Showing papers on "Circular polarization published in 2015"
TL;DR: An ultracompact circularly polarized light detector that combines large engineered chirality, realized using chiral plasmonic metamaterials, with hot electron injection is reported that could lead to enhanced security in fibre and free-space communication, as well as emission, imaging and sensing applications for circularly polarization light using a highly integrated photonic platform.
Abstract: Circularly polarized light is utilized in various optical techniques and devices. However, using conventional optical systems to generate, analyse and detect circularly polarized light involves multiple optical elements, making it challenging to realize miniature and integrated devices. While a number of ultracompact optical elements for manipulating circularly polarized light have recently been demonstrated, the development of an efficient and highly selective circularly polarized light photodetector remains challenging. Here we report on an ultracompact circularly polarized light detector that combines large engineered chirality, realized using chiral plasmonic metamaterials, with hot electron injection. We demonstrate the detector's ability to distinguish between left and right hand circularly polarized light without the use of additional optical elements. Implementation of this photodetector could lead to enhanced security in fibre and free-space communication, as well as emission, imaging and sensing applications for circularly polarized light using a highly integrated photonic platform.
496 citations
01 Jan 2015
TL;DR: In this article, the authors focused on circularly polarized antennas and provided key definitions and governing equations of circular polarization, and extended the concept to the magnetic source counterparts and Huygens sources.
Abstract: This chapter is focused on circularly polarized antennas. Key definitions and governing equations of circular polarization are given. Infinitesimal dipole sources are considered to establish circularly polarized radiation. First, radiation patterns of cross dipoles are mathematically reviewed, from which the condition of circularly polarized waves is concluded. Later, the idea is extended to four displaced sequentially rotated dipole antennas, resulting in circularly polarized waves within a wide angular range in space. The extension of the concept to the magnetic source counterparts and Huygens sources is briefly discussed. Other than point sources, also known as one-dimensional current sources, sources of circularly polarized radiation are further investigated for two-dimensional cases, such as microstrip patch antennas, and threedimensional structures, such as volumetric current sources existing in dielectric resonator antennas. For these cases, the creation of circularly polarized radiation using single-feed and dual-feed, perturbed structures and sequentially rotated method is described. As a design example, numerical andmeasurement results of circularly polarized square patch ring antennas are extensively discussed and presented in this chapter. The square-ring microstrip antenna is selected as it closely approximates the sequentially rotated currents, and also it has not been widely studied in the literature.
327 citations
17 Nov 2015
TL;DR: This work demonstrates the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform and explains the single-atom and macroscopic physics.
Abstract: We present the first circularly-polarized soft X-ray harmonics to photon energies >160eV. Bright phase matched beams are used to characterize important materials with intrinsic perpendicular magnetic anisotropy for the first time using tabletop sources.
254 citations
TL;DR: This work reveals the feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel applications of ultrathin terAhertz meta- devices.
Abstract: Metamaterials open up various exotic means to control electromagnetic waves and among them polarization manipulations with metamaterials have attracted intense attention. As of today, static responses of resonators in metamaterials lead to a narrow-band and single-function operation. Extension of the working frequency relies on multilayer metamaterials or different unit cells, which hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the metasurface operates as a quarter-wave plate at 0.468 THz. After the transition to metal phase, the quarter-wave plate operates at 0.502 THz. At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel applications of ultrathin terahertz meta-devices.
246 citations
TL;DR: It is demonstrated that the Stokes vector of backscattered light depicted on a Poincaré sphere can be used to assess a turbid tissue-like scattering medium and the utility of this approach for characterization of cancerous and non-cancerous tissue samples in vitro is investigated.
Abstract: Polarization-based optical techniques have become increasingly popular in the field of biomedical diagnosis. In the current report we exploit the directional awareness of circularly and/or elliptically polarized light backscattered from turbid tissue-like scattering media. We apply circularly and elliptically polarized laser light which illuminates the samples of interest, and a standard optical polarimeter is used to observe the polarization state of light backscattered a few millimeters away from the point of incidence. We demonstrate that the Stokes vector of backscattered light depicted on a Poincare sphere can be used to assess a turbid tissue-like scattering medium. By tracking the Stokes vector of the detected light on the Poincare sphere, we investigate the utility of this approach for characterization of cancerous and non-cancerous tissue samples in vitro. The obtained results are discussed in the framework of a phenomenological model and the results of a polarization tracking Monte Carlo model, developed in house. Schematic illustration of the experimental approach utilizing circularly and elliptically polarized light for probing turbid tissue-like scattering media.
