Showing papers on "Transmittance published in 2007"
TL;DR: A recently established silver-based negative-index metamaterial design is miniaturized and a real part of the refractive index of -0.6 at a 780 nm wavelength is inferred--which is visible in the laboratory.
Abstract: We further miniaturize a recently established silver-based negative-index metamaterial design. By comparing transmittance, reflectance, and phase-sensitive time-of-flight experiments with theory, we infer a real part of the refractive index of −0.6 at a 780 nm wavelength—which is visible in the laboratory.
732 citations
TL;DR: In this paper, the role of porosity in transmittance of cubic and tetragonal zirconia has been analyzed in the near infrared for 1 1/3 mm thick samples.
Abstract: Transparent samples of cubic (8 mol % yttria) and tetragonal (3 mol % yttria) zirconia were prepared from nanometric powders by the pulsed electric current sintering process. The crystallite size of the resulting dense samples was about 50 nm in both cases. The consolidation pressure had a positive effect on the occurrence of transparency for both modifications. Transmittance in the near infrared for 1 mm thick samples is above the 60 % for the cubic (8 %YSZ) and above 50 % for the tetragonal (3 % YSZ) zirconia, representing between 70 and 80 % of the theoretical values of the two modifications. Samples had a yellowish-brown coloration which was attributed to the presence of color centers. Annealing in oxygen improved transmittance initially, but prolonged annealing resulted in translucent samples. The role of porosity in transmittance is analyzed.
249 citations
TL;DR: Calculations demonstrate that in such structures the Faraday effect spectrum has several resonance peaks in the near-infrared range, some of them coinciding with transmittance peaks, providing simultaneous large Faraday rotation enhanced by an order of magnitude and highTransmittance of about 35%.
Abstract: We predict theoretically a significant enhancement of the magneto-optical Faraday and Kerr effects in the bilayer systems of a metallic film perforated with subwavelength hole arrays and a uniform dielectric film magnetized perpendicular to its plane. Calculations, based on a rigorous coupled-wave analysis of Maxwell's equations, demonstrate that in such structures the Faraday effect spectrum has several resonance peaks in the near-infrared range, some of them coinciding with transmittance peaks, providing simultaneous large Faraday rotation enhanced by an order of magnitude and high transmittance of about 35%.
227 citations
TL;DR: An adaptive filtering approach that improves visibility relative to raw images, and inhibits noise amplification, based on an automatic method for determining the medium transmittance.
Abstract: When imaging in scattering media, visibility degrades as objects become more distant. Visibility can be significantly restored by computer vision methods that account for physical processes occurring during image formation. Nevertheless, such recovery is prone to noise amplification in pixels corresponding to distant objects, where the medium transmittance is low. We present an adaptive filtering approach that counters the above problems: While significantly improving visibility relative to raw images, it inhibits noise amplification. Essentially, the recovery formulation is regularized, where the regularization adapts to the spatially varying medium transmittance. Thus, this regularization does not blur close objects. We demonstrate the approach in atmospheric and underwater experiments, based on an automatic method for determining the medium transmittance.
191 citations
Patent•
02 Mar 2007TL;DR: In this paper, the present invention relates to various thin-film coatings, electro-optic elements and assemblies incorporating these elements, which are becoming commonplace in a number of vehicular and architectural applications.
Abstract: Electro-optic elements are becoming commonplace in a number of vehicular and architectural applications. Various electro-optic element configurations provide variable transmittance and or variable reflectance for windows and mirrors. The present invention relates to various thin-film coatings, electro-optic elements and assemblies incorporating these elements.
174 citations
TL;DR: In this article, a large-area, 100mm in diameter, aluminum nanowire grids with 40nm line/78nm space were fabricated with full-wafer immersion interference lithography.
Abstract: Large-area, 100mm in diameter, aluminum nanowire grids with 40nm line/78nm space were fabricated with full-wafer immersion interference lithography. The aluminum nanowire grids with a 59nm half-pitch work as a highly efficient optical polarizer for deep ultraviolet wavelength down to ∼250nm. In addition, an extremely high contrast from 10 000:1 to 50 000:1 was achieved across the whole visible and near-infrared wavelength range, along with good transmittance (85%–90%). The broadband large-area high-performance polarizer operating down to deep ultraviolet wavelength opens up applications including semiconductor lithography and metrology applications.
166 citations
TL;DR: This first example of LBL layers of cellulose NWs can be seen as an exemplary structure for any rigid axial nanocolloids, for which, given the refractive index match, AR properties are expected to be a common property.
