter-wave plate that transforms a linearly polarized incident wave into a circularly polarized transmitted wave.
Abstract: Two separate transmitarrays that operate at 77 GHz are designed and fabricated. The first transmitarray acts as a quarter-wave plate that transforms a linearly polarized incident wave into a circularly polarized transmitted wave. The second transmitarray acts as both a quarter-wave plate and a beam refracting surface to provide polarization and wavefront control. When the second transmittarray is illuminated with a normally incident, linearly polarized beam, the transmitted field is efficiently refracted to 45 °, and the polarization is converted to circular. The half-power bandwidth was measured to be 17%, and the axial ratio of the transmitted field remained below 2.5 dB over the entire bandwidth. Both designs have a subwavelength thickness of 0.4 mm (λ°/9.7). The developed structures are fabricated with low-cost printed-circuit-board processes on flexible substrates. The transmitarrays are realized by cascading three patterned metallic surfaces (sheet admittances) to achieve complete phase control, while maintaining high transmission. Polarization conversion is accomplished with anisotropic sheets that independently control the field polarized along the two orthogonal axes. The structures are analyzed with both circuit- and fields-based approaches.
305 citations
TL;DR: In this article, a nano-engineered photonic-crystal chiral beamplitter is proposed to split left and right-handed circularly polarized light in the wavelength region around 1.615 µm.
Abstract: The linearly polarizing beamsplitter1, 2 is a widely used optical component in photonics. It is typically built from a linearly birefringent crystal such as calcite, which has different critical reflection angles for s- and p-polarized light3, leading to the transmission of one linear polarization and angled reflection of the other. However, the analogue for splitting circularly polarized light has yet to be demonstrated due to a lack of natural materials with sufficient circular birefringence. Here, we present a nano-engineered photonic-crystal chiral beamsplitter that fulfils this task. It consists of a prism featuring a nanoscale chiral gyroid network4, 5, 6, 7, 8, 9, 10 and can separate left- and right-handed circularly polarized light in the wavelength region around 1.615 µm. The structure is fabricated using a galvo-dithered direct laser writing method and could become a useful component for developing integrated photonic circuits that provide a new form of polarization control.
271 citations
TL;DR: In this article, the authors proposed a method based on general relations between the reflection and transmission coefficients and the polarizabilities of arbitrary bi-anisotropic particles to synthesize different polarization-transforming devices realized as arrays of small particles.
Abstract: We study the possibility of analytically synthesizing different polarization-transforming devices realized as arrays of small particles. The proposed method is based on general relations between the reflection and transmission coefficients and the polarizabilities of arbitrary bi-anisotropic particles. As an example, we reveal all possible types of inclusions which can be used to realize twist polarizers, select one of them and synthesize a novel twist polarizer. The synthesized twist polarizer is then fitted on a standard printed circuit board, optimized numerically, and finally manufactured and measured. The experimental results for the twist polarizer show good correspondence with the simulations and the new method is found to be a useful tool for developing any polarization-transforming devices. As one more example, a novel circular polarization selective surface is synthesized.
209 citations
TL;DR: It is shown that distinct spin and valley polarization can also be seen in the longitudinal magneto-optical conductivity at experimentally attainable energies.
Abstract: We calculate the magneto-optical conductivity and electronic density of states for silicene, the silicon equivalent of graphene, and similar crystals such as germanene. In the presence of a perpendicular magnetic field and electric field gating, we note that four spin- and valley-polarized levels can be seen in the density of states, and transitions between these levels lead to similarly polarized absorption lines in the longitudinal, transverse Hall, and circularly polarized dynamic conductivity. While previous spin and valley polarization predicted for the conductivity is only present in the response to circularly polarized light, we show that distinct spin and valley polarization can also be seen in the longitudinal magneto-optical conductivity at experimentally attainable energies. The frequency of the absorption lines may be tuned by the electric and magnetic field to onset in a range varying from THz to the infrared. This potential to isolate charge carriers of definite spin and valley label may make silicene a promising candidate for spin- and valleytronic devices.
184 citations
TL;DR: Various optical fields containing phase, amplitude and/or polarization modulations are successfully generated and tested using Stokes parameter measurement to demonstrate the capability and versatility of this optical field generator.
