Showing papers on "Transmittance published in 1999"

Transmission Resonances on Metallic Gratings with Very Narrow Slits

Abstract: Transmission metallic gratings with very narrow and deep enough slits can exhibit transmission resonances for wavelengths larger than the period of the grating. By using a transfer matrix formalism and a quasianalytical model based on a modal expansion, we show that there are two possible ways of transferring light from the upper surface to the lower one: by the excitation of coupled surface plasmon polaritons on both surfaces of the metallic grating or by the coupling of incident plane waves with waveguide resonances located in the slits. Both mechanisms can lead to almost perfect transmittance for those particular resonances.

Frequency-Resolved Optical Detection of Photoinjected Electrons in Dye-Sensitized Nanocrystalline Photovoltaic Cells

Abstract: Electron accumulation in illuminated dye-sensitized nanocrystalline TiO2 photovoltaic cells has been detected by measuring the photoinduced change in transmission at 940 nm. The sensitivity of the transmission measurement was enhanced by using intensity-modulated visible light (514 nm) to excite the photosensitizer dye. The intensity modulation was superimposed on a larger dc illumination level in order to allow linearization of the intensity-modulated transmission, photovoltage, and photocurrent responses. The dye-sensitized photovoltaic cell was also characterized by measuring its frequency-dependent impedance under steady illumination. Comparison of the normalized modulated transmittance ΔT/T at open circuit with the corresponding modulated photovoltage response was used to derive the optical absorption cross section of electrons in the cell (σn ≃ 10-17 cm2 at 940 nm). The net electron injection efficiency was found to be 1 at short circuit but only 0.3 at open circuit, indicating that under strong acc...

Near infrared-absorbing electrochromic compounds and devices comprising same

Abstract: Electrochromic compounds capable of reversibly attenuating the transmittance of the near infrared portion of the electromagnetic spectrum are provided. Theses compounds exhibit an energy difference between the singly occupied molecular orbital (SOMO) energy and the highest doubly occupied molecular orbital (HDOMO) energy (ESOMO-EHDOMO) of less than about 3.6 eV. In addition, these compounds have a transition moment of the configuration made up of the HDOMO and SOMO that is 'long axis polarized'.

Atmospheric correction over land for MERIS

Abstract: A three-stage atmospheric correction is proposed for the Medium Resolution Imaging Spectrometer (MERIS) from a validated formulation of the signal. We correct first for the gaseous transmittance. Assuming the ozone correction is well defined, we illustrate the need to include a correction for water vapour continuum which covers most of the MERIS bands. The water vapour transmittance can be computed from the water vapour content obtained from a twoband ratio at 900nm and 890nm. We demonstrate that a direct association between the transmittance in a given band and the two band ratio is more accurate due to the removal of the coupling between absorption and scattering. Secondly, the Rayleigh correction depends on the barometric pressure determined here from a two band ratio method with the oxygen A band. Good accuracy is obtained for the pressure when accounting for the coupling between scattering and gas absorption, which mostly depends on the surface reflectance. The Rayleigh reflectance is computed from a...

Absorption coefficient and refractive index of GaN, AlN and AlGaN alloys

Abstract: The design of optoelectronic devices fabricated from III-nitride materials is aided by knowledge of the refractive index and absorption coefficient of these materials. The optical properties of GaN, AlN and AlGaN grown by MOVPE on sapphire substrates were investigated by means of transmittance and reflectance measurements. Thin (less than 0.5 μm) single crystal films were employed to insure that transmission measurements could be obtained well above the optical band gap. The influence of alloy broadening on the absorption edge was investigated by using a series of AlGaN alloy samples with a range of Al compositions. The optical absorption coefficient above the band gap was obtained for AlGaN having up to 38% Al composition. The refractive index below the band gap was determined for the same series of samples. These properties provide information critical to the optimal design of solar blind detectors or other optoelectronic devices.