213 citations
TL;DR: In this article, the first implementation of non-collinear high harmonic generation with circularly polarized driving lasers was presented. And the authors showed that the non-Collinear mixing enables the generation of isolated attosecond pulses with circular polarization.
Abstract: We generate angularly isolated beams of circularly polarized extreme ultraviolet light through the first implementation of non-collinear high harmonic generation with circularly polarized driving lasers. This non-collinear technique offers numerous advantages over previous methods, including the generation of higher photon energies, the separation of the harmonics from the pump beam, the production of both left and right circularly polarized harmonics at the same wavelength and the capability of separating the harmonics without using a spectrometer. To confirm the circular polarization of the beams and to demonstrate the practicality of this new light source, we measure the magnetic circular dichroism of a 20 nm iron film. Furthermore, we explain the mechanisms of non-collinear high harmonic generation using analytical descriptions in both the photon and wave models. Advanced numerical simulations indicate that this non-collinear mixing enables the generation of isolated attosecond pulses with circular polarization. Scientists have demonstrated non-collinear circularly polarized high-harmonic generation and showed that this method generates bright circularly polarized extreme-ultraviolet beams with both left and right helicity simultaneously.
191 citations
190 citations
TL;DR: A planar chiral antenna array is experimentally demonstrated to produce optical vortex from a circularly polarized light and has the ability to focus the incident light into point, which greatly increases the power intensity of the generated optical vortex.
Abstract: Data capacity is rapidly reaching its limit in modern optical communications. Optical vortex has been explored to enhance the data capacity for its extra degree of freedom of angular momentum. In traditional means, optical vortices are generated using space light modulators or spiral phase plates, which would sharply decrease the integration of optical communication systems. Here we experimentally demonstrate a planar chiral antenna array to produce optical vortex from a circularly polarized light. Furthermore, the antenna array has the ability to focus the incident light into point, which greatly increases the power intensity of the generated optical vortex. This chiral antenna array may have potential application in highly integrated optical communication systems.
181 citations
TL;DR: It is shown that spin–orbit coupling, when the spin of the incident circularly polarized light is converted into lateral electromagnetic momentum, leads to a lateral optical force acting on particles placed above a substrate, associated with a recoil mechanical force.
Abstract: Optical forces allow manipulation of small particles and control of nanophotonic structures with light beams. While some techniques rely on structured light to move particles using field intensity gradients, acting locally, other optical forces can 'push' particles on a wide area of illumination but only in the direction of light propagation. Here we show that spin-orbit coupling, when the spin of the incident circularly polarized light is converted into lateral electromagnetic momentum, leads to a lateral optical force acting on particles placed above a substrate, associated with a recoil mechanical force. This counterintuitive force acts in a direction in which the illumination has neither a field gradient nor propagation. The force direction is switchable with the polarization of uniform, plane wave illumination, and its magnitude is comparable to other optical forces.
176 citations
TL;DR: In this article, a bi-layered linear-to-circular (LTC) polarization conversion metasurface operating in 11.4-14.3 GHz is designed and fabricated, which is composed of two layers of metallic pattern arrays separated by a 1.5mm-thick dielectric spacer.
Abstract: In this paper, we propose to achieve wideband linear-to-circular (LTC) polarization conversion by ultra-thin bi-layered metasurfaces. As an example, an LTC polarization conversion metasurface operating in 11.4–14.3 GHz is designed and fabricated, which is composed of two layers of metallic pattern arrays separated by a 1.5 mm-thick dielectric spacer. When linearly polarized waves impinge on the bi-layered metasurface, LTC polarization conversion transmission is greater than 90% over a wide frequency range from 11.0 GHz to 18.3 GHz. Meanwhile, the axis ratio is lower than 3 dB in 9.8–18.3 GHz. This wide-band and highly efficient LTC polarization conversion transmission is analyzed theoretically. The measured LTC polarization conversion transmissions are well consistent with the simulated results.
