Linear Polarization States Research Articles

Broadband Efficient Dual‐Polarization Airy Beam Generation with Reflective Metasurface

This study demonstrates that continuous amplitude and binary phase modulation suitable for Airy beam encoding can be frequency‐independently obtained with not only cross‐polarized but also copolarized transmitted/reflected electromagnetic field components by rotation of unit cell with reflection symmetry. Maximum device efficiency can be achieved with relevant Airy beam generator, when the eigen polarization states of the unit cell are two orthogonal linear polarization states, and the copolarization reflections of them are out of phase and both have the amplitude of unity. As a proof of principle, broadband and high‐efficiency reflective Airy beam generators based on both copolarization and cross‐polarization modulation approaches are fabricated with cut‐wire structure as unit cell. The measured results show that the efficiency of the devices is approaching the theoretical limit in a wide frequency range.

Multipolarization-Reconfigurable Air-Filled Substrate Integrated Waveguide Cavity-Backed Slot Antenna

A novel single-feed ultrawideband cavity-backed slotantenna with a reconfigurable polarization capability is demon-strated in substrate-independent air-filled substrate integratedwaveguide (AFSIW) technology for Internet-of-Things applica-tions in the [5.15-5.85] GHz frequency band of the unlicensednational information infrastructure. The antenna achieves an ul-trawide impedance bandwidth by exploiting a double ring of slotsand supports four switchable linear polarization states (±45°,0°,+45°,and 90°) by leveraging four quartets of p-i-n diodes. Byelectrically shorting the slots at well-defined positions by these p-i-ndiodes, dynamic polarization reconfiguration is achieved by switch-ing their dc bias current, supplied at the antenna feed through anexternal bias tee and routed from the antenna's back to front cavityplane via the AFSIW sidewalls. This new simple, yet effective, biasnetwork enables the integration of all polarization control electron-ics inside the antenna cavity to protect them from environmentaleffects. Finally, measurements prove that the prototype exhibits anoverlapping impedance bandwidth of 29%, from 4.85 to 6.45 GHz,and a stable conically shaped radiation pattern across the operating band width with a 3 dB beamwidth of 45°and a peak gain of 6.5 dBi for all four states.

Quad-Polarization-Reconfigurable Antenna With a Compact and Switchable Feed

A reconfigurable antenna with a compact size and quad-polarization reconfigurability is presented. By employing a switchable feed scheme, the antenna can operate at single-fed and dual-fed modes. At single-fed mode, the feed structure allows output ports switching to produce the excitations for either slant +45° or -45° linear polarization (LP). At dual-fed mode, it serves as a switchable phase-shifting power splitter for generating left-hand circular polarization (LHCP) or right-hand circular polarization (RHCP). To realize a simple and space-saving configuration, the antenna makes efficient use of the proposed feed structure, which is highly shared among the four polarization states. Measured results show that the antenna exhibits operating bandwidths of 230 and 260 MHz at circular polarization CP and LP states, respectively. Moreover, stable broadside radiation patterns as well as moderate gains could also be obtained.

Generation of vector beams of Bell-like states by manipulating vector vortex modes with plasmonic metasurfaces

Metasurfaces with orthogonal nano-slit pairs arranged on spirals are proposed to generate vector beams (VBs) of Bell-like states and slanted polarizations. The design of the metasurfaces is based on the theoretically derived parameter condition for manipulation of the two vector vortex modes, which is satisfied by matching the three parameters of rotation order m , the spiral order n , and incident polarization helicity σ . The linear polarization states of the VBs are controlled by the initial orientation angle φ 0 of slit pairs. VBs of satisfying quality are experimentally obtained, with the analytical and simulated results validated.

Polarized observations for advanced atmosphere-ocean algorithms using airborne multi-spectral hyper-angular polarimetric imager

