Average Light Transmittance Research Articles

Ultraviolet high-transmitting cross-linked polymer materials derived from mercaptopropyl polyhedral oligomeric silsesquioxane

Abstract In this paper, several cross-linked polymer materials with high light-transmitting properties are presented. First, mercaptopropyl polyhedral oligomeric silsesquioxane (POSS-SH) was synthesized via the hydrolytic condensation of 3-mercaptopropyl triethoxysilane. Then, glycidyl methacrylate (GMA) and allylmethacrylate were allowed to polymerize with POSS-SH, yielding a hybridized composite. The volumetric shrinkage, thermal, and light-transmitting properties of the materials were studied and investigated using a pycnometer, differential scanning calorimeter, and ultraviolet visible spectrophotometer. The results indicated that POSS-SH decreased the volumetric shrinkage of the GMA-based materials. Thermal analysis indicated that the glass transition temperature (T g) of the hybrid composite decreased as the POSS-SH content increased, while the T c and T m of the hybrid composite increased slightly. The light transmittance of the hybrid composite increased as the POSS-SH content increased. When the POSS-SH content increased to 42.9%, the hybrid composite exhibited average light transmittance values of 96% at wavelengths ranging from 200 to 400 nm and 97% at wavelengths ranging from 400 to 800 nm.

Control of the average light transmission in one-dimensional photonic structures by tuning the random layer thickness distribution

In this work we have studied the optical properties of disordered photonic structures, in which we have controlled the distribution of the random layer thickness. Such structures are characterized by the usual alternation of high and low refractive index layers, but the layer thickness follows the aforementioned distribution. We have used two types of distributions: a distribution in which each thickness has the same probability to occur and one in which the thickness follows a Gaussian function. We have simulated the average transmission all over the spectrum for photonic structure characterized by a different width of the distribution. We have found that the choice of the distribution of the layer thickness is a control of the average transmission of a random photonic structure. Photonic structures, fabricated following these distributions, can be interesting for the fabrication of bandpass optical filters.

Effect of nanoscale tin-dioxide layers on the efficiency of CdS/CdTe-based film solar elements

Comparative investigations of the output parameters and optical diode characteristics of ITO/CdS/CdTe/Cu/Au and SnO2: F/CdS/CdTe/Cu/Au film solar cells are carried out with the aim of optimizing the design of the front electrodes. It is established that the high voltage and large filling factor of the solar elements with SnO2: F films are caused by a lower diode saturation current density and series resistance due to the stability of the crystal structure and electrical properties of these films against chloride treatment of the base layer during device fabrication. At the same time, solar elements with an ITO front electrode exhibit a higher short-circuit current density due to the larger average light transmittance of the ITO layers. The use of nanoscale SnO2 layers in the ITO front contacts allows the efficiency of the CdS/CdTe-based solar elements to be enhanced to 11.4% on account of stabilization of the crystal structure and electrical properties of the ITO films and a possible reduction in the cadmium-sulphide-layer thickness without shunting the device structure.

Effects of substrate temperature on properties of HfO2, HfO2:Al and HfO2:W films

The HfO2 films were doped with Al (HfO2:Al) or W (HfO2:W) by simultaneous RF magnetron sputtering of HfO2 and DC magnetron sputtering of Al or W. According to XRD analysis, the monoclinic HfO2 film and a strong 1−11 preferential orientation were obtained as the substrate temperature increased to 500°C. After doping with Al, a (300) preferential orientation in Al2O3 and the coexistence of monoclinic HfO2, orthorhombic HfO2 and Al2O3 were obtained at the substrate temperature of 500°C. By increasing the substrate temperature, the coexistence of monoclinic HfO2 and tetragonal W5O14 was obtained in the HfO2:W film. Doping with Al or W could change the hydrophobicity of HfO2 films into the hydrophilicity. The HfO2:W films exhibited better hydrophilicity and lower average visible light transmission at higher substrate temperature. The hydrophilic HfO2:Al film showed higher average visible light transmission and higher linear refractive index at lower substrate temperature, favoring optical applications.

Light Transmission Properties and Shannon Index in One-Dimensional Photonic Media With Disorder Introduced by Permuting the Refractive Index Layers

In this paper, we have studied, with a numerical method, how introducing disorder affects the light transmission properties of 1-D photonic structures over a wide range of wavelengths. A new type of disorder is introduced by permuting the refractive index layers in the optical medium. We compared the light transmission properties of ideal photonic crystals and of disordered media with the same kind and number of scattering elements for different sample lengths. We have calculated the transmission properties, by the transfer matrix method, of thousands of different disordered structures in order to perform a statistical analysis. We found that, below a certain sample length, disorder induces less average light reflection than ordered structures, whereas above the threshold length, disordered structures show more average reflection. Moreover, we have quantified the disorder of the structures with the Shannon index. We have found a decrease in the average light transmission as a function of the Shannon index. Furthermore, the sample length affects the trend of the average transmission as a function of the Shannon index.