Abstract: Natural nanowires (NWs) of cellulose obtained from a marine animal tunicate display surprisingly high uniformity and aspect ratio comparable with synthetic NWs. Their layer-by-layer assembled (LBL) films show strong antireflection (AR) properties having an origin in a novel highly porous architecture reminiscent of a “flattened matchsticks pile”, with film-thickness-dependent porosity and optical properties created by randomly oriented and overlapping NWs. At an optimum number of LBL deposition cycles, light transmittance reaches nearly 100% (λ ≈ 400 nm) when deposited on a microscope glass slide and the refractive index is ∼1.28 at λ = 532 nm. In accordance with AR theory, the transmittance maximum red-shifts and begins to decrease after reaching the maximum with increasing film thickness as a result of increased light scattering. This first example of LBL layers of cellulose NWs can be seen as an exemplary structure for any rigid axial nanocolloids, for which, given the refractive index match, AR proper...
164 citations
TL;DR: In this article, aluminum doped ZnO thin films (ZnO:Al) were deposited on glass and poly carbonate (PC) substrate by r.f. magnetron sputtering.
159 citations
TL;DR: In this paper, a spark plasma sintering (SPS) technique was used to produce mid-infrared (IR) transparent alumina with the desired transmittance.
Abstract: The spark plasma sintering (SPS) technique was used to produce mid-infrared (IR) transparent alumina with the desired transmittance. An excellent transmittance of 85% has been obtained in a sample sintered at 1300°C for 5 min. The heating rate, sintering time, and annealing have a significant influence on IR transmittance. The improvement in transmission may be attributed to the progressive elimination of residual porosity when applying a slower heating rate, longer sintering time during SPS, and postsinter annealing. It is suggested that localized residual strain/stress at grain boundaries and oxygen vacancy concentration are other factors influencing the optical properties of the SPS-sintered alumina.
144 citations
TL;DR: The results indicated that the shape of filler particles, as well as particle size and filler content, significantly affected the light transmittance characteristics--including light diffusion characteristics--and color of composite resins.
Abstract: The purpose of this investigation was to examine the effect of filler particle size and shape as well as filler content on light transmittance characteristics and color of experimental composite resins. A mixture of 30 mol% Bis-GMA and 70 mol% TEGDMA was prepared as a base monomer and to which a photoinitiator (camphorquinone) and a co-initiator (N,N-dimethylaminoethyl methacrylate) were added. Four different irregular- and spherical-shaped filler types with an average particle size of 1.9-11.1 microm were added to the mixture in three different filler contents of 20, 30, and 40 vol%. Light transmittance characteristics including light diffusion characteristics of the materials were evaluated. Color values and color differences among filler contents of the materials were also determined. Materials containing smaller and irregular-shaped fillers showed higher light transmittance and diffusion angle distribution with a sharper peak, as compared with those containing larger and spherical-shape fillers. It was also found that there was a significant correlation between the specific surface area of fillers and the color difference of the materials containing the fillers. Our results indicated that the shape of filler particles, as well as particle size and filler content, significantly affected the light transmittance characteristics--including light diffusion characteristics--and color of composite resins.
123 citations
TL;DR: In this paper, a 2-m-thick yttrium oxide film was prepared on a quartz substrate by the aerosol deposition process at the room temperature and the deposition rate was very high, 60 m/h.
Abstract: Dense yttrium oxide film was prepared on a quartz substrate by the aerosol deposition process at the room temperature. The deposition rate was very high, 60 m/h. Thick film of 10 m was easily achievable on the quartz substrate. Transmission electron microscopy showed that the film was highly dense without voids and was composed of randomly oriented Y2O3 crystallites of sizes smaller than 20 nm. The interface between the film layer and the quartz substrate was homogeneous. The film (2-m thick) had a high transmittance (55–85%) in the wavelength region of 250-800 nm. The mechanical properties of the film were very good. The adhesion force of the interface between the Y2O3 layer and the quartz substrate was over 80 MPa. The Vickers hardness of the film was 7.7 GPa. The film also had an excellent plasma resistance in a gas mixture of CF4/O2. Outstanding results were noted in eroded depth, surface roughness, nanostructure, and transmittance change after plasma exposure of the film.
TL;DR: In this paper, thin-film transistors were created on silicon wafers and glass substrates using low-density carbon nanotube (CNT) networks as a semiconducting layer.