Airborne measurements of the linear polarization state of light were carried out over coastal and open ocean conditions to study aerosol and water column properties and investigate the possibility of using a multi-spectral, hyper-angular imaging polarimeter for retrieving aerosol and hydrosol optical properties. The instrument, the Versatile Imager for the Coastal Ocean (VICO), is used to support the analysis of ocean color polarized observations and their implication for future space-borne polarimetry such as the polarimeters planned to be deployed with the NASA Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) mission. Several sets of images at different viewing angles from the visible to the near-infrared spectrum were collected and compared with simulations using a vector radiative transfer (VRT) code. The simulations were obtained based on measured seawater inherent optical properties from shipborne instruments and measured atmospheric parameters from the Aerosol Robotic Network (AERONET) and a shipborne sunphotometer at different locations. An uncertainty method has been derived by propagating uncertainties from the measured polarized radiances. The method demonstrates practicable uncertainty formulations that can be used to construct a measurement uncertainty budget for the polarized data products. Results from VICO and the VRT simulation are consistent for both radiance and polarization spectrum at all the measured viewing angles. The total and polarized water-leaving reflectances are retrieved at four bands and varied geometries. It is also shown that the polarized remote sensing reflectance measured at various angles could be used to distinguish between the aerosols’ and hydrosols’ optical signatures by exploiting the fact that the polarized reflectance is fairly insensitive to hydrosols for given acquisition geometries. This study thus provides an opportunity to investigate various relationships between the microphysical properties of the oceanic and atmospheric particulates such as refractive index and particle size properties. It also contributes to the development of polarization-based inverse ocean color algorithms. Finally, the provided analysis gives insights for the validation of the ocean color parameters that will be retrieved from the forthcoming polarimetric satellite missions.

A method for improving information capacity of a signal with variant polarization effects for communication systems in the optical and radio bands

Promising communication systems are developing in the direction of complicating the configuration of networks, expanding the spectrum of signals, and integrating terrestrial, satellite, fiber, and open optical technologies. However, the use of information signal modulation methods remains traditional, which are based on changing parameters in the time domain, such as amplitude, frequency, and phase. Spatial signal modulation techniques have not been effectively used in wireless communication systems. Broader proposals find only polarization-based methods for increasing the multiplexing factor and in binary information transmission systems where two states of linear polarization with a shift of π/2 are used. Polarizing complex signal processing technologies, converting radio signals into optical domains, are promising methods for increasing the spectral efficiency as well as reducing the influence of the atmosphere. The use of complex schemes for modulating the polarization state becomes possible due to the development of polarization-sensitive quantum materials sensitive to light helicity. The paper analyzes the theoretical validity of the effectiveness of spatial modulation parameters to increase the information capacity of signals. The ways of increasing the information capacity of signals, the fundamental schemes of fiber-ether transmission in the optical and radio bands, including in the millimeter band, using polarization effects for spatial modulation of information signals, are analyzed. Schematic diagrams for the formation of radio-frequency pulses in the optical range with spatial modulation using polarization effects are proposed. Similar schemes using wireless sections of the network in the optical and highfrequency radio bands, and fiber lines can be used both in small scale terrestrial networks and in global coverage.

A Multi-Functional Reconfigurable Metasurface: Electromagnetic Design Accounting for Fabrication Aspects

In this paper we present the theoretical considerations and the design evolution of a proof-of-concept reconfigurable metasurface, primarily used as a tunable microwave absorber, but also as a wavefront manipulation and polarization conversion device in reflection. We outline the design evolution and all considerations taken into account, from the selection of patch shape, unit cell size, and substrate, to the topology of the structure that realizes the desired tunability. The presented design conforms to fabrication restrictions and is co-designed to work with an integrated circuit chip for providing tunable complex loads to the metasurface, using a commercially available semiconductor process. The proposed structure can perform multiple tunable functionalities by appropriately biasing the integrated circuit: Perfect absorption for a wide range of incidence angles of both linear polarization states, accommodating a spectral range in the vicinity of 5 GHz, with potential also for wavefront control, exemplified via anomalous reflection and polarization conversion. The end vision is for such a design to be scalable and deployable as a practical HyperSurface, i.e., an intelligent multi-functional metasurface capable of concurrent reconfigurable functionalities: absorption, beam steering, polarization conversion, wavefront shaping, holography, and sensing.

A Parasitic Antenna with Independent Pattern, Beamwidth and Polarization Reconfigurability

In this paper, a reconfigurable antenna design is proposed to realize independent pattern, beamwidth and polarization reconfiguration at an operating frequency of 2.45 GHz. This antenna is comprised of a dual coaxial-feed driven element surrounded by four varactor loaded size-tunable parasitic elements. The pattern and beamwidth reconfiguration is achieved by utilizing the mutual coupling between the active and size-tunable parasitic elements. Reconfigurable feeding network is designed and developed to produce two orthogonal linear polarization (LVP, LHP) and circular polarization (LHCP, RHCP) states. In linear polarization operating mode, main beam of the antenna is continuously scanned from $$\theta$$ = 0 $$^{\circ }$$ to 11 $$^{\circ }$$ , 0 $$^{\circ }$$ to 32 $$^{\circ }$$ , and 0 $$^{\circ }$$ to 40 $$^{\circ }$$ in $$\phi$$ = ±0 $$^{\circ }$$ , ± 45 $$^{\circ }$$ , and ± 90 $$^{\circ }$$ plane respectively, where $$\theta$$ and $$\phi$$ are the beam direction in the elevation and azimuth planes respectively. In circular polarization operating mode, the radiated beam is continuously scanned from 0 $$^{\circ }$$ to 30 $$^{\circ }$$ in $$\phi$$ = ± 0 $$^{\circ }$$ , ± 45 $$^{\circ }$$ and ± 90 $$^{\circ }$$ plane respectively with axial ratio less than 3 dB in all the beam scanning directions. In addition to this, 3-dB beamwidth is continuously tuned in the E-plane, H-plane, and both E-plane and H-plane with LVP and LHP operating mode from 66 $$^{\circ }$$ to 152 $$^{\circ }$$ , 60 $$^{\circ }$$ to 108 $$^{\circ }$$ , and 78 $$^{\circ }$$ to 120 $$^{\circ }$$ respectively.