156 citations
TL;DR: In this article, the authors investigated valley exciton dynamics in MoSe2 monolayers in polarization and time-resolved photoluminescence (PL) spectroscopy at 4'K.
Abstract: We investigate valley exciton dynamics in MoSe2 monolayers in polarization- and time-resolved photoluminescence (PL) spectroscopy at 4 K. Following circularly polarized laser excitation, we record a low circular polarization degree of the PL of typically ≤5%. This is about 10 times lower than the polarization induced under comparable conditions in MoS2 and WSe2 monolayers. The evolution of the exciton polarization as a function of excitation laser energy and power is monitored in PL excitation experiments. Fast PL emission times are recorded for both the neutral exciton of ≤3 ps and for the charged exciton (trion) of 12 ps.
20 Oct 2015
TL;DR: In this article, the photonic spin Hall effect (PSHE) was used in a gap-plasmon metasurface (GPMS) based chiroptical spectroscopy solution.
Abstract: Chiral structures possessing differential optical responses to light circular polarization are very common in biological and organic compounds. Attaining chiroptical effects is of great biochemical importance, yet requires complicated structures. Circular dichroism (CD) spectrometers measuring the differential absorption between left- (LCP) and right-circular (RCP) polarizations involve complex hardware to switch laser polarization and manage data acquisition sequentially. Here, we present compact and power-efficient metasurface-based chiroptical spectroscopy solutions based on gap–plasmon metasurfaces (GPMSs). First, a minimalistic design of a real-time CD spectrometer is obtained by using the photonic spin Hall effect (PSHE) in a single GPMS, which spatially separates LCP and RCP spectra. It is the smallest CD spectrometer to our knowledge. Another GPMS-based device built with the same approach rotates light polarization by 45° through adding a phase shift between LCP and RCP. Thus, PSHE in GPMS can provide efficient solutions to vital applications including biosensing, DNA structural analysis, and stereochemistry.
TL;DR: The design and experimental demonstration of an ultrathin (0.29λ) terahertz quarter-wave plate based on planar babinet-inverted metasurface based on an analytical model is presented, which opens up avenues for new functional teraHertz devices design.
Abstract: Metamaterials promise an exotic approach to artificially manipulate the polarization state of electromagnetic waves and boost the design of polarimetric devices for sensitive detection, imaging and wireless communication. Here, we present the design and experimental demonstration of an ultrathin (0.29λ) terahertz quarter-wave plate based on planar babinet-inverted metasurface. The quarter-wave plate consisting of arrays of asymmetric cross apertures reveals a high transmission of 0.545 with 90 degrees phase delay at 0.870 THz. The calculated ellipticity indicates a high degree of polarization conversion from linear to circular polarization. With respect to different incident polarization angles, left-handed circular polarized light, right-handed circular polarized light and elliptically polarized light can be created by this novel design. An analytical model is applied to describe transmitted amplitude, phase delay and ellipticitiy, which are in good agreement with the measured and simulated results. The planar babinet-inverted metasurface with the analytical model opens up avenues for new functional terahertz devices design.
Abstract: Metallic helical metamaterials give rise to broadband and scalable chiro-optical effects orders of magnitude higher than found in nature. While arrays of gold helices have been suggested as compact circular polarizers, where a large difference of the diagonal elements of the Jones transmission matrix is desired, chiral metamaterials can also be designed to exhibit strong circular-polarization conversions. Here, a novel helical metamaterial design, exhibiting asymmetric, broadband circular-polarization conversion, is introduced. The metamaterial is composed of unit cells with a single helix that changes its handedness halfway along the helix axis. Based on numerical calculations, an intuitive model explaining the principle of operation is given. Furthermore, a novel fabrication approach employing STED-inspired direct laser writing in combination with electrochemical deposition of gold is presented. The experimental data show circular-polarization conversion of up to 75% for an unmatched bandwidth of one octave, in very good agreement with theory.
TL;DR: In this paper, a reconfigurable transmit array with beam steering and polarization manipulation capabilities is presented, which consists of an active side, a 360° reflective phase shifter, and a passive side.
