Transverse Polarization Modes Research Articles

The NANOGrav 15 yr Data Set: Search for Transverse Polarization Modes in the Gravitational-wave Background

Recently we found compelling evidence for a gravitational-wave background with Hellings and Downs (HD) correlations in our 15 yr data set. These correlations describe gravitational waves as predicted by general relativity, which has two transverse polarization modes. However, more general metric theories of gravity can have additional polarization modes, which produce different interpulsar correlations. In this work, we search the NANOGrav 15 yr data set for evidence of a gravitational-wave background with quadrupolar HD and scalar-transverse (ST) correlations. We find that HD correlations are the best fit to the data and no significant evidence in favor of ST correlations. While Bayes factors show strong evidence for a correlated signal, the data does not strongly prefer either correlation signature, with Bayes factors ∼2 when comparing HD to ST correlations, and ∼1 for HD plus ST correlations to HD correlations alone. However, when modeled alongside HD correlations, the amplitude and spectral index posteriors for ST correlations are uninformative, with the HD process accounting for the vast majority of the total signal. Using the optimal statistic, a frequentist technique that focuses on the pulsar-pair cross-correlations, we find median signal-to-noise ratios of 5.0 for HD and 4.6 for ST correlations when fit for separately, and median signal-to-noise ratios of 3.5 for HD and 3.0 for ST correlations when fit for simultaneously. While the signal-to-noise ratios for each of the correlations are comparable, the estimated amplitude and spectral index for HD are a significantly better fit to the total signal, in agreement with our Bayesian analysis.

Ultrabroadband metastructure absorber with angular stability for conformal applications

The sustained growth and development of numerous microwave electronic facilities have boosted the demands for microwave absorbers with high performance in bandwidth, wide incident angle, and adaptability of the curved surface. To satisfy these requirements, a 3D-printed electromagnetic metastructure based on a new design methodology with comprehensive microwave absorption properties was proposed and manufactured in this work. The multi-resonant metastructure based on the composite of polyether-ether-ketone and flaky carbonyl iron was designed, and then the gradient impedance distribution was optimized via simulation and comparison of the broadband impedance matching and microwave attenuation properties in different polarization modes under oblique incidence, followed by structural parameters optimization to achieve the optimal absorption performance with broadband and wide incident angle. In the meantime, the conformal capacity of the metastructure under different types of curved surfaces was also investigated. Experimental results correlated well with simulations and demonstrated excellent absorption performance with effective absorption in the broad frequency range of 3.3–30 GHz, stable absorption in the wide incident angle of 0°–70° for both transverse electric and transverse magnetic polarization modes, and strong backward scattering suppression for different conformal states. This effective strategy will provide a novel and promising route toward the development of microwave absorption metastructures with comprehensive electromagnetic performance and accelerate the applications in electromagnetic protection.

Dispersion Properties of Surface Waves Decaying in Red-Shifted and Blue-Shifted Gaps in Photonic Hypercrystals

The dispersion characteristics of surface waves for transverse electric and magnetic polarization modes of photonic hypercrystals (PHC) are theoretically explored. PHC are composed of a dielectric and hyperbolic metamaterial (HMM) with thin layers of both metal and dielectric surface waves that decay inside red-shifted gaps have a negative group velocity, whereas surface waves that decay inside traditional blue-shifted gaps have more typical characteristics. Curve plotting is used to elucidate on how these surface waves depend on several other structural properties such as filling factor, widths of HMM and dielectric, frequency range and angle of incidence etc.

Disentangling longitudinal and transverse modes of the ϕ meson through dilepton and kaon decays

Angular distributions of $\phi$ meson decay amplitudes of $e^+e^-$ and $K^+K^-$ channels are computed using both specific interaction Lagrangians and simple arguments relying on angular momentum conservation. Based on the obtained results, we assess methods to experimentally disentangle the longitudinal and transverse polarization modes of the $\phi$ meson and discuss advantages and disadvantages of employing either the leptonic or hadronic decay modes for this task.

