Transverse Electric Waves Research Articles

Polarization-dependent and angle-insensitive absorber with hyperbolic material

A polarization-dependent and angle-insensitive absorber based on surface phonon polaritons (SPhPs) is proposed based on a sandwiched layer structure that consists of a patterned α - M o O 3 layer, a dielectric layer, and a gold layer. The absorption remains larger than 95% for TE incidence wave with incident angles from 0° to 30° in the wavelength range from 13.7 to 18.3 µm, which is a broadband absorber. At the same time, the absorption remains larger than 95% for TM incidence wave with incident angles from 0° to 60° in the wavelength range from 11.52 to 11.66 µm, which is a narrowband absorber. It is interesting that the absorber can also be used to fabricate the ideal filter of transverse electric (TE) wave in the wavelength range from 11.52 to 11.66 µm and an ideal filter of transverse magnetic (TM) wave from 15.03 to 18.37 µm. Moreover, one can combine an ideal filter of polarization and a perfect absorber into one single device. The proposed absorber shows promising performance, which has potential applications in sensing, imaging, and detection.

Investigation of TE and TM modes fields and injected electron dynamic in the plasma waveguide with Piet Hein cross section

In this paper, we consider a metallic waveguide with Piet Hein cross section filled by cold unmagnetized plasma. First by introducing a Piet Hein waveguide and considering a suitable approximation, wave equation as two differential equations are presented. Then electromagnetic fields for TM and TE modes in the Piet Hein waveguide filled plasma are analytically obtained and plotted. Using the boundary conditions in the Piet Hein plasma waveguide the dispersion relations for TM and TE modes are analytically derived and plotted. Electron dynamics in the fields associated with a transverse magnetic and electric wave propagating inside the considered Piet Hein plasma waveguide is investigated. The equations of electron motion in the considered Piet Hein plasma waveguide by fourth-order Runge Kutta method for TM and TE modes are solved. The motion path and kinetic energy of electron injected into the purposed configuration for two modes are graphically investigated.

Anomalous Absorption in Arrays of Metallic Nanoparticles: A Powerful Tool for Quantum Dot Optoelectronics.

Periodic arrays of noble metal nanoparticles are emblematic nanostructures in photonics. Their ability to sustain localized surface plasmon resonances has been used throughout the years to demonstrate a variety of passive and active functionalities such as enhanced luminescence in dipolar media and LEDs as well as higher responsivities in photoconductive detectors. Here, we show that additional magnetic resonances, associated with inductive current loops between the nanoparticles and accessible with transverse electric waves, emerge in the limit of dense arrays with subwavelength periods. Moreover, their interplay with the plasmons of the system results in spectrally sharp analogues of electromagnetically induced absorption (EIA). We use these metasurfaces to induce changes and enhancements in the emission, absorption, photoconduction, and polarization properties of active layers of PbS nanocrystals, illustrating the potential of EIA beyond the passive functionalities demonstrated so far in literature.

Metasurfaces for Far-Field Radiation Pattern Correction of Antennas under Dielectric Seamed-Radomes.

A high-index dielectric radome seam is camouflaged with respect to a low-index dielectric radome panel by tuning the seam with carefully engineered metasurfaces. A transmission-line approach is used to model the metasurface-tuned seam and analytically retrieve the corresponding surface impedance, from which the unit-cell design is then tailored. Full-wave simulations and microwave antenna measurements performed on a proof-of-concept prototype validate the undesired scattering suppression effect in the case of normally and obliquely incident transverse electric and transverse magnetic wave illuminations. Robustness of the proposed solution to fabrication tolerances is also reported. The study presents metasurface-tuning as an easily implementable, frequency adjustable, and polarization insensitive solution to reduce the scattering of dielectric mechanical seams and improve the overall transparency performance of radome structures.

Tunable polarization encoder capable of polarization conversion and separation based on a layered photonic structure

In this paper, a polarization encoder with a polarization conversion function is investigated using a layered photonic structure comprising nonlinear materials and indium antimonide. The electric field of the incident linear polarization waves considered are parallel to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x-y</i> plane at an angle of 45° to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> -axis, and can be decomposed into components directed along the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -axes, generating two polarized waves: transverse electric and transverse magnetic waves. Due to the nonlinear effect and the temperature and magnetic flux density tunable properties of indium antimonide, the light intensity, temperature, and magnetic flux density can be used to adjust the reflection phase difference and polarization form. Discussing the influences of these three physical quantities on the phase difference, the incident linear polarization wave and reflected circular polarization wave conversion, the circular polarization conversion of two different rotations and the circular polarization separation of a certain bandwidth can be simultaneously realized with the specific modification of the light intensity or temperature. Moreover, four disparate input logic levels composed of temperature and magnetic flux density achieve specific encoding outputs for all polarization forms. This signifies that polarization selection through control of the logic codes can be easily attained. The consequences show that this form of polarization conversion and encoding is tailored and can be accurately manipulated. Hence, this provides a novel foundation for tunable and diverse polarization splitters and selectors.

