Metal Wire Grid Polarizer Research Articles

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.

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.

Simulation of Resonant Cavity-Coupled Colloidal Quantum-Dot Detectors with Polarization Sensitivity

Infrared detectors with polarization sensitivity could extend the information dimension of the detected signals and improve target recognition ability. However, traditional infrared polarization detectors with epitaxial semiconductors usually suffer from low extinction ratio, complexity in structure and high cost. Here, we report a simulation study of colloidal quantum dot (CQD) infrared detectors with monolithically integrated metal wire-grid polarizer and optical cavity. The solution processibility of CQDs enables the direct integration of metallic wire-grid polarizers with CQD films. The polarization selectivity of HgTe CQDs with resonant cavity-enhanced wire-grid polarizers are studied in both short-wave and mid-wave infrared region. The extinction ratio in short-wave and mid-wave region can reach up to 40 and 60 dB, respectively. Besides high extinction ratio, the optical cavity enhanced wire-grid polarizer could also significantly improve light absorption at resonant wavelength by a factor of 1.5, which leads to higher quantum efficiency and better spectral selectivity. We believe that coupling CQD infrared detector with wire-grid polarizer and optical cavity can become a promising way to realize high-performance infrared optoelectronic devices.

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.

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.

High extinction ratio terahertz broadband polarizer based on the aligned Ni nanowire arrays.

We present a broadband terahertz (THz) polarizer based on the stacks of aligned Ni nanowire (NW) arrays. We demonstrated that the polarizer has an extinction ratio of 58.8 dB and an average extinction ratio of 46.6 dB throughout a frequency range of 0.3-2.3 THz. Compared to carbon-nanotube and metallic wire-grid polarizers, our Ni-NW polarizers with rapid, reliable, low-cost fabrication processes are ideal candidates for emerging THz technologies.

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.

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.

Performance comparison of polarized white light emitting diodes using wire-grid polarizers with polymeric and glass substrates

Polarized white light emitting diodes (WLEDs) packaged with reflective metal wire-grid polarizer of polymeric and glass substrates were investigated. The performance comparison of polymeric wire-grid polarizer film (WGF) and nano wire-grid polarizer (NWGP) with glass substrate was evaluated. The transverse electric field (TE) polarization transmittance of WGF is less than that of NWGP due to its smaller grid parameters. Despite of the higher duty cycle of WGF, the angular-dependent extinction ratio (ER) of the polarized WLEDs (PWLEDs) with WGF is higher than that of with NWGP. Regarding increasing drive currents, the PWLEDs with NWGP had better color stability than that with WGF due to better substrate thermal stability. In summary, linewidth, period and substrate material are the crucial factors for the PWLED packaging using wire grid polarizer.

Carbon nanotube fiber terahertz polarizer

Conventional, commercially available terahertz (THz) polarizers are made of uniformly and precisely spaced metallic wires. They are fragile and expensive, with performance characteristics highly reliant on wire diameters and spacings. Here, we report a simple and highly error-tolerant method for fabricating a freestanding THz polarizer with nearly ideal performance, reliant on the intrinsically one-dimensional character of conduction electrons in well-aligned carbon nanotubes (CNTs). The polarizer was constructed on a mechanical frame over which we manually wound acid-doped CNT fibers with ultrahigh electrical conductivity. We demonstrated that the polarizer has an extinction ratio of ∼−30 dB with a low insertion loss (<0.5 dB) throughout a frequency range of 0.2–1.1 THz. In addition, we used a THz ellipsometer to measure the Müller matrix of the CNT-fiber polarizer and found comparable attenuation to a commercial metallic wire-grid polarizer. Furthermore, based on the classical theory of light transmission through an array of metallic wires, we demonstrated the most striking difference between the CNT-fiber and metallic wire-grid polarizers: the latter fails to work in the zero-spacing limit, where it acts as a simple mirror, while the former continues to work as an excellent polarizer even in that limit due to the one-dimensional conductivity of individual CNTs.

Flexible Sub-THz Metal Wire Grid Polarizer Based on an EGaIn<formula> <tex>$_{24.5}$</tex> </formula> Alloy

A flexible sub-THz polarizer based on an eutectic Gallium-Indium alloy (EGaIn $_{24.5}$ ) on a vinyl acetate substrate is fabricated and tested. The EGaIn $_{24.5}$ alloy shows low melting point, good wettability, and high conductivity, resulting in a low-cost alternative to conductive inks based on metal nanoparticles. These properties are exploited to draw metal wire grid polarizers by using a technical pen on a bendable sheet of vinyl acetate monomer. Measurements are carried out with a transmission THz-TDS setup in the frequency range from 0.1 to 0.6 THz, showing an extinction ratio up to 20 dB. This approach allows a quick low-tech and cost effective implementation of flexible polarizers in the sub-THz band.