Excellent microwave absorption performances of cobalt-doped SrFe12O19 hexaferrite with varying incident angles

The rapid development of electronic technology and wireless communication for electronic equipment is crucial for civilian and military fields nowadays. However, it has been generating electromagnetic (EM) radiation pollution, which has recently gained more attention. Cobalt-doped SrFe12O19 (Co-SrM) samples, which were predicted to be excellent microwave-absorbing materials (MAMs), were successfully prepared using a ball milling method followed by heat treatment. Samples were formed into polygonal shapes with a crystallite size of ∼24 nm and an average grain size of 160−200 nm. The saturation magnetization (Ms) increased with the increase in Co concentration, whereas coercivity (Hc) showed an inverse tendency. The doping also resulted in variations and fluctuations in EM properties, which affected their microwave absorption properties. All Co-SrM-epoxied samples showed good microwave absorption performances in the frequency and thickness ranges of 12−18 GHz (Ku band) and 4−6 mm, respectively. The best value of reflection loss (RL) was −30.7 dB, meaning that ∼99.9% of the incident wave was absorbed. The excellent microwave absorption performance could be attributed to impedance matching, natural resonance, eddy current effects, and dielectric relaxation loss. In both transverse electric and magnetic polarization modes, Co-SrM-epoxied samples maintained (even improved) the RL values with the large incident angle of 0−60° for the Ku band. In addition, Co-SrM-epoxied samples also enhanced the microwave absorption performance in the C and X bands (4 −12 GHz) with an incident angle of 80−89°. These results proved that Co-SrM epoxied samples could be applied as promising MAMs for practical applications.

Raman scattering of light in single crystals of lithium niobate co-doped with copper and gadolinium

The conditions for the excitation of transverse and longitudinal polar modes in the processes of Raman scattering in lithium niobate single crystals with co-doped with copper and gadolinium are established using a backscattering geometry. A significant increase in the intensity of the Raman lines at 175 and 603 cm−1 was found with an increase in the degree of doping of the crystals with copper due to the photorefractive effect.

Growth, microstructure and optical characteristics of doped LiNbO3:Gd and LiNbO3:Cu:Gd lithium niobate crystals

Double- and single-doped lithium niobate (LN) crystals were grown by Czochralski at air from platinum crucibles: sample 1 ([Cu] = 0.57, [Gd] = 0.07 wt%), sample 2 ([Cu] = 0.041, [Gd] = 0.076 wt%), sample 3 ([Gd] = 0.003 wt%), sample 4 ([Gd] = 0.01 wt%), sample 5 ([Gd] = 0.05 wt%) and sample 6 ([Gd] = 0.26 wt%). Macro- and microstructure of as-grown LiNbO3:Cu:Gd and LiNbO3:Gd crystals have been studied by optical microscopy. Laser conoscopy, photoinduced light scattering (PILS) and optical spectroscopy have studied optical transmission, optical uniformity and photorefraction in LN crystals. Such a composition have been determined for a four-component system Li2O–Nb2O5–CuO—Gd2O3, at which a highly compositionally and optically uniform LiNbO3:Cu:Gd crystal (sample 2, [Cu] = 0.041, [Gd] = 0.076 wt%) can be grown. Raman spectra in 180-grade scattering geometry have determined conditions for the excitation of transverse and longitudinal polar modes during Raman scattering in LiNbO3:Cu:Gd crystals. A great increase in 175 and 603 cm−1 Raman bands intensities has been detected at an increase in copper concentration; it has been explained as a manifestation of photorefractive effect.

Non-tensorial gravitational wave background in NANOGrav 12.5-year data set

We perform the first search for an isotropic non-tensorial gravitational-wave background (GWB) allowed in general metric theories of gravity in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 12.5-year data set. By modeling the GWB as a power-law spectrum, we find strong Bayesian indication for a spatially correlated process with scalar transverse (ST) correlations whose Bayes factor versus the spatially uncorrelated common-spectrum process is 107 ± 7, but no statistically significant evidence for the tensor transverse, vector longitudinal, and scalar longitudinal polarization modes. The median and the 90% equal-tail amplitudes of ST mode are $$\cal{A}_{\text{ST}}=1.06_{-0.28}^{+0.35}\times10^{-15}$$ , or equivalently the energy density parameter per logarithm frequency is $$\Omega_{\text{GW}}^{\text{ST}}=1.54_{-0.71}^{+1.21}\times10^{-9}$$ , at frequency of 1/year.