An Adaptive Direction-Dependent Polarization State Configuration Method for High Isolation in Polarimetric Phased Array Radar

High cross-polarization isolation (CPI) is crucial to the accurate polarization measurement using polarimetric phased array radar (PPAR). In this article, we propose an adaptive direction-dependent polarization state configuration ( AD <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> PSC) method to improve the polarization isolation. Compared with the conventional fixed polarization state of radiated wave whether it is linear, circular, or elliptical polarization state, our AD <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> PSC approach configures the polarization state on basis of beam steering. To achieve the adaptive configuration of magnitude and phase of the dual-polarization antenna, an improved steepest descent algorithm is put forward. To facilitate the uniform representation for the polarization measurement application of PPAR, the universal expressions of intrinsic and measured backscatter matrices are derived for arbitrary polarization state. The dual-polarization dipole array is used to assess the priority of our proposed method. Compared with the conventional approaches, our approach could obtain higher CPI while being available for a larger scanning range. The configured CPI meets the specific polarization requirement for PPAR.

Polarization-selective modulation of supercavity resonances originating from bound states in the continuum

Bound states in the continuum (BICs) are widely studied for their ability to confine light, produce sharp resonances for sensing applications and serve as avenues for lasing action with topological characteristics. Primarily, the formation of BICs in periodic photonic band gap structures are driven by symmetry incompatibility; structural manipulation or variation of incidence angle from incoming light. In this work, we report two modalities for driving the formation of BICs in terahertz metasurfaces. At normal incidence, we experimentally confirm polarization driven symmetry-protected BICs by the variation of the linear polarization state of light. In addition, we demonstrate through strong coupling of two radiative modes the formation of capacitively-driven Freidrich-Wintgen BICs, exotic modes which occur in off-Γ points not accessible by symmetry-protected BICs. The capacitance-mediated strong coupling at 0° polarization is verified to have a normalized coupling strength ratio of 4.17% obtained by the Jaynes-Cummings model. Furthermore, when the polarization angle is varied from 0° to 90° (0° ≤ ϕ < 90°), the Freidrich-Wintgen BIC is modulated until it is completely switched off at 90°.

A highly sensitive imaging polarimeter in the x-ray regime

We report on the development of a highly sensitive imaging polarimeter that allows for the investigation of polarization changing properties of materials in the x-ray regime. By combining a microfocus rotating anode, collimating multilayer mirrors, and two germanium polarizer crystals, we achieved a polarization purity of the two orthogonal linear polarization states of 8 × 10−8. This enables the detection of an ellipticity on the same order or a rotation of the polarization plane of 6 arcsec. The high sensitivity combined with the imaging techniques allows us to study the microcrystalline structure of materials. As an example, we investigated beryllium sheets of different grades, which are commonly used for fabricating x-ray lenses, with a spatial resolution of 200 μm, and observed a strong degradation of the polarization purity due to the polycrystalline nature of beryllium. This makes x-ray lenses made of beryllium unsuitable for imaging polarimeter with higher spatial resolution. The results are important for the development of x-ray optical instruments that combine high spatial resolution and high sensitivity to polarization.

A Frequency- and Polarization-Reconfigurable Slot Antenna Using Liquid Metal

In this communication, a microfluidically frequency- and polarization-reconfigurable slot antenna using liquid metal (LM) is proposed. The polydimethylsiloxane (PDMS) structure with narrow-banded microchannels is loaded on the printed circuit board (PCB) of a square slot antenna, providing condition for reconfiguration. The left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP) are achieved by injecting LM into +45° and -45° channels with respect to the x-axis or keeping the channels empty. Three operating frequency bands of LHCP and RHCP states can be realized by filling the microchannels with different lengths. Both states have an overall tuning 3 dB axial ratio bandwidth (ARBW) of 26.42% (2.3-3 GHz). In LP state, the proposed antenna realizes a -10 dB impedance bandwidth of 11.6% (2.03-2.28 GHz). A prototype of the proposed antenna has been fabricated and measured. Good agreement between the simulated and measured results validates the feasibility of this technique.