Abstract: Generation of vectorial optical fields with complex spatial distribution in the cross section is of great interest in areas where exotic optical fields are desired, including particle manipulation, optical nanofabrication, beam shaping and optical imaging. In this work, a vectorial optical field generator capable of creating arbitrarily complex beam cross section is designed, built and tested. Based on two reflective phase-only liquid crystal spatial light modulators, this generator is capable of controlling all the parameters of the spatial distributions of an optical field, including the phase, amplitude and polarization (ellipticity and orientation) on a pixel-by-pixel basis. Various optical fields containing phase, amplitude and/or polarization modulations are successfully generated and tested using Stokes parameter measurement to demonstrate the capability and versatility of this optical field generator.
173 citations
TL;DR: In this article, the authors present a method to generate vector beams of light having polarization singularities on their axis, via partial spin-to-orbital angular momentum conversion in a suitably patterned liquid crystal cell.
Abstract: We present a convenient method to generate vector beams of light having polarization singularities on their axis, via partial spin-to-orbital angular momentum conversion in a suitably patterned liquid crystal cell. The resulting polarization patterns exhibit a C-point on the beam axis and an L-line loop around it, and may have different geometrical structures such as "lemon", "star", and "spiral". Our generation method allows us to control the radius of L-line loop around the central C-point. Moreover, we investigate the free-air propagation of these fields across a Rayleigh range.
169 citations
TL;DR: The electron-ion coincidence technique using multiphoton ionization opens new directions in table-top analytical mass-spectrometric applications of mixtures of chiral molecules.
Abstract: Here, we provide a detailed account of novel experiments employing electron-ion coincidence imaging to discriminate chiral molecules. The full three-dimensional angular scattering distribution of electrons is measured after photoexcitation with either left or right circular polarized light. The experiment is performed using a simplified photoelectron-photoion coincidence imaging setup employing only a single particle imaging detector. Results are reported applying this technique to enantiomers of the chiral molecule camphor after three-photon ionization by circularly polarized femtosecond laser pulses at 400 nm and 380 nm. The electron-ion coincidence imaging provides the photoelectron spectrum of mass-selected ions that are observed in the time-of-flight mass spectra. The coincident photoelectron spectra of the parent camphor ion and the various fragment ions are the same, so it can be concluded that fragmentation of camphor happens after ionization. We discuss the forward-backward asymmetry in the photoelectron angular distribution which is expressed in Legendre polynomials with moments up to order six. Furthermore, we present a method, similar to one-photon electron circular dichroism, to quantify the strength of the chiral electron asymmetry in a single parameter. The circular dichroism in the photoelectron angular distribution of camphor is measured to be 8% at 400 nm. The electron circular dichroism using femtosecond multiphoton excitation is of opposite sign and about 60% larger than the electron dichroism observed before in near-threshold one-photon ionization with synchrotron excitation. We interpret our multiphoton ionization as being resonant at the two-photon level with the 3s and 3p Rydberg states of camphor. Theoretical calculations are presented that model the photoelectron angular distribution from a prealigned camphor molecule using density functional theory and continuum multiple scattering X alpha photoelectron scattering calculations. Qualitative agreement is observed between the experimental results and the theoretical calculations of the Legendre moments representing the angular distribution for the two enantiomers. The electron-ion coincidence technique using multiphoton ionization opens new directions in table-top analytical mass-spectrometric applications of mixtures of chiral molecules.
TL;DR: In this article, an anisotropic meta-mirror for achromatic polarization tuning was proposed and experimental results showed that linear polarized wave can be achromatically transformed to its cross-polarization state or to arbitrary circular polarization after its reflection from the mirror.
Abstract: Polarization states are of particular importance for the manipulation of electromagnetic waves. Here, we proposed the design and experimental demonstration of anisotropic meta-mirror for achromatic polarization tuning. It is demonstrated that linear polarized wave can be achromatically transformed to its cross-polarization state or to arbitrary circular polarization after its reflection from the mirror. Microwave experiments verified that the fraction bandwidth for 90% transformation efficiency can be larger than 3:1. Furthermore, by utilizing photoinduced carrier generation in silicon, a broadband tunable circular polarizer is demonstrated in the terahertz regime.
