TE Polarization Research Articles

The enhanced nonreciprocal radiation in a grating structure containing a Weyl semimetal film under conical incidence

The enhanced nonreciprocal radiation in grating structure for light under conical incidence is investigated. The basic structure is composed of a one-dimensional grating on a continuous Weyl semimetal planar and a thick metallic mirror. The results show that near-perfect nonreciprocal radiation can be observed for transverse electric wave, which cannot be achieved for light in traditional incidence. Such effect results from the guided mode resonance (GMR) excited inside the grating, demonstrated by studying the electromagnetic field amplitude distribution. Moreover, the strong nonreciprocity is also stable for the geometric parameters in a wide varying range, lowering the cost of manufacture. Most of important, the proposed scheme could be employed to realize enhanced nonreciprocity for both TM polarization and TE polarization with different resonant wavelengths along with the same resonant wavelength. The concepts proposed here should pave the way to the development of polarization-dependent and polarization-independent as well as dual-polarization nonreciprocal emitters.

Characteristics of multi-absorption bands in near IR based on a 1D photonic crystal comprising two composite metamaterials

The Matlab program has been utilized in this study to examine the absorption spectral properties of a one-dimensional photonic crystal (1DPCs) comprising two composite metamaterials through near IR wavelengths. The composite metamaterials are designed from Ag of a gyroidal geometry (layer A) and hyperbolic metamaterial (layer B). Therefore, the introduced design is labeled as [ABn]m\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${[A{B}^{n}]}^{m}$$\\end{document} with n and m to define the periodicity of the hyperbolic metamaterial and the whole structure, respectively. The numerical findings have been introduced in the vicinity of the effective medium theory, transfer matrix method and the Drude model as well. In this regard, the numerical results demonstrate the appearance of some spectral absorption bands ranging from 0.7 µm to 3 µm for both TM and TE polarizations. Additionally, these bands are almost insensitive to the changes in the angle of incidence. Interestingly, we have considered the role played by some parameters such as the permittivities and thicknesses of both layers on the introduced absorption bands. Finally, we believe that the investigated results could be promising through many applications such as wavelength selective absorbers, solar energy, and smart windows as well.

Design of narrowband infrared emitters by hybridizing guided-mode resonance structures with van der Waals materials

In this paper, narrowband emitters have been designed using particle swarm optimization (PSO) in the 10–20 μm infrared range. The device structure consists of an anisotropic α-MoO3 layer combined with the one- and two-dimensional guided-mode resonance structures. Well-defined absorption lines are present in the reflection spectrum for both TE and TM polarizations, thereby yielding narrowband emissivity at desired wavelengths. The band structure of the designed emitters under TM polarization demonstrates distinct features unlike its TE counterpart. These features are attributed to the interaction between guided-mode resonances and phonon polaritons. The results are relevant for applications in active and passive photonic elements in mid- and long-wave IR bands.

Electrically tunable birefringence in nanophotonic waveguide with 2D electron gas in semiconductor heterojunction

An electrically tunable birefringence in a nanophotonic waveguide based on MgZnO-CdZnO semiconductor heterojunction is numerically proposed. Electrical control is realized with two-dimensional electron gas (2DEG) at the interface of ZnO based heterojunction and is used to control the polarization. The waveguide is engineered to enhance interaction of guided optical mode(s) with 2DEG providing us with a wide tuning in modal birefringence. We perform numerical analysis of phase and polarization characteristics of 2DEG based nanophotonic waveguide. Electrical tuning of 0.0112 in modal birefringence is reported by varying the applied voltage from 0 Vto −10 V. The proposed device also exhibits voltage variable optical phase modulation in both TE and TM polarizations. The proposed work can be utilized in applications where integrated photonic devices with variable polarization control are desirable.

Switchable and optically transparent ultrawide stopband frequency selective surface for electromagnetic shielding

In view of the fact that high-frequency electromagnetic waves mainly enter buildings through windows and glass doors, switchable optically-transparent shielding with broad stopband is increasingly needed. Herein, a novel design for a switchable and optically transparent frequency selective surface (FSS) with ultrawide-stopband is presented in this study. The structure consists of a polymethyl methacrylate (PMMA) layer sandwiched between polydimethylsiloxane (PDMS) layers which contain liquid metal microchannels arranged in an orthogonal Ω-shaped configuration. The mobility of the liquid metal can switch the FSS response from an all-pass to an ultrawide bandstop behavior. The proposed FSS achieves a rejection bandwidth of 18.1 GHz, covering P, L, S, C, X and Ku bands, while maintaining a transparency of 81% and high angular stability up to 80°, regardless of polarization. Furthermore, the mechanism behind the ultrawide stopband and high angular stability is explored through an analysis of reflection and absorption for both TE polarization and TM polarization. Experimental validation under both normal and oblique incidence demonstrates the ultrawide-stopband performance of the fabricated FSS.

