Wave Polarization Research Articles

Excitation of Surface Waves With On-Demand Polarization at Self-Complementary Metasurface

Surface electromagnetic waves are the main carriers of the highly localized in-plane signal in planar antennas and photonic devices. However, the polarization degree of freedom is generally absent for surface waves as far as it is still a challenge to excite the surface waves with a necessary polarization state. In this letter, for the first time, we propose a method to excite the surface waves of arbitrary polarization using the self-complementary metasurfaces obeying Babinet's duality principle. Namely, we demonstrate the excitation of surface waves with i) linear horizontal and vertical, ii) linear diagonal, iii) right- and left-handed circular, and iv) elliptical polarizations covering, in principle, a whole Poincaré sphere of polarization states. Finally, we analyze the impact of substrate on the efficiency of polarization-demanded surface waves excitation. The results obtained may find the numerous applications in planar photonic and flat optical polarization devices.

Circular Polarization of the Astrophysical Gravitational Wave Background.

The circular polarization of gravitational waves is a powerful observable to test parity violation in gravity and to distinguish between the primordial or the astrophysical origin of the stochastic background. This property comes from the expected unpolarized nature of the homogeneous and isotropic astrophysical background, contrary to some specific cosmological sources that can produce a polarized background. However, in this work we show that there is also a non-negligible amount of circular polarization in the astrophysical background, generated by Poisson fluctuations in the number of unresolved sources, which is present in the third-generation interferometers with signal-to-noise ratio larger than 2. We also explain in which cases the gravitational wave maps can be cleaned from this extra source of noise, exploiting the frequency and the angular dependence, in order to search for signals from the early Universe. Future studies about the detection of polarized cosmological backgrounds with ground- and space-based interferometers should account for the presence of such a foreground contribution.

Effective electromagnetic wave properties of disordered stealthy hyperuniform layered media beyond the quasistatic regime

Disordered stealthy hyperuniform dielectric composites exhibit novel electromagnetic wave transport properties in two and three dimensions. Here, we carry out the first study of the electromagnetic properties of one-dimensional 1D) disordered stealthy hyperuniform layered media. From an exact nonlocal theory, we derive an approximation formula for the effective dynamic dielectric constant tensor ε e (k q ,ω) of general 1D media that is valid well beyond the quasistatic regime and apply it to 1D stealthy hyperuniform systems. We consider incident waves of transverse polarization, frequency ω, and wavenumber k q . Our formula for ε e (k q ,ω), which is given in terms of the spectral density, leads to a closed-form relation for the transmittance T. Our theoretical predictions are in excellent agreement with finite-difference time-domain (FDTD) simulations. Stealthy hyperuniform layered media have perfect transparency intervals up to a finite wavenumber, implying no Anderson localization, but non-stealthy hyperuniform media are not perfectly transparent. Our predictive theory provides a new path for the inverse design of the wave characteristics of disordered layered media, which are readily fabricated, by engineering their spectral densities.

A transparent zinc oxide based metamaterial for perfect absorption of long- wavelength and mid-wavelength infrared spectral bands

A high absorption capabilities in atmospheric transparency windows lies at mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) region is important for various applications, particularly, for passive thermal cooling and camouflage technology compatible with infrared (IR) lasers. In this paper, we proposed a simple and cost-effective design for a tri-layered metamaterial based on zinc oxide (ZnO) which exhibits almost perfect absorption in both the mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) regions with excellent transmission in the visible range. It consists of a metal-dielectric-metal sandwiched structure with a two-dimensional periodic pattern of gallium doped ZnO circular discs at the top, ZnO in the middle, and an aluminum doped ZnO at the bottom. The proposed metamaterial exhibits almost perfect absorption in both the LWIR (∼ 10 µm) and MWIR (∼ 5 µm) regions, while maintaining excellent transmission (∼ 75%) in the visible region. Further, it also exhibits a better angular (0–50°) insensitivity with respect to the incident angle and to the polarization (TE and TM) of electromagnetic wave. The proposed metamaterial has potential applications in thermal cooling/emission and infrared camouflage technology.