TL;DR: A theory for the fluctuations in light scattering from a rotating particle is derived, and it is argued that the high rotation frequencies observed experimentally is the combined result of favorable optical particle properties and a low local viscosity due to substantial heating of the particles surface layer.
Abstract: Controlling the position and movement of small objects with light is an appealing way to manipulate delicate samples, such as living cells or nanoparticles. It is well-known that optical gradient and radiation pressure forces caused by a focused laser beam enables trapping and manipulation of objects with strength that is dependent on the particle’s optical properties. Furthermore, by utilizing transfer of photon spin angular momentum, it is also possible to set objects into rotational motion simply by targeting them with a beam of circularly polarized light. Here we show that this effect can set ∼200 nm radii gold particles trapped in water in 2D by a laser tweezers into rotation at frequencies that reach several kilohertz, much higher than any previously reported light driven rotation of a microscopic object. We derive a theory for the fluctuations in light scattering from a rotating particle, and we argue that the high rotation frequencies observed experimentally is the combined result of favorable opt...
TL;DR: The Hilbert fractal perturbation in the twisted split ring resonator element results in compact metamaterial and breaking mirror symmetry, which readily forms chirality over triple bands, and the discrepancy between co-polarization conversion and cross-polarsization conversion over multiple bands is explored.
Abstract: We propose a kind of chiral metamaterial inspired from the fractal concept The Hilbert fractal perturbation in the twisted split ring resonator element results in compact metamaterial and breaking mirror symmetry, which readily forms chirality over triple bands The discrepancy between co-polarization conversion and cross-polarization conversion over multiple bands can be explored for multifunctional devices A multiband circular polarizer is then numerically and experimentally studied in the X band based on the bilayered twisted Hilbert resonator with mutual 90° rotation The ability of transforming linearly polarized incident waves to circularly polarized waves is unambiguously demonstrated with high conversion efficiency and large polarization extinction ratio of more than 20 dB across dual bands Moreover, exceptionally strong optical activity and circular dichroism are also observed
TL;DR: In this article, a compact circular polarizer based on a twisted double split-ring resonator (DSRR) is presented, which is rotated 90° with respect to the top one.
Abstract: A compact circular polarizer is presented, which is based on a twisted double split-ring resonator (DSRR). The bottom DSRR is rotated 90° with respect to the top one. When the structure is illuminated by a normally incident linearly polarized wave, the two linear components of the transmitted wave have nearly equal amplitudes and 90° (−90°) phase difference around the resonant frequency. This means that the transmitted wave with left-handed circular polarization is much larger (smaller) than the one with right-handed circular polarization. The electric fields and currents on the structure are analyzed to illustrate this phenomenon. The size of each unit cell in this structure is extremely small compared with the wavelength in all three dimensions. Both simulations and measurements verify our design at microwave frequencies.
TL;DR: It is demonstrated numerically that metal-insulator-metal (MIM) configurations in which the top metal layer consists of a periodic arrangement of nanobricks, thus facilitating gap-surface plasmon resonances, can be designed to function as efficient and broadband quarter-wave plates in reflection by a proper choice of geometrical parameters.
Abstract: We demonstrate numerically that metal-insulator-metal (MIM) configurations in which the top metal layer consists of a periodic arrangement of nanobricks, thus facilitating gap-surface plasmon resonances, can be designed to function as efficient and broadband quarter-wave plates in reflection by a proper choice of geometrical parameters. Using gold as the metal, we demonstrate quarter-wave plate behavior at λ ≃ 800 nm with an operation bandwidth of 160 nm, conversion efficiency of 82%, and angle of linear polarization fixed throughout the entire bandwidth. This work also includes a detailed analytical and numerical study of the optical properties and underlying physics of structured MIM configurations.
TL;DR: It is reported that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited.
Abstract: Electron–nuclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck–Condon assumption, ascribed to the enhanced sensitivity of photoelectron circular dichroism (compared with other observables like cross-sections or the conventional anisotropy parameter-b) to the scattering phase off the chiral molecular potential, inducing a dependence on the nuclear geometry sampled in the photoionization process. Important consequences for the interpretation of such dichroism measurements within analytical contexts are discussed.
Patent•
23 Aug 2013
TL;DR: In this article, a compact, agile polarization diversity, multiple frequency band antenna with integrated electronics for terrestrial terminal use in satellite communications systems includes an antenna feed having highly integrated microwave electronics that are mechanically and electromagnetically coupled in a distributed arrangement so that diverse polarization senses having a low axial ratio and electronic switching control of the polarization senses is provided.