Transverse components of the electromagnetic field in a waveguide with modulated in space and in time magnetodielectric filling

The propagation of transverse magnetic (TM) and transverse electric (TE) electromagnetic waves in a regular ideal waveguide of arbitrary cross section is considered. It is assumed that the permittivity and permeability of the magnetodielectric filling of the waveguide are functions that depend on the coordinate and time. Analytical expressions for the transverse components of the magnetic and electric vectors of the TM- and TE-fields in the waveguide are obtained from the system of Maxwell equations. They are expressed in terms of the longitudinal components of the electric and magnetic vectors, which describe the transverse magnetic and transverse electric fields in the waveguide. For the above longitudinal components of the electric and magnetic vectors, the wave equations are given, which are also obtained from the system of Maxwell's equations. Keywords: Maxwell equations, propagation of electromagnetic waves, waveguide with modulated filling, transverse components, Helmholtz equations, Dirichlet and Neumann problems.

Low-Profile Broadband Dual-Polarization Double-Layer Metasurface Antenna for 2G/3G/LTE Cellular Base Stations

A double-layer metasurface is proposed to realize the low profile of a broadband dual-polarized antenna for cellular base-station applications. The proposed metasurface is formed by the two layers of printed metallic patch unit cells on either substrate surface to miniaturize the metasurface size and enhance design flexibility by regulating the extent of electromagnetic coupling between the two layers. Despite the low profile of the antenna, a wideband operation is accomplished by operating the metasurface in the nonresonant region that facilitates wideband phase compensation and its truncation to a finite dimension with an additional transverse electric (TE) surface wave resonance. The guidelines for the design of the surface is derived from a comparison of unit cell structures and an approach is introduced to correlate their potential with surface susceptibility parameters. A detailed parametric study addresses the critical concern on the overall dimensions of the finite metasurface. A ±45°-polarized dipole antenna with an overall thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.15~\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the wavelength in free space at the center operating frequency) is designed as example. The measured results show a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert \le -10$ </tex-math></inline-formula> dB impedance bandwidth of 46.4% over the frequency range of 1.69–2.71 GHz with average boresight gain of 9 dBi with a ground plane of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1\lambda _{0} \times 1.1\lambda _{0}$ </tex-math></inline-formula> , well covering 2G (1.71–1.92 GHz), 3G (1.88–2.17 GHz), and LTE (2.3–2.4 GHz and 2.5–2.69 GHz) bands.

Investigating the absorption performance of a monolayer-coated absorber at oblique incidence

There is a widely observed phenomenon in the microwave absorption field that an absorber always exhibits good oblique incidence absorption capacity if it has high performance at normal incidence. However, if a certain angle is exceeded, this kind of effective absorptive capacity will no longer be maintained. Besides, an absorber performs differently for incident transverse electric (TE) and transverse magnetic (TM) waves: for the TE case, the absorber can no longer obtain effective absorption; for the TM case, another efficient absorption region was observed at higher frequencies even when the incident angle exceeded 80°. These phenomena are widely found in the literature, which demonstrates that they are caused by physical laws rather than material properties. To demonstrate the underlying reason, in this study, the common spherical carbonyl iron-polyurethane composite absorbers were fabricated as a typical example. Their absorbing performance was investigated via both simulation and experiment. All the phenomena mentioned above were observed, studied in detail by employing the multiple reflection model, and explained quantitatively. Further, along with establishing the underlying mechanism of electromagnetic wave transmission in the absorber, two formulas were deduced to predict: (a) the maximum incident angle for efficient absorption of the TE polarized wave; and (b) the required absorber thickness for obtaining efficient absorption for a large incident angle of the TM polarized wave.

