Showing papers on "Transmittance published in 1990"

Sensitive measurement of optical nonlinearities using a single beam

Abstract: A sensitive single-beam technique for measuring both the nonlinear refractive index and nonlinear absorption coefficient for a wide variety of materials is reported. The authors describe the experimental details and present a comprehensive theoretical analysis including cases where nonlinear refraction is accompanied by nonlinear absorption. In these experiments, the transmittance of a sample is measured through a finite aperture in the far field as the sample is moved along the propagation path (z) of a focused Gaussian beam. The sign and magnitude of the nonlinear refraction are easily deduced from such a transmittance curve (Z-scan). Employing this technique, a sensitivity of better than lambda /300 wavefront distortion is achieved in n/sub 2/ measurements of BaF/sub 2/ using picosecond frequency-doubled Nd:YAG laser pulses. >

Large-Area Chromogenics: Materials and Devices for Transmittance Control

Abstract: Chromogenic materials can alter their optical properties in a persistent yet reversible manner when subjected to a change in external conditions such as irradiation intensity, temperature, or electric-field strength. In the future chromogenic materials may be used on large scale to regulate the throughput of radiant energy for windows in buildings and cars, so that comfortable lighting and temperature are maintained without excessive air conditioning. The purpose of this book is to give a broad coverage of large-area chromogenics and to discuss their applications. The book is divided into the following areas: applications; photochromic materials; thermochromic materials; inorganic electrochromic materials; inorganic electrochromic materials; organic electrochromic materials; conductors for ions and electrons in electrochromic devices; electrochromic devices; and liquid crystals materials and devices. Separate abstracts were prepared for 33 papers in this book.

Matrix formalism for calculation of electric field intensity of light in stratified multilayered films

Abstract: A new algorithm has been proposed for the calculation of the electric field intensity in stratified multilayered films when light is incident on the system. The algorithm utilizes matrix formulas based on Abeles’s formulas for the calculation of reflectance and transmittance. Equations for calculating patial absorptance due to a certain depth in the films are also derived. Some examples of the application of the electric field description are given for the analysis of three kinds of reflection spectroscopic methods which use metal surfaces: reflection–absorption, surface electromagnetic wave, and metal overlayer ATR methods. The algorithm given here offers a useful tool in understanding the mechanism of light absorption in various spectroscopic methods, and is convenient to use where intensity of the IR spectrum is of interest.

Vacuum ultraviolet thin films. 1: Optical constants of BaF 2 , CaF 2 , LaF 3 , MgF 2 , Al 2 O 3 , HfO 2 , and SiO 2 thin films

Abstract: An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

Thermally induced optical property changes in myocardium at 1.06 μm

Abstract: Light in the visible and near-infrared region is diffusely scattered in tissues by macromolecules. It was therefore hypothesized that tissue coagulation caused by high-power continuous wave laser irradiation might significantly alter tissue optical properties, resulting in a redistribution of laser energy during the laser ablation process. Infrared transmittance studies confirmed the hypothesis by demonstrating an irreversible decrease in light transmittance (45%) during heating of a 0.75 mm thick slice of tissue. Absorption and scattering coefficients were then determined from transmittance and reflectance measurements on thin slices of raw and coagulated myocardium irradiated with a Nd:YAG laser (1.06 microns). The scattering coefficient was found to increase fourfold (0.427 mm-1----1.74 mm-1) during tissue coagulation, while the absorption coefficient remained relatively unchanged (0.044 mm-1----0.051 mm-1). Calculations indicate that the coagulation-induced changes in tissue optical properties substantially increase surface back-scattering and reduce tissue penetration.

Retrieval of Precipitable Water from Observations in the Split Window over Varying Surface Temperatures

Abstract: The split window technique makes use of two differentially absorbing channels in the 11 μm region to remove the attenuating effects of atmospheric absorption so as to achieve a better estimate of the underlying skin temperature than could be produced by a single channel measurement. Since the primary absorber in this region is water vapor, it follows that split window measurements should be able to produce bulk water vapor retrievals as well. When observations are made with split window channels under conditions where the surface contribution to measured radiance changes, but the atmospheric contribution does not, it is possible to estimate the ratio of the transmittance of the two split window channels. This transmittance ratio is inversely related to precipitable water. This paper applies this technique to observations from the Advanced Very High Resolution Radiometer, and the VISSR Atmospheric Sounder, and demonstrates the capability of both instruments to determine precipitable water under tw...

