TE Waves Research Articles

A theoretical study based on coherent perfect absorption and polarization separation in one-dimensional magnetized plasma photonic crystals.

This article presents a study on tunable narrowband coherent perfect absorption (CPA), which can be altered by adjusting the initial phase to the ranges of 1.03α-1.13α (with α = 2πc/d) and 1.29α-1.43α. The relative bandwidths of these ranges are determined to be 8.5% and 7.4%, respectively. The study utilizes the transfer matrix method for calculations of the largest CPA amplitudes within one-dimensional (1D) magnetized plasma photonic crystals (MPPCs) across two absorption bands, achieving a maximum of 0.99 and 0.98, respectively. In addition, the phase modulation and amplitude modulation characteristics of the CPA are also discussed, and the results show that its absorption amplitude can be gradually modulated from 0.08 to 0.99 by the former and from 0.60 to 0.98 by the latter. The external magnetic fields have also been shown to limit the CPA amplitude between 0.41 and 0.99 within one band and between 0.52 and 0.99 within another band. The study further highlights the effect of plasma frequency and dielectric layer thickness on coherent band shifts towards high or low frequencies. Notably, the article presents the multiband polarization separation properties of 1D MPPCs, with calculated transmittance differences between the TM and TE waves of up to 0.70 and 0.74 at 1.13α and 1.37α, respectively.

Polarization-sensitive broadband bidirectional absorber in the optical communication band

Here, we propose a polarization-sensitive broadband bidirectional plasmonic absorber in the optical communication band. The proposed structure can achieve an excellent absorption performance (>90%) under the TE wave illumination at the wavelength range from 1370 nm to 1630 nm within an incident angle up to 45°. The analysis of the electromagnetic field distribution reveals that the coupling of propagating surface plasmons resonance and local surface plasmon resonance dominates the perfect absorption performance. The symmetry of the structure determines that the device has the characteristics of bidirectional absorption. In addition, the effect of interlayer alignment accuracy on absorption performance is discussed, and the result indicates that low alignment accuracy is allowed. The bidirectional broadband plasmonic absorber shows a promising prospect in electromagnetic wave shielding, optical sensors, photodetectors, and communication.

Bifunctional metasurface for cross-polarization conversion and ultra-broadband absorption in terahertz range

A bifunctional terahertz (THz) metasurface based on vanadium dioxide (VO2) was proposed, which can achieve near-perfect cross-polarization conversion (CPC) and ultra-broadband absorption. When VO2 is in insulator state, the metasurface acts as a cross-polarization converter, converting linearly polarized (LP) and circularly polarized (CP) waves into the corresponding cross-polarized waves. The polarization conversion ratio (PCR) exceeds 99.5% in the frequency range of 4.1∼6.7 THz at normal incidence, and can be maintained more than 98.3% even at an incident angle of 20°. When VO2 is in metal state, the metasurface becomes a THz broadband absorber with absorption efficiency above 90% in a wide frequency range of 2.9 THz∼8.4 THz. The absorption efficiency is almost unchanged when the incident angle increases from 0° to 15° for TE wave. In addition, the absorption efficiency can maintain above 90% at 4.0∼7.1 THz when the incident angle is up to 60° for TM wave. Moreover, the interference theory model was utilized for verifying theoretically the validity of the numerical simulation results of our proposed metasurface, and the theoretical calculation results are in good agreement with the simulation results. We believe that this proposed metasurface has potential applications in many fields, such as sensing, imaging, non-destructive detectors, super lenses, and telecommunications.

A novel dual‐band miniaturized frequency selective surface with high selectivity

AbstractIn this paper, a novel dual‐band multilayer frequency selective surface (FSS) with high selectivity and miniaturization characteristics is proposed. The FSS consists of a top and bottom resonant layer and an intermediate coupling layer. The top and bottom resonant layers provide dual‐band passbands, and the cross‐coupling between the three layers makes the structure produce four transmission zeros (TZs) distributed two‐by‐two on both sides of the passband to improve the sharp roll‐off characteristics of the structure. Use bent structures in the top and bottom layers of the cell design to achieve miniaturization of the elements. FSS provides stable performance in incident angles from 0° to 45° with different polarizations of incident waves (TE and TM wave). The lower band of FSS works at 9.1 GHz and the higher band works at 10.26 GHz, the cell size of FSS is , FSS samples were made and tested, and the test results fit well with the simulation results.