Dynamically switchable terahertz absorber based on a hybrid metamaterial with vanadium dioxide and graphene

We numerically demonstrate a switchable metamaterial absorber with two states (i.e., ultra-broadband and narrowband) in the terahertz region. Such switchable functionalities are accomplished by using a simple absorption system consisting of a hybrid metamaterial with vanadium dioxide ( V O 2 ) and graphene. Theoretical calculations show that when V O 2 is in the metal state, the absorption system without a graphene ring can act as a broadband absorber. For the broadband absorber, the absorption bandwidth of 5.05 THz (i.e., 93%) can be obtained under the condition of over 90% absorption rate, covering a frequency range of 2.91–7.96 THz. Meanwhile, the absorber exhibits tunable characteristics, whose absorption rate can be continuously adjusted from 1% to 99% by controlling the conductivity of V O 2 from 2 × 1 0 2 to 2 × 1 0 5 S / m . It is polarization-insensitive with a large angle tolerance in both transverse electric and transverse magnetic waves. Multiple interference theory is used to analyze the mechanism of the broadband absorber, and the theoretical results are in good agreement with simulations. When the V O 2 is changed to the insulator state, the absorber system with a graphene ring can be switched to a narrowband absorber. This work will have great potential applications in the terahertz regime, such as tunable broadband absorbers, dynamic sensing, cloaking, and photodetectors.

Polarization-insensitive dual-wideband fractal meta-absorber for terahertz applications.

Terahertz (THz) metamaterial absorbers have realized a prodigious reputation due to the limitation of natural absorbing materials in this range. Getting wideband absorption characteristics is challenging and arduous, especially in the THz band. Self-similar repeated fractal elements offer a promising solution to attain broadband absorption response due to their inherent multiple resonance characteristics. Therefore, by captivating the advantage of fractal geometry, we proposed a dual and wideband meta-absorber operating in the THz regime. The metamaterial absorber design comprises the assembly of self-similar square-shaped blocks arranged in a specific pattern to construct the fractal geometry. The proposed THz absorber demonstrates 90% absorption under normal incident waves for two operating bands from 9.5-10.55 THz and 12.3-13.35 THz. The suggested metamaterial absorber also shows good and stable absorption responses under different oblique incidence angles for transverse electric (TE) and transverse magnetic (TM) wave polarization. Moreover, this absorber manifests over 85% absorptivity in its entire operating range (9-14 THz) under the incidence angle of 60° and 70° for TM mode. Furthermore, it gives a polarization-insensitive behavior under the effect of different polarization angles. This kind of wideband absorber catches fascinating applications in THz detection, imaging, cloaking, and optoelectronic devices.

A 4-Bit Multistate Frequency-Selective Surface With Dual-Band Multifunction Response

In this letter, a novel 4 b multistate frequency-selective surface is proposed. Four p-i-n diodes are used to maneuver multifunction behavior of the structure with seven different functional states. The 4 b binary state operations 0000, 1100, 0011, and 1111 offer transverse electric (TE)/transverse magnetic (TM) waves both transmit, TE transmit/TM shield, TM transmit/TE shield, and TE/TM both shield, respectively, at 2 GHz frequency. The passband at 2 GHz frequency has <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-\text{10}$</tex-math></inline-formula> dB fractional bandwidth of 117%. The binary states 1101 and 1110 are symmetric, which select the TE wave transmit/TM wave shield to the passband at 3.45 GHz frequency with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-\text{10}$</tex-math></inline-formula> dB fractional bandwidth of 49%, whereas binary states 1011 and 0111 allow the TM wave to transmit at 3.45 GHz and shield the TE wave. The four symmetric binary states 0101, 0110, 1010, and 1001 provide transmission band at 3.45 GHz frequency for dual-polarized plane wave incidence. The transmission of both the passbands can be shielded by selecting the binary state equal to 1111. An equal circuit model is used to elaborate the contribution of different passive structural elements in terms of lumped components. A prototype of the structure is fabricated, and transmission coefficients for different states at normal and oblique incidence of the electromagnetic plane wave are measured, which verifies the simulated responses of the structure.

Broadband THz Absorber for Large Inclination Angle TE and TM Waves

Terahertz (THz) electromagnetic wave absorbers are finding new applications both in military and civilian sectors. This is the reason why constant efforts have been made worldwide to enhance the working performance of these absorbers. One downside of the available absorbers is their response to Transverse Electric (TE) and Transverse Magnetic (TM) waves at different frequency bands. Specific strategic applications require response of an absorber in same frequency band for TE and TM electromagnetic waves, for large inclination and polarization angle of the incoming signal. In this work, we present a metasurface based THz absorber with improved functionality. The fractional bandwidth is 91.64% w.r.t the center frequency of 1.97 THz, that shows an absorptivity of more than 90%. Due to the fourfold symmetry, the absorber is polarization insensitive. It shows more than 80% absorptivity for incoming wave inclinations upto <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$60^{\circ }$</tex-math></inline-formula> . The thickness of the absorber is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> /11. The good point is that the absorber shows all these improved performance for both TE and TM incoming signals in the same frequency range. Overall, the designed absorber is a much improved version of its peers available in the literature.

