Transverse Electric Polarization Research Articles

Dual-insensitive zero refraction based on annular photonic crystals

Over the past few years, zero refraction (ZR) represents an important breakthrough in field of distinctive dynamic optical beam tuning for double-zero-index (media with zero relative permittivity and permeability) photonic crystals (PCs). Because accidental ZR effects for conventional PCs is sensitive to the structural or refractive index parameters, how to enhance the robustness of ZR design is vital for applications. Here, we report a pioneering wave property that reveals a non-accidental Dirac-like cone dispersion composed of low- or high-energy bands, corresponding to dual-insensitive ZR effects for both transverse magnetic and transverse electric polarizations based on the same annular PCs. The performance of non-accidental ZR is simultaneously based on refractive index-insensitivity and structural- insensitivity, attributed to a satisfactory filling ratio.

Ultra-broadband terahertz metamaterial absorber using a simple design method

Using a simple design method cutting away some parts of a circular metallic patch resonator, we propose an ultra-broadband terahertz metamaterial absorber (MA) with bandwidth of 4.11 THz. Simulation results demonstrate that the simple design method greatly improves the absorption performance compared with previously reported absorbers. The proposed absorber exhibits the co-polarization ultra-broadband absorption performance with absorptivity above 90% in the range of 2.65–6.76 THz and the relative absorption bandwidth (RAB) of 87.35%. Moreover, the proposed absorber can maintain high absorptivity above 80% for incident angles up to 40° under both transverse electric (TE) and transverse magnetic (TM) polarizations. The ultra-broadband absorption originates from the combination of dipolar and LC resonances. The simple design method can also be applied to some other structures such as square metallic patch resonator. Furthermore, by adjusting the dimensions of proposed absorber, a broadband microwave MA can be easily obtained. Therefore, it can become an effective design method to achieve broadband absorption in various frequency ranges from microwave to optical frequencies.

TM polarization preferentially implemented in the next generation of high-intensity laser systems based on multilayer dielectric gratings

The laser-induced damage (LID) response of multilayer dielectric gratings (MDGs) to transverse magnetic (TM) and transverse electric polarization was investigated based on polarized-independent MDGs. It was found that TM-polarized MDGs have the superiority of a high LID threshold, low sensitivity to laser excitation strength, low response to damaged structure, and reduced LID growth speed and dynamics. These results provide a strong motive to preferentially develop and mount TM-polarized MDGs in the next generation of high-intensity picosecond-petawatt laser systems.

Metamaterial perfect absorber using elliptical nanoparticles in a multilayer metasurface structure with polarization independence.

A metamaterial perfect absorber (MPA) using elliptical silver nanoparticles is proposed and investigated to provide 100% absorption for both transverse electric and transverse magnetic polarizations with a wide range of incident angles and polarization independence. Metamaterial absorbers with narrow absorption performance over a wide frequency range are significantly desired in sensing applications. Incident angle insensitivity and polarization angle independence are key features of MPAs. The output characteristics are examined using the three-dimensional finite difference time domain method. The effective medium theory and transmission line theory are applied to investigate the simulation results. Here, the 100% absorption occurs at resonance wavelength of λres = 2290 nm, and maximum sensitivity and figure of merit become 200 nm/RIU and 720 RIU-1, respectively. The results show that an absorption spectrum is insensitive to the incident angle of 0°-60°. The proposed device can be used as a high-performance biosensor and photodetector.

Approach for eliminating the zeroth order by T-type grating with polarization loss reduction

We describe a two-port reflective beam splitter with the elimination of the zeroth order based on T-type metal grating. Under the condition of a normal incidence wavelength λ = 1.550 μm, for transverse electric (TE) polarization, the grating efficiencies of the zeroth and ±first orders can reach 1.35% and 48.28%, respectively. And for transverse magnetic (TM) polarization, efficiencies reach 0.49% and 48.30%, respectively, where energies of the zeroth order are suppressed well for both TE and TM polarizations. Furthermore, the numerical analysis indicates that the grating has a wide incident bandwidth (the efficiencies of over 47% at a bandwidth of 118 nm) as well as an excellent process tolerance in period and duty cycle. The grating performance is also stable with a simple structure so that it has a wide application prospect in optical polarization devices, laser systems, polarization imaging, etc.

