Metal Wire Grid Research Articles

A Dual-Mode Polarization Image Sensor Design Based on In-Pixel Dual-Band Metal Wire Grid for Trustworthy Sensing

In this article, we present the design of an on-chip polarization image sensor with a hardware root of trust (RoT) for trustworthy sensing provided by an interconnection metal-wire-grid (MWG) structure using a standard complementary-metal-oxide-semiconductor (CMOS) process. The proposed MWG structure features dual operation modes, which are polarization image sensing mode at the visible spectrum and physical unclonable function (PUF) mode at the near-infrared spectrum. By integrating the MWG on top of the photo-sensing pixel, the corresponding photocurrent is read out with a mainstream three-transistor-active-pixel-sensor (3T-APS). Moreover, prototype chips are fabricated using a 65-nm 1P8M CMOS process to validate the proposed design. For the polarization mode at 630 nm, the extinction ratio (ER) is measured to be 17 dB. For the PUF mode at 875 nm, the averaged unstable bits and bit error rate (BER) of 15 test chips are reported to be 3.5% and 0.29%, respectively. The responses generated in the PUF mode of the fabricated sensor chips also passed the widely adopted National Institute of Standards and Technology (NIST) and the autocorrelation function (ACF) randomness tests.

1: A Miniaturized Polarization‐multiplexed Dual‐plane Head‐mounted Display System for Augmented Reality

A dual-plane head-mounted display system based on polarization-multiplexing is proposed. A metal wire grid polarizer is employed to separate the two orthogonal polarizations to different optical paths due to its excellent polarization-selective characteristics within large angle and spectrum ranges. System parameters including the curvatures of the reflective mirrors and the aspheric lens have been optimized to achieve good image quality within a field of view of ~50 degrees at different focal depths. Our system could provide correct depths for full-color 3D images, so that the vergence-accommodation conflict and visual fatigue problems could be solved.

Terahertz difference-frequency-generation quantum cascade lasers on silicon with wire grid current injectors.

We propose the concept and experimentally verify the operation of terahertz quantum cascade laser sources based on intra-cavity Cherenkov difference-frequency generation on a silicon substrate with the current injection layer configured as a metal wire grid. Such a current injector configuration enables high transmission of TM-polarized terahertz radiation into the silicon substrate while simultaneously providing a low-resistivity metal contact for current injection.

P‐68: Student Poster: A Miniaturized Polarization‐multiplexed Dual‐plane Head‐mounted Display System for Augmented Reality

A dual‐plane head‐mounted display system based on polarization‐multiplexing is proposed. A metal wire grid polarizer is employed to separate the two orthogonal polarizations to different optical paths due to its excellent polarization‐selective characteristics within large angle and spectrum ranges. System parameters including the curvatures of the reflective mirrors and the aspheric lens have been optimized to achieve good image quality within a field of view of ~ 50 degrees at different focal depths. Our system could provide correct depths for full‐color 3D images, so that the vergence‐accommodation conflict and visual fatigue problems could be solved.

A high-performance terahertz back-reflections blocker based on wire grid and metasurface quarter-wave plate

Terahertz back-reflections blocker is a kind of device that effectively isolated the harmful reflected waves in an optical system, and plays an important role in the applications of terahertz transmission and communication. In this paper, a high-performance terahertz back-reflections blocker based on the metal wire grid polarizer and metasurface quarter-wave plate is demonstrated. By designing the metasurface with high-efficiency polarization conversion and low loss, the maximum blocking efficiency reaches 50.7 dB at 1.51 THz, and the blocking efficiency bandwidth of 20 dB reaches 280 GHz in the experiment. The combination of a metasurface quarter-wave plate and a wire grid polarizer is simple in construction and has low requirements for the operating environment, such as no magnetic field, low temperature and other conditions. Moreover, the ultra-thin nature of the metasurfaces makes this high-efficiency and low-loss back-reflections blocker have broad application prospects in the field of THz integrated on-chip systems.