Polarization conversion filter based on electromagnetically induced transparency-like effect

Owing to the large losses in the conversion process of traditional polarization converters, there is an increasing demand for metasurfaces with excellent transmission performance. In this work, an efficient polarization conversion metasurface is proposed based on electromagnetically induced transparency-like (EIT-like) effect in the terahertz band. The multi-level bright mode paths are excited by an asymmetric structure to obtain orthogonal circular polarization conversion windows. The transmission window is generated by the mutual interference of two sets of bright modes with similar resonant frequencies. Then an asymmetric structure is constructed to achieve transmission window shift under TE polarization and TM polarization, thereby realizing dual-frequency polarization conversion. The metamaterial unit structure consists of four open metal resonant rings and four metal resonant strips. The working mechanism is explored by analyzing the surface current distribution, frequency response, and incident angle characteristics. The results show that electromagnetically induced transparency can be achieved under different polarizations. Furthermore, based on the EIT resonance between the two incident polarizations, the conversion from linear polarization to right-hand circular polarization is achieved at 0.692 THz, and the conversion from linear polarization to left-hand circular polarization is realized at 0.782 THz, transmission coefficients are 0.7 and 0.68 respectively. According to the Stokes parameters, the corresponding ellipticity <i>η</i> values are 96% and 98%, respectively. This EIT-based polarization conversion metasurface with low loss and ultra-thin characteristics has great potential applications in compact antennas, derived radar phased arrays, and military detectors.

Determination of temperature profile inside a PV module operating under specific conditions using a model coupling internal heating to optical absorption

In this study, the complex dynamics behind heat transfer within photovoltaic (PV) solar modules under spectral solar illumination are investigated. A new model coupling internal heating to optical absorption is derived from equations governing light-matter interaction throughout PV module multilayered structure. Reflection and transmission at each interface between two neighboring layers inside a PV module as well as absorption in each layer are taken into account. Dielectric properties of each interface are used to calculate its wavelength dependent reflectance and transmittance according TE and TM light polarization modes. Optical properties of each layer are utilized to determine its absorption coefficient and internal source of warming. Effects of incidence angle and light polarization modes on internal heat function are also analyzed. Heat equation is then solved in steady state limiting case and Temperature profiles inside a PV module under STC and NOCT conditions are determined.

Envisioning the future: optically transparent metasurface-based solar thermophotovoltaic with high conversion efficiency

Transparent solar thermo-photovoltaic (TPV) technology combines visible transparency and solar energy conversion. They are developed for their potential applications in buildings and vehicles windows, where conventional opaque solar cells may not be feasible. TPV’s offer a promising solution to harness solar energy without compromising aesthetics or functionality of transparent surfaces. Broadband absorption at UV and IR frequencies and simultaneous transmission at visible frequencies can be achieved by fabricating metamaterials that employ semi-conducting oxides. In this study, an optically transparent metasurface (OTM) based STPV composed of indium tin oxide (ITO) is introduced as the transparent metal and ZnS as a substrate layer. Our design offers a cost-effective and scalable solution for large-scale fabrication. The designed OTM structure exhibits exceptional absorption capabilities, achieving an absorption rate of up to 99% in the UV region. Additionally, it achieves over 90% absorptivity in the far infrared range and maintains a high average transmittance at visible frequencies. Furthermore, the absorption remains consistently high, exceeding 90%, even when the incident angle is less than 70° for both TE and TM polarization waves. This innovative design holds promise for various applications requiring high-performance transparent metasurface absorbers/emitters. The proposed transparent metasurface based STPV holds great potential for efficient utilization in combined solar/thermal conversion systems.

Grating couplers for efficient integration of surface-emitting blue lasers and silicon nitride waveguide

We report here a theoretical investigation on high efficiency grating coupling for surface emitting blue lasers integrated with silicon nitride (Si3N4) waveguide. DBRs (distributed Bragg reflectors) were introduced into the design which located at the upper and one side of the Si3N4 grating coupler region, and oxide buffer layers was also incorporated simultaneously. By optimizing the grating coupler parameters and the DBR structure, the configuration can be adapted for single polarization or TE/TM simultaneous coupling. The coupling efficiency for TE polarization can reach 72.4 %, and the polarization-independent coupling efficiency of 48 % at vertical incidence was also achieved. This work presents a PIC (photonic integrated circuits) on III-V laser strategy for visible light PICs and innovative applications based on blue laser integrated devices.

