bluuebunny/crossref_metadata_2025 huggingface dataset:
El adverbio relativamente y las clases de comparación
Authors: Ynduráin Pardo de Santayana Carlo
Published: February 2023

El objetivo de este artículo es hacer explícitos los procesos inferenciales que subyacen a la interpretación de aquellos enunciados en los que se emplea el adverbio relativamente. Esta palabra suele acompañar a adjetivos y (otros) adverbios que expresan propiedades cuyo valor cuantitativo debe ser modulado siempre respecto a una única clase de comparación. Entendemos, sin embargo, que relativamente se emplea para llamar la atención sobre el hecho de que, en un contexto dado, existen dos categorías relevantes respecto a las que es posible relativizar el valor del adjetivo o adverbio al que acompaña y que solo respecto a una de esas categorías resulta pertinente la atribución de la propiedad con que se relacionan estas palabras. Así, ante la afirmación El Sol es una estrella relativamente cercana a la Tierra entendemos, en principio, que el Sol está cerca de la Tierra si comparamos su ubicación con la de otros cuerpos celestes similares. El adverbio relativamente, sin embargo, advierte al oyente de que, respecto a otra categoría que también resultaría significativo activar como contraste (probablemente, la de los objetos con que interactuamos habitualmente), la nunca diríamos del sol que es una entidad cercana.
Merging engine implementation for intra-frame sharing in multi-tenant virtual passive optical networks
Authors: Ahmad Akhlaque , Ahmed Ashfaq , Al-Dweik Arafat , Ali Syed Taha , Ahmad Arsalan
Published: February 2023

High up-front capital expenditures impede the widespread deployment of passive optical networks (PONs). A multi-tenant solution, in which multiple network operators virtually share PON infrastructure and bandwidth resources, can result in significant cost savings. First, we investigate the viability of virtual PONs, in which virtual network operators share a portion of the upstream bandwidth in a frame. Each PON schedules its frame-level capacity using a dedicated dynamic bandwidth assignment algorithm, resulting in the generation of an independent bandwidth map (BMap). Second, we implement at the optical line terminal a merging engine that combines individual virtual BMaps into a single physical BMap, which is then transmitted to all optical network units. Our novel traffic merging algorithm is capable of consolidating traffic across all transmission containers. We apply this merging engine on top of the 10-Gbit-capable PON module and validate our approach using network simulator 3. The results show that our proposed intra-frame sharing technique, when integrated with our traffic merging algorithm, significantly outperforms the standard inter-frame sharing approach in terms of both latency and packet loss. Furthermore, we observed that best-effort traffic is affected most for all resource constraint scenarios of intra-frame sharing.
Photodetectors
Authors: Forrest Stephen R.
Published: February 2023

No summary of this tutorial or biographical information was available at press time. (Tutorial paper)
Photon-counting infrared solid-state photomultiplier
Authors: Stapelbroek Maryn G.
Published: February 2023

A solid-state device capable of continuous detection of individual photons in the wavelength range from 0.4 to 28 μm has been demonstrated using arsenic-doped silicon. Operated with a do applied bias, the device responds to the absorption of an incident photon with a submicrosecond rise-time current pulse with amplitude well above the electronic readout noise level. A counting quantum efficiency of over 30% has been demonstrated at 20 μm and over 50% was observed in the visible light region. Optimum photon-counting performance occurs between 6 and 10 K and for count rates of <1010 counts/s per cm2 of detector area. Operation of the device relies on impurity band conduction. Extremely fast internal charge amplification by impact ionization of impurity-band electrons results in a pulse of nearly equal amplitude for each photogenerated carrier. These devices are in effect avalanche photodiodes. However, impurity-band to conduction-band impact ionization is utilized rather than the usual valence-band to conduction-band impact ionization employed in other devices.
Neural computing in the spectral domain
Authors: Ersoy O. K. , Yu P.-T. , U. Purdue
Published: February 2023

Neural computing has the promise of solving random problems much more effectively than previous approaches. However, the very large number of interconnections necessary are difficult to achieve cost-effectively, even with optical computers. Formation of the neural network in the spectral domain drastically reduces the inherent problems due to data compression.
Distinction between CIE luminance and individual observer luminance
Authors: Kaiser Peter K.
Published: February 2023