Circular polarization detection metasurface inspired by the polarized vision of mantis shrimp

Mantis shrimps can recognize polarization states that are invisible to human eyes. Inspired by its polarization vision, we propose a simple micro-nano integrated structure including a metasurface array with diamonds overlapped partially, and metal wire grids. Here, because of the asymmetry of the designed nanostructure, the device is sensitive to polarized light. The consistency between the results of FDTD simulations and our theoretical derivation shows that the design can effectively distinguish the rotation of circular polarizations by achieving differential detection of circular polarization states. The design differs from the common single-layer metasurface, achieves higher extinction ratio while maintaining a high transmittance. Especially, the peak of extinction ratios up to 1800 in the 700–1000 nm wavelength range. Therefore, the advantages of the design are enabling applications requiring high resolution and precision such as polarization detection and imaging, biomedical diagnosis, and weak magnetic detection.

HOMOGENIZATION OF METAL GRID REINFORCED COMPOSITES FOR NEAR-FIELD LOW FREQUENCY MAGNETIC SHIELDING

The purpose of this paper is to provide simple analytical homogenization methods for composite materials containing a metallic wire grid. Estimating their effective electrical properties facilitates the numerical simulation of composite structures for shielding applications in the automotive industry. The presented methods are based on surface impedance approaches and effective media theory. The obtained results show that the shielding properties of the described wire grid composites can be accurately estimated and bounded, using the proposed theories in the low frequency range. The frequency limits vary according to the studied sample. For the presented materials, the validity of the results is shown to be up to a few megahertz. The experimental validation is done by measuring the shielding effectiveness of composite samples using a near-field test bench.

Development of Infrared Wide Band Polarizing Elements with Subwavelength Metal Wire Grids

Development of Infrared Wide Band Polarizing Elements with Subwavelength Metal Wire Grids

Terahertz Polarizers Based on 2D Ti3C2Tz MXene: Spin Cast from Aqueous Suspensions

Herein, the fabrication of terahertz (THz) polarizers is reported on by simply spin casting two‐dimensional (2D) MXene Ti3C2Tz nanosheets on a photolithographically patterned THz‐transparent substrate and subsequent immersion in acetone. Lines 30 nm‐thick and 10–20 μm wide result in electric field (E) extinction ratios (ER) of up to 3 dB, or power ER of up to 6 dB. Simulations show the possibility of achieving ER beyond 16 dB, or power ER higher than 32 dB by increasing the thickness of the MXene lines to 1.5–2 μm and optimizing the metasurface patterns. The Ti3C2Tz nanosheets are solution‐processed and can be deposited on a variety of substrates, including flexible ones. Once encapsulated, chemically stable THz polarizers, that combine high performance and low production costs, can be readily manufactured, with characteristics that compare favorably with the much more involved metallic wire grid polarizers, including gold and tungsten. Moreover, recent demonstration of dynamic tunability of Ti3C2Tz THz conductivity by ultrafast optical pulses opens the possibility of using MXene wire‐grids in high‐speed THz modulators.

Electromagnetic characteristics influence caused by wire cage replacing hollow conductor cylinder in hybrid simulator

The focus of this paper is the electromagnetic characteristics of cylindrical wire grid cage, an equivalent substitute for a hollow conductor cylinder. First of all, the equivalent radius is derived based on the conformal transformation and the equivalent electromagnetic field theory, respectively. Then, the electromagnetic simulation software CST is used to simulate the influence of the density and thickness of the metal wire grid on the risetime, pulse width and peak value of the electric field in the test area. Further, the electric field distributions of the cylindrical wire cage and the hollow conductor cylinder are compared. The results show that the cage structure can completely replace the hollow conductor cylinder and verify the rationality of the equivalent radius theory.