Abstract: A reconfigurable transmitarray with beam steering and polarization manipulation capabilities is presented. The transmitarray element consists of an active side, a 360° reflective phase shifter, and a passive side. The active side is made of a polarization tunable patch structure, which can radiate electromagnetic wave at dual linear polarization. The passive side composed of a two-layer patch structure is unitized as a receiver cell. We adopt ${8} \times {8}$ unit cells to construct the whole transmitarray, and then place it above a horn antenna. The measured results show that the transmitarray-based horn antenna achieves beam steering with the scan range of $\pm {60}^\circ \times \pm {60}^\circ $ at 5.4 GHz, and this steering capability can be realized in two orthogonal linearly polarized modes. The polarization manipulation capability of this transmitarray is then studied, and it is found that four different output polarization modes, including two circular polarizations [right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP)] and two linear polarizations, can be obtained over an 8.5% fractional bandwidth, with cross-polarization ratio larger than 15 dB.
TL;DR: In this article, a polarization reconfigurable wheel-shaped antenna with wide bandwidth and conical-beam radiation pattern is proposed. But the antenna can operate at the downlink of standard C band (3.625 to 4.2 GHz) for geostationary satellite communication.
Abstract: This paper introduces a polarization reconfigurable wheel-shaped antenna with wide bandwidth and conical-beam radiation pattern. A wideband circular-monopolar patch surrounded by eight reconfigurable coupling loop stubs can generate conical-beam radiation patterns with different polarizations. This polarization reconfigurable characteristic is realized by controlling PIN diodes on the coupling loop stubs. The center-fed circular patch operates with the vertically-polarized conical-beam radiation and the coupling loop stubs radiate the horizontally-polarized wave propagation. With choosing proper magnitudes and phase differences between the two orthogonal radiations from the monopolar patch and the loop stubs, a circularly-polarized conical-beam radiation can be obtained. In addition, the presence of a back reflector yields a wide axial ratio bandwidth, enhances the front-to-back ratio of the radiation pattern, and avoids EM interferences between DC biasing lines and the antenna. This proposed antenna can generate three types of polarizations with the conical-beam radiation pattern including vertical polarization, left-handed circular polarization, and right-handed circular polarization by controlling the PIN diodes. Measured impedance and axial ratio bandwidths are 28.6% (3.45 to 4.6 GHz) and 15.4% (3.6 to 4.2 GHz), respectively, for the two CP modes. The maximum CP gain is 4.4 dBic. Furthermore, a dual-band operation (3.35 to 3.44 GHz and 4.5 to 4.75 GHz) can be observed for the LP mode. The antenna can operate at the downlink of standard C band (3.625 to 4.2 GHz) for geostationary satellite communication.
TL;DR: In this paper, the authors investigated valley exciton dynamics in MoSe2 monolayers in polarization and time-resolved photoluminescence (PL) spectroscopy at 4K.
Abstract: We investigate valley exciton dynamics in MoSe2 monolayers in polarization- and time-resolved photoluminescence (PL) spectroscopy at 4K. Following circularly polarized laser excitation, we record a low circular polarization degree of the PL of typically $\leq5\%$. This is about 10 times lower than the polarization induced under comparable conditions in MoS2 and WSe2 monolayers. The evolution of the exciton polarization as a function of excitation laser energy and power is monitored in PL excitation (PLE) experiments. Fast PL emission times are recorded for both the neutral exciton of $\leq3$ ps and for the charged exciton (trion) of 12 ps.
TL;DR: It is shown that a weak transverse magnetic field closes the EIT transitions, thereby generating phase- dependent dark states which in turn lead to phase-dependent transparency, in agreement with the measurements.
Abstract: Recent years have seen vast progress in the generation and detection of structured light, with potential applications in high capacity optical data storage and continuous variable quantum technologies. Here we measure the transmission of structured light through cold rubidium atoms and observe regions of electromagnetically induced transparency (EIT), using the phase profile as control parameter for the atomic opacity. With q plates we generate a probe beam with azimuthally varying phase and polarization structure, and its right and left circular polarization components provide the probe and control of an EIT transition. We observe an azimuthal modulation of the absorption profile that is dictated by the phase and polarization structure of the probe laser. Conventional EIT systems do not exhibit phase sensitivity. We show, however, that a weak transverse magnetic field closes the EIT transitions, thereby generating phase-dependent dark states which in turn lead to phase-dependent transparency, in agreement with our measurements.