Analysis of asymmetric Z-scan measurement for large optical nonlinearities in an amorphous As 2 S 3 thin film

Abstract: We have extended the conventional Z-scan theory by employing an aberration-free approximation of a Gaussian beam through a nonlinear medium and derived a simple analytical formula for Z-scan transmittance, including the effects of both nonlinear absorption and nonlinear refraction, which could be applicable to the sample with large nonlinear phase shifts. We verified the extended Z-scan theory in an amorphous chalcogenide As2S3 thin film by measuring the Z-scan transmittance with both open and closed apertures. The nonlinear refractive index γ=7.6×10-5 cm2/W and the nonlinear absorption coefficient β=1.6 cm/W of As2S3 were measured at subbandgap 633-nm illumination.

Fluorescence detecting device

Abstract: The present invention provides a fluorescence detecting device comprising a light source, an excitation filter set, a dichroic mirror, an objective, an absorption filter set and an observation optical system, wherein the excitation filter set includes two interference films with a transmittance of 25% or more at a wavelength by 20 nm shorter than the cross-over wavelength when the wavelength at the crossing point between the transmittance spectrum at a longer wavelength side of the excitation filter set and the transmittance spectrum at a shorter wavelength side of the absorption filter set is defined as a cross-over wavelength, thereby enabling to obtain a bright fluorescent image with a very high S/N ratio without requiring a filter with higher precision.

Refractive index changes of Pd-coated magnesium lanthanide switchable mirrors upon hydrogen insertion

Abstract: The optical effect upon insertion of hydrogen into Pd-coated magnesium lanthanide switchable mirrors is investigated in terms of the changes of their complex refractive indices. A significant change in the optical constants of LnMg layers is seen between the as-deposited state and the dehydrided state after one cycle. Furthermore, the optical effect of switching the Pd cap layer to a PdH cap layer was determined. It is shown that the Pd layer mainly limits the visible transmittance of the hydrided stack to about 35%–40%. Whereas the extinction coefficient of dehydrided LnMg layers at 550 nm is between 2.2 and 3.1, it is as low as 10−4 in the transparent state. This is of great promise to applications requiring large optical contrast (e.g., optical switches).

Spectrophotometric analysis of aluminum nitride thin films

Abstract: The optical functions of AlN thin films deposited on the quartz substrates by the reactive radio frequency magnetron sputtering, such as refractive index, extinction coefficient, optical band gap, and film thickness were determined from the transmittance and reflectance spectra in the range of 190–820 nm. For these analyses, an inverse synthesis method was established after literature survey. The results were doublechecked with a modified envelope method, and compared with those of previous reports. Spectroscopic ellipsometry analyses were performed to confirm the accuracy of the methods. Refractive indices of AlN films in this study were in the range of 1.95–2.05 at 633 nm and 2.26–2.38 at 250 nm, depending on the preparation conditions. The extinction coefficients were small (<5×10−4) and nearly constant at low energy region (<2 eV), but exhibited various dispersion features at 2.2–3.5 eV, indicating different amount and kinds of defects of AlN films. The absorption coefficient at near-band-gap energy e...

Transmission properties of multilayer films composed of magneto-optical and dielectric materials

Abstract: In this paper, we investigated the transmission properties of multilayer films composed of magneto-optical and dielectric materials, in relation to layer stacking structure. The basic structures are made of alternating layers of these materials having a conventional symmetric periodicity with the center of the structure. Films with these basic structures exhibit an enhanced Faraday rotation effect. The rotation increases to an angle close to 45/spl deg/, which is required for an optical isolator, as the repetition number of alternating layers increases. However, the transmittance decreases in these films as the rotation increases. To clarify the possibility of improving the transmittance, we also investigated films composed of multiple stacks of the basic structures. We found that, by using the multiple stacks, the transmittance can be improved without degrading the rotation characteristics.