The CIE definition of luminance requires a standard luminous efficiency function V lambda. There are in fact three CIE standard luminous efficiency functions: the CIE 2 and 10° photopic functions and the CIE scotopic function. Visual scientists frequently need to measure the amount of light with reference to their observer’s spectral sensitivity. Heterochromatic flicker photometry is the most frequently used method. When light measures are a function of an individual observer's spectral sensitivity function, visual scientists use the word luminance. Using this expression for both the standard CIE function and individual observer function can be an annoying source of confusion. This paper discusses how we can emulate auditory science where a similar potential confusion is avoided by distinguishing between sound pressure level and sensation level. When luminance measures are based on an individual's spectral sensitivity they could be referred to as sensation luminance or s-luminance for short. Visual scientists distinguish between luminance and retinal illuminance; the unit of measurement for the latter is the troland. I propose that the unit of measurement for s-luminance be the ives in honor of Herbert E. Ives who did the pioneering work in heterochromatic flicker photometry.
Phenomenology of blackness Induction
Authors: Volbrecht Vicki J. , Werner John S. , Wooten Bill R.
Published: February 2023

Three color-normal observers described the appearance pf colors in conditions of temporal induction. One of four inducing fields (unique blue, unique green, unique yellow, unique white) was foveally viewed for 5 s followed immediately by a reference stimulus of the same size (0.75°) and spatial location as the inducing field. After presentation of this temporal sequence, the observers described the reference stimulus by assigning percentages to the terms red, green, yellow, blue, black, and white. The reference stimulus was 3 or 5 trolands and appeared achromatic to the observer when viewed without the inducing field. The inducing field ranged in intensity from −0.4 to 3.2 log td. At the low illuminance levels the reference stimulus changed its appearance; both chromatic and achromatic color induction occurred. As the illuminance of the inducing field increased, the reference stimulus gradually became blacker and the chromatic components less prominent. The retinal illuminance level at which the reference stimulus appeared 100% black was the same for the four different inducing fields.
Thick target bremsstrahlung for diagnosing a Raman tree-electron laser
Authors: Chu Cheng , Lu Zaitong , Shi Ruigen , Wang Zhijiang
Published: February 2023

We have measured the bremsstrahlung emission from a thick target to determine the electron beam movement and distribution in our Raman free-electron laser. The principle of the method and measurement results of the electron distribution in the diode and drift tube of the Raman free-electron laser are presented. Based on such a diagnosis, the optimum free-electron laser operating conditions were determined, and the performance of the laser was improved significantly. The electronic efficiency of the free-electron laser was increased by about an order of magnitude to 0.8% for a cusp wiggler and 1.4% for an electromagnetic wiggler.
Classes of color normal observers
Authors: Elsner Ann E. , Burns Stephen A.
Published: February 2023

It has been suggested by Alpern and Neitz and Jacobs that the L and M cone pigments are not identical for all normal observers. We have examined this hypothesis by comparing the color matches for standard wavelengths of 560, 570, 580, 590, 600, and 610 nm and mixture primaries of 546 and 650 nm in bleached and unbleached conditions. For a 590-nm standard and 4° field, we found that the distribution of matches for our observers was broader for males than females but only at low illuminances. However, when the high illuminance color matches of the experienced observers are plotted, the data fall clearly into two groups of four observers each. That is, the data are separated by an R/G ratio of a 0.05 log unit in bleached conditions. The difference between these two groups cannot be due to differences in the amount of pigment bleached, since there is no significant difference in the half-bleach illuminances. The difference between groups is less distinct in unbleached conditions. A difference is also present for the 610-nm standard, which indicates that the difference cannot be due to lens density.
Enhancement of cone-detected grating acuity by short-term rod and cone adaptation
Authors: Naarendorp Franklin , Frumkes Thomas E.
Published: February 2023

The influence of rod- and cone-stimulating adapting flashes (AFs) on the visibility of 18 cycles/deg square wave gratings was determined in the foveal and parafoveal retina. The threshold grating luminance (i.e., the TGL, luminance, luminance of the 54-min of arc diam 10-ms duration test grating just permitting detection of grating orientation) served as an index of spatial acuity. TGL was determined at many time intervals in respect to the onset and offset of the 20° diam 500-ms AF. Rod-stimulating (<1-scotopic td) AFs decrease TGL (enhance acuity); this effect gradually increases to a maximum value 250 ms after AF onset and wanes to a negligible value several hundred milliseconds after AF offset. Cone-stimulating AFs increase TGL (reduce acuity) several hundred milliseconds prior to and during AF presentation. But within 400 ms after AF offset, TGL is lower (acuity enhanced) than control value, returning to control level ~1 s later. With no AF present, the action spectrum for TGL adheres to the sensitivity of the CIE photopic observer; when enhanced by either rod or cone stimulating AFs, the action spectrum for TGL exhibits enhanced long-wavelength sensitivity.
Nonlinearities and negative afterimages
Authors: Swift Dan J. , Smith Robert A.
Published: February 2023

It has long been known that sine-wave gratings appear somewhat distorted in shape, especially for high contrasts and low spatial frequencies. The bright areas appear to be considerably wider than the dark areas. This distortion is undoubtedly caused by a nonlinearity.
Measured TM-TM coupling in waveguide gratings
Authors: Weller-Brophy Laura A. , Hall Dennis G.
Published: February 2023