TL;DR: This work proposes and experimentally demonstrate a simple and compact approach to measure the ellipticity and handedness of the polarized light using an ultrathin (40 nm) gradient metasurface.
Abstract: The miniaturization of measurement systems currently used to characterize the polarization state of light is limited by the bulky optical components used such as polarizers and waveplates. We propose and experimentally demonstrate a simple and compact approach to measure the ellipticity and handedness of the polarized light using an ultrathin (40 nm) gradient metasurface. A completely polarized light beam is decomposed into a left circularly polarized beam and a right circularly polarized beam, which are steered in two directions by the metasurface consisting of nanorods with spatially varying orientations. By measuring the intensities of the refracted light spots, the ellipticity and handedness of various incident polarization states are characterized at a range of wavelengths and used to determine the polarization information of the incident beam. To fully characterize the polarization state of light, an extra polarizer can be used to measure the polarization azimuth angle of the incident light.
TL;DR: In this paper, the authors extended the super-oscillation concept into the vectorial-field regime to work with circularly polarized light, and experimentally demonstrated a circularly polarized optical needle with sub-diffraction transverse spot size (0.45l) and axial long depth of focus (DOF) of 15l using a planar SOL at a violet wavelength of 405 nm.
Abstract: Planar optical lenses are fundamental elements of miniaturized photonic devices. However, conventional planar optical lenses are constrained by the diffraction limit in the optical far-field due to the band-limited wavevectors supported by free-space and loss of high-spatial-frequency evanescent components. As inspired by Einstein’s radiation ‘needle stick’, electromagnetic energy can be delivered into an arbitrarily small solid angle. Such sub-diffraction optical needles have been numerically investigated using diffractive optical elements (DOEs) together with specially polarized optical beams, but experimental demonstration is extremely difficult due to the bulky size of DOEs and the required alignment precision. Planar super-oscillatory lenses (SOLs) were proposed to overcome these constraints and demonstrated that sub-diffraction focal spots can actually be formed without any evanescent waves, making far-field, label-free super-resolution imaging possible. Here we extend the super-oscillation concept into the vectorial-field regime to work with circularly polarized light, and experimentally demonstrate, for the first time, a circularly polarized optical needle with sub-diffraction transverse spot size (0.45l) and axial long depth of focus (DOF) of 15l using a planar SOL at a violet wavelength of 405 nm. This sub-diffraction circularly polarized optical needle has potential applications in circular dichroism spectroscopy, super-resolution imaging, high-density optical storage, heat-assisted magnetic recording, nano-manufacturing and nano-metrology.
TL;DR: A review of the available theoretical and experimental tools and their performances can be found in this paper, with a particular emphasis on single-photon valence-shell ionization induced by VUV continuous sources such as synchrotron radiation and observed by electron imaging.
TL;DR: In this article, a broadband frequency tunable and polarization reconfigurable circularly polarized (CP) antenna is presented, using a novel active electromagnetic band gap (EBG) structure.
Abstract: This paper presents a broadband frequency tunable and polarization reconfigurable circularly polarized (CP) antenna, using a novel active electromagnetic band gap (EBG) structure. The EBG surface employs identical metallic rectangular patch arrays on both sides of a thin substrate, but rotated by 90 $^{\circ}$ from each other. The active bias circuits are also orthogonal for each surface, enabling the reflection phases for orthogonal incident waves to be tuned independently in a wide frequency range. By placing a wideband coplanar waveguide (CPW) fed monopole antenna above the EBG surface, and properly tuning the bias voltages across the varactors in each direction, CP waves can be generated at any desired frequency over a broad band. In accordance with simulations, the measured 3 dB axial ratio (AR) bandwidth reaches 40% (1.03–1.54 GHz), with good input matching $(S_{11})$ and radiation patterns at six presented sampling frequencies. The polarization reconfigurability is verified by simulations and measurements, and shown to be capable of switching between left hand circular polarization (LHCP) and right hand circular polarization (RHCP).