Surface Ferron Excitations in Ferroelectrics and Their Directional Routing

The duality between electric and magnetic dipoles inspires recent comparisons between ferronics and magnonics. Here we predict surface polarization waves or “ferrons” in ferroelectric insulators, taking the long-range dipolar interaction into account. We predict properties that are strikingly different from the magnetic counterpart, i.e. the surface Damon–Eshbach magnons in ferromagnets. The dipolar interaction pushes the ferron branch with locked circular polarization and momentum to the ionic plasma frequency. The low-frequency modes are on the other hand in-plane polarized normal to their wave vectors. The strong anisotropy of the lower branch renders directional emissions of electric polarization and chiral near fields when activated by a focused laser beam, allowing optical routing in ferroelectric devices.

Generations of cross-polarized focusing and vortex beam for terahertz wave based on graphene metasurfaces

As a novel material, graphene has been widely applied in the field of metasurface to dynamically control wavefront and polarization of electromagnetic wave in recent years. In this work, four graphene-based meta-atoms are designed for polarization manipulation. Using a hybrid structure of patterned graphene and patched metal, reflective phase of meta-atom can be tuned by Fermi level. When Fermi level is 0.01 eV, cross-polarized waves with phase difference of 90° are generated by meta-atoms with polarization conversion ratio 87% at 2 THz. As Fermi level is adjusted to 0.70 eV, phase difference between four meta-atoms is cancelled with the corresponding polarization conversion ratio only 5%. Then, four metasurfaces are designed for wavefront control and polarization manipulation, and they are focusing metalenses and vortex beam generators. Simulations indicate that the proposed metasurfaces are able to achieve the combination of wavefront control and polarization manipulation, greatly enhancing the ability to control electromagnetic wave. The proposed approach may be applied in the fields of terahertz focusing and communication.

Theoretical Study of Helicity Control of Circular Polarization Waves in Terahertz Region Based on Vanadium Dioxide Metamaterials

Theoretical Study of Helicity Control of Circular Polarization Waves in Terahertz Region Based on Vanadium Dioxide Metamaterials

Flexible Control of Phase and Polarization based on All‐Dielectric Metamaterials

AbstractA metasurface is a planar structure that can flexibly control the polarization, phase, and amplitude of incident electromagnetic waves. An all‐dielectric hexagonal cell structure to reduce the interaction between cells and achieve efficient parametric regulation of electromagnetic waves is proposed. The single resonant transmission phase and the geometric phase are superimposed to realize the composite phase unit structure and construct a multifunctional flat metasurface device. The designed metasurface can flexibly tune the phase and polarization of incident electromagnetic waves and enable multifunctional integration phenomena, such as polarization separation, light intensity convergence, and vector light generation, on a single metasurface.

Angle-Selective Photodetection in Ge/Si Quantum Dot Photodiodes Enhanced by Microstructured Hole Arrays

We report on the near-infrared (NIR) photoresponse of a micropatterned Ge/Si quantum dot (QD) pin photodiode at different angles of radiation incidence. The photon-trapping hole array was etched through the n+-type top contact layer to reach the buried QDs. The normal-incidence responsivity was observed to be resonantly increased at wavelengths of 1.4, 1.7, and 1.9 μm by factors of 40, 33, and 30, respectively, compared with the reference detector without holes. As the incident angle θ increases, the resonance peaks are disappeared and at θ>40∘ a new resonance with a 25× enhancement arises at a wavelength of 1.8 μm. Simulation of the near-field intensity, Poynting vector distribution and wave polarization showed that at small θ, the strong electric field is primarily localized under the air holes (1.4 μm, TM mode) or between the holes (1.7 and 1.9 μm, TE modes) inside the region occupied by QDs, resulting in the strong NIR photocurrent. At large θ, the dominant resonance detected at 1.8 μm is the result of coupling between the TE and TM modes and formation of a mixed near-field state.

Characterization of Environmental Seismic Signals in a Post‐Wildfire Environment: Examples From the Museum Fire, AZ

AbstractThe 2019 Museum Fire burned in a mountainous region near the city of Flagstaff, AZ, USA. Due to the high risk of post‐fire debris flows and flooding entering the city, we deployed a network of seismometers within the burn area and downstream drainages to examine the efficacy of seismic monitoring for post‐fire flows. Seismic instruments were deployed during the 2019, 2020, and 2021 monsoon seasons following the fire and recorded several debris flow and flood events, as well as signals associated with rainfall, lightning and wind. Signal power, frequency content, and wave polarization were measured for multiple events and compared to rain gauge records and images recorded by cameras installed in the study area. We use these data to test the efficacy of seismic recordings to (a) detect and differentiate between different energy sources, (b) estimate the timing of lightning strikes, (c) calculate rainfall intensities, and (d) determine debris flow timing, size, velocity, and location. We then calculate forward models of seismic signals associated with debris flows and rainfall to better interpret our results and characterize these events. Our observations and modeling show that we can differentiate between these sources and that seismic data can provide insight into post‐fire debris flow characteristics, including relative particle sizes and velocity.