The coupling of guided modes obliquely incident to periodic and aperiodic waveguide gratings has been modeled by a variety of analytical formalisms including coupled-mode and boundary perturbation techniques. While the various methods used to model the grating response result in the same analytical expression for the near-Bragg-matched reflectivity, there are striking differences in the predicted coupling coefficients needed to evaluate this formula. This is especially evident for the case of TM-TM coupling. The TM-TM coupling coefficients predicted using the local normal and ideal mode expansions of coupled-mode theory demonstrate significantly different angular dependences. In particular, the zeros obtained by these methods occur for different angles of incidence. Thus, in certain circumstances, the ideal mode theory predicts a peak grating reflectivity of 100% while that predicted using the local normal mode expansion is virtually 0%.
Statistics of laser intensity amplified by a slightly saturated optical amplifier with a random gain medium
Authors: Yang C. C.
Published: February 2023

Recently, attention has been paid to the laser noise caused by the turbulence in the gain cell of a gas or liquid laser. In such a gain medium, the spatial and/or temporal variations of resonance molecules are supposed to be stochastic. Therefore, the gain coefficient and propagation constant in this medium become random. In this research, the statistics of a linearly polarized monochromatic plane wave are evaluated after the wave is propagated through an optical amplifier with a random gain medium. A partially homogeneously broadened slightly saturated laser amplifier is considered. To deal with nonlinear propagation, the perturbation method is used in which the slight saturation is regarded as the perturbative factor. As for the random molecule distributions, the relative fluctuation of molecule number density is assumed to follow a Gaussian probability distribution. Also, a Gaussian correlation function is used for describing the random structure. The average laser intensity and the contrast of intensity fluctuation are to be evaluated. The couplings among the random gain, random propagation constant, and nonlinear effect are discussed. Here only weak turbulences are considered. Numerical examples are presented.
New light source for high-speed photography, holography, and interferometry
Authors: Yao Jianquan , Shen Lixin , Fu Weiqiao , Zhang Dapeng
Published: February 2023

A 30-W output frequency-doubled YAG laser was recently achieved by our group. Because the output is high and it works in the visible spectrum (0.532 µm), and because it can operate either in the cw mode or the acoustooptically Q-switched mode (frequency 1-10 kHz; pulse width <100 ns; average cw output 30 W), we have used it as a high-speed photographic light source, as a cw source for a frame camera, and as a stroboscopic source for a drum camera. As high as 10,000-fps frame rate pictures including general, shadow, and schlieren pictures, were obtained. It seems that the output is high enough for much higher frame rates. Moreover, the laser is a coherent source, and electrooptic Q-switching and phase-locking techniques can also be used in the system; the 30-W output is achieved without any optical amplification.
Squeezed light generation in a monomode optical fiber
Authors: Potasek M. J. , Yurke B.
Published: February 2023

Squeezed light, in which the quantum noise in one amplitude component is reduced below the vacuum level, has been generated using parametric processes. The starting point described here is the nonlinear Schrodinger equation which models light propagating through optical fibers. When such a dispersive nonlinear medium with a third-order susceptibility is pumped with an optical beam, squeezing can result. It is found that the degree of squeezing oscillates as a function of fiber length in the normal dispersion regime, whereas in the anomalous dispersion regime, it grows exponentially with fiber length. Examination of squeezing near the fiber’s zero dispersion wavelength shows that odd-order dispersive terms have no effect on squeezing. However, small values of higher-order even terms have significant effects on squeezing. In practice, high-frequency components of the squeezing spectrum are difficult to obtain. However, it is shown that a cross-correlation technique may be used to explore the frequency dependence of the squeezing spectrum.
Sub-shot-noise light in parametric downconversion
Authors: Tapster P. R. , Rarity J. G. , Satchell J. S. , Jakeman E.
Published: February 2023

Nondegenerate parametric downconversion is used to produce two identical photon trains. Shot-noise fluctuations in one photon train are fed back to reduce the noise in the other to below the shot-noise limit. A watt of 413-nm light illuminates a deuterated potassium dihydrogen phosphate (KD*P) crystal. The intensity of this light is classically stabilized by a feedback loop using an electrooptic modulator (EOM). Apertures are used to select two downconverted beams from the cone of downconverted light produced in the crystal. The aperture positions are adjusted to satisfy the phase matching conditions for 826 ± 50-nm photon pairs. The beams are detected using silicon PIN diodes with low-noise (<1-fA/Hz1/2) preamplifiers. When the apertures are correctly aligned a high degree of shot-noise correlation is observed between detectors. One of the detector outputs is fed back to the EOM, and the noise in both detectors falls below the shot noise limit.
Gaussian beam system design: principles and methods
Authors: Shack Roland
Published: February 2023