Abstract: A compact, agile polarization diversity, multiple frequency band antenna with integrated electronics for terrestrial terminal use in satellite communications systems includes an antenna feed having highly integrated microwave electronics that are mechanically and electromagnetically coupled thereto in a distributed arrangement so that diverse polarization senses having a low axial ratio and electronic switching control of the polarization senses is provided. The arrangement of the integrated distributed transceiver configuration enables the mechanical rotation of the orientation of a first transceiver for skew alignment while a second transceiver remains stationary relative to the antenna feed assembly. The first transceiver can be a high-band transmitter and receiver pair that supports linear polarization senses, and the second transceiver can be a low-band transmitter and receiver pair that supports circular polarization senses. The antenna system presented is highly compact and offers improved polarization performance previously achievable by only larger devices.
TL;DR: It is shown that when the topological charges of the polarization and the attached spiral phase are equal in number, the local polarizations undergo an abrupt transition from linear to circular polarizations at the focal point, and the associated orbital angular momentum partially converts into the spin of photons.
Abstract: We experimentally and theoretically study the abrupt polarization transitions of vector autofocusing Airy beams associated with the spin-orbit interactions. It is shown that when the topological charges of the polarization and the attached spiral phase are equal in number, the local polarizations undergo an abrupt transition from linear to circular polarizations at the focal point, and the associated orbital angular momentum partially converts into the spin of photons. The experimental results are theoretically explained from the far-field properties of the beams in terms of Hankel transformations.
TL;DR: It is shown that an azimuthal vortex beam provides good images for a variety of object structures and pinhole sizes, and plays an important role in high-numerical-aperture optical imaging.
Abstract: Imaging of object structures using cylindrical vector beams in an aplanatic solid immersion lens (SIL) microscope is investigated. Based on a complete optical model of an aplanatic SIL microscope, images of some object structures using radial polarization, azimuthal polarization, and azimuthal vortex beams are simulated. Some interesting imaging effects of these object structures are observed. For example, counterintuitively, it is found that, compared to linear and circular polarizations, radial polarization requires a larger pinhole to acquire a good image and resolution. Similarly, it is shown that an azimuthal vortex beam provides good images for a variety of object structures and pinhole sizes. Theories and explanations are provided to justify the observed effects. The presented results play an important role in high-numerical-aperture optical imaging.
TL;DR: This work has demonstrated the polarization manipulation of light by employing a thin subwavelength slab of metamaterial with an extremely anisotropic effective permittivity tensor and suggested all-optical ultrafast control of reflected or transmitted light polarization by employing metal nonlinearities.
Abstract: One of the basic functionalities of photonic devices is the ability to manipulate the polarization state of light Polarization components are usually implemented using the retardation effect in natural birefringent crystals and, thus, have a bulky design Here, we have demonstrated the polarization manipulation of light by employing a thin subwavelength slab of metamaterial with an extremely anisotropic effective permittivity tensor Polarization properties of light incident on the metamaterial in the regime of hyperbolic, epsilon-near-zero, and conventional elliptic dispersions were compared We have shown that both reflection from and transmission through λ/20 thick slab of the metamaterial may provide nearly complete linear-to-circular polarization conversion or 90° linear polarization rotation, not achievable with natural materials Using ellipsometric measurements, we experimentally studied the polarization conversion properties of the metamaterial slab made of the plasmonic nanorod arrays in different dispersion regimes We have also suggested all-optical ultrafast control of reflected or transmitted light polarization by employing metal nonlinearities
TL;DR: A metal/phase-change material/metal tri-layer planar chiral metamaterial in the shape of a gammadion is numerically modelled to accomplish a wide tuning range of the circular dichroism in the mid-infrared wavelength regime.
Abstract: A metal/phase-change material/metal tri-layer planar chiral metamaterial in the shape of a gammadion is numerically modelled. The chiral metamaterial is integrated with Ge2Sb2Te5 phase-change material (PCM) to accomplish a wide tuning range of the circular dichroism (CD) in the mid-infrared wavelength regime. A photothermal model is used to study the temporal variation of the temperature of the Ge2Sb2Te5 layer and to show the potential for fast switching the phase of Ge2Sb2Te5 under a low incident light intensity of 0.016mW/μm2.