Elliptical Birefringent Rib‐Channel Chirowaveguides for Quasicircularly Polarized Light Applications in Integrated Photonics

Polarization in photonic‐integrated circuits (PICs) is governed by transverse electric (TE) and magnetic (TM) polarizations due to the planar structure of the chips. Therefore, all states of polarization (SOPs) other than TE and TM, in particular circular polarization, cannot be routed without modification across the chips. Herein, the realization of rib‐channel chirowaveguides supporting elliptically polarized guided modes by combining linear and circular birefringences as predicted by the coupled mode approach is shown. The sol–gel process and the imprint technique to make channel chirowaveguides with different sizes and consequently modulate ellipticity of the eigenmodes from linear to quasicircular are used. Circularly polarized light propagates therefore with a low polarization beating and in particular without handedness inversion. These results open the field of application of PICs to all domains where circularly polarized light is relevant.

Manipulation of photon states in photonic crystals based on silicon

Coupling between the active centers generated by localized states and the two-dimensional photonic crystals (2D-PCs) has been used to select model in the nano-laser and the optical interconnects on silicon chip. The photonic crystals have been investigated in the simulating calculation, and the physical model has been built in the manipulation of photon states. New quantum phenomena appear in the photonic crystals as well as in the atomic crystals. We have numerically studied on the band structure of 2D-PCs with different types of lattice and various shapes in the optical communication windows. The simulating calculation results show that the band gap of photon states can be effectively manipulated in 2D-PCs by using the competition between the quantum confinement effect and the lattice symmetry effect, in which the band gap width of the photon states will obviously increase by changing the lattice symmetry and by increasing the filling rate of the air hole to restrain photons in 2D-PCs on silicon. It is interesting to make a comparison between the transverse electric (TE) polarization and the transverse magnetic (TM) polarization, in which a wider band gap occurs in the TM mode. By adjusting the defect mode in 2D-PCs, the photon states can be localized into the second and third windows of optical communication for selecting modes and resonating on silicon chip.

Light Polarization in Tunnel Junction Injected UV Light‐Emitting Diodes

The polarization of the light emitted by an ultraviolet light‐emitting diode (LED) has a direct impact on the device performance: a transverse electric polarization of the emission is preferred for extraction from the surface of the diode grown along the c axis. While this is the case for most UV LEDs grown on AlN, this state of events could be called into question when a tunnel junction (TJ) is added to make up for the poor p doping in Al‐rich (Al,Ga)N and improve the hole injection. Indeed, nitride‐based TJs mainly inject holes with a Γ7 symmetry, which could lead to transverse magnetic polarization of the light emitted by the diode. We have experimentally investigated this important issue and delivered a clear answer to this question.

Using critical coupling to achieve monolayer graphene perfect absorber with high-sensitivity and polarization-independence

In this paper , by using critical coupling theory analysis and the finite-difference time-domain (FDTD) method for simulation calculations, we indicate theoretically that the graphene-cylinder-metal arrays structure is a perfect absorber with high-sensitivity and polarization-independent in the near-infrared region. The results show that the absorber can achieve a perfect absorption of 99.14%, which is more than 43 times the absorption of bare monolayer graphene (2.3%). In the case of the same geometric parameters, whether transverse magnetic (TM) or transverse electric (TE) polarizations, the absorption and resonance peak wavelength of the absorber are equal , because the graphene-cylinder-metal arrays structure is a highly symmetric structure. Furthermore, through numerical simulation and theoretical analysis, on the one hand, the absorber has high sensitivity up to 939.30 nm/RIU. On the other hand, when the incident light source is normally incident, the absorption performance of the arrays structure does not vary with the change of the polarization angle, that is, the system has polarization-independent characteristics. We believe this work provides a good reference for studying the interaction of enhanced light with monolayer graphene, and opens up new possibilities for the practical application of new photons and optoelectronic devices (such as detectors, sensors, etc.). By using critical coupling theory and the finite-difference time-domain (FDTD) method simulations, we indicate theoretically that the graphene-cylinder-metal arrays structure is a monolayer graphene perfect absorber in the near-infrared. Through numerical simulation and theoretical analysis, the absorber has high sensitivity up to 939.30 nm/RIU and the absorption performance of the arrays structure is polarization-independent. • The proposed graphene-cylinder-metal arrays structure can achieve a perfect absorption of 99.14%. • The sensitivity (S) and figure of merits (FOM) of the proposed perfect absorber can reach 939.30 nm/RIU and 161.11, respectively. • In the critical coupling state, the perfect absorber has high-sensitivity and polarization-independent.