No summary of this tutorial or biographical information was available at press time.
Comparison between computer and biological algorithms for extracting curvature
Authors: Richards Whitman , Wilson Hugh R.
Published: February 2023

Most machine vision systems compute curvature in three steps: (1) blob or contour extraction; (2) tangent computation along an edge list; and (3) tangent differentiation to obtain curvature. Such a procedure requires choosing the spatial scale for these different operators (blob, tangent, and curvature). Customarily, a range of 2-D masks and 1-D curvature operators is used to capture as much information as possible. In contrast, our recent psychophysical data suggest that the human visual system computes curvature using only one spatial scale, namely, the finest, except when pressed to perform on fuzzy contours. Furthermore, two different types of mechanism are required to cover the range of curvatures discriminated. For low curvatures, the mechanism resembles the cocircularity comparison of bar masks proposed by Parent and Zucker (1985). For high curvatures, our visual system uses a single receptive field operator analogous to that proposed by Koenderink and van Doom (1986). (12 min)
Amplitude-stabilized chaotic light
Authors: Li Z.W. , Radzewicz C. , Raymer M. G.
Published: February 2023

We have devised a method to produce intense light pulses whose intensity is temporally smooth but whose phase has rapid fluctuations with uniform distribution. This is achieved by using a single-mode frequency-doubled Nd:YAG laser to pump a cavityless dye laser which produces chaotic light. The intensity fluctuations of this light are temporally smoothed by means of passing the pulse through a strongly saturated dye amplifier pumped by a single-mode Nd:YAG laser pulse.
Three-dimensional diffraction analysis of phase and/or amplitude, single, or cascaded anisotropic gratings
Authors: Glytsis E.N. , Gaylord Thomas
Published: February 2023

Gratings with modulation varying with depth are important in both bulk and integrated optics. These gratings can be modeled as a cascaded stack of planar slab gratings. In addition, single or cascaded anisotropic gratings with external anisotropic regions are important in integrated optics for switching, modulation, and optical data processing.
Pattern classification using linear associative memory mapping
Authors: Eichmann George , Kasparis T.
Published: February 2023

Pattern clustering algorithms or similarity measures have been used to classify extracted pattern features among reference classes. A new approach is to use properly trained linear associative memory mapping (LAMM). Associative recall may in general be defined as a mapping in which a finite number of input vectors is transformed into a given set of output vectors. In the case of erroneous input vectors, it has been shown that this mapping is least-squares sense optimal. This error tolerance suggests its applicability to pattern classification. For the purpose of classification, the inputs are feature vectors derived using some algorithm, where the outputs are codes (tags) for each pattern. The simplest code vectors could be orthonormal unity vectors. The associative memory matrix is derived during a training process using reference feature vectors and their corresponding code vectors. For texture classification, features can be extracted using a proposed algorithm based on normalized Hough transform. These features remain invariant under geometrical transformation such as rotation, translation, or scaling.
Perceptual organization using generic models
Authors: Pentland Alex , Murdock Janet
Published: February 2023

Perceptual organization is the ability to group (segment) automatically imagery into meaningful parts, which may then be matched against known objects (i.e., recognition) or combined into a coherent whole (i.e., learning new objects). This ability is critical to any general-purpose vision capability, and yet despite much research into use of grouping criteria such as continuity, nonaccidentalness, and goodness of form, there has been surprisingly little progress. We believe that a robust perceptual organization capability cannot be achieved by use of such low-level image-based grouping criteria but rather must rely on knowledge of generic formative processes that act to product coherence in the 3-D world. We describe a working system that employs generic knowledge about the shape of man-made structures (that they may be described as the union of rectangles) and about the shape of plants (that they may be described as the union of circles) to segment aerial imagery into meaningful parts, which are then grouped into houses, roads, and trees.
Scene segmentation using laser projected structured light
Authors: Brown C. David , Ih Charles S. , Arce Gonzalo R. , Fertell David A.
Published: February 2023

A formidable task in many image processing applications is the segmentation of the scene into regions of interest. A major distinguishing feature between these regions is often the 3-D texture of these regions. Typical methods of textural image segmentation are very computationally intensive, often lack the required robustness, and are incapable of sensing the 3-D texture of various regions of the scene. Scanned laser lines of structured light viewed by a stereoscopically located single video camera result in an image in which the 3-D characteristics of the scene are represented by the discontinuity of the projected lines. The discontinuities of these scan lines can provide the required information for quick identification of the texture in various regions. The image of the laser scan lines is actually a 2-D representation of the 3-D texture of various regions of the scene. This image is conducive to processing with simple regional operators to classify rapidly and robustly regions according to their texture.
Fast vector median filter algorithm
Authors: Kasparis T. , Eichmann George
Published: February 2023