TL;DR: In this article, two kinds of bi-layered chiral metamaterials were proposed to enhance the asymmetric transmission effects for circular polarized electromagnetic waves which are only found in planar CHs according to previous studies.
Abstract: In this paper, two kinds of bi-layered chiral metamaterials were proposed to enhance the asymmetric transmission effects for circular polarized electromagnetic waves which are only found in planar chiral metamaterials according to previous studies. It was found that the magnitude of the asymmetric transmission parameters mainly depends on the distances between the two metal layers. With appropriate distance, the asymmetric transmission parameter for circular polarized electromagnetic waves can increase to 0.6. Moreover, both proposed configurations show no asymmetric transmission for linear polarized electromagnetic waves which is widely studied in other bi-layered metamaterials.
TL;DR: In this paper, high-resolution spectropolarimetric observations of superpenumbral fibrils in the He I triplet with sufficient polarimetric sensitivity to infer their full magnetic field geometry are presented.
Abstract: Atomic-level polarization and Zeeman effect diagnostics in the neutral helium triplet at 10830 A in principle allow full vector magnetometry of fine-scaled chromospheric fibrils. We present high-resolution spectropolarimetric observations of superpenumbral fibrils in the He I triplet with sufficient polarimetric sensitivity to infer their full magnetic field geometry. He I observations from the Facility Infrared Spectropolarimeter are paired with high-resolution observations of the Hα 6563 A and Ca II 8542 A spectral lines from the Interferometric Bidimensional Spectrometer from the Dunn Solar Telescope in New Mexico. Linear and circular polarization signatures in the He I triplet are measured and described, as well as analyzed with the advanced inversion capability of the "Hanle and Zeeman Light" modeling code. Our analysis provides direct evidence for the often assumed field alignment of fibril structures. The projected angle of the fibrils and the inferred magnetic field geometry align within an error of ±10°. We describe changes in the inclination angle of these features that reflect their connectivity with the photospheric magnetic field. Evidence for an accelerated flow (~40 m s–2) along an individual fibril anchored at its endpoints in the strong sunspot and weaker plage in part supports the magnetic siphon flow mechanism's role in the inverse Evershed effect. However, the connectivity of the outer endpoint of many of the fibrils cannot be established.
TL;DR: Novel intensity and polarization patterns obtained from the superposition of two vector LG beams may find applications in the field of molecular imaging, optical manipulation, atom optics, and optical lattices.
Abstract: We present a systematic study of the superposition of two vector Laguerre-Gaussian (LG) beams. Propagation depended field distribution obtained from the superposition of two vector LG beams has many interesting features of intensity and polarization. Characteristic inhomogeneous polarization distribution of the vector LG beam appears in the form of azimuthally modulated intensity and polarization distributions in the superposition of the beams. We found that the array of polarization singular points, whose number depends upon the azimuthal indices of the two beams, evolves during propagation of the field. The position and number of C-points generated in the field were analyzed using Stokes singularity relations. Novel intensity and polarization patterns obtained from the superposition of two vector LG beams may find applications in the field of molecular imaging, optical manipulation, atom optics, and optical lattices.
TL;DR: The resonant scattering and diffraction beamline P09 at PETRA III is designed for X-ray experiments requiring small beams, energy tunability, variable polarization and high photon flux.
Abstract: The resonant scattering and diffraction beamline P09 at PETRA III is designed for X-ray experiments requiring small beams, energy tunability, variable polarization and high photon flux. It is highly flexible in terms of beam size and offers full higher harmonic suppression. A state-of-the-art double phase-retarder set-up provides variable linear or circular polarization. A high-precision Psi-diffractometer and a heavy-load diffractometer in horizontal Psi-geometry allow the accommodation of a wide variety of sample environments. A 14 T cryo-magnet is available for scattering experiments in magnetic fields.
TL;DR: In this article, a triple-band single-fed compact microstrip antenna with varied polarization states and radiation patterns is proposed based on two-dimensional artiflcial metamaterial transmission line (TL).