A polarization-insensitive, wide-angle dual-band tunable graphene metamaterial perfect absorber with T-shaped strips and square ring

Metamaterial perfect absorbers play an essential role in many optoelectronic devices. In this paper, a dual-band tunable metamaterial perfect absorber based on graphene is proposed. The simulation results present that under normal incidence two absorption peaks of 99.9% and 99.9% occur at the frequencies 1.69 THz and 4.30 THz, respectively. Impedance matching theory is employed to elaborate this dual-band perfect absorption phenomenon. While at oblique incidence, the absorption of the absorber remains more than 90% over a wide incident angle from 0° to 75° for the transverse electric (TE) polarization and 60° for the transverse magnetic (TM) polarization separately. Furthermore, it is also independent to the polarization angles. In addition, the effects of different geometrical parameters and the chemical potential of graphene on the resonant frequencies are investigated in detail. The two peaks of the absorber can be dynamically tuned by the variation of the chemical potential of graphene. Due to its good performances, the designed metamaterial perfect system has great potential applications in biosensing, photodetectors, stealth, and imaging devices.

Frequency-tunable wide-angle polarization selection with a graphene-based anisotropic epsilon-near-zero metamaterial

In this paper, we achieve frequency-tunable wide-angle polarization selection based on an anisotropic epsilon-near-zero (AENZ) metamaterial mimicked by a subwavelength graphene/SiO2 multilayer. The physical mechanism of wide-angle polarization selection can be explained by the analysis of the iso-frequency curve (IFC). Under transverse electric polarization, only the incident lights which are close to normal incidence can transmit through the designed multilayer since the IFC of the AENZ metamaterial is an extremely small circle. However, under transverse magnetic polarization, all the incident lights can transmit through the designed multilayer since the IFC of the AENZ metamaterial is a flat ellipse. Therefore, polarization selection can work in a broad angular width. By changing the gate voltage applying to the graphene, the operating frequency of polarization selection can be flexibly tuned. The optimal operating angular width of high-performance polarization selection where the polarization selection ratio is larger than 102 reaches 54.9°. This frequency-tunable wide-angle polarization selector would possess potential applications in liquid crystal display, read-write magneto-optical data storage, Q-switched lasing, and chiral molecule detection.

Ultralight and Low-Cost Structural Absorbers With Enhanced Microwave Absorption Performance Based on Sustainable Waste Biomass

As a practical microwave absorber, besides satisfying the basic broadband absorption performance, the density, cost, and process complexity are considerable factors in radar stealth and electromagnetic protection fields as well. Here, a simple and economical structural absorber (SA) is proposed to remarkably broaden the absorption bandwidth of biochar from banana peel. By optimizing the size parameters of the unit cell, the optimal SA shows more than 90&#x0025; absorption in the frequency range from 3.4 to 18 GHz by employing a lightweight porous carbon derived from sustainable biomass. The lightweight porous biochar provides the SA low-density properties with a surface density of only 0.574 <inline-formula> <tex-math notation="LaTeX">$\text{g}\cdot $ </tex-math></inline-formula>cm<inline-formula> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula>. In such a SA, the greatly enhanced absorption performance mainly originates from the synergistic effect of microscopic and macroscopic scales. By optimizing the pattern design of the SA, the effective impedance is matched with free space in a wide frequency range, thus dissipating more electromagnetic waves through multiple resonances and edge scattering effects. In addition, whether transverse electric or transverse magnetic polarizations, stable broadband absorption can be maintained in a wide incidence angle. Thus, this work provides a new prospect for waste utilization of banana peel and a facile low-cost route to greatly extend the microwave absorption bandwidth.