Vanadium nitride-based ultra-wideband nearly perfect metamaterial absorber

Vanadium nitride (VN)-based metamaterial absorber was investigated for ultra-wideband (UWB) nearly perfect absorber in the visible to infrared regime of the electromagnetic spectrum considering four different VN samples, namely VN6, VN8, VN10, and VN12. The absorption properties were extracted for the transverse electric and transverse magnetic incidence waves under different obliquities, and also, considering different parametric conditions of the metamaterial. The constitutive properties of VN samples were initially extracted, followed by the effective constitutive properties of metasurface comprising the nanostrips of VN6 and VN10 mediums as the illustrative examples. The results determine achieving nearly perfect UWB absorption in the stated regime of operating wavelength. Spectral characteristics were also obtained while using other reflectors at the bottom. The results demonstrate using VN at the bottom yields significantly improved spectral features. The absorption related results were also evaluated exploiting the interference theory, and the obtained discrepancies were highlighted.

Sub-Millimeter-Wave Polarization-Independent Spatial Power Divider for a Two-Port Dual-Polarized Antenna

An antenna system is proposed that uses a novel polarization-independent spatial power divider to align the beams from two orthogonally oriented dual-polarized feeds. This antenna system uses a common aperture for transmitting and receiving and provides high port isolation while maintaining compatibility with fully polarimetric radar. Unlike conventional two antenna radar systems, a radar using this antenna does not suffer from the parallax problem. The spatial power divider is designed using an all-dielectric metasurface approach and is fabricated on a silicon wafer using standard micromachining technology. The measured device exhibits at most 0.9 dB of difference between the reflection and transmission for both transverse electric and transverse magnetic incident waves at 45° incidence, over a band from 221 to 250 GHz. Conical horns are fabricated as feeds and together with the spatial power divider, a focusing lens, and microwave absorbers, are assembled in a three-dimensional-printed housing to complete the antenna system. Its measured gain is approximately 39 dB for each port and polarization, and isolation between ports is at least 40 dB for all polarization combinations over the band of interest.

Dual-broadband and single ultrawideband absorbers from the terahertz to infrared regime

This paper presents the design and analysis of broadband metamaterial absorbers with single and dual absorption bands from terahertz to infrared frequencies. The absorbers are made of a composite graphene/metallic structure. A metallic patch array is printed on a ground-plane-backed dielectric slab. A graphene patch array is stacked on top of the metallic array, whereas a dielectric spacer separates the graphene and patch spacer from each other. The tunable property of the graphene surface conductivity at terahertz frequencies together with the complex permittivity of metal at the infrared regime are used to design broadband absorbers from the terahertz to infrared regime. The design is based on the combination and excitation of the plasmon polaritons of graphene and metallic patterned arrays at terahertz and infrared frequency bands, respectively. Two broad absorption bands occur from 4.56–9.02 THz and 16.95–60.23 THz with the fractional bandwidths of 67% and 112%, respectively. Furthermore, by a proper design of the parameters, a single ultrawide absorption spectra from 6.6–58.13 THz can be achieved with a fractional bandwidth 160%. In order to validate the simulation results, a circuit model-based analysis is developed, where the patterned arrays are modeled as the surface admittances, and the dielectric spacers are modeled by transmission line stubs. The results obtained by the full-wave simulations in the high-frequency structure simulator are in good agreement with the circuit model results. The absorbers show great stability with respect to the incidence angle for both the transverse electric and transverse magnetic waves.

Design of a transmission-line metamaterial with a negative index of refraction at S-Band / Concepção de um metamaterial de linha de transmissão com um índice negativo de refracção na banda S

A metamaterial based on a two-dimensional transmission-line network loaded with inductors and capacitors enabling to achieve negative-refractive-index (NRI) is developed. The dispersion characteristics are calculated by their equivalent circuit model and an operating frequency of 2.95 GHz in which there is impedance matching with free space is chosen in the S-Band. This NRI metamaterial supports transverse electric (TE) waves, thus it can be used in applications such as lensing.

Orbital angular momentum generator with multiple retroreflection channels enabled by an angle-selective metasurface.