Abstract: We have investigated two possible fields of application for carbon nanotube (CNT) networks in flexible displays. Transparent and conductive layers of CNTs were spray coated onto glass and plastic substrates. The spectral transmission of the produced layers is almost even for all wavelengths in the visible regime. A sheet resistance of 400 Ω/□ at a transmittance of 80% was achieved. Thin-film transistors (TFT) were created on silicon wafers and glass substrates using low-density CNT networks as a semiconducting layer. The process used for device fabrication on glass substrates is fully compatible to application on plastic foils. The transistors reach on/off ratios of more than five orders of magnitude and show device charge carrier mobilities in the order of 1 cm 2 /Vs. These values promise an application in active matrix liquid crystal displays (AMLCD). Issues that need to be addressed are the homogeneity and reproducibility of the device properties.
TL;DR: In this article, a uniform and transparent TiO 2 films were successfully prepared on glass by pulsed bias arc ion plating, and the influence of pulsed substrate bias on film optical properties was investigated by varying pulsed negative biases from 0 to 900 V.
Abstract: Uniform and transparent TiO 2 films were successfully prepared on glass by pulsed bias arc ion plating. The influence of pulsed substrate bias on film optical property was investigated by varying pulsed negative biases from 0 V to − 900 V. Film structure, surface morphology, and optical properties were measured with X-ray diffraction, SEM, AFM, and UV–VIS transmittance spectroscope. The results show that the as-deposited films are amorphous. The film deposited at − 300 V is atomically smooth in droplet-free zone with Rrms 0.113 nm, which results in a high refractive index, 2.51 at 550 nm, close to the maximum values reported to date. With increasing biases, the absorption edge first shifts to longer wavelengths, then to shorter ones. The band gap is nearly constant, at 3.27 eV.
TL;DR: In this article, a graphical approach with signal flow graph is employed for the analytical derivation of the optical transfer functions in Z-domain of filters, including the transmittance and group delay of the drop port with respect to the input port.
TL;DR: In this paper, the authors developed numerically validated models for predicting the through-plane effective index of refraction and absorption index of nanocomposite thin films by minimizing the root mean square of the relative errors between the computed and theoretical transmittance and reflectance.
Abstract: This paper aims at developing numerically validated models for predicting the through-plane effective index of refraction and absorption index of nanocomposite thin films. First, models for the effective optical properties of such materials are derived from previously reported analysis applying the volume averaging theory (VAT) to Maxwell’s equations. The transmittance and reflectance of nanoporous thin films are computed by solving Maxwell’s equations and the associated boundary conditions at all interfaces using finite element methods. The effective optical properties of the films are retrieved by minimizing the root mean square of the relative errors between the computed and theoretical transmittance and reflectance. Nanoporous thin films made of SiO2 and TiO2 consisting of cylindrical nanopores and nanowires are investigated for different diameters and various porosities. Similarly, electromagnetic wave transport through dielectric medium with embedded metallic nanowires are simulated. The numerical r...
TL;DR: In this paper, a technique to enhance the electrical conductivity of transparent single-walled carbon nanotube (SWNT) films with a negligible loss of their optical transmittance was reported.
Abstract: We report a new technique to enhance the electrical conductivity of transparent single-walled carbon nanotube (SWNT) films with a negligible loss of their optical transmittance. Hybridization of the SWNT films with gold nanoparticles increased the electrical conductivity 2-fold to a maximum of 2.0 × 105 S/m while maintaining the transmittance of the initial value. The same trends are shown for other SWNT films with various initial conductivities and transparency levels. Functional changes in the gold-nanoparticle-coated SWNT films suggest that the electrical conductivity change is due to an electron depletion mechanism as a result of a doping effect.
TL;DR: A method to calibrate the reduced scattering coefficient of a liquid diffusive medium and the absorption coefficient of an absorbing medium with a standard error smaller than 2% both on mu'(s) and on mu(a).
Abstract: In spite of many progresses achieved both with theories and with experiments in studying light propagation through diffusive media, a reliable method for accurate measurements of the optical properties of diffusive media at NIR wavelengths is, in our opinion, still missing. It is therefore difficult to create a diffusive medium with well known optical properties to be used as a reference. In this paper we describe a method to calibrate the reduced scattering coefficient, mu'(s) , of a liquid diffusive medium and the absorption coefficient, mu(a), of an absorbing medium with a standard error smaller than 2% both on mu'(s) and on mu(a). The method is based on multidistance measurements of fluence into an infinite medium illuminated by a CW source. The optical properties are retrieved with simple inversion procedures (linear fits) exploiting the knowledge of the absorption coefficient of the liquid into which the diffuser and the absorber are dispersed. In this study Intralipid diluted in water has been used as diffusive medium and Indian ink as absorber. For a full characterization of these media measurements of collimated transmittance have also been carried out, from which the asymmetry factor of the scattering function of Intralipid and the single scattering albedo of Indian ink have been determined.