Electro-optic device incorporating a discrete photovoltaic device and method and apparatus for making same

Abstract: Improved electro-optic devices are provided which may be in the configuration of variable transmittance windows, variable transmittance eyeglasses, variable transmittance light filters and displays and other devices wherein the transmittance of light therethrough automatically varies as a function of light impinging thereon. The electro-optic devices include a self-erasing electro-optic medium, and the transmittance of light through such medium varies as a function of electrical signals applied thereto through the agency of at least one photovoltaic cell, enclosed within the electro-optic device, and obviating the necessity of providing external drive voltage or external bleeder resistors or external wiring. In addition, a method and apparatus are provided for making such electro-optic devices.

Single-beam integrating sphere spectrophotometer for reflectance and transmittance measurements versus angle of incidence in the solar wavelength range on diffuse and specular samples

Abstract: A multipurpose instrument for the measurement of reflectance and transmittance versus angle of incidence for both specular and diffuse samples in the solar wavelength range has been constructed and evaluated. The instrument operates in the single-beam mode and uses a common light source for three experimental setups. Two integrating spheres, 20 cm in diameter, are used for diffuse transmittance and reflectance measurements. The transmittance sphere can be turned around an axis through the sample to vary the angle of incidence. The reflectance sphere uses a center mounted sample and a special feature is the position of the detector, which is mounted on the sample holder at the center of the sphere. This way the detector always sees the same part of the sphere wall and no light can reach the detector directly from the sample. The third setup is an absolute instrument for specular samples. It uses a small averaging sphere as a detector. The detector is mounted on an arm which rotates around the center of the sample, and it can thus pick up both the reflected and transmitted beams including all multiply reflected components. The averaging sphere detector is insensitive to small side shifts of the detected beams and no multiple reflections between detector and optical system occur. In this report a number of calibration procedures are presented for the three experimental setups and models for the calculation of correct transmittance and reflectance values from measured data are presented. It is shown that for integrating sphere measurements, the geometry of the sphere and the diffusivity of the sample as well as the sphere wall reflectance and port losses are important factors that influence the result. For the center mounted configuration these factors are particularly important and special emphasis is given to the evaluation of the reflectance sphere model. All three instrument setups are calibrated using certified reference materials and nonscattering mirrors and substrates. The results are also compared to the results of a double-beam Beckman integrating sphere for near normal angles of incidence and Fresnel calculations. The results in this article show that good agreement is obtained between results from the different instruments if, and only if, proper evaluation procedures are applied to the measured signals.

Light-colored glass of high transmittance and method for production thereof, glass plate with electrically conductive film and method for production thereof, and glass article

Abstract: A light-colored glass having high transmittance which contains 0.02 % or more and less than 0.06 %, in terms of Fe2O3 as a colorant, of total iron oxide, less than 0.024 % of FeO and 0 to 0.5 % of cerium oxide, has a composition wherein the ratio of the amount of FeO in terms of Fe2O3 to that of total iron oxide is less than 40 %, and has, in the case of a thickness of 3.2 mm, a transmittance of solar radiation of 87.5 % or more and a transmittance of visible light by C source of 90 % or more; and a glass plate with an electrically conductive film comprising said glass and a transparent, electrically conductive film formed on the surface thereof.

Spectral Radiative Properties of Open-Cell Foam Insulation

Abstract: A method to determine radiative properties of open-cell foam insulation is described. The spectral volumetric absorption and scattering coefficients and the spectral phase function are predicted from the dimensions and hemispherical reflectivity of particles that constitute the solid structure by applying to these particles a combination of geometric optics laws and diffraction theory. Three types of carbon foam of different porosities are studied. Particle dimensions and porosity can be obtained from microscopic analysis, but solid hemispherical spectral reflectivity is very difficult to obtain directly. It is determined by the Gauss method of linearization, applied to bidirectional spectral transmittance data obtained from an experimental device using Fourier-transform infrared spectroscopy. Results obtained from this approach are consistent. Good agreement is observed between the experimental results of transmittance and reflectance and the theoretically predicted values computed from the identified values of particle hemispherical reflectivity.

