TE Polarization Research Articles

Design of polarization-independent multilayer dielectric gratings: a reflection-phase threaded approach

We present a method to design polarization-independent multilayer dielectric gratings. In this method the reflection phases in TE and TM polarizations of the multilayer stack thread surface-relief grating at the top and the multilayer stack at the bottom together, allowing the two parts first to be designed separately and efficiently, and then to be combined to achieve simultaneously high diffraction efficiency and large fabrication tolerance. We find numerically that in general a periodic stack is unable to provide the top-grating-demanded phase difference between TM and TE polarizations; adequate aperiodic layers atop of a periodic stack are needed. The analytic diffraction efficiency formula of a recent work [J. Opt. Soc. Am. A 41, 252 (2024)] is used at various places of the presented optimization algorithm to save computation time. An example grating with rectangular surface-relief profile and another with trapezoidal profile were successfully designed, validating the effectiveness of this design method.

Tunable Graphene‐Based Absorber Using Nanoscale Grooved Metal Film at Telecommunication Wavelengths

Graphene‐based absorbers have various modern applications across industries due to their exceptional properties. Some common applications include: thermal management and energy storage. Herein, the design and simulation of a broadband tunable absorber based on graphene with perfect absorption spectra in the near‐infrared region are reported. The proposed structure consists of an MgF2 layer and golden disc surrounded by L‐shaped golden arms placed on single layer of graphene. The structure guarantees polarization‐insensitive (PI) performance under normal incident due to the symmetrical design. The investigation of the PI of the structure reveals almost similar absorption for oblique incident angles up to 55° for TM and up to 60° for TE polarization. The desirable resonance wavelength is achievable by tuning the geometrical parameters. By changing the chemical potential of graphene, the absorption and bandwidth of absorber are controllable. A full width at half maximum of 330 nm is another superiority of this absorber. These considerable aspects of the proposed structure make it practical for varieties of applications such as cloaking, sensing, switching, and so on.

Design of Band Stop Filter Using Epsilon-Negative Frequency Selective Surface

This paper focuses on designing a band stop filter based on epsilon-negative frequency-selective surface (FSS). The unit cell has an electrical length of 0.104λ0 × 0.104λ0 which offers a bandwidth of 2.53 GHz from 1.24 GHz to 3.77 GHz. It has a center frequency of 2.44 GHz and the obtained fractional bandwidth is above 100%. Additionally, the behavior of the presented FSS is explained by the equivalent circuit model and surface current distribution. Within the entire bandwidth, it offers a negative permittivity. The refractive index of BSF is almost zero for 2.45−3.98 GHz range of frequency. The proposed FSS structure exhibits polarization-independent properties and offers a stable frequency response for normal and oblique angles under both TE and TM polarization. Good agreement between the simulated and measured results is obtained for the designed prototype.

High-sensitivity fiber temperature sensor based on composite film structure and lossy mode resonance

In this work, we proposed and demonstrated a high-sensitivity optical fiber temperature sensor based on lossy mode resonance (LMR). The sensor is composed of a D-shaped fiber and a thin composite film. The composite film consists of tin dioxide (SnO2) and polydimethylsiloxane (PDMS). PDMS is inserted as an intermediate layer between D-shaped fiber and SnO2 layer, realizing the separation of TM and TE polarization to reduce polarization crosstalk, while also serving as a temperature sensitive layer. The polarization state of the excited LMR can be freely controlled by adjusting the thickness of the composite film. The proposed sensor exhibits a high temperature sensitivity of −1.1883 nm/°C with a measurement range of 10–90 °C. Meanwhile, a fast response time of ∼ 109 ms was observed due to the ultra-thin PDMS interlayer.

1 × 2 broadband polarization-independent beam splitter based on air annular photonic crystal designed by a particle swarm optimization algorithm

We propose a 1×2 broadband polarization-independent beam splitter based on air annular photonic crystals. The inner and outer radii of the air annular photonic crystals at the V-shaped waveguide side and corners can influence the transmittance and broadband performance. To improve the design efficiency and transmittance of the broadband splitter, particle swarm optimization was used to reverse-design the splitter. The performance of the designed splitter was studied, and the results show that the designed splitter has a wide bandwidth range of 1530–1565 nm. It exhibits a minimum transmittance of 84% and an average transmittance of 87.8% for TE polarization and a minimum transmittance of 81% and an average transmittance of 83% for TM polarization. The response times for both polarizations are below 0.7 ps. This device has promising applications in all-optical communication networks and photonic high-density integration.