Preparation and measurement of subwavelength bilayer metal wire grid polarizers on flexible plastic substrates

Abstract This paper presents a process for the fabrication of subwavelength bilayer metal wire grid polarizers and describes the performance characterization of polarizers that were produced using the proposed method. These polarizers have a period of 278 nm and were fabricated on flexible plastic substrates using nanoimprint lithography followed by an aluminum deposition process. Transmission efficiency in excess of 0.55 and an extinction ratio of more than 32 dB were achieved in the visible range when the aluminum layer thickness of the polarizer was 70 nm. When a polarization analyzer with a six-channel sensor prototype was tested, an average error of 0.2002°was obtained, with a maximum error of 1.105°and a standard deviation of 0.7255°. The proposed fabrication method will be suitable for many applications in optics, including the manufacture of compound eye structures.

Multiband and Wideband 90° Polarization Rotators

Inspired by techniques utilized in the design of frequency-selective surfaces, multiband and wideband 90° polarization rotators are proposed in this letter. The basic structure is constructed from three layers. The front and back layers contain metal wire grids orthogonal to each other, whereas the middle layer consists of resonant elements with 45°-twisted angle, which plays the main role in determining the overall response of the structure. Employing single and multiple resonators in the middle layer, first-order single- and multiband are achieved. By cascading two first-order middle layers, a second-order response is accomplished. A very wideband response is achieved by utilizing a wideband resonant element in the middle layer. Several design examples are presented and simulated, two of them are fabricated and tested to validate the simulated results.

Topologically induced transparency in a two-phase metamaterial

It is theoretically and numerically demonstrated that a mixture of two topologically distinct material phases is characterized by an anomalous “transparency window” in a spectral range wherein the individual material phases are strongly reflecting. In particular, it is shown that a metamaterial formed by a metallic wire grid embedded in a magnetized plasma may support the propagation of waves with long wavelengths, notwithstanding the components, when taken separately, completely block the electromagnetic radiation. The effect is explained in terms of topological properties of the magnetoplasmon. Furthermore, it is highlighted that some naturally available materials may be regarded as a mixture of two topologically distinct phases, and hence may be characterized by a similar anomalous transparency effect as well.

Performance optimization of polarized-light-emitting source based on aluminum metal grid for display application

The effective polarized light, i.e., the amount of light participating in an actual liquid-crystal-display operation, was enhanced using a metal polarizer on a conventional nitride-based light-emitting-diode (LED) package. The optimal structure of the metal wire grid was demonstrated using finite-difference time-domain simulations; its performance was evaluated in terms of the polarization ratio and transmittance. In addition, a feasible structure of polarized light source was proposed to maximize the performance of displays in terms of energy efficiency. When an aluminum (Al) wire grid with a line width of 51 nm, aspect ratio of 3.5, and duty cycle of 0.37 was applied on top of an encapsulated LED package, an approximately 70% larger effective polarized light could be achieved. These results are promising to reduce the total power consumption of a display.

Metallic wire grid behavior and testing in a low pressure gaseous noble elements detector

High voltage performance has been a challenge for noble element detectors. One piece of this challenge is the emission of electrons from metal electrodes when applying high voltage. This has become a major concern for low-background detectors such as LUX-ZEPLIN (LZ). LZ is a liquid xenon Time Projection Chamber (TPC) searching for Weakly Interactive Massive Particles (WIMPs). In this work, we demonstrate a method to measure electron emission from metallic electrode grids via detection of proportional scintillation light. We find consistency with Fowler-Nordheim emission with a surface parameter β = 1988 after electro-polishing treatment of a stainless steel grid.