Theoretical study on the polarization-separated and nonreciprocal tailored electromagnetically induced absorption with layered photonic structure

In this paper, the behaviors of nonreciprocal and polarization-separated tailored electromagnetically induced absorption (EIA) realized by a layered photonic structure containing InSb are investigated by the transfer matrix method, which shows that the EIA peak can be up to 97.3 % and 98 % in the forward and backward propagation, and the interval between their frequency points of them can be up to 0.28 THz when the incident angle (θ) is 0° and the magnetic induction intensity (B) is 0 T. The theory of the two-oscillator model is used to further prove the reality of EIA. By adjusting θ to 36°, the frequency difference of the EIA peaks under the TE and TM waves is 4 GHz when B is 0 T, indicating a good capability of polarization separation (PS). With the alteration of the temperature, such a difference value is always larger than 3 GHz. With the escalation of θ, the frequency points of EIA of the forward and backward incidence is approximately 0.28 THz, and show good performance of PS. Besides, the adjustment of the number of periods and B can realize the function of regulating EIA. Depending on its high-quality factors and good sensitivity, this research is of great help in realizing the sensors.

Tungsten nanopore-based near-ideal spectral selective solar absorber for a wide temperature range

An efficient and simple spectral selective solar absorber is vital for solar-thermal systems that operate under a wide temperature range (673–1573 K). However, few absorbers are competent for this wide temperature range due to their suboptimal spectral selectivity under specific conditions or complex structures that are difficult to be fabricated. Here, we proposed a near-ideal spectral selective solar absorber consisting of simple regular hexagonal tungsten nanopores filled with silicon dioxide. A strong solar absorptivity up to 0.9632 and a reduced total emissivity down to 0.0961 were realized due to its good spectral selectivity. Meanwhile, the near-ideal spectral selective solar absorber obtains high photothermal efficiencies of 95.25 % at 673 K, 95.84 % at 873 K, and 89.38 % at 1573 K when the concentration ratios are 100, 1000, and 2000 suns, respectively. Subsequently, mechanism analysis implies that the excellent performance of the near-ideal absorber results from the electromagnetic field enhanced by the cavity resonances, localized surface plasmon resonances, and surface plasmon polaritons. Further, the impedance matching also plays an important role in achieving the excellent performance. In addition, the near-ideal absorber also shows insensitivity to incident angle and polarization angle with both TE and TM waves. All the above positive properties presented by the near-ideal absorber indicate that it is a good option for solar energy capture in the wide temperature range of 673–1573 K.

The Transmission Properties of One-Dimensional Photonic Crystals with Gradient Materials.

In this paper, we studied the transmission properties, including photonic band gap (PBG) and defect mode properties, of one-dimensional photonic crystals (1D PCs) consisting of gradient materials. When keeping the average refractive index of the gradient materials in the 1D gradient-material PCs (1D GPCs) the same as the index of the corresponding normal materials in the 1D normal-material PCs (1D NPCs), by transfer matrix method, we found that the complete 1D GPCs with high-index gradient materials benefit to achieve larger omni-PBG than that in 1D NPCs. In our high-index gradient material case, for TE(TM) wave, the optimal omni-PBGs in 1D GPCs with first- and second-order gradient materials are 38.6% (50.2%) and 15.9% (22.3%) larger than that in 1D NPCs; while for the optimal relative bandwidths of omni-PBG, the corresponding promotions are 41.1% (52.3%) and 16.1% (22.6%), respectively. In addition, when defective 1D GPCs have gradient-material defect, the position of defect modes can be adjusted by selecting proper parameters of the gradient materials. These types of research are useful for designing wide PBG devices and tunable narrow-band filters which have potential application in optical communication.