Median filters (MFs) (or the more general rankorder filters) have proved very powerful in image processing. However, rank-order filters are generally considered to be more time-consuming than linear, e.g., averaging, filters. Several fast algorithms were devised for on-line or off-line filtering. Some of them are based on histogram calculation, whereas others are based on bit-by-bit calculation of the median. The vector median filter (VMF), introduced earlier by the authors, is a two-parameter family of median-type filters that outputs at each position a set of elements, i.e., a median vector. The VMF has the same fundamental properties of the MF; i.e., it preserves edges while filtering out narrow impulses. The main advantage of the VMF is that it is computationally more efficient than the MF with a performance comparable to the MF. Furthermore, since the VMF is a two-parameter filter, it offers a wider range of filtering possibilities. Here, based on a histogram calculation, a fast VMF algorithm is described. Computer run times are presented for both fast MFs and fast VMFs.
Interferometry in lithium niobate crystals with fixed reference holograms
Authors: Magnusson R. , Mitchell J. H. , Black T. D. , Wilson D. R.
Published: February 2023

Holograms that are highly resistant to optical erasure can be recorded in lithium niobate using thermal fixing or multiphoton techniques. In interferometry, such holograms have the potential of serving as permanent reference holograms and thus reducing double-exposure interferometry to single-exposure interferometry. We have recently applied this technique using thermally fixed reference holograms in iron-doped crystals of lithium niobate. First, the reference scene is recorded as a Fourier transform hologram and thermally fixed in the crystal. Then, in the same crystal volume, a hologram of the scene of interest is superimposed. Reconstruction reveals the output interferogram. These initial experiments indicate the feasibility of this approach.
Novel common path interferometer for surface profilometry
Authors: Arunkumar K. A.
Published: February 2023

Subwavelength surface profiling demands interferometers with a high degree of stability, usually not available in interferometers with separated beam paths. It takes a ΔT~ 1.44°C between the two beam paths to generate random phase noise of ~2π when the beam’s separation is ~8 in. Elimination of such random noise is essential to achieving a subwavelength profiling capability. We have an interferometer capable of achieving this. The part of the beam that gets through the hole acts as the reference beam whereas the portion that is focused by the lens is the object or probe beam. The latter carries local surface (phase) information on return, whereas the reference beam wavefront returns with an average phase value. The detector output can be represented as S = S
o
(1 +αcosϕ). In the quadrature condition, small changes in ϕ, dϕ, caused by the surface features, are directly proportional to variation in detector output dS. With this interferometer, surface features smaller than 50 Å have been measured with minimal precautions against environmental perturbations.
Numerical solution of the time-dependent radiative transfer equation
Authors: Tessendorf J. , Piotrowski C. , Kelly R.
Published: February 2023

An algorithm and numerical results are presented for the causal evolution of a radiance field which satisfies the time-dependent radiative transfer equation in a scattering and absorbing medium. Propagation from point to point requires a method of spatial interpolation which does not violate causality, i.e., a method which ensures that the radiance propagates at a predetermined physical speed and not at a speed which is determined by the spatial grid. A causal interpolation scheme is illustrated, and example results for a cylindrically symmetric pulsed beam are presented. This scheme can introduce artificial oscillations which do not affect the long-time behavior of the solution and can be controlled.
Dependence of the enhancement effect of the backscattered intensity on the incident beam size in a turbulent medium
Authors: Lure Y. M. , Yang C. C.
Published: February 2023

The enhancement effect of the backscattered intensity in a random medium, continuous or discrete, has been observed when multiple scattering is significant. In the past in theoretical studies a point source was always assumed. In this research, a laser or maser beam is used for the incident wave. The dependence of the enhancement effect on this beam size in a turbulent medium is investigated. To this end, the path integral technique and the conception of propagator are used. The statistical saturation is assumed to be reached in a one-way trip between the transmitter and target. In describing the random structure of the turbulent medium, two power spectrum functions are considered: Gaussian and Bessel-function spectra. The Gaussian one, although perhaps not realistic, produces a simple analytic result and provides some insight. The one with Bessel functions, which can be reduced to a power-law spectrum, gives better descriptions on the turbulent structure; however, it produces more complicated mathematics. The results based on these two spectra are compared and discussed. The result due to a point source can be recovered by taking the limit of small beam size.
New laser alignment instrument
Authors: Fan Yuzhen , Yu Keming
Published: February 2023