Spontaneous growth of polarizing refractory metal ‘nano-fins’

Traditional polymer polarizers degrade in harsh environments and at high temperatures, reducing the polarization effect. In contrast, polarizers produced with refractory metals have vastly improved thermal stability and resistance to harsh environments but are expensive to fabricate. Here we demonstrate prototype refractory metal wire grid polarizers produced by co-sputtering molybdenum and aluminum under specific conditions. Removal of the aluminum through selective dissolution enables the nanostructure array to transmit light. The polarization spans 500–1100 nm and the extinction ratio significantly increases to >100. Possessing broadband polarization and sufficient extinction ratios, the new polarizing film has potential applications in coatings for sunglasses, windows, pyrometers, scientific instruments, and LCD panels.

飞秒激光微加工制备金属线栅太赫兹偏振片

飞秒激光微加工制备金属线栅太赫兹偏振片

Dynamic wavefront measurement with a pinhole linear polarizer point-diffraction interferometer.

We propose a pinhole linear polarizer point-diffraction interferometer (PLP-PDI) for dynamic wavefront measurements. The proposed interferometer uses a metallic wire grid linear polarizer that acts as a point-diffraction plate to generate an ideal spherical wave, from which we can obtain orthogonally polarized reference and test beams. The special polarization phase-shifting configuration allows four phase-shifted interferograms to be captured in a single shot with high precision and stability. The wavefront can then be reconstructed using a phase-unwrapping algorithm. In this paper, we describe the theory of the PLP-PDI and analyze the possible errors introduced by the device. The feasibility of the proposed PLP-PDI was verified by direct measurements of a wavefront. The experimental results show that the proposed PLP-PDI is an effective and efficient tool for the dynamic measurement of wavefronts.

The use of polymeric and metallic geogrid on a full-scale MSE wall/embankment on hard foundation: a comparison of field data with simulation

A full-scale reinforced earth embankment was designed and constructed by the Department of Highways of Thailand on a hard foundation in Phitsanulok Province, Thailand. Two types of reinforcement were used in the embankment. One side was reinforced with polymeric reinforcement consisting of polyester (PET), polypropylene (PP) and high-density polyethylene (HDPE) and referred to as a reinforced steep slope (RSS), with an angle of 70° from horizontal. On the other side, the embankment was reinforced with metallic reinforcement consisting of metallic strips (MS) and steel wire grids (SWG) combined with vertical segmental concrete facing and referred to as a mechanically stabilised earth wall (MSEW). The behaviour of the reinforced soil slope and the mechanically stabilised earth wall on a hard foundation were observed and compared with predictions from the PLAXIS 3D software. The lateral displacements and settlements were very small in the case of the MSEW with inextensible reinforcement. The corresponding lateral and vertical deformations in the RSS were much larger due to its extensible reinforcing materials. The stiffnesses of the reinforcing materials decrease in the following order: MS, SWG, PP, HDPE and PET. The results obtained from three-dimensional (3D) finite element method simulations (using PLAXIS 3D) were in good agreement with the field measurements in terms of vertical and lateral deformations and strains in the reinforcement.

Selection of absorptive materials for non-reflective wire grid polarizers

Wire grid polarizers often have reflective characteristics, such that some incident light is transmitted through the polarizer, while the rest is reflected. For some applications, such as anti-reflective films in OLEDs, non-reflective (or absorptive) wire grid polarizers are necessary; these can be realized by the deposition of an absorptive material on the nanoscale metal wire grid. However, because this deposited absorptive layer can severely affect the polarization characteristics, its material must be selected carefully. The polarization characteristics of a given nanowire grid polarizer can be simulated using rigorous coupled-wave analysis (RCWA). In this study, several types of metal oxides and nitrides were tested as candidate materials for the absorptive layer of a non-reflective polarizer. Nanopatterned double layers with absorptive and reflective functions were modeled using RCWA. Simulations were conducted for various pattern widths, depths, and periodicities. CuO and Fe3O4 showed optimal polarization characteristics among the simulated absorptive layers. Simulations indicated that the performance of non-reflective wire grid polarizers could be enhanced using CuO or Fe3O4. The design of absorptive polarizers was fully characterized by simulation for future experimental research.