Anti-reflection metasurface synergizing plasma and lattice modes: an efficient route to wideband electromagnetic transparency under extreme angles

All-angle wideband electromagnetic (EM) transparency for dual polarizations is desired for many practical applications. Conventionally, surface-mount anti-reflection materials or films are usually used to reduce the reflection and thus enhance transparency. In this paper, we propose to achieve wideband EM transparency under extreme angles for both TE- and TM-polarizations using embedded anti-reflection metasurface. The metasurface is composed of a pair of long and short metallic strips, which can introduce both plasma and lattice modes into the original half-wave wall. The plasma mode can create an angle-stable transmission peak at a lower frequency while the lattice mode renders a transmission peak under extreme angles at a higher frequency due to scattering cancellation between short strips and the substrate. By synergizing the plasma, half-wave, and lattice modes consecutively, wide-band transparency can be achieved under extreme angles for TE polarization. Due to the anisotropy of the metasurface, wideband transparency under TM-polarization is maintained. This finally enables us to obtain wideband EM transparency for dual polarizations under extreme angles. More importantly, the metasurface can also be customized to operate best under any given incident angle. Prototypes were designed, fabricated, and measured. Both the simulation and experiment results verify our method. This work provides an efficient route to wideband EM transparency under extreme angles and may find wide applications in communication, radar, and others.

A Computationally Efficient Electromagnetic Wave Scattering Analysis Method for Electrically Large Multilayered Dielectric Structures

The paper presents a computationally efficient method based on the modified equivalent current approximation for electromagnetic wave scattering analysis of electrically large multilayered lossy dielectric structures. The proposed method can be an effective alternative to commercially available tools and methods, which tend to become computationally intensive with increase in size and losses of structures. The proposed method is applied to compute the radar cross-section of various multilayered dielectric and coated PEC structures for both TE and TM polarization under normal and oblique incidences and compared with method of moments (MoM). The result shows excellent agreement and reduced computational resources and time by a factor of fifteen compared to MoM. The proposed method can be applied directly to study scattering problems involving electrically large multilayer dielectric and conducting structures.

Causal optimal and optically transparent ultra-wideband microwave metamaterials absorber with high angular stability.

Wideband microwave absorbers, especially those with high optical transparency, are significantly used in civil and military fields. This paper proposes an ultra-wideband optically transparent metamaterial absorber (MMA) with causal optimal thickness and high angular stability. Based on the equivalent circuits model of the MMA, a genetic algorithm is adopted to identify the best circuit parameters that can realize broadband microwave absorption. High transparent indium tin oxide and poly-methyl methacrylate are utilized to realize the absorber. Optimization and simulation results show that the designed MMA presents a high microwave absorption above 90%, covering a wide frequency of 2.05-15.5 GHz with an impressive FBW of 153.3%. The proposed MMA exhibits extraordinary angular stability. For TM polarization, it can still maintain a fractional bandwidth (FBW) over 114.5% at an incidence angle of 70° and over 142% at an incidence angle of 60°, while the FBW of both TE polarization and TM polarization exceeds 150% when the incidence angle is below 45°. Furthermore, the proposed absorber has the advantages of high transparency and polarization insensitiveness. A prototype of the proposed MMA is fabricated and experimentally tested. The measured results are in excellent agreement with the optimized design and the full-wave simulation results, demonstrating its excellent performance. Most significantly, the overall thickness of the absorber is 0.102 λ at the lowest working frequency and only 1.08 times the causality-dictated minimum sample thickness. The MMA proposed herein provides methods to achieve high compatibility with wideband microwave absorption, optical transparency, and wide-angle incidence, thus enabling a wide range of applications in stealth, electromagnetic pollution reduction, and electromagnetic compatible facilities.

Trapezoidal dual-function splitter under second Bragg incidence

In this paper, a reflective trapezoidal dual-functional beam splitter grating is proposed, which performs two independent functions at 1550 nm. For TE polarization, the grating can achieve a uniform three-port output with efficiencies of 32.85%, 32.89%, and 32.75% for 0th, -1st, and -2nd orders respectively. For TM polarization, the grating can achieve a highly-efficient single-channel output of order -2nd with an efficiency of 93.27%. HfO2 is chosen as the material of grating ridge layer, the structural parameters of the grating are studied by using rigorous coupled-wave analysis (RCWA) and simulated annealing algorithm (SAA), and the results are verified by using finite element method (FEM). In addition, the influence of structure and incident error on grating efficiency was also analyzed, the results indicate that the grating has good incident bandwidth and manufacturing tolerance with excellent performance.