Small compressive strain tuning of α-TeO2 and β-TeO2 polymorphs: Electronic, linear, and nonlinear optical properties from first-principles calculations

This study examines the effects of 2 % compressive strain on the structural, electronic, and optical properties of α-TeO2 and β-TeO2 polymorphs. α-TeO2’s bandgap increases from 3.64 eV to 3.70 eV, while β-TeO2’s decreases from 3.632 to 3.53 eV. Lattice parameters uniformly reduce in α-TeO2, but vary dissimilarly in β-TeO2. PDOS analysis shows O-2p and Te-5p states dominate near the band edges. Optical behavior is anisotropic, with enhanced polarizability and refractive indices under strain. Nonlinear optical properties improve with increased strain, especially the non-linear susceptibility components, which are relevant for second-harmonic generation. Born Effective Charges show increased Te polarization and reduced oxygen polarization, impacting dielectric response.

Analysis of Slitted Parallel‐Plate Waveguides Using the Method of Kobayashi Potential

AbstractA new solution for the analysis of slitted parallel‐plate waveguide is proposed using the method of Kobayashi Potential (KP). The interior and exterior problems are studied for the TE and TM polarizations. Simplified forms of Weber‐Schafheitlin (WS) integrals are utilized for problem formulation. The Fourier function space is exploited to construct the governing linear system of equations. A simple strategy is suggested for the evaluation of the required integrals. Numerical results are validated through convergence analysis and available reports based on the Moment Method (MM). It is shown that the KP is superior to the conventional MM in the sense of tracking edge singularities, especially when the radiation problem is of interest.

Robust Multi-Band DNG metamaterial absorber for GPS (L1), ISM, and 5G application with Enhanced polarization and angle stability

This research introduces a triple-band metamaterial absorber characterized by insensitivity to both polarization and incident angles. The structure includes square ring resonators on the upper side and a continuous metal ground on the lower side, separated by an FR4 substrate. At the lowest operating frequency, the unit cell’s thickness, and length measure 0.0128λ and 0.156λ, respectively. Under normal incidence, the proposed absorber demonstrates three clear absorption peaks at 1.56, 2.43, and 3.36 GHz, achieving absorption rates of 98 %, 99 %, and 97 %, respectively. The absorption response exhibits variation with incident angles up to 70° for both TM and TE polarizations due to its high-level symmetry. This configuration attains negative permittivity and permeability suitable for operational frequencies in the L-band and S-band. The study examines the electric field, impedance, and surface current to provide additional evidence for the absorption analysis. A validated RLC circuit equivalent to the proposed structure has been confirmed using Advanced Design System (ADS). The results indicate a slight deviation, especially at frequencies beyond the resonance frequencies. The structure underwent fabrication and testing in an anechoic chamber, revealing a strong correlation between the simulated and measured results. The suggested absorber holds promise for ISM applications, radar systems, sensing technologies, and energy harvesting systems.

Comparative Analysis of Two Different MIM Configurations of a Plasmonic Nanoantenna

AbstractTwo plasmonic nanoantenna configurations—nanodisk and nanostrip arrays—in a metal–insulator-metal (MIM) setup were proposed, optimized, and compared by simulating their optical properties in three-dimensional models using COMSOL Multiphysics software. The optical responses, including electric field enhancement, absorption, reflection, and transmission spectra, were systematically investigated. Optimized geometrical parameters led to a significant enhancement of the electric field within the gap layers and almost perfect light absorptance for both structures. The results showed that the enhancement of the electric field depends on the polarization of the incident light. For both polarizations, the periodic circular nanodisk array showed a stronger field enhancement with an electric field enhancement factor of 6.6 × 106 and TE polarization, and a larger absorptance of 98% at its dipole resonance wavelength, indicating the fundamental plasmonic mode. In addition, weaker resonant modes were observed in the absorptance and reflectance spectra of both nanostructures, with the nanostrips exhibiting sharper and stronger higher-order modes, making them suitable for applications requiring precise wavelength selectivity and narrow-band responses. Despite their different geometric shapes, both structures exhibited similar optimized metal film thickness and nanoparticle height, comparable modes in number and position, and identical optimized light incidence angles. Furthermore, increasing the dielectric gap layer thickness and optimizing it to a specific value revealed its ability to measure the refractive index, making it a promising candidate for sensing applications.

