High Reflectance Contrast Research Articles

Electrospun Materials with High Reflectance and Polarization Contrast for Sensing Applications in the Mid-Infrared Atmospheric Window

Electrospun Materials with High Reflectance and Polarization Contrast for Sensing Applications in the Mid-Infrared Atmospheric Window

Low-Cost and Fast Hydrogen Alarm System With Optical Readout Based on Suspended Palladium Film

A low-cost and high-efficiency hydrogen sensor can greatly promote the development of the hydrogen economy. It has been demonstrated that the light scattering induced by volume expansion of Pd film during hydrogenation can enable fast and high-contrast optical hydrogen sensing. Here, we present an optical hydrogen alarm system based on light scattering on a Pd film during hydrogenation. Two fibers are used to connect the sensing chip with the LED and photodiode in the alarm system, which separates the explosive detection area from the electronics and thus avoid the potential risk of spark induced by electric current. The sensing chip consists of a Pd/PMMA bilayer on a PDMS substrate with a micropillar array on the surface. This forms a partially suspended Pd/PMMA bilayer, which can reduce the constraint from the substrate on Pd film and improve the response rate. We optimize the structural parameters of the sensing chip and reduce the response time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</sub> to about 2.2 s with a high reflectance contrast of about 960% at 650-nm wavelength when exposed to 4% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mixed with air. Such a large optical response can reduce the requirements of the detection equipment and save cost. Meanwhile, the sensor exhibits high recyclability and hydrogen selectivity in the air, which shows great potential for practical hydrogen alarm applications.

Pd films on soft substrates: a visual, high-contrast and low-cost optical hydrogen sensor

For the rapid development of the hydrogen economy, a reliable and low-cost hydrogen sensor appears to be extremely important. Here, we first show that a palladium film deposited on polydimethylsiloxane (PDMS) can obtain an exceedingly high-reflectance contrast of 25.78 over the entire visible band upon exposure to 4 vol% hydrogen gas (H2) mixed with nitrogen gas. This high-reflectance contrast results from the surface deformation induced by the volume inflation after exposure to H2, leading to the transition of the near-specular surface to a diffusing surface. In addition, a change in brightness is readable by naked eye upon exposure to H2 with various concentrations from 0.6 to 1 vol% under the illumination of a fluorescent tube. Furthermore, this sensor possesses an excellent recyclability and quick response time of a few seconds. Compared with Pd nanostructure-based hydrogen sensors, this visual, high-contrast and low-cost sensor is of great potential for practical hydrogen sensing.

Compact linearly polarized ceramic laser made with anisotropic nanostructured thin films.

A novel method is proposed for the fabrication of polarizing laser mirrors for compact solid-state lasers using glancing angle deposition. Changing the inclination angle and the azimuthal orientation of the substrate during deposition allows one to create and control in-plane birefringence of a deposited thin film by changing its nanostructure. Principal refractive indices of tungsten trioxide films were determined for various deposition angles using transmission and reflection ellipsometry. High-reflectance contrast between orthogonal linear polarization directions was obtained using a single material without any additional processing steps. These birefringent films were the building blocks of a Bragg mirror that was tested as an output coupler of a (Yb0.1Y0.9)3Al5O12 ceramic laser in a laser-diode end-pumped configuration. Continuous-wave, linearly polarized, transverse single-mode laser emission was obtained at a wavelength of 1030 nm with a polarization extinction ratio higher than 973 (30 dB).

P‐121: Fast‐Response Reflective TN Mode with Enhanced Contrast and Reflectance

AbstractThe distinguished NTSC and power efficient performance make field sequential RGB LCOS becomes popular solution for the pico‐projectors. One of the difficulties of field sequential projectors is how to make fast response, high reflectance and high contrast LCOS. In this paper, a new LC mode design approach is proposed which give excellent contrast 800 and fast total response time &lt; 1.2ms while reasonable polarization conversion efficiency 95% is obtained. The LED turn on duty can be 97% for 100% NTSC.

P‐141: The Advanced Transflective IPS LCD by Photo Alignment Technology

AbstractWe have developed 2.4″ QVGA transflective IPS LCDs with novel cell configuration. Transflective LCDs have intrinsically the difference of the optical phase retardation between the transmissive part and the reflective part. In order to compensate for this optical path length difference, we have newly designed the separate LC alignments for each transmissive and reflective parts with photo‐alignment technique. The transmissive part has a homogenous liquid crystal alignment driven by an in plane electric switching field, which exhibits superb wide viewing angle characteristics. In the reflective part, the twisted liquid crystal alignment is adopted. Based on this new configuration, high reflectance and better contrast ratio can be provided without any compensation film or patterned retarder unlike conventional transflective LCDs.