Dual-band polarized optical switch with opposite thermochromic properties to vanadium dioxide

A dual-band polarized wavelength-selective optical switch whose thermochromic transmission property is opposite to VO2 itself is proposed. The switch shows a low and high transmittance during phase transition from insulating VO2 to metallic VO2, respectively. The multi-mode coupled circuit model is employed to calculate and tailor the operating frequency of the switch in xz sections for TM waves and yz sections for TE waves. The switch exhibits a transmittance difference of more than one order of magnitude between “on” and “off” modes when the structure is same in the x and y directions under circularly polarized light incidence. For the condition that the structure is not same in the x and y directions, thermochromic transmittance becomes polarization-dependent. By superimposing two polarization states, a dual-band as well as broadband thermochromic transmission property is obtained. The mechanisms of suppressed and enhanced transmission lie in the excitation of MPC and MPV2, respectively. This study may have theoretical guiding significance for design and tailoring of metamaterials with wavelength-selective broadband thermochromic transmission property and potentially apply in active filters and architectural energy-efficient glass.

Ultra-broadband wave-absorbing metamaterials with open-hole effect

In this paper, propose the open-hole effect, which can improve the absorption effect of electromagnetic absorbers in the X- and Ku-band by regularly opening certain shaped through-holes in the dielectric material. Based on this effect, an ultra-wideband metamaterial absorber with a special open-hole structure is designed and successfully prepared by numerical simulation, and the effective wavelength bandwidth (absorption > 90 %) covers X- and Ku-band. By optimizing the dielectric material and structural parameters of the absorber, an ultra-broadband metamaterial absorber with a thickness of 2.2 mm, a maximum absorption rate of 99.35 % and an effective absorption bandwidth of 11.6 GHz was obtained. Simulations of TE and TM waves at different angles show that the absorber has excellent electromagnetic wave absorption at different angles of incidence (θ < 30°).

Lightweight broadband microwave absorbing metamaterial with CB-ABS composites fabricated by 3D printing

The self-similarity, high geometric symmetry and spatial utilization properties of fractal structures provide new methods for the development of absorbing metamaterials. In this paper, the microwave absorption properties of the gradient dendritic fractal metamaterial structure (GDFMs) based on carbon black and acrylonitrile–butadiene–styrene composites were investigated. The optimal metamaterial structure has an effective absorption in the frequency range of 4.5–40 GHz. The rotational-symmetry GDFMs leads to the polarization independence, and the GDFMs exhibits a wide-angle absorption performance for both TE and TM waves. It is expected that the proposed GDFMs has good application prospects in electromagnetic wave absorption.

Nonreciprocal wide-angle bidirectional absorber based on one-dimensional magnetized gyromagnetic photonic crystals

We propose magnetized gyromagnetic photonic crystals (MGPCs) composed of indium antimonide (InSb) and yttrium iron garnet ferrite (YIGF) layers, which possess the properties of nonreciprocal wide-angle bidirectional absorption. Periodical defects in the MGPCs work as filters. Absorption bands (ABs) for the positive and negative propagations arise from the optical Tamm state and resonance in cavities respectively, and they prove to share no overlaps in the studied frequency range. Given ω = 2.0138 THz, for the positive propagation, the ABs in the high-frequency range are localized in the interval between 0.66ω and 0.88ω. In the angular range, the ABs for the TE and TM waves reach 60° and 51°, separately. For the negative propagation, the ABs in the low-frequency range are localized in the interval between 0.13ω and 0.3ω. The ABs extend to 60° for the TE waves and 80.4° for the TM waves. There also exists a narrow frequency band in a lower frequency range. The relevant factors, which include the external temperature, the magnetic fields applied to the YIGF, the refractive index of the impedance matching layer, and the defect thickness, are adjusted to investigate the effects on the ABs. All the numerical simulations are based on the transfer matrix method. This work provides an approach to designs of isolators and so on.