Compact simply-connected SOI spot size converters for TE and TM polarizations

Spot size converters (SSCs) are pivotal building blocks of silicon on insulator (SOI) on-chip optical systems, which enable efficient coupling of modes between waveguides of different widths. In this paper, we propose two SSCs for TE and TM polarizations based on level-set and adjoint methods, which can convert modes between 0.5 µm and 10 µm wide waveguides. The devices’ lengths are 22.4 µm and 23.7 µm, respectively, with simply-connected structures and the 200 nm minimum feature size. The simulation results demonstrate minimal insertion losses of 0.04 dB and 0.12 dB for the two SSCs, with respective 1 dB bandwidths exceeding 170 nm and 250 nm. Within the wavelength range of 1520–1590 nm, the insertion losses are below 0.42 dB and 0.24 dB. Experimental results, normalized with a referenced 250 µm length adiabatic linear taper, indicates insertion losses of less than dB and dB within the 1520–1590 nm wavelength range for the proposed SSCs, demonstrating a ten-fold reduction in length while maintaining comparable performance to the reference taper. Our devices hold the potential to facilitate the utilization of grating couplers in high-efficiency and high integration applications.

Controlling Thermal Radiation in Photonic Quasicrystals Containing Epsilon-Negative Metamaterials

The transfer matrix approach is used to study the optical characteristics of thermal radiation in a one-dimensional photonic crystal (1DPC) with metamaterial. In this method, every layer within the multilayer structure is associated with its specific transfer matrix. Subsequently, it links the incident beam to the next layer from the previous layer. The proposed structure is composed of three types of materials, namely InSb, ZrO2, and Teflon, and one type of epsilon-negative (ENG) metamaterial and is organized in accordance with the laws of sequencing. The semiconductor InSb has the capability to adjust bandgaps by utilizing its thermally responsive permittivity, allowing for tunability with temperature changes, while the metamaterial modifies the bandgaps according to its negative permittivity. Using quasi-periodic shows that, in contrast to employing absolute periodic arrangements, it produces more diverse results in modifying the structure’s band-gaps. Using a new sequence arrangement mixed-quasi-periodic (MQP) structure, which is a combination of two quasi periodic structures, provides more freedom of action for modifying the properties of the medium than periodic arrangements do. The ability to control thermal radiation is crucial in a range of optical applications since it is frequently unpolarized and incoherent in both space and time. These configurations allow for the suppression and emission of thermal radiation in a certain frequency range due to their fundamental nature as photonic band-gaps (PBGs). So, we are able to control the thermal radiation by changing the structure arrangement. Here, the We use an indirect method based on the second Kirchoff law for thermal radiation to investigate the emittance of black bodies based on a well-known transfer matrix technique. We can measure the transmission and reflection coefficients with associated transmittance and reflectance, T and R, respectively. Here, the effects of several parameters, including the input beam’s angle, polarization, and period on tailoring the thermal radiation spectrum of the proposed structure, are studied. The results show that in some frequency bands, thermal radiation exceeded the black body limit. There were also good results in terms of complete stop bands for both TE and TM polarization at different incident angles and frequencies. This study produces encouraging results for the creation of Terahertz (THz) filters and selective thermal emitters. The tunability of our media is a crucial factor that influences the efficiency and function of our desired photonic outcome. Therefore, exploiting MQP sequences or arrangements is a promising strategy, as it allows us to rearrange our media more flexibly than quasi-periodic sequences and thus achieve our optimal result.

A low-profile metamaterial absorber with ultrawideband reflectionless and wide-angular stability

An ultrawideband reflectionless metamaterial absorber (MA) is proposed by replacing the metallic ground with the complementary split-ring resonator (CSRR) structure. The proposed MA exhibits −10 dB reflectivity spectrum from 1 GHz to 20 GHz, which maintains more than 90% absorption from 1.5 GHz to 20 GHz. Furthermore, it achieves angle stability for TE and TM polarization at oblique incident angles up to 40° and 65°, respectively. To achieve broadband absorption spectrum, we have adopted a single-layer high-impedance surface (HIS) loaded with a double-layer magnetic material (MM) structure. To further realize the RCS reduction into a lower frequency range, we have employed the scattering cancellation technology into the traditional metallic ground. Finally, we have fabricated a sample exhibiting the 10 dB RCS reduction from 1 GHz to 20 GHz with a thickness of 10 mm. Measurement and simulation results confirm that the proposed MA exhibits excellent comprehensive performance, making it suitable for many practical applications.