Demonstration of a high extinction ratio TiN-based TM-pass waveguide polarizer

A high extinction ratio transverse magnetic (TM)-pass plasmonic waveguide polarizer has been designed and optimized. This device exploits two parallel TiN strips embedded in a silicon dioxide cladding to cut off the transverse electric (TE) polarization state, which is either reflected or absorbed, while the TM mode can pass through the main silicon waveguide with significant low losses. Given a device of 5 µm length, an extinction ratio as high as 60.7 dB and an insertion loss of 2.23 dB were achieved at the target wavelength of 1.55 µm. To our knowledge, this extinction ratio is one of the highest values ever reported. In the wavelength of 1.45–1.59 µm, the proposed device provides an optical bandwidth of 140 nm for an extinction ratio more than 30 dB and an insertion loss less than 3 dB. This device is relatively simple and is easier to be fabricated than other architectures that are found in the literature.

Using an Equivalent-Circuit Model to Design Ultra-Wide Band-Stop Frequency-Selective Surface for 5G mm-Wave Applications

In this work we propose a system of two frequency-selective surface (FSSs) with an ultra-wide band-stop response for 5G millimeter-wave applications. The analyses are based on the equivalent circuit method, which predicts the transmission characteristics for a plane wave with normal and oblique incidence, and the scattering matrix technique, which provides the result of the cascaded structure. The geometries used in the single-layer FSSs are simple to design, and a series of basic equations are described in order to calculate the inductance and capacitance of conducting strips. FSSs prototypes were fabricated and measured in an anechoic chamber. The first FSS is shaped with the four-arms star geometry, which has a resonant frequency at 27.92 GHz for both measured and simulated results. The second FSS is based on the quasi-square geometry, whose resonant frequency for the experimental and numerical results are 35.68 GHz and 35.76 GHz, respectively, for the transverse electric polarization. These two single-layer FSSs present theoretical resonant frequency at 28 GHz (FSS #1) and 35.8 GHz (FSS #2). Cascading of the two FSSs was realized by using an air gap whose effect was analyzed. A gap space in the order of about &#x03BB;/4 matched with the predicted resonant frequency of the individual structures. Numerical and measured results show excellent agreement with a maximum error of 1.03%. All measured results closely follow those of simulated ones, thus validating the design approach and applications.

Electromagnetic Imaging of Uniaxial Objects by Artificial Intelligence Technology

The electromagnetic imaging of uniaxial objects by the Artificial Intelligence (AI) technology is presented in this paper. We study the two-dimensional inverse scattering problem from uniaxial objects illuminated by the TM (Transverse Magnetic) and TE (Transverse Electric) polarized incident waves. As the uniaxial objects have different components of permittivity along different transverse directions, the problem of TE polarization will be more severe than that of TM polarization. We use the Dominant Current Scheme (DCS) and Back Propagation Scheme (BPS) to calculate the preliminary permittivity distribution. By combining with deep learning and neural networks, the permittivity distribution of those uniaxial objects can be reconstructed more accurately. U-Net is used to reconstruct the permittivity distribution, because U-Net has shared the weights and biases, which can effectively reduce the network complexity and is very suitable for solving image processing problems. In the numerical results, we added different noises to compare the reconstruction results of the DCS and BPS initial estimations through the U-Net. Numerical results show that the reconstruction permittivity for the DCS initial estimation is better than that for the BPS’s. Our diversity is that we have reconstructed the uniaxial objects by neural network successfully with less time-consuming effort and real-time imaging.

Sensitivity characterization of polarization operating by embedded reflective grating

In this paper, a novel embedded reflective grating (ERG) is presented to realize bi-function polarization operating at infrared band by finite element analysis (FEM). For transverse electric (TE) polarization, a two-port output (0th and −2nd orders) with an efficiency of more than 47% and excellent uniformity can be obtained. For transverse magnetic (TM) polarization, a high efficiency output of 94.72% can be achieved at the −2th order. The results of the analysis of the electric field intensity distribution, angular and wavelength bandwidths further demonstrate the advantages of the proposed grating. In addition, the tolerance analysis of period and duty cycle prove the feasibility of the grating in practical production.

Triangular metallic ring-shaped broadband polarization-insensitive and wide-angle metamaterial absorber for visible regime.