Chromogenic materials for transmittance control of large-area windows

Abstract: Chromogenic materials have optical properties that can be changed in a persistent and reversible manner under the action of an external stimulus. They can regulate the throughput of radiant energy between widely separated extrema, and hence they can be used in future “smart windows” in buildings, cars, etc., and for many other applications. This article summarizes the state-of-the-art for: Photochromic (light sensitive) materials, with a focus on glass and spirooxazine compounds Thennochromic (temperature sensitive) materials, particularly vanadium-oxide-based coatings and “cloud gels” Electrochromic (electric charge dependent) materials integrated in multilayer configurations, with emphasis on transition metal oxide coatings and ion intercalation into these Certain liquid-crystal-based (electrically switched) materials of the guest-host as well as the polymer dispersed and encapsulated types

Temporal and Spatial Behavior of the Field-Induced Transition between Antiferroelectric and Ferroelectric Phases in Chiral Smectics

Abstract: Optical transmittance change and stroboscopic micrographs have been obtained in homogeneously aligned thin cells of S-MHPOBC, C8H17O–--COO–COO-*CH(CH3)C6H13, and R-TFMNPOBC, C8H17O–--COO–-COO-*CH(CF3)C8H17, by varying the initial applied DC voltage stepwise into the final one across the threshold. There exist two components, fast and slow, in the transmittance change due to the phase transition from antiferroelectric SmCA* to ferroelectric SmC*. The fast component is due to the pretransitional effect. The movement of the domain boundaries is responsible for the slow component. In the transmittance change due to the transition from SmC* to SmCA*, only the slow component is observed. The movement speed is mainly determined by the difference between the final and threshold voltages.

Theory of angular selective transmittance in oblique columnar thin films containing metal and voids

Abstract: The transmittance T and reflectance R of s- and p-polarized light, incident at various angles onto thin films which contain metal and voids in an oblique columnar structure, are analyzed using suitably modified thin film equations. Columnar aluminum is treated for various column angles in uniaxial and biaxial models to demonstrate that the model can predict the novel features found in recent experiments. Dielectric constants from quasistatic effective medium theory are used. The p-wave transmittance can be very asymmetric as incident angle theta varies about the normal, but R(p), R(s), and T(s) are symmetric. It is differences in the forward and reverse imaginary part of the complex p-wave phase shift for each theta that causes T(p) to be asymmetric. This difference leads to a modification to the standard thin film equations, or transfer matrix elements, which do not vanish when intensity amplitudes are calculated. Angular selective transmittance of luminous and solar radiation then becomes possible, which is important for several energy related applications.

Infrared and ultraviolet radiation absorbing green glass composition

Abstract: Green-colored, infrared energy and ultraviolet radiation absorbing glass compositions comprise conventional soda-lime-silica float glass ingredients, a high concentration of moderately reduced iron, and ceric oxide. The resultant glass exhibits an Illuminant A visible light transmittance greater than 70 %, a total solar energy transmittance less than about 46 %, and an ultraviolet radiation transmittance less than about 38 %, at glass thicknesses in the range of 3 mm to 5 mm. Optionally, a portion of the ceric oxide can be replaced with a predetermined quantity of titanium oxide. Further the glass may be used in an automobile glazing unit comprising two sheets of the glass integrally adhered together through an interposed layer of transparent resinous material such as polyvinyl butyryl.

ON THE INTERPRETATION OF ABSORPTION SPECTRA OF LEAVES–I. INTRODUCTION and THE CORRECTION OF LEAF SPECTRA FOR SURFACE REFLECTION

Abstract: — Reflectance and transmittance spectra of leaves and their sum can be corrected to relate only to the light actually entering the leaf, if the reflectance of the epidermal surface is known. The latter is found if the leaf reflectances at several wavelengths near the transmittance minimum in the red are plotted vs the transmittances of a homogeneous suspension of the native pigment-proteins at the same chlorophyll content per unit area and at the same wavelengths. With non-senescent leaves, the relation is linear and the extrapolation of the pigment transmittance to zero gives the value for the surface reflection. Surface reflectance data (both adaxial and abaxial) are given for the leaves of a number of trees and a few herbs, plus examples of the raw and corrected spectra. With normal, glaucous leaves, the adaxial reflectance averaged 4.5% of the incident light (n= 23, range = 3.7 −5.9, standard deviation = 0.4). The reflectances of the abaxial surfaces ranged between 7 and 13% since additional near-surface reflection occurred at the inside of the epidermis and in the spongy mesophyll. Reflectance and transmittance data demonstrated strong absorption in the epidermis below 480 nm.