Coherent combination of two intracavity eigenmodes producing linearly polarized emission in an isotropic laser.

The behavior of directly linearly polarized emission was investigated in an isotropic Nd:YAG laser with a weakly anisotropic Fabry-Perot cavity. In order to explore the polarization mechanism, the intracavity eigenmodes were analyzed theoretically. A theoretical model was developed and shown to be suitable for describing the orientation-dependent beam profiles of the polarizer-specific features observed in experiments. This model indicates that the linear polarization emission results from the coherently combined state of intracavity eigenmodes as opposed to an intrinsic polarization state. The coherent combination is attributed to the frequency degeneracy and spontaneous phase locking of polarized eigenmodes. For the first time, the polarization coupling mechanism based on the coherent combination of eigenmodes in an isotropic solid-state laser was demonstrated. Moreover, this study also contributes an effective method to judge different types of linear polarization states.

Plasmon-Assisted Direction- and Polarization-Sensitive Organic Thin-Film Detector.

Utilizing Bragg surface plasmon polaritons (SPPs) on metal nanostructures for the use in optical devices has been intensively investigated in recent years. Here, we demonstrate the integration of nanostructured metal electrodes into an ITO-free thin film bulk heterojunction organic solar cell, by direct fabrication on a nanoimprinted substrate. The nanostructured device shows interesting optical and electrical behavior, depending on angle and polarization of incidence and the side of excitation. Remarkably, for incidence through the top electrode, a dependency on linear polarization and angle of incidence can be observed. We show that these peculiar characteristics can be attributed to the excitation of dispersive and non-dispersive Bragg SPPs on the metal–dielectric interface on the top electrode and compare it with incidence through the bottom electrode. Furthermore, the optical and electrical response can be controlled by the organic photoactive material, the nanostructures, the materials used for the electrodes and the epoxy encapsulation. Our device can be used as a detector, which generates a direct electrical readout and therefore enables the measuring of the angle of incidence of up to 60° or the linear polarization state of light, in a spectral region, which is determined by the active material. Our results could furthermore lead to novel organic Bragg SPP-based sensor for a number of applications.

Geometry phase for generating multiple focal points with different polarization states

Conventional lenses are always large and bulky to achieve desired wave-manipulating functions, hindering the development of integrated and miniaturized optical systems. Metasurfaces, two-dimensional counterparts of metamaterials, can accurately tailor the wavefront of electromagnetic waves at subwavelength scale, providing a flexible platform for designing ultra-compact and ultra-flat lenses, namely as metalenses. However, the previous geometry-phase-based metalenses usually generate focal point(s) with only one special polarization state, i.e., either linearly-polarized (LP) state or circularly-polarized (CP) state, which inevitably degrades further applications. Here, we propose and experimentally demonstrate an approach for designing terahertz (THz) metalenses based on geometry phase that can generate multiple focal points with different polarization states. Under the illumination of LP THz waves, three focal points with left-hand CP (LCP), right-hand CP (RCP) and LP states are observed. Furthermore, the position of each focal point can be flexibly manipulated in free space. Geometry metasurfaces consisting of micro-rods with the same shape but different in-plane orientations are fabricated to demonstrate these properties. This unique approach may enable an unprecedented capability in designing multifunctional THz devices with potential applications in imaging, detecting and communications.

Performances of Polarization-Retrieve Imaging in Stratified Dispersion Media

We constructed an active imaging model within 10 km of the atmosphere from the satellite to the ground based on Monte Carlo (MC) algorithm, and, because of the inhomogeneous distributions of the scattering particles in atmosphere environment, 10 km atmosphere layer was divided into ten layers in our model. The MC algorithm was used to simulate the transmission process of photons through the atmosphere. By launching lasers of linear polarization states from satellites to ground, the intensity, degree of polarization (DoP), polarization difference (PD), and polarization retrieve (PR) images can be obtained. The contrast of the image, peak signal to noise ratio (PSNR), and structural similarity index (SSI) were used to evaluate the imaging quality. The simulated results demonstrate that the contrast of images is degraded as the atmosphere becomes worse. However, PR imaging have a better contrast and better visibility in different atmospheric conditions. Meanwhile, we found that Mueller matrix (MM) can retrieve the original images very well in a certain range of atmospheric conditions. Finally, the simulation also shows that different wavelengths of light sources have different penetration characteristics, and, in general, infrared light shows better performances than visible light for imaging.