Generalized Random Grid and Its Applications in Visual Cryptography

Random grid (RG) is a method to implement visual cryptography (VC) without pixel expansion. However, a reconstructed secret with lower visual quality reveals in RG-based VC due to the fact that average light transmission of a share is fixed at 1/2. In this work, we introduce the concept of generalized RG, where the light transmission of a share becomes adjustable, and adopt generalized RG to implement different VC schemes. First, a basic algorithm, a (2,2) generalized RG-based VC, is devised. Based on the (2,2) scheme, two VC schemes including a (2,n) generalized RG-based VC and a (n,n) xor-based meaningful VC are constructed. The two derived algorithms are designed to solve different problems in VC. In the (2,n) scheme, recovered image quality is further improved. In the (n,n) method, meaningful shares are constructed so that the management of shadows becomes more efficient, and the chance of suspicion on secret image encryption is reduced. Moreover, superior visual quality of both the shares and recovered secret image is achieved. Theoretical analysis and experimental results are provided as well, demonstrating the effectiveness and advantages of the proposed algorithms.

An Ellipsoidal Tool as a Nanoscale Removal Processes for Computer and Digital System

A newly designed ellipsoidal electrode tool used for micro-electrochemical etching (μ-ECE) in a precise reclamation process that removes defective In2O3SnO2 conductive microstructure from the surface of LCD color filters is presented. The electrochemical removal of ITO film eliminates the danger of scoring the surface of the substrate. The efficiency of the electrochemical process, enhanced by the ellipsoidal shaped electrode, also allows the feed rate of the workpiece (display color filter) to be higher and this reduces production costs. In the current study, a higher current rating and a faster workpiece feed effectively resulted in more effective removal. An ellipsoidal anode with a small major axis coupled with a narrow gap between the cathode and the workpiece also reduces the time taken to remove the In2O3SnO2. An ellipsoidal anode with small minor axis also provides better discharge mobility and removal. A thin cathode or one with a small arc radius also gives a higher removal rate for In2O3SnO2. The effective ellipsoidal anode provides more discharge mobility and removes the In2O3SnO2 easily and cleanly in a short time. The surface roughness, the average light transmittance and chromaticity of the three primary colors is also maintained at the same level after the μ-ECE process as it was before the removal of the ITO.

Inhomogeneous two-dimensional photonic media: A statistical study

Photonic media, in which disorder is introduced, are interesting materials for light management. In this paper, we have performed a statistical study of the average light transmission, over the range of wavelengths 450–1400nm, for two-dimensional photonic structures with different homogeneity (quantified by the Shannon index). The photonic structure is a square lattice of circular pillars and the homogeneity is varied by clustering pillars in the crystal unit cells. We have calculated the light transmission for 50 different crystal realizations (permutating cluster position in the crystal) for each Shannon index value. Such Monte Carlo Markov Chain method produced the “a posteriori” distribution of the light transmission. We have observed a linear trend of the average transmission as a function of the crystal homogeneity. Furthermore, we have found a linear dependence of the average light transmission on the mean distance between pillars in the photonic structures.

Light transmission behaviour as a function of the homogeneity in one dimensional photonic crystals

The average light transmission of one-dimensional photonic media has been studied as a function of the medium homogeneity, quantified by the Shannon–Wiener index. We have found a decrease in the average light transmission by increasing the Shannon–Wiener index up to minimum (corresponding to H′=0.9375): from this point, the transmission increases following the Shannon–Wiener index. The behaviour has been confirmed for different pairs of materials forming the photonic structure. Nevertheless, we have observed that the trend slope is proportional to the refractive index ratio between the two materials (nhi/nlow).

Remote plasma sputtering of indium tin oxide thin films for large area flexible electronics

Indium tin oxide (ITO) thin films with a specific resistivity of 3.5 × 10 − 4 Ω cm and average visible light transmission (VLT) of 90% have been reactively sputtered onto A4 Polyethylene terephthalate (PET), glass and silicon substrates using a remote plasma sputtering system. This system offers independent control of the plasma density and the target power enabling the effect of the plasma on ITO properties to be studied. Characterization of ITO on glass and silicon has shown that increasing the plasma density gives rise to a decrease in the specific resistivity and an increase in the optical band gap of the ITO films. Samples deposited at plasma powers of 1.5 kW, 2.0 kW and 2.5 kW and optimized oxygen flow rates exhibited specific resistivity values of 3.8 × 10 − 4 Ω cm, 3.7 × 10 − 4 Ω cm and 3.5 × 10 − 4 Ω cm and optical gaps of 3.48 eV, 3.51 eV and 3.78 eV respectively. The increase in plasma density also influenced the crystalline texture and the VLT increased from 70 to 95%, indicating that more oxygen is being incorporated into the growing film. It has been shown that the remote plasma sputter technique can be used in an in-line process to produce uniform ITO coatings on PET with specific resistivities of between 3.5 × 10 − 4 and 4.5 × 10 − 4 Ω cm and optical transmission of greater than 85% over substrate widths of up to 30 cm.