Numerical study of a near-infrared to mid-infrared perfect absorber based on tunable GaAs metamaterial

An infrared perfect absorber structure is designed based on GaAs/Au/SiO2 metamaterial with numerical simulation, in which gold split ring resonators (SRR) embedded in the GaAs layer. The absorption exceeds 99% at 1360 nm under the plane wave excitation with its polarization perpendicular to the opening direction of the SRR. When the polarization of the plane wave is parallel to the opening direction, the absorption exceeds 97% and 56% at 970 and 2070 nm, respectively, which realize dual-band absorption. The absorption peaks are effectively modulated by controlling surface current density distribution and resonant electromagnetic response. In addition, the resonant wavelengths are further manipulated by optimizing the resonant ring structural parameters, which achieve ultrawide-band absorption ranging from near-infrared to mid-infrared region. The absorber remains absorption peaks above 96% under wide-angle plane wave incidence, and the resonant peak positions are independent of the incident angle. This work exhibits the promise of GaAs-based metamaterial in practical applications in energy harvesting and night vision imaging.

A Wideband, 1-bit, Electronically Reconfigurable Phase Shifter for High-Power Microwave Phased-Array Applications

We present the design and high-power experimental characterization of a wideband, high-power-capable, electronically reconfigurable phase shifter for high-power phased-array applications. The device studied in this work offers an electronically switchable, 1-bit phase shift using the concept of polarization rotation (PR). The PR-based phase shifter is designed to work in a custom-designed, double-ridge (DR) waveguide environment. Two p-i-n diodes are used to control the transmission phase of the signal by rotating the polarization of the incident wave by either <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+90^\circ$</tex-math> </inline-formula> or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-90^\circ$</tex-math> </inline-formula> with respect to that of the incident wave, thereby creating a wideband, 1-bit phase shift between the two states. Simulation results demonstrated that this element can work over one octave bandwidth ranging from 6 to 12 GHz. A prototype of the device was fabricated and experimentally characterized at low and high power levels. The measurement results confirmed the simulations and demonstrated the wideband, high-power-density capability of the device. High-power continuous-wave (CW) experiments were conducted across the entire 6–12 GHz band and demonstrated that the unit-cell-averaged, CW power handling capability of the device exceeds 23.6 W/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> . High-power pulsed power experiments conducted at 9.382 GHz demonstrated that the unit-cell-averaged, peak power handling capability of the device exceeds 347 W/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> for short-duration pulses.

Wideband 3-D-Printed Transmit-Reflect-Array Antenna With Independent Beam Control

This paper proposes a wideband 3D-printed transmit-reflect-array (TRA) antenna. The transmission and reflection functions of this TRA antenna are determined by the polarization of the incident electromagnetic wave. The proposed TRA element is composed of a dielectric post and three copper wires, which can be realized by the low-cost 3D printing. Attributed to the independent control of transmission and reflection phase shift of the proposed element within a wide bandwidth, the proposed TRA antenna can generate two independent transmission and reflection beams over a wide bandwidth. A 12 × 12 TRA is designed, fabricated, and measured to verify the design concept. The measured results show that a peak gain of 24.4 dBi with a bandwidth of 46.8% (18–29 GHz) for the transmitarray function and a peak gain of 22.9 dBi with a bandwidth of 52.2% (17–29 GHz) for the reflectarray function are achieved simultaneously by the 3D-printed TRA antenna. The wide bandwidth, high gain, independent beam control capability, combined transmit/reflectarray functions and low fabrication cost make the proposed antenna appealing for various wireless applications.