SNOM study of ferroelectric domains in doped [formula omitted] crystals

This work shows a study of the periodic ferroelectric domains formed in LiNbO3 crystals doped with rare earths by means of scanning near field optical microscopy (SNOM) technique. It has been observed periodic structures associated with ferroelectric domains with an unexpected high value of the optical contrast working under reflectance SNOM mode. From Raman-Nath diffraction patterns, a refractive index modulation of Δn∼10−4 has been calculated. These results were correlated with the ferroelectric periodic domains obtained by the SNOM technique. A light waveguide effects along the ferroelectric domains is suggested to explain the high reflectance contrast observed in SNOM experiments.

P‐195: Enhanced Outdoor Readability in AFFS Plus Technology by Negative LC

AbstractIn this paper, we have developed 10.4 inch XGA tablet with upgraded advanced fringe‐field switching plus (AFFS+ Ver.2). AFFS+ Ver.2 adopts optimized electro‐dynamics technology of negative LC with high reflectance (∼ 2.0%) and high contrast ratio (∼ 900:1) as well as high transmittance (∼9.3%) for superior outdoor readability.

67.3: Electrochemical Reaction Display with Dual Reflective and Emissive Modes

AbstractWe have developed an electrochemical reaction display (ECRD) that can be operated in dual reflective and emissive modes in an entire pixel area of a single device. The ECRD utilizes electrochromic (EC) and electrogenerated chemiluminescence (ECL) reactions. These two electrochemical reactions can be controlled independently by adding a luminescent molecule to a liquid electrolyte of an EC cell with three electrodes. In the reflective mode, the ECRD cell exhibits high reflectance (47%) and high contrast ratio (6:1). In the emissive mode, the cell can show luminescent moving images because of the fast response time (10 ms).

Influence of the Adjacency Effect on Ground Reflectance Measurements

It is well known that the adjacency effect has to be taken into account during the retrieval of surface reflectance from high spatial resolution satellite imagery. The effect results from atmospheric scattering, depends on the reflectance contrast between a target pixel and its large-scale neighborhood, and decreases with wavelength. Recently, ground reflectance field measurements were published, claiming a substantial influence of the adjacency effect at short distance measurements (< 2 m), and an increase of the effect with wavelength. The authors repeated similar field measurements and found that the adjacency effect usually has a negligible influence at short distances, decreasing with wavelength in agreement with theory, but can have a small influence in high-reflectance contrast environments. Radiative transfer calculations were performed to quantify the influence at short and long distances for cases of practical interest (vegetation and soil in a low-reflectance background). For situations with large reflectance contrasts, the atmospheric backscatter component of the adjacency effect can influence ground measurements over small-area targets, and should therefore be taken into account. However, it is not possible to draw a general conclusion, since some of the considered surfaces are known for exhibiting strong directional effects

Electrically tunable porous silicon active mirrors

We demonstrate tunable mirrors that consist of a porous silicon microcavity infiltrated with liquid crystal molecules. We show theoretically that by utilizing the electro-optic properties of liquid crystals and the sensitivity of the microcavity resonance position to small changes in optical thickness, the porous silicon active mirror can be switched on (high reflectance) and off (low reflectance) by simply applying a voltage. We discuss the issues of obtaining uniform infiltration of liquid crystal molecules in the constricted geometry of the porous silicon microcavity and determining the necessary change in the liquid crystal orientation to achieve a high reflectance contrast. We also present preliminary experimental results showing a greater than 40% change in the reflectance of our active mirror with the application of voltage.

Electrochromic devices based on soluble and processable dioxythiophene polymersElectronic supplementary information (ESI) available: details of the synthesis of PProDOT(CH2OC18H37)2 and PProDOT(CH2OEtHx)2 and their polymerization. See http://www.rsc.org/suppdata/jm/b3/b306365h/

Reflective and absorptive/transmissive polymer electrochromic devices (ECDs) composed of spray-coated films of poly(3,3-bis(octadecyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) (PProDOT(CH2OC18H37)2) and poly(3,3-bis(2-ethylhexyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) (PProDOT(CH2OEtHx)2) layers as cathodically coloring polymers and poly(3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-methyl-9H-carbazole) (PBEDOT-NMeCz) as the anodically coloring polymer have been constructed and evaluated. These devices exhibit low switching voltages (±1.2 V), high visible contrast values, sub-second switching times, and high switching stability in atmospheric conditions. The reflective ECD comprising PProDOT(CH2OEtHx)2 as the active layer demonstrates an unusual electrochromic behavior. By regulating the applied voltage, a high reflectance contrast of greater than 70% ΔT was achieved in the NIR region (2 µm) without any noticeable color change of the device.

Younger and Older Adults' Perception of the Wundt-Hering Illusion as a Function of Display Illumination and Reflectance Contrast

Reflectance contrast (i.e., black as compared to grey figures on white ground) and display illumination were manipulated to vary the brightness contrast of Wundt-Hering figures. 16 college students and 16 older adults were presented with high, medium, and low reflectance contrast figures. For half the participants, display illumination was manipulated by covering the figures with a .5 yellow neutral density filter. Magnitude of the illusion increased significantly with increased reflectance contrast for college students, and college students were significantly more susceptible to the high contrast figures than were older adults. Display illumination had no effect on the performance of either group.