Tunable Phase Retarder of 1D Layered Photonic Structure Combining Nonlinear Kerr Dielectric Defect Layers and Magnetized Plasma Materials

AbstractIn this article, through the optimized arrangement of the magnetized plasma, dielectric, and nonlinear Kerr dielectric, a tunable reflection phase retarder with a certain bandwidth is investigated. When the electric field of the incident electromagnetic wave is parallel to the xoy plane and has an angle of 45° with the x‐axis, the electric field can be further decomposed into Ex and Ey along the x‐ and y‐axes, indicating TM and TE waves, respectively. The results show that under reasonable parameters, the 180° or −180° phase delay of the reflected wave of the proposed structure is obtained and adjusted. In particular, the nonlinear bistable response at this performance is also demonstrated. Furthermore, to verify the superiority of the obtained bandwidth of the phase retarder, the influences of the incident angle, the plasma frequency, the external magnetic field, and the nonlinear light intensity on the bandwidth of the phase retarder have been studied. It is observed that the total phase retarder bandwidth can reach 2.6 GHz by appropriately optimizing those parameters. Additionally, this work provides constructive suggestions for tunable broadband phase blockers and half‐wave plates, and it still holds some potential significance in the radome.

Design of ultra-high absorptivity solar absorber based on Ti and TiN multilayer ring structure

The goal of this project is to design a solar absorber that can achieve better absorption spectrum range and absorption. We adopt TiN and Si3N4 laminated ring structure, and after adding two layers of Ti–Si3N4 film, the absorption efficiency of the absorber is greater than 90% and the absorption bandwidth was great than 2450 nm. More noteworthy is that the weighted average absorption rate under AM1.5 is more than 98% (280 nm–3000 nm). On the basis of polarization independence, the solar absorber proposed by us also had strong stability to angular polarization of incident. When the incident angle reaches 60, the absorption of TE wave and TM wave remains above 90%. We also analyzed the effects of different metal materials on the solar absorber, and calculated the emission efficiency of the solar energy absorber at 375 K is 89.82%. Ultra-high absorption solar absorbers have great potential in energy utilization fields, such as converting solar light and heat into public electricity, infrared thermal imaging and information detection.

General strategy for ultrabroadband and wide-angle absorbers via multidimensional design of functional motifs

Developing wide-angle, polarization-independent, and effective electromagnetic absorbers that endow devices with versatile characteristics in solar, terahertz, and microwave regimes is highly desired, yet it is still facing a theoretical challenge. Herein, a general and straightforward strategy is proposed to surmount the impedance mismatching in the ultrabroadband and wide-angle absorber design. A vertical atom sticking on N × N horizontal meta-atoms with conductive film is proposed as the functional motif, exhibiting the strong ohmic dissipation along both vertical and horizontal directions. Assisted by the intelligent optimization strategy, the structure dimension, location, and film distribution are designed to maintain absorbing performance under different incident angles. As a demonstration, an absorber was designed and proved in both simulation and experiment. Significantly, the over 10 dB absorption from 5 to 34 GHz is achieved in the range of 0° to 70° for both TE and TM, and even 3 to 40 GHz from 60° to 70° for the TE wave. Meanwhile, the proposed multidimensional design of functional motifs can be attached with optical transparency function at will. That is to say, our effort provides an effective scheme for expanding matching area and may also be made in optical, infrared, and terahertz regimes.

Ultra-broadband metamaterial perfect solar absorber with polarization-independent and large incident angle-insensitive

Broadband metamaterial perfect absorbers have attracted a great attention to the people who study its use in solar energy harvesting. However, it is an extremely challenge to integrate such properties as ultra-broadband, perfect absorption, polarization-independent, angle-insensitive to a large incident angle and so on into a simple absorber structure. In this paper, we use FDTD to design a simple ultra-broadband metamaterial perfect absorber, consisting of x-cavity titanium nano-disk array based on a Silicon nitride-Titanium-Silicon nitride-Titanium four-layer structure. The optimized results indicate that the absorber broadband absorption spectra range from 400 nm to 2500 nm with 97.6% average absorption at normal incidence. The interactions among SPR, MR and CR lead to a high absorption. Moreover, the absorber is both polarization-independent and large incident angle-insensitive for both TE and TM-polarized waves. In addition, the absorber has an extremely high tolerance to fabrication errors, which is of great significance for practical production and application.