Laser alignment instruments usually operate by using the laser beam itself, i.e., the locus of its energy center, as the axis of the collimating and measuring base line. However, the locus of the laser beam energy center is not a steady-state straight line; it follows any variation in the laser output and thus can drift. This has a direct influence on the precision of the collimation measurement. The new type of laser aligner we introduce here, however, uses the axis of an annular interference pattern as a base; this pattern has a high degree of stability both in space and time, so that it is essentially unaffected by the drift of the laser beam (including its translation and angular displacement).
Study of the false color processing method by digital segmentation and optical combination and Its use In medicine
Authors: Wu Jl-Zong , Zhang Feng-Lin , Huang Shi-Ke
Published: February 2023

The principle and method of false color processing techniques for black and white images processed by digital segmentation and optical combination have been studied. The results of medical images processed by this method are given.
Shear and longitudinal GHz GaP Bragg cell devices
Authors: Soos Jolanta I. , Rosemeier Ronald G. , Rosenbaum Joel
Published: February 2023

Longitudinal GaP acoustooptic Bragg cells which have respective operational frequencies in the range of 200 MHz to 3 GHz and diffraction efficiencies in the range of 120 to 1 %/rf watt have recently been fabricated. Comparatively, shear GaP devices which have operational frequencies in the range of 200 MHz up to 2 GHz and diffraction efficiencies from 80 to 7%/rf watt have also been constructed.
(Non)rigid motion interpretation: a regularized approach
Authors: Aloimonos John (Yiannis) , Schulman David
Published: February 2023

Determining 3-D motion from a time-varying 2-D image is an ill-posed problem: unless we impose additional constraints, an infinite number of solutions are possible. The usual constraint is rigidity, but many naturally occurring motions are not rigid and not even piecewise rigid. A more general assumption is that the parameters (or some of the parameters) characterizing the motion are approximately (but not exactly) constant in any sufficiently small region of the image. If we know the shape of a surface we can uniquely recover the smoothest motion consistent with image data and the known structure of the object through regularization. This paper develops a general paradigm for the analysis of nonrigid motion. The variational condition we obtain includes maximizing isometry, rigidity, and planarity as special cases. If the variational condition is applied at multiple scales of resolution, it can be applied to turbulent motion.
Measuring the Inner scale of atmospheric turbulence by laser beam wandering
Authors: Consortini A. , O’donnell K. A. , Conforti G.
Published: February 2023

Values of the inner scale of atmospheric turbulence can be obtained through measurements of either differential angle-of-arrival fluctuations or intensity fluctuations of laser radiation propagated through the atmosphere. Here we propose a method based on the measurement of correlation functions of wandering of beams that have propagated through the turbulent path. A theoretical analysis is developed for different models of the atmospheric turbulence. Some experimental results are also described.
Infrared laser spectroscopy of cluster beams
Authors: Scoles G.
Published: February 2023

The evolution of the IR spectrum in the 10-μm region of the spectra of a molecule embedded in a noble gas cluster as a function of cluster size is discussed from both the experimental and theoretical points of view. In particular, the ability of this technique for giving information on the state of aggregation and structure of the cluster is evaluated. The fact that different molecule/solvent combinations behave very differently is documented. The probability for a molecule to reside on the surface of the cluster vs the probability of being fully coated by the solvent atoms is evaluated with the help of a crossed-beam surface deposition technique. The same technique is used to investigate the reaction between two neutral molecules in a cluster. Studies involving changes of the chemical nature of the molecule deposited on the surface and variation of the cluster size are presently being carried out in an attempt to determine the rate of diffusion of molecules in clusters. Finally, we are setting up and, with some luck, also report on experiments which make use of continuously tunable lasers in the 1.5-μm region that have the capability of operating either cw or with picosecond pulses.
Antireflection surface-relief gratings on dielectric and lossy substrates
Authors: Gaylord Thomas K. , Glytsis E. N. , Moharam M. G.
Published: February 2023

Zero reflectivity (unity transmissivity) surfaces on materials are useful for eliminating unwanted reflections. If the substrate is lossy and sufficiently thick, the incident radiation is totally absorbed. Using an impedance matching approach, the filling factor and groove depth of a rectangular-groove grating to produce zero reflectivity are calculated for lossless (dielectric) and lossy (metallic) substrates. These gratings are equivalent to a single homogeneous layer in the long-wavelength limit. The analysis is applicable to both TE and TM polarization and any angle of incidence. The antireflection behavior is verified for the gratings using the rigorous (without approximations) coupled-wave analysis of grating diffraction. Example zero-reflectivity gold gratings for an incident free space wavelength in the 0.44-12.0-μm range are presented.
Optical properties of reactively evaporated tungsten oxide films
Authors: Demiryont H. , Nietering K.E.
Published: February 2023