Quantum mechanical four-dimensional non-polarizing beamsplitter

Some quantum optics researchers might not realize that classical electromagnetism predicts a mathbf {pi } phase shift between S- and P-polarized reflection and might think the reflection coefficients of the transverse modes are independent, or that such a phase shift has no measurable consequences. In this paper, we discuss theoretical grounds to define elements of a 4x4 matrix to represent the beamsplitter, accurately accounting for transverse polarization modes and phase relations between them. We also provide experimental evidence confirming this matrix representation. From a scientific point of view, the paper addresses a non-trivial equivalence between the classical fields Fresnel formalism and the canonical commutation relations of the quantized photonic fields. That the formalism can be readily verified with a simple experiment provides further benefit. The beamsplitter expression derived can be applied in the field of quantum computing.

Polarization selection characteristics of carbon fiber orientation and interweaving for electromagnetic interference shielding behaviors

In this paper, to determine the impact of carbon fiber orientation and interweaving on electromagnetic interference (EMI) shielding behaviors, anisotropic and isotropic samples were developed by conductive/dielectric weaving of spatially distributed carbon fiber and glass fiber. Effortless and cost-effective, the electromagnetic shielding efficiency (SE) was up to 42 dB and the SE/thickness) was 41 dB/mm, which had apparent polarization selection characteristics. In addition, the angle (θ) sensitivity for the SE in transverse electric and transverse magnetic polarization modes was given in detail. SE was generally proportional to θ. Moreover, the fingerprint-like radar chart of anisotropic carbon hybrid woven fabrics in the X-band was performed, which makes polarization selection characteristics more intuitive. This paper presented an easy and effective route for assembling hybrid carbon fiber fabrics with high EMI shielding performance, which offers a clear perspective on the simulation and study of carbon fiber electromagnetic properties.

Polar modes and overtone states in Raman spectra of lithium tantalate crystals

The conditions for the excitation of transverse and longitudinal polar modes in the processes of Raman scattering of light in mono- and polydomain lithium tantalate single crystals are established using a backscattering geometry. The relative intensity of the overtone Raman spectrum on the longitudinal and transverse fundamental polar excitations is much higher in the polydomain sample. Unfortunately, the exact reason for the difference in the Raman spectra of the mono- and polydomain lithium tantalate samples is unknown. The frequencies of the two overtone bands exceeded the exact value of the overtone frequency corresponding to the fundamental longitudinal polar mode $4{A}_{1}(\text{LO})$, which clearly indicates the existence of bound phonon pairs (biphonons). This is consistent with theory and has been shown for both mono- and polydomain samples. On the basis of the general theory of bound states of quasiparticles, the possibility of the existence of bound states of quadrupole excitations of the antipolar type in the vibrational spectrum of a polydomain crystal of lithium tantalate is predicted.

Highly boosted Higgs bosons and unitarity in vector-boson fusion at future hadron colliders

We study the observability of new interactions which modify Higgs-pair production via vector-boson fusion processes at the LHC and at future proton-proton colliders. In an effective-Lagrangian approach, we explore in particular the effect of the operator {h}^2{W}_{mu nu}^a{W}^{a,mu nu} , which describes the interaction of the Higgs boson with transverse vector-boson polarization modes. By tagging highly boosted Higgs bosons in the final state, we determine projected bounds for the coefficient of this operator at the LHC and at a future 27 TeV or 100 TeV collider. Taking into account unitarity constraints, we estimate the new-physics discovery potential of Higgs pair production in this channel.