TL;DR: St stimulated emission depletion-inspired three-dimensional laser lithography is used to fabricate metal-helix metamaterials and it is shown experimentally that polarization conversions are minimized, in good agreement with theory.
Abstract: In analogy to wire-grid polarizers for linear polarization, metal-helix metamaterials can act as broadband circular polarizers. This concept has brought circular-polarization capabilities to mid-infrared and terahertz frequencies, which were previously difficult to access. Due to the lack of rotational symmetry, however, single-helix metamaterials exhibit unwanted circular-polarization conversions. Recent theoretical work showed that conversions can be fully eliminated by intertwining N=3 or 4 helices within each unit cell. While direct laser writing in positive-tone photo-resist yielded good results for single-helix metamaterials operating at mid-infrared frequencies, the axial resolution is insufficient for N-helix metamaterials. Here, we use stimulated emission depletion-inspired three-dimensional laser lithography to fabricate such microstructures. We measure all entries of the Jones transmission and reflection matrices and show experimentally that polarization conversions are minimized, in good agreement with theory.
TL;DR: This work proposes a novel method for the generation of Airy vortex and Airy vector beams based on the modulation of dynamic and geometric phases that can be extended to generate any other types of optical beams with desirable phase and polarization.
Abstract: We propose a novel method for the generation of Airy vortex and Airy vector beams based on the modulation of dynamic and geometric phases. In our scheme, the Airy beam is generated by the dynamic phase with a spatial light modulator, and the vortex phase or the vector polarization is modulated by the geometric phase with a dielectric metasurface. The modulation of the geometric phase provides an extra degree of freedom to manipulate the phase and the polarization of Airy beams. This scheme can be extended to generate any other types of optical beams with desirable phase and polarization.
TL;DR: This demonstration shows the potential of using dielectric metasurfaces for high efficiency beam shaping applications in general, and specifically for polarization coded beam shaping.
Abstract: Metasurfaces consisting of ultrathin nanostructures are utilized to control the properties of light including its phase, amplitude and polarization. Hereby, we demonstrate the capability of such structures to perform arbitrary polarization selective beam shaping using dielectric nanoscale metasurfaces implemented in silicon. By illuminating the structure with right handed circular polarization we reconstruct a desired image. When switching the polarization into its orthogonal state, we obtain the reconstruction of a different image. This demonstration shows the potential of using dielectric metasurfaces for high efficiency beam shaping applications in general, and specifically for polarization coded beam shaping.
TL;DR: In this paper, a novel circularly polarized antenna is proposed at 902-928 MHz Industrial, Scientific, and Medical band for implantable applications, where the slow wave concept is utilized by loading patches to the radiated loop antenna to achieve miniaturization.
Abstract: A novel circularly polarized antenna is proposed at 902–928 MHz Industrial, Scientific, and Medical band for implantable applications. By properly positioning the feed and shorts, either right-hand circular polarization property or left-hand circular polarization property can be realized. Slow wave concept is utilized by loading patches to the radiated loop antenna to achieve miniaturization. Thus, a compact size of 13 mm $\,\times\,$ 13 mm $\,\times\,$ 1.27 mm is obtained. Compared to the unloaded loop antenna of the same size, the centre frequency shifts from 1.93 GHz to 882.5 MHz, which suggests a miniaturization of 54.4%. The simulated results show that a wide bandwidth of 18.2% can be realized with $\vert S_{{11}}\vert$ below ${-}10$ dB and axial ratio below 3 dB. The simulated realized gain is ${-}32$ dBi at 915 MHz. The measurement is carried out in both skin-mimicking gel and pork, and a bandwidth of 27.8% and 29.4% can be achieved with $\vert S_{{11}}\vert$ below ${-}10$ dB, respectively. The measurement of $\vert S_{{21}}\vert$ reveals that circular polarization can be obtained for the proposed configuration.
TL;DR: In this paper, the authors have demonstrated that self-complementary metasurfaces can provide linear-to-circular polarization conversion with high precision, and they have also validated their theory through numerical simulations for structures made of ideal lossless materials.