Cu(InGa)Se2 Thin-film Solar Cells with High Resistivity ZnO Buffer Layers Deposited by Atomic Layer Deposition

Abstract: The aim of our experiments is to improve the performance of Cd-free ZnO/Cu(InGa)Se2 solar cells using a high-resistivity ZnO buffer layer. Buffer layers were deposited by atomic layer deposition (ALD) using diethylzinc (DEZn) and H2O as reactant gases. The structural and electrical properties of the ZnO films on glass substrates were characterized. A high resistivity of more than 103 Ωcm and a transmittance of above 80% in the visible range were obtained. We focused on determining the optimum deposition parameters for the ALD-ZnO buffer layer. Results indicate that the thickness and resistivity of the ALD-ZnO buffer layer, as well as the heat treatment prior to the deposition of the buffer layer, affect the device characteristics. The best efficiency obtained with an ALD-ZnO buffer layer of solar cells without an antireflective coating was 12.1%. The reversible light soaking effect was observed in these devices.

Wavelength selective applied films with glare control

Abstract: A solar control film having low visible light transmittance and low visible light reflectance is comprised of a first sheet of transparent substrate material (40) having deposited thereon a solar-load-reduction film (46) for preferentially reducing infrared light energy transmitted through the film, and a second sheet of transparent substrate material (52) having deposited thereon a thin, transparent film (50) of metal effective to partially block light transmittance, wherein the first sheet of transparent substrate and the second sheet of transparent substrate are separated by an optically massive layer that prevents the constructive and destructive interference of reflected light. A preferred embodiment of a solar control film includes, in order, a pressure-sensitive adhesive layer (42), a polyethylene terephthalate layer (44), a Fabry-Perot interference filter layer (46), an adhesive layer (48), a grey metal layer (50), another polyethylene terephthalate layer (52), and a hardcoat layer (54). The preferred solar control film provides wavelength selectivity in the infrared range while controlling visible light transmission and minimizing visual light reflectance.

Coating solution for forming a film for cutting off solar radiation and the film formed therefrom

Abstract: A solution for forming a film having a high transmittance and a low reflectivity for visible light, a low transmittance for near infrared radiation, and a surface resistivity of at least 10 6 ohms/square. It contains fine particles of a hexaboride of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, Sr or Ca, and fine particles of ITO or ATO in a weight ratio of from 0.1:99.9 to 90:10. Also disclosed is a film formed on at least one side of a resin film as a base, for cutting off solar heat radiation.

Infrared absorption filter

Abstract: The infrared absorption filter of the present invention has a transmittance of not higher than 30% in the near-infrared region in the wavelength range of 800 to 1100 nm; a difference of 10% or less between a maximum value and a minimum value of transmittance in the visible light region in the wavelength range of 450 to 650 nm; and a transmittance of not lower than 50% at a wavelength of 550 nm, the filter being so excellent in environmental stability that after being left to stand in the air atmosphere at a temperature of 60° C. and a humidity of 95% for 1000 hours, the filter can maintain said spectral property in said range. Consequently, when used for a plasma display or the like, the filter can absorb the unwanted infrared rays radiated from the display, resulting in preventing erroneous operation of a remote control using infrared radiation even in such a high-temperature and high-humidity environment. The filter is gray in color so that when placed in front of a display, the color originated in the display can be seen without discoloration.

Sub-THz spectroscopic system using a multimode laser diode and photoconductive antenna

Abstract: A system for measuring transmittance of electromagnetic waves in the sub-THz region is proposed. The electromagnetic radiation is generated by the excitation of a photoconductive antenna with a commercially available multimode laser diode. The spectral coverage of the radiation is increased by defocusing the light spot on the photoconductive antenna. Transmitted radiation is detected by a hot-electron bolometer through a Martin–Puplett-type interferometer. Transmittance is measured for n-type Si wafers with various doping levels. The carrier densities calculated from the transmittance agree well with those obtained from the dc conductivity measurement.