TL;DR: Improvements in the optical limiting efficiency of the composites and in the dispersion and alignment properties of carbon nanotubes in the polymer matrix could be realized by variation of both nanostructured guest and polymer host, and by ex situ alignment and other methods.
Abstract: Optical limiting is an important application of nonlinear optics, useful for the protection of human eyes, optical elements, and optical sensors from intense laser pulses. An optical limiter is such a device that strongly attenuates high intensity light and potentially damaging light such as focused laser beams, whilst allowing for the high transmission of ambient light. Optical limiting properties of carbon nanotube suspensions, solubilized carbon nanotubes, small molecules doped carbon nanotubes and polymer/carbon nanotube composites have been reviewed. The optical limiting responses of carbon nanotube suspensions are shown to be dominated by nonlinear scattering as a result of thermally induced solvent-bubble formation and sublimation of the nanotubes, while the solubilized carbon nanotubes optically limit through nonlinear absorption mechanism and exhibit significant solution-concentration-dependent optical limiting responses. In the former case the optical limiting results are independent of nanotube concentrations at the same linear transmittance as that of the solubilized systems. Many efforts have been invested into the research of polymer/carbon nanotube composites in an attempt to allow for the fabrication of films required for the use of nanotubes in a real optical limiting application. The higher carbon nanotube content samples block the incident light more effectively at higher incident energy densities or intensities. The optical limiting mechanism of these composite materials is quite complicated. Besides nonlinear scattering contribution to the optical limiting, there may also be other contributions e.g., nonlinear absorption, nonlinear refraction, electronic absorption and others to the optical limiting. Further improvements in the optical limiting efficiency of the composites and in the dispersion and alignment properties of carbon nanotubes in the polymer matrix could be realized by variation of both nanostructured guest and polymer host, and by ex situ alignment and other methods. It would be very desirable, from the practical application point of view, if one can design broadband optical limiting chromophores that would function in a multimechanistic fashion.
TL;DR: In this paper, a high pressure low temperature sintering technique (HPLT) was used to construct YAG nanoceramics composed of nanosized grains.
Patent•
11 Jun 2007TL;DR: In this article, an electrical control system for controlling a plurality of variable transmittance windows is described. But the authors do not discuss the electrical performance of the windows and do not describe the methods for the manufacture of an electrochromic device used in variable transmission windows.
Abstract: An electrical control system is disclosed for controlling a plurality of variable transmittance windows. The electrical control system comprises a master control circuit and user input circuits for supplying control signals representing transmittance levels for the variable transmission windows, and a plurality of slave window control circuits coupled to the master control circuit, user input circuits and the variable transmittance windows. Each slave window control circuit controls the transmittance of at least one of the variable transmission windows in response to control signals received from the master control circuit and/or user input circuits. Also disclosed are novel methods for the manufacture of an electrochromic device used in variable transmittance windows. Novel structural features for improving heat transfer away from the windows, shielding the window from external loads, and improving the electrical performance of the windows are also disclosed.
TL;DR: In this paper, a modified two-flux approximation is examined as a simplified basis of the identification procedure, and a comparison with the exact numerical solution confirms a good accuracy of this approach for identification of the absorption coefficient of ceramics.
TL;DR: In this paper, homogeneously aligned nematic liquid crystal (LC) cells doped with carbon nanotubes (CNTs) driven by an in-plane field were fabricated and their electrooptic characteristics were investigated.
Abstract: Homogeneously aligned nematic liquid crystal (LC) cells doped with carbon nanotubes (CNTs) driven by an in-plane field were fabricated and their electro-optic characteristics were investigated. The effective cell retardation values showed no difference between doped and undoped LC cells in the absence of electric field. However, in the presence of electric field, it was smaller in the CNT-doped cell than in the undoped cell, resulting in the decrease of transmittance. Furthermore, the CNT-doped cell exhibited a slight increase in the driving voltage due to the increase of the twist elastic constant (K22) and the decrease in the decay response time due to the decrease in the rotational viscosity (γ) and γ∕K22 compared to the undoped cell.
TL;DR: A system for absorption and scattering spectroscopy of diffusive media based on time-resolved reflectance and transmittance measurements using mode-locked lasers tunable in the 550-1050 nm spectral range is described.