Raman scattering of light on overtone states of transverse and longitudinal polar optical modes in a single crystal of lithium tantalate

Raman scattering spectra in single crystals of lithium tantalate at 180-degree scattering geometry in a wide spectral frequency range (50 ÷ 2800 cm−1) were studied. Raman peaks were found in 1300 ÷ 2000 cm−1 region with frequencies exceeding doubled frequencies of LiTaO3 crystal lattice fundamental vibrations of A1 and E-type. The conditions for the manifestation of bound polar phonons in lithium tantalate Raman spectra were analyzed. The spectral intensity of Raman scattering in the overtone region of the spectrum of lithium tantalate was calculated taking into account the presence of a biphonon, and a satisfactory agreement between theory and experiment was obtained.

Gravitational Waves in Scalar–Tensor–Vector Gravity Theory

In this paper, we study the properties of gravitational waves in the scalar–tensor–vector gravity theory. The polarizations of the gravitational waves are investigated by analyzing the relative motion of the test particles. It is found that the interaction between the matter and vector field in the theory leads to two additional transverse polarization modes. By making use of the polarization content, the stress-energy pseudo-tensor is calculated by employing the perturbed equation method. Additionally, the relaxed field equation for the modified gravity in question is derived by using the Landau–Lifshitz formalism suitable to systems with non-negligible self-gravity.

Iridescence and thermal properties of Urosaurus ornatus lizard skin described by a model of coupled photonic structures

This research shows that the morphological characteristics of the external microstructure of the beautiful skin of the Urosaurus ornatus lizard contribute to the explanation of the origin of their iridescent and thermal properties. High-resolution scanning electron microscopy studies revealed that the skin surface of the U. ornatus lizard is constituted by a semi-ordered array of hexagonal photonic crystals with sub-micrometric structural parameters. The iridescence properties of the ventral patch and dorsal surface of the U. ornatus lizard were numerically simulated modeling both surfaces by a set of coupled photonic crystals with structural parameters proposed from statistical measurements of the lattice parameter and holes diameter of its skin surface. The dorsal surface showed the ability to reflect visible light and at least in a significant range the ultraviolet and near infrared radiation. A complete photonic band gap for the transverse magnetic polarization mode of the incident light in both dorsal and ventral surfaces was predicted by calculations. The spectral reflectance and the structure of photonic bands obtained explain the reflection of the infrared radiation by the dorsal surface which might help to the thermoregulation of the lizard body. The results obtained suggest that the selective reflection of incident light performed by the photonic structural array defined on the skin surface of the U. ornatus has a significant contribution to its apparent color.

Electromagnetic wave absorbing performance of aspirin powder during 2450 MHz microwave drying

The absorbing performance of pharmaceutical powders has an important effect on the efficiency of microwave drying. In this study, in order to achieve optimal microwave absorption, the reflection loss (RL) of aspirin powder is calculated based on the theory of electromagnetic wave transmission line under different temperatures, moisture contents, microwave incident angles and polarization modes. In addition, the effect of the dielectric-assisted absorbing layer (SiC ceramics) on the microwave absorbing performance of aspirin powder (weak absorbing materials) with low moisture content is analyzed. The results show that the RL curve of aspirin powder fluctuates with increasing thickness; several absorption peaks appear, and the absorption peaks shift to smaller thicknesses as the temperature and moisture content increase. The RL of aspirin powder in the transverse electric polarization mode decreases monotonically as the incident angles increase. The effect of Brewster’s angle causes the RL of aspirin powder in the transverse magnetic polarization mode to first decrease and then increase with the increasing incident angle, and an absorption peak occurs. However, the RLs of both polarization modes are close to zero at 90°. The use of SiC ceramics as the susceptor can reduce the RL of the double-layer absorber and widen the aspirin powder thickness interval for an RL below −20 dB. This research can help to optimize the microwave drying process parameters of pharmaceutical powders and the design of microwave drying equipment.