16.4L: Late‐News Paper: A Novel Wide‐Viewing‐Angle Technology: Ultra‐Trans View™

Abstract: A novel nematic liquid crystal display of in-plane switching controlled by fringe-field has been developed. The device exhibits wide viewing angle over 160° and high transmittance comparable to the twisted nematic TN cell, a solution for long standing problem of previous wide viewing angle technologies with low transmittance. In this paper, the device with optimized design, i.e., less sensitive to process will be discussed.

Laser polishing of diamond plates

Abstract: Results are reported on laser polishing of 150–400-μm-thick free-standing diamond films with either a copper vapor laser (510 nm wavelength) or an ArF excimer laser (193 nm wavelength). Studies were focused on three particular goals. First, we aimed at a choice of optimum conditions for laser polishing of thick diamond films. It was shown that the laser polishing conditions and the resulting surface roughness were controlled by varying the angle of incidence of a scanning laser beam and by polishing time. Second, the laser ablation technique was applied to remove a defective layer from the “substrate” side of the diamond plates in order to reduce optical losses due to absorption in this layer. Third, the structure of the laser-graphitized diamond surface was studied using UV, visible, and IR optical spectroscopy techniques in the course of the “step-by-step” oxidative removal of the graphitic layer with increasing temperature of the oxidation in ambient air. Once the graphitic layer was removed, the optical transmission in the UV-visible-IR spectral range of the diamond films polished under optimum conditions was measured and compared with the optical transmission of the mechanically polished diamond films. It was shown that the optical quality (in the long-wave infrared region) of the laser-polished diamond plates was sufficient to reach the transmittance value very close to the theoretical limit.

Reflection and transmission of waves in surface-disordered waveguides

Abstract: The reflection and transmission amplitudes of waves in disordered multimode waveguides are studied by means of numerical simulations based on the invariant embedding equations. In particular, we analyze the influence of surface-type disorder on the behavior of the ensemble average and fluctuations of the reflection and transmission coefficients, reflectance, transmittance, and conductance. Our results show anomalous effects stemming from the combination of mode dispersion and rough-surface scattering: For a given waveguide length, the larger the mode transverse momentum is, the more strongly is the mode scattered. These effects manifest themselves in the mode selectivity of the transmission coefficients, anomalous backscattering enhancement, and speckle pattern both in reflection and transmission, reflectance and transmittance, and also in the conductance and its universal fluctuations. It is shown that, in contrast to volume impurities, surface scattering in quasi-one-dimensional structures (waveguides) gives rise to the coexistence of the ballistic, diffusive, and localized regimes within the same sample.

LCD of high aperture ratio and high transmittance preventing color shift having transparent pixel and counter electrodes producing oblique electric fields

Abstract: The present invention is directed to prevent color shift in liquid crystal display devices and to improve their aperture ratio and transmittance. High aperture ratio and high transmittance liquid crystal display preventing color shift comprising: an upper substrate and a lower substrate opposed to be separated by selected distance; a liquid crystal layer including a plurality of liquid crystal molecules and interposed between inner surfaces of the upper and lower substrates; a first electrode formed on the inner surface of the lower substrate; and a second electrode formed on the inner surface of the lower substrate, wherein the first electrode and the second electrode form an electric field for driving the liquid crystal molecules; wherein in the absence of electric field between the first and second electrodes, the liquid crystal molecules are aligned such that their long axis are parallel to surfaces of the substrates in a first direction; wherein after a selected voltage is applied therebetween, first and second diagonal electric fields are simultaneously formed in a pixel, the two diagonal electric fields are formed to be symmetrical with respect to the first direction; wherein the first and second electrodes are made of transparent materials; wherein the distance between the first and second electrodes is shorter than the distance between the upper and lower substrates; wherein widths of the first and second electrodes are determined such that liquid crystal molecules overlying the two electrodes are driven by the electric field generated between the first and second electrodes.