Multifunctional plasmonic metamaterial absorber in the middle infrared range for polarization detection

It is significant to enhance the absorption rate, extend bandwidth and obtain the polarization information of electromagnetic radiation for detection technology. Here, we design and propose the simulation model of broadband and highly polarization-sensitive mid-IR metamaterial absorber by regulating the light field with the plasmonic response. The absorber is based on a simple subwavelength metal grating construction. Its absorption response can cover the 3–5 μm infrared atmospheric window. Detection technology in the mid-IR range has a strong ability to detect objects at high temperatures. In this waveband, the maximum absorption rate can reach more than 98% for TM polarization radiation. In comparison, it is less than 2% for TE polarization radiation, and the extinction ratio of 50 is concurrently achieved. The absorption spectrum can be broadened to the high and low-frequency direction by reasonably adding nanostrips in the unit cell. We also investigate the relationship between incident angle and spectral absorption and clarify the absorption stability of the absorber under oblique incidence. By integrating with the infrared focal plane detector, the device can make the infrared photodetector integrate and develop from a single sensor to multi-dimensional information and promote the development of polarization detector to miniaturization, high efficiency and high integration.

A closely spaced dual band polarization insensitive FSS for 5G applications

This study presents a novel single layer Frequency Selective Surface (FSS) for fifth generation (5G) applications with a polarization independent closely spaced dual band response. The proposed design consists of four split ring apertures etched on a square patch printed on a RT5880 dielectric substrate. The FSS has two stop-bands at 24.78 GHz and 28 GHz center frequencies with attenuations around 55 dB. The S21<−10 dB bandwidths (BW) of these bands are 14.48 % and 9.25 %, respectively and these closely spaced bands succeed 1.13 frequency ratio. It shows a stable frequency response for both TE and TM polarizations. Furthermore, the FSS represents a single layered and quite thin (thickness 0.042λl) structure with its unit cell size (0.70λl × 0.70λl, where λl is the free-space wavelength at lower frequency). The novelty of the presented FSS is not only achieving a small closely spaced band ratio in the mmWave band and exhibiting polarization insensitivity but also providing these features with a simple geometry and, uncomplicated single layer structure. The simulation results were confirmed by well accordant measurement results. All these results make the presented FSS a good candidate for 5G electromagnetic interference (EMI) shielding applications.

Graphene-based metamaterial ultrawideband absorber with enhanced terahertz performance

In this paper, we present a graphene-based metamaterial ultrawideband absorber operating in the terahertz regime. The absorber is composed of two patterned and continuous graphene layers, a bottom gold layer, and a SiO2 substrate that separates the continuous graphene layer from the gold layer. The absorption spectrum is enhanced by integrating a graphene resonator with water, which has frequency-dependent permittivity. The water is encapsulated in polytetrafluoroethylene (PTFE) in the form of a circular ring sandwiched between the two graphene layers. Simulation results show that the absorber attains a 90 % absorption bandwidth of about 14.55 THz. The proposed absorber is polarization-insensitive under normal incidence. For TE polarization, the absorption level remains stable for incident angles θ from 0° to 55° across the entire frequency band (14.55 THz), except for the 5–8 THz range. For TM polarization, the absorption level remains stable for θ ranging from 0° to 60° over the entire bandwidth. Additionally, the absorption level is consistent for both TM and TE polarizations across the entire bandwidth for incident angles φ from 0° to 90°.