Light transmittance characteristics and refractive indices of light-activated pit and fissure sealants

We examined the light transmittance characteristics and refractive indices of light-activated pit and fissure sealants. Five commercial pit and fissure sealants and human enamel were studied, along with the CIE L*a*b* color values of the materials and enamel. The light transmittance spectra of the pit and fissure sealants showed a similar trend to the enamel, especially at wavelengths below 530 nm. The average light transmittance values from 400 to 500 nm of the materials at 0.5-mm-thick ranged from 10.0% to 40.4%. The refractive indices at 589.3 nm ranged from 1.504 to 1.546, and were approximately 4-8% lower than that of enamel. The measurements for the surface hardness of materials indicate that the light-attenuating effect of enamel and the material itself reduced the polymerization efficiency of the material. For all materials, chromatic a* showed negative and b* showed positive values, as did enamel. Significant differences in light transmittance characteristics and refractive indices between the materials and enamel may affect color matching between them.

Microphotometric dynamic analysis of the histochemical acetylcholinesterase reaction

Dynamic analysis of the histochemical reaction of Karnovsky-Roots for acetylcholinesterase activity (AChE) is reported. Two methods were used. The first method was videography and densitometric analysis of frames from the film. The second method was direct microphotometric analysis of the reaction dynamics by the plug-method (measurement of average light transmission through a limited area of preparation or image). Special microchambers were used on the stage of an inverted microscope. The results showed the dynamics of final product accumulation in two structures of rat caudate nucleus: AChE-positive neuropil and the AChE-negative myelin bundle during histochemical incubation. Videography and densitometry of the digital images allowed morphologic and microphotometric analysis of changes in tissue sections during incubation, and the dynamic analysis permitted the study of enzyme kinetics in situ. Problems associated with microphotometric analysis of digital images for quantitative histochemical studies of the enzyme activity are discussed.

Light Transmission Through Colored Polyethylene Mulches Affects Weed Populations

Weed control is one of the benefits associated with the use of plastic mulches used for vegetable production. The mulches decrease light transmission and prevent development of most weed species. Plastics chemistry has developed films varying in their ability to reflect, absorb, and transmit light. Laboratory and field experiments were conducted to 1) measure light transmitted through colored mulches, 2) evaluate weed populations under each mulch type, and 3) determine if light transmission could be used as an indicator for weed populations in the field. The polyethylene mulches were black, gray, infrared transmitting brown (IRT-brown), IRT-green, white, and white-on-black (co-extruded white/black). On average, 1%, 2%, 17%, 26%, 42%, and 45% light in the 400 to 1100 nm range was transmitted through the black, white/black, gray, IRT-brown, IRT-green, and white mulches, respectively. In field experiments, density and dry biomass of weeds growing under the mulches were evaluated. The white mulch had the highest weed density with an average of 39.6 and 155.9 plants/m2 in 2001 and 2002, respectively. This was followed by the gray mulch, with 10.4 and 44.1 weed seedlings/m2 in 2001 and 2002, respectively. Weed density was <25 plants/m2 with the other mulches in both years. Weed infestation was correlated with average light transmission for white, black, white/black, and gray mulches. However, both light quantity and quality were necessary to predict weed infestations with the IRT mulches. Weed infestation under the IRT mulches was better estimated when only wave lengths in the photosynthetically active radiation range (PAR; 400 to 700 nm) were considered. Low weed pressure and high light transmission with the IRT mulches would make them appropriate for use in areas where both weed control and soil warming are important factors.

Freibewitterung von Lichtplatten aus Kunststoffen. Eine Langzeitstudie während elf Jahren

Due to their numerous advantages such as low weight, high transparency and impact resistance, transparent multible-skin plastic sheets (e.g., PVC, PMMA, PC, GF-UP) are widely used in applications such as greenhouses, windows, roofs etc. Since degradation due to sunlight and humidity is a critical behaviour inherent to most polymeric materials, it is necessary to determine the influence of prolonged weathering. With this aim, nineteen different sheets were exposed over a period of eleven years at Dübendorf. Test methods as visual inspection, average light transmittance and resistance to hail impact turned out to characterise the influence of weathering on the sheets very well. On the base of the mentioned test methods, the four different materials could be classified in the following range. Because of moderate changing of mechanical behaviour and appearance, the GF-UP materials were most suitable for the application followed by PC sheets. PMMA materials do have an advantage because of their excellent optical properties, but the mechanical behaviour is unsuitable from the beginning. Sheets from PVC showed strong changes of their optical and mechanical behaviours after short-time period and aren't well applicable for long-term exposure.