Abstract: In this work, we have demonstrated that self-complementary metasurfaces can provide linear-to-circular polarization conversion. For illustration of this general approach, we studied several particular structures based on periodic self-complementary patterns etched on metal sheets of negligible thickness. The advantage of using self-complementary metasurfaces over previous proposals of thin polarizers is the rigorous constancy of the phase difference between transmission (or reflection) coefficients corresponding to orthogonal linear polarizations, which is just ${90}^{\ensuremath{\circ}}$ at any frequency. Also, this unusual phenomenon is stable under oblique incidence. The general proposed theory of self-complementary metasurfaces was first validated through numerical simulations for structures made of ideal lossless materials. Through simulations with realistic materials and experimental measurements, we have also demonstrated that this conversion can be reached in reality with high precision.
TL;DR: In this article, an asymmetric cross-shaped metasurface (MS) was proposed to reconfigure the polarization of the slot antenna between RHCP, LHCP, and linear polarization.
Abstract: This letter presents a polarization-reconfigurable compact slot antenna with reduced radar cross section (RCS) using an asymmetric cross-shaped metasurface (MS). The proposed MS can reconfigure the polarization of the slot antenna between right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), and linear polarization (LP) by rotating it with respect to the center of the slot antenna. In addition, the MS reduces the RCS of the slot antenna significantly in all polarization states. The cross-slot MS is placed just over the planar slot antenna without any air gap. The simulated monostatic RCS of $- $ 19.5 dBsm is observed at 4.4 GHz for LHCP and RHCP cases and $- $ 17.0 dBsm for LP mode of operation. Antenna performance in terms of its input matching, far-field parameters, monostatic RCS, and axial ratio are measured at its three polarization states, which are in agreement with simulated results.
TL;DR: A novel method is proposed to generate vector beams with arbitrary spatial variation of phase and linear polarization at the nanoscale using compact plasmonic metasurfaces with rectangular nanoapertures using completely compensating for the Berry phase.
Abstract: A novel method is proposed to generate vector beams with arbitrary spatial variation of phase and linear polarization at the nanoscale using compact plasmonic metasurfaces with rectangular nanoapertures. The physical mechanism underlying the simultaneous control of light polarization and phase is explained. Vector beams with different spiral phasefronts are obtained by manipulating the local orientation and geometric parameters of the metasurfaces. In addition, radially and azimuthally polarized vector beams and double-mode vector beams are achieved through completely compensating for the Berry phase, which provides additional degrees of freedom for beam manipulation.
TL;DR: In this paper, bound states in the radiation continuum (BSC) in a linear periodic array of dielectric spheres in air above the light cone were demonstrated. But the results were limited to the case where the radius of the spheres is bounded by a constant.
Abstract: We demonstrate bound states in the radiation continuum (BSC) in a linear periodic array of dielectric spheres in air above the light cone. We classify the BSCs by orbital angular momentum m = 0,±1,±2 according to the rotational symmetry of the array, Bloch wave vector ꞵ directed along the array according to the translational symmetry, and polarization. The most simple symmetry protectedBSCshavem = 0,ꞵ = 0 and occur in a wide range of the radius of the spheres and dielectric constant. More sophisticated BSCs with m 6= 0,ꞵ = 0 exist only for a selected radius of spheres at fixed dielectric constant. We also find robust Bloch BSCs with ꞵ 6= 0,m = 0. All BSCs reside within the first but below the other diffraction continua. We show that the BSCs can be easily detected by bright features in scattering of different plane waves by the array as dependent on type of the BSC. The symmetry protected TE/TMBSCs can be traced by collapsing Fano resonance in cross-sections of normally incident TE/TM plane waves. When plane wave with circular polarization with frequency tuned to the bound states with OAM illuminates the array the spin angular momentum of the incident wave transfers into the orbital angular momentum of the BSC.This ,inturn, gives rise to giant vortical power currents rotating around the array. Incident wave with linear polarization with frequency tuned to the Bloch bound state in the continuum induces giant laminar power currents. At last, the plane wave with linear polarization incident under tilt relative to the axis of array excites Poynting currents spiralling around the array. It is demonstrated numerically that quasi-bound leaky modes of the array can propagate both stationary waves and light pulses to a distance of 60 wavelengths at the frequencies close to the bound states in the radiation continuum. A semi-analytical estimate for decay rates of the guided waves is found to match the numerical data to a good accuracy.