Enhanced the sensing sensitivity of the metamaterial absorbers with patterned convex graphene in the terahertz

Abstract In this paper, a patterned graphene metamaterial terahertz absorber is theoretically designed. The proposed absorber consists of a gold layer, a dielectric layer of SiO2, and graphene. The sensing sensitivity of the proposed absorber is simulated for the absence and presence of a square convex nanostructure, trapezoidal convex nanostructure, and rounded convex nanostructure. The sensitivity comparison between convex and absent convex nanostructures is studied, compared to no convex nanostructure, the simulated results show that the sensing sensitivity can be improved with the convex nanostructures, it is found that the absorber has two obvious absorption peaks, and it is insensitive to TE and TM polarization, and the maximum sensitivity corresponding to low-frequency and high-frequency modes is 0.911 THz RIU−1 and 1.561 THz RIU−1, respectively. Our work will play an important role in improving the sensing sensitivity of the graphene metamaterial absorber. Meanwhile, it can also greatly promote the application of biological sensing, modulation, integrated photodetectors, frequency selectors, sensors, filters and so on.

Sensitivity detection of imidacloprid pesticide using a metasurface sensor in THz spectrum regime

Imidacloprid (C9H10ClN5O2) pesticide is frequently used in agriculture as it effectively controls various insect pests. Accurate detection of imidacloprid concentrations is crucial for food safety and other fields. This work proposes a novel metasurface (MS) sensor with efficient sensitivity in the THz frequency regime to detect imidacloprid pesticides. The MS sensor has an electrical size of 7.17λ × 7.17λ with the smallest wavelength. The transmission coefficient remains stable for the metasurface sensor’s TE and TM polarization modes. Due to the symmetrical design, it exhibits strong electric and magnetic field enhancement with polarization insensitivity for different incident angles. The sensing capability is tested by implementing different sample analyte thicknesses of imidacloprid in the top surface of the MS sensor. Imidacloprid analyte thickness increases cause a red and blue change in the metasurface’s transmission frequency. The simulation results show that the suggested MS sensor has a refractive index (RI) sensitivity of 0.125 THz/RIU, and a Q factor of 5.262 and 4.084. This is a simple, cost-effective, sufficiently sensitive, and efficient THz MS sensor with a wide range of applications in pesticide concentration measurement, including imidacloprid.

An ultra broadband metamaterial absorber based on metal-dielectric-metal technology for THz spectrum

This paper introduces a novel ultra-broadband Metamaterial Absorber (UBMA) demonstrating significant absorption capabilities across a wide terahertz frequency range from 2.42 THz to 6.11 THz. The 3.7 THz bandwidth represents 87% of the central frequency. The proposed UBMA comprises three layers: a star-shaped metal patch on top, a dielectric substrate in the middle, and a metallic ground plane below. Simulations using CST Microwave Studio software reveal that the design achieves high absorption at five distinct frequencies: 2.47, 3.45, 4.89, 6.01, and 6.87 THz, with absorption rates of 99% for the first four peaks and 90% for the fifth peak. The study of electric field and surface current distribution provides insights into the absorption mechanism. While the UBMA exhibits polarization-independent performance, its angular response shows some sensitivity to the incident angle, especially beyond 30° Despite this, the absorber maintains over 70% absorptivity up to a 45° incidence angle for both TE and TM polarizations within specific frequency ranges. The simple structure combined with high absorption efficiency makes the UBMA suitable for THz imaging, detection, and stealth applications, although its angular sensitivity must be considered for certain applications.

Metal Mesh Metasurfaces as Dual-Band Bandpass Filters for Terahertz Frequencies

In the paper, we propose a new strategy to design of metal mesh filters (MMFs) based on spatial symmetry analysis of bound states in the continuum(BICs) and manipulating and control with resonances, when BICs transformed to the resonances due to spatial perturbations in the MMF structure. The design of a dual-band polarization-insensitive terahertz bandpass filter with wide upper stopband characteristics using a single conducting layer patterned with rectangular holes is presented. The transmission response of the MMF with two poles is obtained to realize dual-band characteristics and three zeros to suppress the stopband. The proposed design has achieved broadband bandpass transmission characteristics under both TE and TM polarizations with canter frequencies at 0.516THz and 0.734THz and 3dB bandwidths of 25% and 17%, respectively, and upper stopband from 0.887THz to 1.6THz with over 10dB suppression.