Visible and NIR transparent broadband microwave absorption metamaterial based on silver nanowires

In this study, a visible and near infrared (NIR) transparent and broadband microwave metamaterials absorber based on resistive silver nanowires (AgNW) films is designed and fabricated. The metamaterial unit consists of a concentric annular resonant pattern, a continuous conductive AgNW film and a transparent polymer frame. By using different types of support frames, the absorber can switch between rigidity and flexibility. The absorber has over 90% broadband microwave absorption from 4.1 to 18.2 GHz with 75% visible transparency and 66% NIR transparency. The absorber is polarization insensitive and can keep efficient absorption of TM or TE waves with an oblique incidence angle less than 30°. The radar cross section (RCS) of the absorber is reduced to more than 10 dB, covering all reflection angles and matching the absorption bandwidth range. Compared with traditional transparent microwave absorber (TMA) with indium tin oxide (ITO), the TMA in this work, specifically with high transparent in NIR has a great application in transparent electromagnetic windows of near infrared hyperspectral sensors and optical/laser seekers.

Tunable dual-band linear-to-circular polarization conversion based on the electromagnetically induced transparency utilizing the graphene metamaterial

A tunable dual-band linear-to-circular polarization conversion (LTCPC) related to electromagnetically induced transparency (EIT) is theoretically proposed by employing the graphene metamaterial in the terahertz (THz) regime. Since the electric resonance (bright mode) and the magnetic resonance (quasi-dark mode) for the x - and y -polarized (TM and TE) waves are mutually coupled, the EIT behavior is realized due to the destructive interference. Two transparent EIT windows have emerged in 1.452–1.661 THz and 1.348–1.683 THz when the TM and TE waves are incidents. The corresponding values of the maximum group delay and group index respectively are 225 ps, 162 ps, 1636, and 1177. The LTCPC is achieved at 1.432 THz and 1.676 THz when the graphene does not exist. While the graphene is introduced, the LTCPC is dynamically adjustable by controlling the Fermi energy ( E f ) of the graphene. The optimal ARs can dynamically change between 1.438 (1.689) THz and 1.452 (1.696) THz while the E f changes from 0.1 eV to 0.9 eV. A theoretical investigation of two-oscillator model further confirms the effectiveness and consistency of the simulation results. The presented metamaterial with a thickness of subwavelength and high transparency for the electromagnetic waves opens a new path to the applications in beam steering and polarization controls. • The dual-band linear-to-circular PC of EIT phenomenon can be simultaneously realized. • The structure is equipped with graphene which can adjust the EIT behavior and circular polarization features. • The presented structure is great transparency for the EM wave, and its thickness is subwavelength. • The proposed structure provides a new idea to manipulate the polarization state of the EM wave. • The device is stable for the circular polarization feature within 10°.

Synthetic 2D tellurium nanosheets with intense TE wave polarization absorption by employing the PVD method

Synthetic 2D tellurium nanosheets with intense TE wave polarization absorption by employing the PVD method

Tunable optical whispering gallery mode in a magnetic microsphere suspended in a ferrofluid

Recent developments in microfluidic technologies have led to a growing interest in whispering gallery mode (WGM) optical resonators. In this report, we showed that in the case of TE waves, it is possible to induce such a mode in magnetizable microspheres suspended in a ferrofluid by applying static magnetic fields. The refractive index of a ferrofluid is dependent on the applied magnetic field. Considering this and using a quantum mechanical analog, radial distribution of the pseudo-potential is calculated for different fields and two different visible wavelengths. It is shown that within a certain range of the applied field, potential well is generated and WGM can be generated. Characteristics of the generated potential well are discussed. The finding may be useful for sensing applications in biotechnology and chemical technology.

On the Existence of Nonlinear Coupled Surface TE and Leaky TM Electromagnetic Waves in a Circular Cylindrical Waveguide

On the Existence of Nonlinear Coupled Surface TE and Leaky TM Electromagnetic Waves in a Circular Cylindrical Waveguide