Method and apparatus for semiconductor device fabrication diagnosis and prognosis

Abstract: A sensor (210) for diagnosis and prognosis of semiconductor device fabrication processes measures specular, scattered, and total surface reflectances and transmittances of semiconductor wafers (124). The sensor (210) comprises a sensor arm (212) and an opto-electronic control box (214), for directing coherent electromagnetic or optical energy in the direction of semiconductor wafer (124). Opto-electronic control box (214) includes circuitry for measuring the amounts of laser powers coherently reflected from and transmitted through the semiconductor wafer (124) surface and the amounts of electromagnetic powers scatter reflected from and transmitted through the semiconductor wafer (124) surface. The present invention determines specular, scattered, and total reflectance and transmittance as well as surface roughness values for semiconductor wafer (124) based on measurements of coherent and scatter reflected and transmitted laser powers. The sensor (210) of the present invention can also provide a go/no-go test of semiconductor fabrication process quality. A process control computer associates with the sensor (210) to respond to spectral reflectance and transmittance measurements yielding surface roughness and thickness measurements as well as diagnosis/prognosis analysis results and control signals.

Use of optical spectrometry to evaluate the condition of used motor oil

Abstract: Methods and apparatus employing optical spectrometry techniques to measure metallic wear debris contamination in used motor oil, even in the presence of carbon particulates. Measurement results based on optical spectrometry as disclosed herein correlate closely with results of laboratory analysis based on atomic spectrometry. Variation in transmittance of a sample of oil as a function of wavelength within the approximate range of 300 nm (violet) to 1300 nm (near-infrared) is measured as an indicator of metallic wear debris contamination. Conveniently, measurements may be taken at just two wavelengths within the range, for example 565 nm (green) and 660 nm (red). The ratio of transmittance at the shorter of the two wavelengths to transmittance at the longer of the two wavelengths is determined as an indication of the amount of metallic wear debris contamination, decreases in the ratio from a ratio of unity indicating increasing levels of contamination. Oil degradation not necessarily accompanied by metallic wear debris contamination may also be measured.

Optical and mechanical properties of dc sputtered carbon films

Abstract: Amorphous carbon films were deposited on glass by dc magnetron sputtering from a graphite target in mixtures of argon and hydrogen Hydrogen flow and other deposition parameters affected the optical and mechanical properties of these films Increasing hydrogen content caused the average visible transmittance to vary from 16% to 86% for 500-A thick films Maximum compressive stress and hardness occur between 0 and 1% hydrogen flow, resulting in rapid delamination Low sputtering power moderately increases transmittance and hardness while relieving stress Transparency is induced in both the high-hydrogen and low-power films by formation of sp3 C–C bonds In the case of the hydrogenated films, however, a softer polymeric structure is formed

Surface reflections and optical transport through random media: Coherent backscattering, optical memory effect, frequency, and dynamical correlations

Abstract: The effects of internal surface reflections on the transport of optical waves through random media are considered theoretically. Simple closed-form expressions for both transmission through and reflection from a finite slab are obtained for the following phenomena: the coherent backscattering of light, the form factors of the optical memory effect, the frequency-dependent correlation functions of static systems, the time-dependent correlation functions of dynamic systems, and the diffuse reflectance and transmittance. In every instance surface reflections are found to cause significant, sometimes dominant, effects under realistic experimental conditions. Good agreement is found between the theory and recent experiments for the optical memory effect.

Electrochemically lithiated V2O5 films: An optically passive ion storage for transparent electrochromic devices

Abstract: LiyV2O5 films were produced by reactive de magnetron sputtering followed by electrochemical posttreatment in LiClO4. X-ray diffraction showed an orthorhombic structure. Spectrophotometric transmittance and reflectance measurements demonstrated that the luminous and solar absorptance increased moderately when y increased from zero to unity. It is argued that LiyV2O5 is useful as an ion storage material operating in conjunction with electrochromic films.

Hybrid diffractive optical filter

Abstract: A hybrid filter having an inherently planar interference stack adhered to a nonplanar diffractive grating. The filter can have a planarization layer between the stack and grating. The hybrid filter has a spectral light transmittance value that is at least equal to or greater than the transmittance value of the least transmissive filter component. The filter also has a spectral bandwidth that is narrower than the spectral bandwidth of either filter component.