Oxides of tungsten are deposited by (a) reactive evaporation of tungsten and (b) thermal evaporation of WO3. Optical properties of as-deposited films are studied. Optical parameter spectra of the films deposited on Corning 7059 glass are deduced from specrtrophotometric transmittance and reflectance characteristics. Bond properties of the WOx films are examined by Fourier transform infrared (FTIR) spectral data.
Effect of near-surface gas-phase collisions on desorption measurements
Authors: Kelly Roger , Dreyfus R. W.
Published: February 2023

If desorbed particles have a sufficiently low number density they disperse collisionlessly. This means that if, for example, the mechanism is thermally activated, a time-of-flight spectrum yields the surface temperature through the relation kT = Ê/2, Ê being the most probable kinetic energy, and the signal is proportional to cosθ. If, on the other hand, the number density is high enough for a few (estimates range from 3 to 20) collisions to occur, a so-called Knudsen layer is formed. We first show how this problem can be solved analytically and then explore its consequences to thermally activated desorption. In particular, when there is a Knudsen layer, (1) 18-24% of the desorbed particles are found to recondense, (2) the temperature falls to 70-90% of the value at the surface, but this is more than compensated by a center-of-mass velocity, (3) the relation between kT and Ê changes significantly, and (4) the angular distribution becomes strongly forward peaked (~cos3θ). We finally consider the effect of a Knudsen layer on an electronic desorption process, especially on the energy spectrum and on the angular distribution.
Wave propagation modeling method applied to branching optical waveguides
Authors: Thurston R. N. , Kapon Eli , Silberberg Yaron
Published: February 2023

A multimode waveguide that branches into several single-mode guides, all of different propagation constants, can route each mode into a different output channel. Such branching waveguides are important in splitting and recombining optical signals in guided-wave optoelectronic devices. A branching waveguide is fabricated as a sequence of waveguide sections, joined end to end. The distance between the parallel guiding channels is stepped discontinuously at the junctions between sections. Preserving this feature of the fabrication in our model, we first determine the local guided modes (supermodes) in each section. The field in each section is then represented as a superimposition of the guided modes of that section, with mode coefficients determined to satisfy approximately the boundary conditions at the junctions between sections. The step size of the fabrication process and the section length define an angle. We find that to achieve low intermode crosstalk, this angle must be small, of the order of a few milliradians. We find a range of angles over which the crosstalk decreases with decreasing angle, almost independently of the step size. For still smaller angles, there is a section length dependence caused by interference of the intermode scattering off the junctions.
Spectral behavior of an integrated optical Mach-Zehnder interferometer: measurement and simulation
Authors: Hawkins Raymond J. , Perlmutter P. , Baran J. E.
Published: February 2023

We present preliminary results of a study of the optical wavelength dependence on the switching voltage of an integrated optical Mach-Zehnder interferometer. The optical wavelength dependence of the operational characteristics of integrated optical components is important since future telecommunications systems are expected to be extremely broadband. The switching voltage is of particular present interest because it is quite costly at high speeds, and thus its minimization is a high priority. To effect a broadband minimization, however, we need to understand fully the factors that contribute to the wavelength-dependent changes in the switching voltage. To this end we measured the optical wavelength dependence of the switching voltage of a titanium-indiffused lithium niobate Mach-Zehnder interferometer. The measurements were made from 1.2 to 1.7 μm using a white light system with a tungsten-halogen light source. The measured switching voltage (or voltage-length product) was verified to be a supralinear function of wavelength. We modeled this wavelength dependence by calculating the overlap between the optical and modulating electric fields. These calculations were made using a parameterfree variational finite-difference approach. We found the calculated wavelength dependence to be the same as that found experimentally.
Ab Initio calculations of the propagation properties of semiconductor waveguides: a variational finite-difference approach
Authors: Hawkins Raymond J. , Deri R. J.
Published: February 2023

We present a constrained variational finite-difference method for calculating the modal properties of dielectric waveguide structures and compare the predictive results of the method with measurements of the coupling lengths of semiconductor directional couplers. The method is based on a finite-difference treatment of a functional of the scalar Helmholtz equation and contains no adjustable parameters. The functional is minimized subject to a field normalization constraint whereby the functional becomes the modal propagation constant. This minimization is implemented numerically using successive overrelaxation of a Gauss-Seidel iteration scheme. The resulting numerical method is easily implemented numerically and rather efficiently: the 2-D modal field distribution and propagation constants are typically calculated within a minute of CPU time on a VAX 8650. To illustrate the utility of this method in waveguide design, we compared calculated and measured coupling lengths for a variety of GaAs-AlGaAs rib waveguide directional couplers. (For this set of experiments the average experimental standard deviation was 13% of the mean.) The difference between the predicted and measured coupling lengths was less than the experimental uncertainty (one standard deviation) in all cases.
Programmable optical Boolean logic gates using a microchannel spatial light modulator
Authors: Yu Francis T. S. , Song Q. W. , Lu X. J.
Published: February 2023