Polarization-Reconfigurable Yagi-Configured Electrically Small Antenna

An electrically small, high-directivity, Yagi-configured, near-field resonant parasitic (NFRP) antenna with four reconfigurable polarization states is presented. The antenna is composed of two NFRP elements and a customized, electrically controlled, reconfigurable driven element. The elements are stacked vertically in a Yagi configuration. The upper NFRP element acts as the director, and the lower one acts as the reflector. Both elements have a cross-shaped Egyptian axe dipole form. By integrating four p-i-n (PIN) diodes into its coax-fed asymmetric driven element, four polarization states, i.e., two orthogonal linear polarization (LP) and two circular polarization (LHCP and RHCP), are enabled which are controlled with the ON/OFF-states of the PIN diodes. The measured and simulated results of this electrically small (ka = 0.7) sized polarization-reconfigurable system are in good agreement. This simple, Yagi-configured antenna exhibits stable radiation performance in all four of its polarization states. The measured results demonstrate that, in its x (y)-LP state, the peak realized gain, front-to-back ratio, and radiation efficiency values are, respectively, ~3.08 (3.2) dBi, ~11.0 (11.05) dB, and ~77% (73%), and that, in its LHCP (RHCP) state, they are, respectively, ~3.0 (3.1) dBi, ~12.1 (11.18) dB, and ~72% (70%).

Design and Fabrication of Contour Shape Microstrip Patch Antenna for Biomedical Application

This paper presents the design of a contour shape reconfigurable microstrip patch antenna. The reconfigurable microstrip patch antenna is one of the excellent candidates for portable wireless device very simple because of its low profile, light weight and low cost. However, the requirement of frequency bandwidth is becoming greater in present wireless communication system. It is presenting for biomedical application band which covering from 8GHZ to 12GHZ frequency range. This microstrip patch antenna is capable of operating on both linear and circular polarization. This type of patch antenna fabricated on FR4 substrate and also fed by feed line is same substrate. By controlling the bias voltage of four PIN diodes, the polarization of antenna can be switched between four states two state of linear polarization for (vertical and horizontal) and two states for circular polarization for (RHCP & LHCP). There are several steps to design this antenna including determine the antenna specific characteristics antenna simulation construction and analysis. The explanation detail for design procedure simulation results, methods and techniques are discussed in this paper

Deterministic aperiodic photonic crystal with a 2D array of metallic nanoparticles as polarization-sensitive dichroic filter

We demonstrate the possibility of using a two-dimensional array of spheroidal metallic nanoparticles embedded in a one-dimensional photonic crystal to obtain a narrow-bandpass, polarization-sensitive dichroic filter operating in the near-UV and visible domains. The optical anisotropy of the array of identically oriented nanoparticles results in two spectrally distinct plasmon resonances independently excited for two mutually orthogonal linear polarization states of light, which ensures polarization and spectral selectivity of the composite structure. The narrow transmission bands of the filter are defect modes due to a layer located at the center of the structure and hosting the nanoparticle array. In order to suppress these transmission windows, it is essential that the defect modes closely coincide with the plasmon resonances excited in the array. We show that the use of deterministic aperiodic distributed reflectors surrounding the defect layer makes it possible to adjust the spectral positions of two defect modes in two separate bandgaps in order to achieve such a coincidence. Among the various parameters governing the precise position of transmittivity windows of the filter, we establish the strong influence of the thickness of the defect layer. We also show that a strong localization of the optical field in the plane of the nanoparticle array is essential to enhance the efficiency of plasmonic excitation and obtain the desired control of the defect modes. Our study opens up possibilities for the further development of polarization-controlled nanophotonic devices.

Theory of grating-coupled excitation of Dyakonov surface waves

Excitation of Dyakonov surface waves guided by a plane wave incident on a columnar thin film (CTF) deposited on a surface-relief grating decorating a dielectric substrate was studied using the rigorous coupled-wave approach, when the grating plane, the plane of incidence, and the morphologically significant plane of the CTF are all different. The absorptance for a specific linear polarization state of the incident plane wave was plotted as a function of the polar angle of incidence, at a fixed azimuthal angle, and those absorptance peaks were identified that are independent of the thicknesses of the CTF and the dielectric substrate. The angular locations of these absorptance peaks were correlated with the solution of the canonical boundary-value problem for surface-wave propagation. Dyakonov surface waves can be excited in a wider range of directions in the interface plane by p-polarized illumination than by s-polarized illumination. When the incidence and the grating planes do not coincide, it is possible to excite Dyakonov surfaces for multiple values of the polar angle of incidence.