Vortex beams carrying orbital angular momentum (OAM) have aroused great attention on account of the remarkable potential in the field of communication. It has the characteristics of higher spectrum efficiency, greater channel capacity and stronger anti-interference, which will revolutionize the wireless communications in the future. However, target tracking on a vortex generator in practical applications is becoming a challenge because the backscattering of electromagnetic (EM) waves under oblique incidence is too small for detection. Currently, the main way to solve this problem is to load an extra retroreflector such as Luneburg lens, which in turn leads to increased weights and bulky volumes. In this paper, we propose a vortex generator simultaneously with retroreflective characteristics utilizing an angle-selective metasurface. The meta-atom can achieve broadband polarization conversion under normal incidence and efficient retroreflection under oblique incidence. Without the need for an additional retroreflection phase arrangement, an OAM generator composed of such meta-atoms can be achieved in 15.0-21.0GHz under both x- and y-polarized normal incidence. Meanwhile, four retroreflection channels are opened under oblique illumination of both transverse electric (TE) and transverse magnetic (TM) waves at 20.0GHz. Both the simulated and measured results show excellent performances. The integration of an OAM generator and retroreflector will greatly reduce the weight and volume and save in the cost of production, which will promote the development of miniaturized, multi-role, and even intelligent functional devices.

Magnetic plasmons induced in a dielectric-metal heterostructure by optical magnetism

Abstract We investigate numerically and experimentally the optical properties of the transverse electric (TE) waves supported by a dielectric-metal heterostructure. They are considered as the counterparts of the surface plasmon polaritons (i.e., the transverse magnetic (TM) waves) which have been extensively studied in the last several decades. We show that TE waves with resonant wavelengths in the visible light spectrum can be excited in a dielectric-metal heterostructure when the optical thickness of the dielectric layer exceeds a critical value. We reveal that the electric and magnetic field distributions for the TE waves are spatially separated, leading to higher quality factors or narrow linewidths as compared with the TM waves. We calculate the thickness, refractive index and incidence angle dispersion relations for the TE waves supported by a dielectric-metal heterostructure. In experiments, we observe optical resonances with linewidths as narrow as ∼10 nm in the reflection or scattering spectra of the TE waves excited in a Si3N4/Ag heterostructure. Finally, we demonstrate the applications of the lowest-order TE wave excited in a Si3N4/Ag heterostructure in optical display with good chromaticity and optical sensing with high sensitivity.

Broadband terahertz metamaterial absorber based on graphene resonators with perfect absorption

The applications of terahertz waves and metamaterials in electromagnetic wave absorbers are one of the key focus areas of current interdisciplinary scientific research. In this study, we propose a metamaterial absorber composed of graphene double-open rectangular ring and graphene strip cross structures. The experiment uses numerical analysis software to study the proposed absorber. Transverse electric waves were normally incident on the absorber from the plane port, where resonance coupling was achieved. With an increase in the incidence angle alpha, the trough in the middle of the absorption spectrum continued to deepen. The bandwidth that the spectral absorption maintains above 0.9 is 2.88 GHz (1.260–1.548 THz). The maximum spectral absorption has reached 99.9%, which is approximately perfect absorption. The absorber under transverse magnetic wave incidence also exhibited a bandwidth advantage. As the Fermi energy continued to increase, the absorption bandwidth first increased and then decreased, and reached the maximum at ef = 0.5 eV. Simultaneously, the relative absorption bandwidth also reached its maximum. By adjusting the Fermi level of graphene, dynamic tuning of the metamaterial absorber could be achieved. Adjustment of the Fermi level shifted the absorption range and absorption bandwidth, and helped in controlling the increase in the relative absorption bandwidth. The findings of this study can be of theoretical and engineering significance in the domains of thermal photovoltaics, solar cells, and sensors, among others.

Ultra-wideband, optically transparent, and flexible microwave metasurface absorber

In this work, an ultra-wideband microwave metasurface absorber with optically transparent and flexible properties is proposed. The metasurface is composed of a reflective backplane and a microwave absorption layer sandwiched between two dielectric substrates. The impedance matching curves of the microwave absorption layer are deduced based on the impedance matching theory, which is quite helpful and useful to improve the accuracy and efficiency of the broadband optimization design. Simulated results show that absorption higher than 90% can be achieved in the frequency band ranging from 5.8 GHz to 27.3 GHz, which covers the radar wavebands of C, X, Ku and K. The relative bandwidth reaches up to 130%, thus realizing ultra-wideband absorption while the thickness of the metasurface is only 0.12 times the upper-cutoff wavelength. For the TE (transverse electric) wave incidence, the metasurface maintains good performance when incident angle θ ≤ 50°, while for the TM (transverse magnetic) wave incidence, the absorption higher than 90% can be still achieved in a broad frequency band when θ ≤ 60°. It can be seen that using double-layer dielectric substrate in the metasurface not only greatly expands the microwave absorption bandwidth, but also improves the oblique incident properties. In addition, the metasurface is insensitive to polarization since its unit cell is symmetrical. Moreover, by rationally designing materials, the metasurface in this work is optically transparent and flexible, thus quite suitable for window radar stealth and equipment conformal stealth.