Image sensor pixel with on-chip high extinction ratio polarizer based on 65-nm standard CMOS technology

In this study, we demonstrate a polarization sensitive pixel for a complementary metal-oxide-semiconductor (CMOS) image sensor based on 65-nm standard CMOS technology. Using such a deep-submicron CMOS technology, it is possible to design fine metal patterns smaller than the wavelengths of visible light by using a metal wire layer. We designed and fabricated a metal wire grid polarizer on a 20 × 20 μm(2) pixel for image sensor. An extinction ratio of 19.7 dB was observed at a wavelength 750 nm.

Selective electroless plating of silver nanograting patterns with no lateral growth for the fabrication of polarizers

Metal patterning has been useful for fabricating many optical and electronic devices. Among all the patterning methods, selective electroless plating in combination with micro-contact printing (μCP) is a simple process compatible with roll-to-roll processing. However, this process suffers from the difficulty to avoid lateral growth during the electroless plating of metal. That will place a limitation on the fabrication of nanoscale patterns, such as the metal wire grid polarizer. In this study, we launch a new approach to restrict the lateral growth of metal by depositing metal selectively in the grooves of a three-dimensional template. The template was first treated with a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) only on the protrusion surface using μCP, and then treated in SnCl2 solution to activate the surface of the trenches for the selective electroless plating (ELP) of silver inside the trenches. A wire-grid polarizer was thus fabricated by selectively depositing 70nm-thick silver in the trenches of a nanograting template with a trench width of 100nm and a pitch of 180nm. The maximum extinction ratio of the polarizer thus obtained was about 130 in the wavelength range of 635–650nm.

Achromatic polarization splitting effect of metallic gratings with sub-50 nm wide slits

We report on a broadband polarization splitting phenomenon in an aluminum grating with its period much smaller than the wavelength of incident light. Under oblique incidence, grating is highly transparent for one polarization, but it is opaque and reflects the orthogonal polarization. By using the Fourier modal method and planar waveguide theory, we show that, comparing with the traditional metallic wire grid polarizers, the improved confinement of TM0 mode within the sub-50 nm wide grating slits is responsible for this polarization splitting effect.

Fabricating bi-layered metallic wire-grid polarizers by nanoimprint and O2 plasma etching

This paper proposes an efficient process for fabricating bi-layered metallic wire-grid polarizers (WGP), which consist of a metallic (aluminum) layer on the top and a dielectric (PMMA) layer at the bottom. The proposed architecture was fabricated from the insertion structure, which was accomplished through only three steps, i.e., nanoimprint, aluminum deposition and chemical mechanical polishing (CMP), to embed the Al wire grating into PMMA substrate. By taking the advantage of the characteristic of the insertion structure, this technique fabricated PMMA wires with O2 plasma etching by employing the nano-scale Al wire gratings as a mask to achieve bi-layered structures. The proposed bi-layered structures of metallic WGP can achieve superior optical performance, such as the extinction ratio of 497 and brightness gain of 1.18, from 0^o to 40^o of incident angles at a wavelength of 650nm of incident light. In this paper, FE-SEM and FIB images show that the bi-layered wire-grid structure with wire gratings 100nm in linewidth, 240nm in pitch, and 300nm in total height, i.e., 150nm each for Al and PMMA wire gratings, was successfully replicated on a PMMA substrate of 1cm^2. Various O2 plasma etching periods were employed to accomplish the desirable bi-layered structures as well as its optical performance. In addition, we demonstrate that the deeper PMMA wire gratings of bi-layered structures cannot acquire the higher extinction ratio because of the increases of the P-polarization as well as the S-polarization.