Abstract: We describe a system for absorption and scattering spectroscopy of diffusive media based on time-resolved reflectance and transmittance measurements. The system is operated with mode-locked lasers tunable in the 550-1050 nm spectral range and on a detection chain based on time-correlated single-photon counting. All measurement procedures such as laser tuning and optimization, signal conditioning, data acquisition, and analysis are completely automated, permitting spectral measurements over the whole range in a few minutes. The criticalities of the system are discussed together with the strategies to compensate them. The Medphot protocol devised for the characterization of photon migration instruments was applied to assess the system performances in terms of accuracy, linearity, noise, stability, and reproducibility. Finally, an example of application of the instrument to the spectroscopy of powders is presented.
TL;DR: In this paper, the authors examined the light absorbing behavior of dye-sensitized solar cells (DSCs) having cathodes (negative electrodes) comprised of highly ordered TiO2 nanotube arrays using the electromagnetic computational technique, finite-difference time domain (FDTD).
Journal Article•
TL;DR: In this paper, a transparent indium-doped ZnO thin films were deposited by spray pyrolysis method onto glass substrates and the content of indium in the starting solution was 05 at % The crystallographic structure of the film was studied by X-ray diffraction (XRD) measurement shows that the film is crystallized in the wurtzite phase and presents a preferential orientation along the c-axis.
Abstract: Transparent indium-doped ZnO thin films were deposited by the spray pyrolysis method onto glass substrates The content of indium in the starting solution was 05 at % The crystallographic structure of the film was studied by X-ray diffraction (XRD) XRD measurement shows that the film is crystallized in the wurtzite phase and presents a preferential orientation along the c-axis The texture coefficient (TC), grain size value and lattice constants have been calculated The absorption coefficient and the thickness of the films were calculated from interference of transmittance spectra Optical constants such as the refractive index n and extinction coefficient k have been determined from transmittance spectrum in the ultraviolet–visible–near infrared (UV–VIS–NIR) regions using the envelope method The thickness of the films strongly influences the optical constants
TL;DR: In this article, an optical model has been proposed to simulate the optical constants and thicknesses of the thin indium tin oxide (ITO) films from transmittance data, which combines the Forouhi-Bloomer model and modified Drude model.
TL;DR: In this article, a theoretical analysis of the three-, four-and five-photon absorption process using the open aperture Z-scan technique is presented, where the normalized transmittance equations presented here can be used to fit the experimental data, allowing the determination of material's multiphoton absorption cross-section.
TL;DR: In this article, dual-metallic grating structures composed of slits arrays, with the longitudinal interval G and the lateral displacement L, are investigated by using the finite-difference time-domain method.
Abstract: Electromagnetic (EM) transmission through dual-metallic grating (DMG) structures composed of slits arrays, with the longitudinal interval G and the lateral displacement L, is investigated by using the finite-difference time-domain method. The results show that the EM transmission property can be controlled by changing G or/and L, such as tunable wavelength of high transmission, changeable transmittance for a special wavelength, and suppressed EM transmission over a broad spectral range. The DMG structures have potential applications in the future photonics. In addition, some advantages of DMGs with respect to the single-metallic gratings are also discussed.
TL;DR: X-ray diffraction measurements and scanning electron microscope images have shown that the surfaces of the e-beam evaporated AZO became smoother for the growth temperature at and above 200^oC, which explains its relation with the crystal quality of the film.
TL;DR: It is demonstrated that the novel broadband antireflection coatings in a wide range of visible wavelength can be easily obtained by the organosilicate bilayer thin films described in this study.
Abstract: Thermally stable nanoporous organosilicate thin films were realized by the microphase separation of pore-generating polymers mixed with an organosilicate matrix to be antireflective coatings (ARCs), for which a thin film with a refractive index (n) of 1.23 for zero reflection is required. The refractive index of such nanoporous organosilicate films can be tuned from 1.39 down to 1.23 by incorporating nanopores within the films. With a nanoporous single layer with n approximately 1.23, the light transmittance of the glass above 99.8% was achieved in the visible range (lambda approximately 550 nm). To overcome the limitation on the narrow wavelength for high transmittance imposed by a single antireflective nanoporous thin film, bilayer thin films with different refractive indices were prepared by placing a high refractive index layer with a refractive index of 1.45 below the nanoporous thin film. UV-vis transmittance of a glass coated with the bilayer films was compared with nanoporous single-layer films and it is demonstrated that the novel broadband antireflection coatings in a wide range of visible wavelength can be easily obtained by the organosilicate bilayer thin films described in this study. Also, ARCs developed in this study demonstrate excellent AR durability owing to the hydrophobic nature of the organosilicate matrix.