Prompt Appearance of Large‐Amplitude EMIC Waves Induced by Solar Wind Dynamic Pressure Enhancement and the Subsequent Relativistic Electron Precipitation

AbstractElectromagnetic ion cyclotron (EMIC) waves play an important role in relativistic electron dynamics. In this study, we find a large‐amplitude EMIC wave event induced by the prompt enhancement of solar wind dynamic pressure on 6 November 2015. These large‐amplitude EMIC waves are simultaneously observed by multiple satellites over 13 hr in magnetic local time (MLT) with a peak amplitude of ∼4 nT. Satellites at different locations observed different bands of EMIC waves, implying the importance of background plasma density in EMIC wave generation. Electron pitch angle distributions show obvious responses to EMIC wave activities. During EMIC wave appearance, the fluxes of relativistic electrons with pitch angles around 90° increase, while the fluxes of field‐aligned relativistic electrons decrease, showing distinct “bite‐out” signatures, indicating pitch angle scattering by EMIC waves, and the scattering efficiency depends on the amplitude and polarization of EMIC waves. Combined with phase space density profiles of electrons that are nearly constant at energies below the minimum resonant energy of electrons (Emin) but show dropout at energies above the Emin after EMIC wave activities, we conclude that large‐amplitude EMIC waves can cause rapid electron loss down to several hundred keV. In addition, simultaneous observations of hundreds of keV electron precipitation and tens of keV proton precipitation by Polar Operational Environmental Satellites near the region where EMIC waves are observed, provide direct evidence of relativistic electron precipitation caused by the large‐amplitude EMIC waves, ultimately driven by solar wind structures.

Nondiffracting beam length adjustment by using 3-bit coding metasurfaces

In this paper, a nondiffracting beamforming scheme employing 3-bit coding metasurfaces to adjust the beam lengths is proposed. The 3-bit coding is implemented with a four-layer phase control unit whose phase can be adjusted by tuning the side length of the metal square. Simulation and measured results show that the electric field distributions generated by the metasurface is independent of the polarization of the incident wave due to the central symmetry of the structure. Experimental results are provided which verifies the feasibility of the proposed scheme in adjusting the nondiffracting beam lengths. A relative error as small as 6.0% in the beam lengths is observed, and all results prove the proposed 3-bit coding metasurfaces can be applied to generate different nondiffracting beam lengths.

Спектральные характеристики плазменных волн ионосферы при возбуждении мощными КВ-радиоволнами на частотах излучения вблизи гирогармоник электронов и критической частоты слоя F2

We present the result of the studies into characteristics of high-latitude ionospheric F-region longitudinal plasma waves (Langmuir and ion-acoustic), caused by the impact of powerful HF radio waves of ordinary (O-mode) or extraordinary (X-mode) polarization of the EISCAT/Heating facility, Tromsø, Norway. The powerful HF radio waves on October 20, 2012 and February 26, 2013 were emitted in the direction of the magnetic zenith with a step change in the effective radiation power (ERP). The radiation frequency fH of the EISCAT/Heating facility on February 26, 2013 was close to the F2-layer critical frequency foF2 (fH/foF2~1) and exceeded the electron gyroresonance frequency fH&gt;5fce. On October 20, 2012, the conditions fH/foF2~0.85–0.95 and fH&lt;6fce were fulfilled. Analysis of EISCAT measurements of an incoherent scatter radar (ISR) at a frequency of 930 MHz, spatially aligned with the heating facility for radiation conditions ERP&lt;200 MW, has shown that parametric decay instabilities are excited at the ionospheric heights where the pump frequency is close to the plasma Langmuir frequency, fH≈fPL. We have studied peculiarities of excitation of the decay parametric instabilities as a function of height in the ionosphere and pump wave polarization, the ratios between fH and foF2, and also fH and nfce.

Cosmic ray fluctuations and MHD waves in the solar wind

During large-scale solar wind disturbances, variations in galactic cosmic rays with periods from several minutes to 2–3 hours, which are called cosmic ray fluctuations in the scientific literature, often occur. Such fluctuations are not observed in the absence of disturbances. Since cosmic rays are charged particles, their modulation in the heliosphere occurs mainly under the influence of the interplanetary magnetic field, or rather its turbulent part — MHD waves. In order to adequately describe the relationship between their fluctuation spectra, it is necessary to be able to isolate a certain type of MHD waves from direct measurements of the interplanetary medium parameters. In this paper, we consider some methods for determining the contribution of three solar wind MHD turbulence branches, namely, Alfvén, fast, and slow magnetosonic waves corresponding to the turbulence spectrum inertial region frequencies 10⁻⁴&lt;ν&lt;10⁻¹ Hz, at which cosmic ray fluctuations are observed, to the observed power spectra of interplanetary magnetic field modulus fluctuations. To do this, we apply the methods of spectral and polarization analysis. In the absence of measurement data on SW parameters, to identify the type of MHD turbulence we use the known wave polarization properties that Alfvén and magnetosonic waves are polarized in different planes relative to the plane containing the average IMF vector and wave vector.&#x0D; Our results show that with the correct determination of the spectra of three MHD wave types, their sum, within the limits of errors, agrees well with the observed spectra of the interplanetary magnetic field modulus, and a small difference can be attributed to static inhomogeneities and oscillations frozen into plasma, as well as to various discontinuities that are always inevitably present in the solar wind.