Angular dependence of the optical reflectance in two-dimensional Si-ZnO photonic crystals

In this work, we present an experimental study of the angular dependence of the optical reflectance in two 2-dimensional photonic structures, built on a silicon substrate coated with a ZnO thin film. Photonic structures studied describe a regular square lattice with a lattice constant a = 1.05 μm and circular air holes with a radius r = 0.63a. Additionally, one of these photonic structures contains a pattern of nine quasi-circular micro-cavities embedded in a regular square lattice photonic crystal, describing a secondary square lattice. A comparison of the optical reflectance of the two photonic structures as a function of the incidence angle for transverse magnetic polarization mode in the visible (Vis) and near-infrared (NIR) ranges of the electromagnetic spectrum was accomplished. Results obtained revealed a strong angular dependence of the reflective optical properties of the two 2-dimensional photonic structures on the illumination incidence angle. The photonic structure with the array of resonant optical cavities presented a very unusual behavior regarding the reflectance of the substrate, this because its reflectance described specific modulations dependent on the incidence angle of illumination.

A reconfigurable scheme for realization of electro-optical logic gate based on silicon-graphene Mach–Zhender interferometer

In this paper, we propose a reconfigurable scheme for implementation of an electro-optical logic gate by utilizing a Mach–Zehnder interferometer (MZI)-based structure. In order to achieve high performance and small footprint for the proposed logic gate, we have used a compact, broadband, low power and high speed MZI-based electro-optical switch which consists of a silicon-graphene slot waveguide as phase shifter in each arm of the MZI structure. Our design can perform electro-optical AND, OR and XOR logic functions in three different operational modes by using three electrical control signals. The functionality of the reconfigurable electro-optical logic gate is investigated with the help of eye diagram analysis for all three operational modes. Simulation results show that the proposed reconfigurable logic gate is able to work under at least 62.5 Gbit/s with high extinction ratio (ER) about 24.6 dB for transverse electric polarization mode at telecommunication wavelength of 1.55 [Formula: see text]m.

Nanobeam extraction with periodic optical grating staircase structure

AbstractWe propose the unique design of nanobeam focusing on multiple grating with two‐dimensional silicon waveguide staircase structures. Beam focusing is also employed with two‐dimensional Finite Difference Time Domain simulations. Nanobeam extraction is achieved on 15 µm × 35 µm wafer size. Single mode fiber of 9 µm size is focused to the 50 nm optical beam. It is also observed that 50 nm focusing can be achieved irrespective of different grating periodicity. The device operates with Transverse Electric polarization mode. The proposed focusing structure works on 1550 nm wavelength. Simulation results of the propose design shows the good focusing efficiency at the waveguide end for nanophotonics structure. Reported results show the mathematical and simulation similarities for multiple designs. This focusing structure is highly compatible with next‐generation photonics circuits because of its linear focusing on nanowaveguide.

Topologically protected edge states for out-of-plane and in-plane bulk elastic waves

Topological phononic insulators (TPnIs) show promise for application in the manipulation of acoustic waves for the design of low-loss transmission and perfectly integrated communication devices. Since solid phononic crystals exist as a transverse polarization mode and a mixed longitudinal-transverse polarization mode, the realization of topological edge states for both out-of-plane and in-plane bulk elastic waves is desirable to enhance the controllability of the edge waves in solid systems. In this paper, a two-dimensional (2D) solid/solid hexagonal-latticed phononic system that simultaneously supports the topologically protected edge states for out-of-plane and in-plane bulk elastic waves is investigated. Firstly, two pairs of two-fold Dirac cones, respectively corresponding to the out-of-plane and in-plane waves, are obtained at the same frequency by tuning the crystal parameters. Then, a strategy of zone folding is invoked to form double Dirac cones. By shrinking and expanding the steel scatterer, the lattice symmetry is broken, and band inversions induced, giving rise to an intriguing topological phase transition. Finally, the topologically protected edge states for both out-of-plane and in-plane bulk elastic waves, which can be simultaneously located at the frequency range from 1.223 to 1.251 MHz, are numerically observed. Robust pseudospin-dependent elastic edge wave propagation along arbitrary paths is further demonstrated. Our results will significantly broaden its practical application in the engineering field.