Design of Broadband and Ultra-Wide-Angle Low-RCS Open-Ended Cavity Based on Phase Cancellation

In this paper, it is proposed to employ phase cancellation metasurface (PCM) to substantially reduce the RCS of an electrically large open-ended cavity (EOC) by scattering the energy to the nonthreatening region, achieving broadband and ultra-wide-angle RCS reduction of the cavity. The PCM, constituted by the collection of polarizing reflectors, is loaded on the inner and outer walls of the composed cavity structure in accordance with the orthogonality principle to obtain a low-RCS cavity. The main benefits of using the polarizing reflector to build a PCM are as follows: On the one hand, it reduces the number of units that make up the PCM, which in principle only requires half of the quantity. On the other hand, it is possible to form a phase difference of 180 degrees that is completely stable. Both the simulation and measured results show that the RCS reduction of 10 dB for normal incidence relative to the original state of the cavity (that is, the metal cavity) over a frequency range of 6.3 GHz to 13.2 GHz under TE polarization and 7.8 GHz to 13.4 GHz under TM polarization has been obtained. Furthermore, the RCS reduction performances of the cavity loaded with the composed PCM under variable azimuth angles are also studied. Numerical and experimental results demonstrate that the ultra-wide-angle RCS reduction from -180° to 180° is acquired. To the best of our knowledge, this is the first time that the PCM, which is made up of a number of polarizing reflectors, has been used to get broadband and ultra-wide-angle RCS reduction for the EOC. This method, which is simple, effective, and low cost, has great application prospects in the RCS reduction design of the cavity.

Dark field imaging of high aspect ratio structures - a simple model.

A simplified model for dark-field optical imaging of three-dimensional high aspect ratio micro- and nano- structures is proposed, to reduce the time taken to simulate object fields with in-plane scattering between different parts of the object. Primary scattering is found by assuming that illumination of Manhattan geometries generates a set of spherical edge waves, following the incremental theory of diffraction. Secondary scattering is found by assuming that primary scattering is re-scattered from nearby features. Diffraction coefficients are simplified, and the number of illuminating beams is limited to those generating waves that enter the objective lens. Images obtained using TE and TM polarizations are compared, and results are benchmarked against a vectorial finite element model. Applications lie in simulating optical inspection of structures containing vertically etched features including MEMS and NEMS.

Polarization-insensitive silicon optic switch based on mode manipulated power splitters and phase shifters

A polarization-insensitive thermo-optic switch is proposed and demonstrated on the silicon-on-insulator platform with a 220 nm silicon core layer. The present device is based on the Mach–Zehnder interferometer structure, consisting of polarization-insensitive power splitters and polarization-insensitive phase shifters (PIPSs). The polarization-insensitive power splitter has been realized by employing an adiabatic directional coupler, which utilizes the fast adiabatic mode evolution by introducing cubic Bézier curves on outer contours, providing broadband 3-dB power splitting for TE and TM polarization modes with only 70 µm coupling length. For the novel PIPSs, the ridge waveguide with large aspect ratio, based on the mode hybridness property, could obtain the same power consumption (Pπ) for an optical switch working at TE and TM polarizations. Experimental results indicate that the measured insertion losses are less than 2 dB and the extinction ratios are larger than 15 dB over a 40 nm wavelength band (covering the C-band).

Dynamic multiplexing manipulation of amplitude and phase in metasurfaces with vanadium dioxide

In this study, we reported the amplitude and phase modulation based on the VO2 tunable metasurface and verified the impact of incident angle on the reflection spectrum. The maximum reflectance modulation is 80.5 % when VO2 changes from insulating to metallic state, at resonance wavelength 1550 nm the phase shifts of TE polarization and TM polarization are 219° and 141°, respectively. We also investigated the angular dispersion characteristics of this metasurface, and the results showed that the resonance wavelength under TE polarization is not affected by the incident angle, while the resonance wavelength under TM polarization shifts when increasing incident angle. In addition, the resonate peak spacing of TE and TM modes is over 200 nm. Angular dispersion and polarization dependence give our device the ability of angle multiplexing and polarization multiplexing.