Флуктуации космических лучей и МГД-волны в солнечном ветре

During large-scale solar wind disturbances, variations in galactic cosmic rays with periods from several minutes to 2–3 hours, which are called cosmic ray fluctuations in the scientific literature, often occur. Such fluctuations are not observed in the absence of disturbances. Since cosmic rays are charged particles, their modulation in the heliosphere occurs mainly under the influence of the interplanetary magnetic field, or rather its turbulent part — MHD waves. In order to adequately describe the relationship between their fluctuation spectra, it is necessary to be able to isolate a certain type of MHD waves from direct measurements of the interplanetary medium parameters. In this paper, we consider some methods for determining the contribution of three solar wind MHD turbulence branches, namely, Alfvén, fast, and slow magnetosonic waves corresponding to the turbulence spectrum inertial region frequencies 10⁻⁴&lt;ν&lt;10⁻¹ Hz, at which cosmic ray fluctuations are observed, to the observed power spectra of interplanetary magnetic field modulus fluctuations. To do this, we apply the methods of spectral and polarization analysis. In the absence of measurement data on SW parameters, to identify the type of MHD turbulence we use the known wave polarization properties that Alfvén and magnetosonic waves are polarized in different planes relative to the plane containing the average IMF vector and wave vector. &#x0D; Our results show that with the correct determination of the spectra of three MHD wave types, their sum, within the limits of errors, agrees well with the observed spectra of the interplanetary magnetic field modulus, and a small difference can be attributed to static inhomogeneities and oscillations frozen into plasma, as well as to various discontinuities that are always inevitably present in the solar wind.

Spectral features of ionospheric plasma waves excited by powerful HF radio waves radiated at frequencies near electron gyroharmonics and F2-layer critical frequency

We present the result of the studies into characteristics of high-latitude ionospheric F-region longitudinal plasma waves (Langmuir and ion-acoustic), caused by the impact of powerful HF radio waves of ordinary (O-mode) or extraordinary (X-mode) polarization of the EISCAT/Heating facility, Tromsø, Norway. The powerful HF radio waves on October 20, 2012 and February 26, 2013 were emitted in the direction of the magnetic zenith with a step change in the effective radiation power (ERP). The radiation frequency fH of the EISCAT/Heating facility on February 26, 2013 was close to the F2-layer critical frequency foF2 (fH/foF2~1) and exceeded the electron gyroresonance frequency fH&gt;5fce. On October 20, 2012, the conditions fH/foF2~0.85–0.95 and fH&lt;6fce were fulfilled. Analysis of EISCAT measurements of an incoherent scatter radar (ISR) at a frequency of 930 MHz, spatially aligned with the heating facility for radiation conditions ERP&lt;200 MW, has shown that parametric decay instabilities are excited at the ionospheric heights where the pump frequency is close to the plasma Langmuir frequency, fH≈fPL. We have studied peculiarities of excitation of the decay parametric instabilities as a function of height in the ionosphere and pump wave polarization, the ratios between fH and foF2, and also fH and nfce.

A single-layer efficient polarization-insensitive electromagnetic rectifying metasurface for wireless power transfer

In this paper, an efficient electromagnetic rectifying metasurface (ERM) is proposed for wireless power transfer. The unit cell for the proposed ERM is composed of a cross-shaped energy capture structure that can absorb the electromagnetic power from the free space. The capture efficiency of the centrally symmetric structure exhibits insensitivity to the polarization of the incident wave. By directly connecting the Schottky diode to the ERM unit cell, the received electromagnetic power can be converted to DC power. The merit of the proposed ERM design is that no extra matching circuit is required, which can reduce the size, complexity, and insertion loss. To demonstrate the concept, a prototype of a 4 × 4-element ERM was fabricated and measured. The experimental results show that the proposed ERM array can produce up to 166 mW output DC power with an efficiency of 71.1% at an incident power density of 1050 μW/cm2. The polarization stability of the ERM is also verified by measurement with less than 10% efficiency reduction for different polarizations of the incident wave.