Direct Metal Transfer Lithography for Fabricating Wire-Grid Polarizer on Flexible Plastic Substrate

This paper reports on the fabrication of polymer-based metallic wire-grid polarizers using a direct metal contact printing method. The proposed method can directly transfer a metal pattern from a silicon mold to a soft plastic substrate simply by roller pressing and infrared (IR) heating. With properly chosen loading contact pressure and heating temperature, metallic linear grating structures with a linewidth of 60 nm, a period of 170 nm, and an area size of 2.5 ×2.5 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are successfully formed on the surface of a polyethylene terephtalate (PET) substrate. The optical performance of the fabricated flexible polarizers is experimentally measured and numerically analyzed in the near-IR spectrum with wavelength from 800 to 1500 nm. Inspired by the numerical simulation results, the optical characteristics of the flexibe polarizers are further enhanced by reactive ion etching on the PET substrate. Good agreements between experiments and theoretical simulation are obtained. Future developments and potential applications of this metal contact transfer lithography method will be addressed.

Fabrication and characterization of bilayer metal wire-grid polarizer using nanoimprint lithography on flexible plastic substrate

In this work, we demonstrate the fabrication of bilayer metal wire-grid polarizers and the characterization of their performance. The polarizers with 200 nm period were fabricated on flexible plastic substrates by nanoimprint lithography (NIL), followed by aluminum deposition. Transmission efficiency over 0.51 and extinction ratio higher than 950 can be achieved in the visible range when the aluminum thickness of the polarizer is 100 nm. The fabrication process only involves direct imprinting on flexible plastic substrates and aluminum deposition, without any resist spin-coating, lift-off, and etching processes, which is much simpler, less costly, and applicable to large volume production.

Polarization Analyzing Image Sensor with On-Chip Metal Wire Grid Polarizer in 65-nm Standard Complementary Metal Oxide Semiconductor Process

A polarization analyzing complementary metal oxide semiconductor (CMOS) image sensor with a fine on-chip metal wire grid polarizer in the 65-nm standard process is presented. The extinction ratio is an important characteristic for a polarizer that depends largely on the feature size of the metal wire grid pitch and the fabrication CMOS process. To improve the extinction ratio, we designed and fabricated a sensor chip in the 65-nm process. The design rules of the 65-nm process realize the fine metal wire grid pitch compared with the wavelength of visible light. Improvement of extinction ratio is expected by such a fine structure. With the fabricated sensor, an extinction ratio greater than 40 was achieved. The difference between the measured value and the simulation value of the extinction ratio, and pixel crosstalk of the fabricated sensor are discussed.

Polarization Analyzing Image Sensor with On-Chip Metal Wire Grid Polarizer in 65-nm Standard Complementary Metal Oxide Semiconductor Process

A polarization analyzing complementary metal oxide semiconductor (CMOS) image sensor with a fine on-chip metal wire grid polarizer in the 65-nm standard process is presented. The extinction ratio is an important characteristic for a polarizer that depends largely on the feature size of the metal wire grid pitch and the fabrication CMOS process. To improve the extinction ratio, we designed and fabricated a sensor chip in the 65-nm process. The design rules of the 65-nm process realize the fine metal wire grid pitch compared with the wavelength of visible light. Improvement of extinction ratio is expected by such a fine structure. With the fabricated sensor, an extinction ratio greater than 40 was achieved. The difference between the measured value and the simulation value of the extinction ratio, and pixel crosstalk of the fabricated sensor are discussed.

Direct printing of silver nanoparticles by an agarose stamp on planar and patternedsubstrates

In this study, we have used an agarose stamp to conduct direct printing of silver nanoparticles,nanowires and nanoplates on both planar and structured substrates. Nanoparticle solutioncould be first coated on an agarose stamp, and then transferred to a planar substrate.Micro-patterns comprising metal nanoparticles could be printed on planar substrates withoutthe formation of residual layers. Thus a three-dimensional metal microstructure could beeasily fabricated. The patterning of electrodes by printing Ag nanowires directly onTiO2 was also demonstrated to fabricate resistive random access memory (RRAM) devices byall-solution-processing methods. By using a flat agarose stamp, the patterns printed on themicrostructured substrates were quite different from those on the nanostructuredsubstrates. On the microstructured substrates, direct printing could print silvernanoparticles onto the protrusion surface, and could print silver layers as thickas several microns, useful for high conductivity electrodes. On the substrateswith nanostructures such as photonic crystals or nano-gratings, direct printingcould transfer nanoparticles into the grooves or cavities only due to the contactof the agarose stamp with the groove or concavity surface. A new approach tofabricate metal wire grid polarizers was further demonstrated. A nanoporousagarose stamp has a good potential for printing using nanoparticle suspension.