Abstract: A novel triple-band single-fed compact microstrip antenna with varied polarization states and radiation patterns is proposed based on two-dimensional artiflcial metamaterial transmission line (TL). The TL element is composed of complementary split ring resonators (CSRRs) etched in the ground plane and a capacitive gap embedded in the stepped-impedance conductor line. By inserting a 2 £ 2 array of the original element in conventional patch and feeding the resultant structure with an annular-ring slot along the diagonal, an antenna working in three resonant modes (n = i1, n = 0, and n = +2) is engineered at three speciflc well-separated frequencies fi1 = 1:5, f0 = 2:4 and f+2 = 3:5GHz, respectively. As a result, both the numerical and experimental results illustrate that the antenna exhibits a patch-like radiation with pure linear polarization in the n = i1 mode, a monopolar radiation with circular polarization in the n = 0 and also an asymmetric quasi monopolar radiation with a hybrid linear polarization in the n = +2 mode. The antenna features compact whose patch occupying only an area of 0:246‚0 £ 0:246‚0 £ 0:03‚0 at fi1 and exhibits groups of advantages such as high radiation e-ciency. Moreover, the proposed prescription, free of any metallic via, perturbation structure and complicated feeding network, is of practical value and opens an alternative avenue toward new types of antenna with agile polarization capability and versatile radiation patterns.
TL;DR: In this paper, a compact circularly polarized diagonally symmetric slotted microstrip-patch antennas with compact size was proposed, which can be achieved using any arbitrarily shaped slots in diagonal directions on the square microstrip patch antenna.
Abstract: Circularly polarized diagonally symmetric slotted microstrip-patch antennas are proposed with compact size The compact circularly polarized (CP) diagonally symmetric slotted microstrip-patch (DSSMP) antenna design rules are also summarized Circularly polarized radiation can be achieved using any arbitrarily shaped slots in diagonal directions on the square microstrip-patch antenna Different shapes for the slots are studied and compared, based on the fixed overall volume of the antenna for circularly polarized diagonally symmetric slotted microstrip-patch antennas The cross-shaped-slot diagonally symmetric slotted microstrip-patch antenna is compact when compared with the circular-, square-, and circular-ring-shaped diagonally symmetric slotted microstrip-patch antennas A measured 3 dB axial-ratio (AR) bandwidth of around 07% (60 MHz) with 20% (180 MHz) impedance bandwidth was achieved The measured boresight gain was more than 33 dBic over the operating band, while the overall antenna size was 0272λ0 × 0272λ0 × 00138λ0 at 0905 GHz
TL;DR: Based on the idea of a single-layer multiple-resonance structure for a linearly polarized reflect array, two broadband circularly polarized reflectarray elements are presented in this article. But the performance of these reflectarrays is limited.
Abstract: Based on the idea of a single-layer multiple-resonance structure for a linearly polarized reflectarray, two broadband circularly polarized reflectarray elements are presented in this letter. One is a double-ring-shaped element, and the other is an I-ring shaped element. The principle of broadband circular polarization is studied by analyzing the surface current distribution of the elements. Then, by using an angular rotation technique, reflectarrays with these two elements are designed and measured. The reflectarrays (6.5λt6.5λ at the center frequency of 10 GHz) demonstrate excellent performance of more than 30% antenna bandwidth [the overlapping 3-dB axial-ratio (AR) and 1-dB gain bandwidths]. The aperture efficiency can go up to 58.55% and 59.94%, respectively.
TL;DR: In this paper, the spectrum of driven topological surface excitations in the presence of an external light source was characterized for both linear and circular polarizations of the incident light, and it was shown that the circularly polarized light gaps out the surface states, whereas linear polarization gives rise to an anisotropic metal with multiple Dirac cones.
Abstract: (Received 29 May 2013; revised manuscript received 11 August 2013; published 23 October 2013) Motivated by recent photoemission experiments on the surface of topological insulators we compute the spectrum of driven topological surface excitations in the presence of an external light source. We completely characterize the spectral function of these nonequilibrium electron excitations for both linear and circular polarizations of the incident light. We find that in the latter case, the circularly polarized light gaps out the surface states, whereas linear polarization gives rise to an anisotropic metal with multiple Dirac cones. We compare the sizes of the gaps with recent pump-probe photoemission measurements and find good agreement. We also identify theoretically several new features in the time-dependent spectral function, such as shadow Dirac cones.