The inherent bandwidth limitations make it quite challenging to achieve the wideband response of metamaterial absorbers. In this paper, a metamaterial absorber based on triangular metallic rings has been proposed to attain wideband absorption (>90%) in the wavelength span of 400-750 nm. The absorber is constituted of periodically placed unit cells, where each unit cell contains three concentric triangular chromium metal rings. The absorption of the design remains stable (above 70%) over a wide range of incidence obliquity (0°-60°) under transverse electric (TE) and transverse magnetic (TM) polarization. Further, the absorber shows polarization-insensitive behavior over different polarization states. The low-cost and thermally endurable chromium metal, wide absorption, and wide-angle stability make the proposed absorber a suitable candidate for applications like solar energy harvesting, solar detectors, solar thermal photovoltaics, and photonic devices.

High-Performance Polarization Splitter-Rotator Based on Lithium Niobate-on-Insulator Platform

We propose and experimentally demonstrate a high-performance polarization splitter-rotator based on the lithium niobate-on-insulator platform, consisting of an adiabatic taper, an asymmetric directional coupler, and a multimode interference mode splitter. Two injecting modes with orthogonal polarization states were separated, and the transverse magnetic (TM) polarization state was rotated to the transverse electric (TE) polarization state simultaneously. The designed device is fabricated in a single-step etching process, providing an extinction ratio of 20 dB over 80 nm wavelength range and insertion loss of less than 0.65 dB for both TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> modes launched. Lithium niobate-on-insulator, polarization splitter-rotator, extinction ratio.

Performance Analysis of ZigBeePRO Network Using the Shortest Path Algorithm for Distributed Renewable Generation

The communication requirement for integrating Distributed Renewable Generation (DRG) into Smart Grid (SG) is not strict, where the reliability and critical demand of data delivery are compromised due to the low-data rate and power of ZigBee. However, the presence of various dielectric constant materials in the DRG can cause transmission impairments of the electromagnetic wave. In this paper, we have analysed the performance of the ZigBeePRO network by applying the shortest path algorithm while delivering energy data from the solar DRG to the SG. The DRG architecture is created by considering a real test-bed of 35 kW solar DRG at Universiti Putra Malaysia (UPM). The numbers of nodes are calculated from specifications of the ZigBeePRO enabled Waspmote embedded board, inverters, and electrical parameters of a Photovoltaic (PV) module. The results of the obtained propagation path loss model indicate that the Transverse Electric (TE) and Transverse Magnetic (TM) polarizations are proportional to the loss of the propagation path at different incident angles (α); however, an exception is observed for the TM polarization at α = 55 o. Due to this polarization effect, the brick-built type cabin at the DRG site is a consequence of a higher propagation path loss than the Iron (III)-made cabin. The other performance parameters, including network throughput, data loss, and ZigBeePRO collision, are also evaluated.

Facile Molecular Weight Determination of Polymer Brushes Grafted from One-Dimensional Diffraction Grating by SI-ATRP Using Reflective Laser System.

Gelatin was immobilized selectively on the amide groups-modified bottom of a trench array of a photoresist template with 2 μm resolution by the ethyl(dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide reaction. The gelatin-immobilized line array was brominated to generate a macroinitiator for atom transfer radical polymerization. Poly(methacrylic acid) (PMAA) brushes were grafted from the macroinitiator layer as line arrays of one-dimensional diffraction gratings (DGs) for various grafting polymerization times. A laser beam system was employed to analyze the optical feature with a characteristic diffraction effect of the PMAA DGs at a 45° incident angle along the transverse magnetic and transverse electric polarization. The growth of the PMAA brush lines increased both their heights and widths, leading to a change in the reflective diffraction intensity. The PMAA brushes under various grafting polymerization times were cleaved from the substrate by digestion of gelatin with trypsin, and their molecular weights were obtained by gel permeation chromatography. The change degree of the diffraction intensity varied linearly with the molecular weight of the PMAA brushes over a wide range, from 135 to 1475 kDa, with high correlation coefficients. Molecular weight determination of polymer brushes using the reflective diffraction intensity provides a simple method to monitor their growth in real time without polymer brush cleavage.