Prediction of the transfusion effect of platelet concentrates as measured by a model of primary hemostasis ex vivo.

A method to determine primary hemostasis ex vivo (Thrombostat) was modified to monitor the transfusion effect of platelet concentrates (PC) in 12 patients with thrombocytopenia following bone marrow transplantation. It was possible to measure platelet function in patients with a platelet count lower than 2 x 10(10)/l. In addition, the platelet aggregometer (Born) was adapted to determine cell function in PC anticoagulated with acid citrate dextrose of citrate phosphate dextrose. It was possible to make a prediction (r = 0.89) of the effect of a given PC on a patient's ex vivo primary hemostasis parameters. Platelet aggregation following addition of 20 muM ADP to PC, obtained from 12 single donors, resulted in an average maximal light transmission (light transmission/age of concentrate in days) of 61%/1 day and 37%/5 days, respectively. The same experiment gave only 39%/1 day and 13%/4 days for pooled platelets. To avoid possible immunization and bleeding complications, a reliable monitoring of platelet transfusion seems highly desirable.

Development of a multichannel fiber-to-fiber optical connector for the D0 upgrade tracker

A tracking detector using scintillating fibers is being developed for the D0 collaboration at Fermilab. The scintillating fibers will be coupled to clear fibers that will transport light to the photodetectors. We have developed connectors which couple the two types of fibers. The first 128-channel prototypes were machined using Delrin plastic to have v-shaped grooves. Fibers were glued into the grooves and their ends were finished with diamond fly-cut tools. Mating connectors were optically coupled by optical grease. Using a green light-emitting diode and a silicon photodiode, we measured average light transmission between 97% and 99%. Later versions of the v-groove connectors were made of acrylonitrile-butadiene-styrene plastic by injection molding.

The effect of glycosylated albumin on platelet aggregation.

Albumin has a role in the complicated process of platelet aggregation. Although it is known that quantitative changes in plasma albumin alter platelet aggregation, less is known about the interaction between qualitative changes in plasma albumin and platelets. One common qualitative change in plasma albumin is nonenzymatic glycosylation, which occurs during states of prolonged hyperglycemia. Albumin was selectively removed from normal plasma by means of an affinity column. Glycosylated albumin was added to this albumin-poor plasma, and it was used to study platelet aggregation induced by low concentrations of arachidonic acid. Platelet aggregation was determined by light transmittance. As the concentration of glucose in which albumin was incubated was increased, there was progressive augmentation of platelet aggregation. At a plasma glucose of 150 mg/dL, average light transmittance was 9.4%, and at 200 mg/dL, it was 24.6%. These values were significantly different at a p value < .01. At glucose levels of 300 mg/dL and 400 mg/dL, mean light transmittance was 40.6% and 74.4%, respectively, and these values were significantly different with p values of < .01. Platelet aggregation in response to a relatively low concentration of arachidonic acid is enhanced in the presence of albumin that has been incubated in a medium containing levels of glucose that are higher than would be seen in normal patients but are consistent with those seen in diabetics with less than optimal control. This augmentation of platelet aggregation is statistically significant.

Preparation by reactive deposition and some physical properties of amorphous tin oxide films and crystalline SnO 2 films

Tin oxide films were reactively deposited at oxygen pressures of (0.3–5) × 10 -3 Torr and at substrate temperatures of 60–420 °C. The dependence of the crystalline phase of the films on the deposition conditions was studied by X-ray diffraction. It was found that, depending on the substrate temperature, amorphous films or crystalline SnO 2 films were deposited at pressures above about 10 -3 Torr. The amorphous films were non-conducting but their resistivity could be reduced to less than 1 Ω cm by heat treatment in air at 250 or 300 °C. This decrease in resistivity was accompanied by an increase in the light transmission to about 90%. The crystalline SnO 2 films were conducting, had a resistivity of the order of 10 -2 Ω cm and were highly transparent with an average light transmission of about 90%.

Proposed method for measuring picosecond pulsewidths and pulse shapes in CW mode-locked lasers

A new method is proposed for measuring the widths, and possibly even the detailed shapes, of picosecond pulses in CW mode-locked lasers. The pulses are passed through an electro-optic modulator, which is biased for zero transmission with zero applied voltage, and which is driven at a harmonic of the pulse-repetition frequency. The variation in average light transmission through the modulator is monitored while the relative phase between the light pulses and the modulator drive is varied. The pulsewidth may be deduced from one such measurement made at a microwave light-modulation frequency sufficiently high that the pulsewidth is a finite fraction of a period at the modulation frequency. By making such measurements at a number of harmonics, the complete Fourier expansion (including both amplitudes and phases) of the picosecond pulse envelope can, at least in principle, be determined without ambiguity.