Long‐Infrared Broadband Polarization‐Sensitive Absorber with Metasurface Based on Ladder Network

AbstractPlasmonic resonant and metamaterial structures allow for manipulating the polarization properties of electromagnetic waves to achieve polarization beam splitting. Broadband polarization‐sensitive metamaterial absorbers based on surface plasmon polaritons have the advantages of high‐energy utilization and excellent stability, which may replace traditional polarizing devices. Here, an absorber based on a ladder network construction is designed theoretically and investigated experimentally. The absorber can possess almost 92% average absorptivity for TM polarization light in 8–12 µm range (experimental result: 83% from 7 to 11 µm). It is especially sensitive to the polarization angle of incident light, and with the increase of polarization angle, the broadband absorption response can present analogously monotonous reduction. The theoretical and experimental results for TE polarization light are 12% and 25%, respectively. The broadband absorption response performs angle insensitive property under oblique incidence. The proposed metamaterial absorber opens a path to realize broadband polarization‐sensitive absorption based on simple nanostructure. It will possess great potential applications in high‐performance polarimetric photodetectors and imaging fields.

A bilayer angular selective surface with transmission at non-zero incident angle based on odd resonance of square ring slot FSS

In this paper, a bilayer angular selective surface (AGSS) is proposed and designed based on the first odd mode resonance of frequency selective surface (FSS). It can realize angular selective transmission (AST) at non-zero incident angles whereas reflection occurs at other angles. Based on the band pass FSS with square ring slot (SRS) structure, we cascade two uniform SRS structures with air space to form the quarter-wave stack. It can realize AST at 30° or 60° for TE or TM polarization, respectively. In addition, a bilayer FSS with maximum transmission at 30° under TE polarization is fabricated and measured. The measurement result shows good agreement with the simulation one, with -3 dB transmitted angular width of 10° The proposed angular selective surface can be applied in high efficient energy harvesting system and radar system with increased signal-to-noise ratio (SNR) level.

Polarization-Insensitive Lithium Niobate-on-Insulator Interferometer.

The key components of a polarization-independent electro-optic (EO) interferometer, including the beam splitter, mode converter, and directional coupler, are designed based on a lithium niobate (LN) platform on an integrated insulator to ensure high extinction ratios. By elaborately designing the geometric structure of the multimode interference (MMI) coupler, beam splitting of equal proportions and directional coupling of higher-order modes are realized. The most prominent characteristic of the proposed interferometer is polarization insensitivity, which is realized by converting TM polarization into TE polarization using a mode converter, providing conditions for the study of light with different polarizations. At 1550 nm, the visibility of the interferometer is 97.59% and 98.16% for TE and TM, respectively, demonstrating the high performance of the proposed LN polarization-independent interferometer.

Towards a CMOS compatible refractive index sensor: cointegration of TiN nanohole arrays and Ge photodetectors in a 200 mm wafer silicon technology

In this work, we present the monolithic integration of a TiN nanohole array and a Ge photodetector towards a CMOS compatible fabrication of a refractive index sensor in a 200 mm wafer silicon technology. We developed a technology process that enables fabrication with high yields of around 90%. Ge photodetectors with a Ge layer thickness of 450 nm and an area of 1600 µm2 (40 µm x 40 µm) show dark current densities of around 129 mA/cm2 and responsivities of 0.114 A/W measured by top illumination (TE polarization; λ = 1310 nm; angle of incidence = 14 °) at a reverse bias of 1 V. Nanohole arrays were structured in a 150 nm thick TiN layer. They were integrated into the back end of line and placed spatially close to the Ge photodetectors. After the metallization, passivation, and pad opening, the nanohole arrays were released with the help of an amorphous silicon stop layer. A significant impact of the TiN nanohole arrays on the optical behavior of the photodetector could be proven on the wafer level. Photocurrent measurements by top illumination confirm a strong dependence of optical properties on the polarization of the incident light and the nanohole array design. We demonstrate very stable photocurrents on the wafer level with a standard deviation of σ &lt; 6%.