Phase diagram and phase separation in LC/prepolymer mixture

Abstract: A new method to obtain liquid crystal and polymer composite(LCPC) material is reported This material is a new electro-optic material which can control scattering and transparent states in an electric field e obtained this material by the photo-polymerization-induced phase separation from liquid crystal and prepolymer mixture where both monomer and oligonier are used as prepolymer We have found new type of phase diagram in this mixture which has a nematicisotropic line in addition to binodal and spinodal lines Electro-optic properties of this material are strongly affected by the point on the phase diagram at which the polymerization-induced phase separation starts This method enables us to control these properties such as voltage-transmittance characteristics Typical devices using these materials are also shown They have high contrast ratio and high transmittance in ON state and are suitable for display devices Drive voltage can be reduced by optimizing this material and the device with high contrast ratio about 200:1 in low drive voltage below 6Vrms was obtained

Vacuum ultraviolet thin films. 2: Vacuum ultraviolet all-dielectric narrowband filters

Abstract: We report the design and performance of narrowband transmission filters employing the rapidly changing extinction coefficient that is characteristic of BaF2 and SiO2 films within certain wavelength intervals in the vacuum ultraviolet. We demonstrate the design concept for two filters centered at 135nm for BaF2 and at 141 nm for SiO2. It is found that these filters provide excellent narrowband spectral performance when combined with narrowband reflection filters. The filter centered at 135 nm has a peak transmittance of 24% and a bandwidth of 4 nm at full width at half-maximum for collimated incident light. The transmittance for λ0 ≤ 130 nm is <0.1% and for 138 ≤ λ0 ≤ 230 nm the average transmittance is <3%. Another filter centered at 141 nm has a peak transmittance of 25% and a bandwidth of 3.5 nm.

Preparation of ZnO films films by activated reactive evaporation

Abstract: High quality films of zinc oxide were prepared by an activated reactive evaporation technique onto 7059 Corning glass substrates. Film resistivities of approximately 10-3 Omega cm and optical transparency of more than 88% in the wavelength range 300-800 nm were prepared by adjusting depositing parameters. The electron carrier densities in the range 2-12*1019 cm-3 and mobilities of 10-45 cm2 V-1 s-1 were observed. The energy gap of zinc oxide film was evaluated as 3.3 eV from optical absorption measurements.

Irradiance transmittance through the air/water interface

Abstract: For some applications the results of atmospheric models can be used as inputs for the computation of underwater irradiance provided that the effect of transmittance through the air-water interface can be accurately estimated. In this work the computations of refraction and transmission through the air-water interface are reviewed, the effect of a variety of atmospheric types investigated, and a simple table provided for estimation of air-water transmittance. The propagation of spectral irradiance as well as the propagation of photosynthetically active radiation is considered.

Z-Scan: A Simple And Sensitive Technique For Nonlinear Refraction Measurements

Abstract: We describe a sensitive technique for measuring nonlinear refraction in a variety of materials that offers simplicity, sensitivity and speed. The transmittance of a sample is measured through a finite aperture in the far-field as the sample is moved along the propagation path (z) of a focused Gaussian beam. The sign and magnitude of the nonlinearity is easily deduced from such a transmittance curve (Z-scan). Employing this technique a sensitivity of better than λ/300 wavefront distortion is achieved in n2 measurements of BaF2 using picosecond frequency doubled Nd:YAG laser pulses.

Optical correlator performance using a phase-with-constrained-magnitude complex spatial filter.

Abstract: Certain kinds of spatial light modulators (SLMs) can be used in a mode where the phase transmittance at a given point has the desired value, measured modulo-2π, and the magnitude transmittance has approximately the desired value. Computer simulations, based on a specific model of a deformable-mirror SLM, show that these phase-with-coupled-magnitude SLMs perform better for the particular cases studied, in terms of discrimination and signal-to-clutter ratio, than phase-only and binary phase-only SLMs in coherent optical pattern-recognition correlators where the input is distorted by variable illumination, rotation, and noise relative to the template pattern.

Surface radiation budget at Barrow, Alaska

Abstract: At Barrow, the most northerly point in the U.S., radiation measurements were carried out. It was found that multiple reflection between the ground and stratus clouds, due to high surface albedo in winter, enhances the global radiation. These measurements are in agreement with model results. This, together with cloud amount, makes effective transmittance of the atmosphere highest in spring, resulting in the highest values of irradiation in May. For the same cloud amount, the effective transmittance of the atmosphere is always larger in winter, when there is a highly reflective surface, than in summer.