Optical Boolean logic gates are the basic elements in a digital optical computer. We discuss a system that can perform all sixteen basic two-operand Boolean operations with one MSLM and three LCTVs. The MSLM is used as an adder, subtractor, inverter, or just as a buffer. The LCTVs are used with a microcomputer as programmable input interfacing devices. The basic advantage of the system is the real-time programmable processing capability. Adding a feedback loop to the system, its function can be expanded to execute consecutively Boolean calculations.
Surface magnetooptic characterization using long-range surface magnetoplasmons
Authors: Hickernell Robert K. , Sarid Dror
Published: February 2023

Recently we developed the theory of long-range surface magnetoplasmons propagating along a thin magnetic metal film bounded by nonmagnetic dielectrics in the presence of a transversely applied magnetic field. Experimental verification of the theory was obtained by measuring the transverse Kerr reflectance from prism-coupled modes in thin nickel films. The narrow resonance of the long-range mode makes it highly sensitive to the magnetic properties of metal surfaces compared to other optical techniques. We analyze the response of four measurement geometries to a thin magnetic metal film with a surface whose magnetooptic coefficient differs from that of the rest of the film. Kerr reflectance in our geometry is more sensitive to surface magnetooptic properties than the Otto or Krestchmann geometries or reflectance from bare nickel films. Experimental studies of nickel films guiding long-range surface magnetoplasmons indicate a magnetically inert surface layer of 1-nm thickness. We believe that this layer is due to the absorption of organic coupling fluid. Other possible explanations, such as an oxide layer or surface roughness, do not agree with the measurements.
P and M neural pathways and the perception of color and brightness
Authors: Shapley Robert
Published: February 2023

P and M ganglion cells connect the retina to the visual cortex in monkeys and man. P cells project to the parvocellular layers of the lateral geniculate nucleus, while M cells project to the magnocellular layers. M cells have the highest senstivity to luminance contrast and may be the neural vehicle for contrast detection. P cells are color selective and are most sensitive to coarse colored patterns. Brightness must depend on the combined activity of M and P cells. Color may also result from interaction between M and P cells in the visual cortex. Experiments on color exchange show that while M cells are silenced at one particular color balance, their null points are distributed widely enough that the M population may contribute to color perception.
Optical crosswind profiling system
Authors: Ochs Gerard R. , Wilson James J. , George Robin , Lataitis Richard J.
Published: February 2023

A wind-profiling system has been developed that uses zero-mean transmitting and receiving filters to shape and analyze the intensity scintillation produced by refractive-index irregularities along the light path. The method is a variation of a technique first proposed by Lee. Two transmitting filters and three pairs of receiving filters are employed, and five of the six combinations are used to form filters in space which are sensitive to refractive-index irregularities, moving across the light path, of a specific spatial wavelength and at a specific location.
Diffraction of Gaussian beams by stationary and traveling grating combinations
Authors: Haghighatjou T. , Larson Don A. , Black Truman D.
Published: February 2023

The diffraction of Gaussian beams by multiple-grating configurations is analyzed using a general operator representation. Analytical intensity expressions were obtained for the 0 and ± 1 orders of diffraction for two gratings separated by a distance L. These results exhibit features that were not evident from simpler plane wave analyses of comparable configurations. In particular, the fundamental dynamic amplitudes due to the relative motion of the gratings vary as the Gaussian beam parameters change.
Highly efficient holographic lens arrays for optical interconnect applications
Authors: Kirsch James C. , Gregory Don A.
Published: February 2023

Many problems and limitations are foreseen in the near future of VLSI electronic circuit design. Perhaps one of the more important limitations is the interconnection between chips. The interconnects in use today are limited by space, speed, and interference effects. Optical interconnects have been offered as a solution to this limitation. Optical interconnects are not subject to propagation delays, loading effects, and interference effects that limit fan-out. The idea presented here is based on the use of a holographic optical element (HOE) as the optical interconnection between different devices. The HOE provides more freedom in designing the network as well as a means for reprogramming the interconnections. Several constraints are placed on the HOE. It must be highly efficient to ensure the best use of available power as well as to reduce optical noise in the system. A new photopolymer developed by Polaroid has the potential of providing the high efficiency needed for the HOE. Previously published results as well as preliminary investigations into the production of HOEs have been extremely encouraging. Small holographic lens arrays produced in the photopolymer currently exhibit high-diffraction efficiency.
Unusual effects in the RT spectra of thin substrates
Authors: Edgerton Robert F.
Published: February 2023

Spectrometers with a spectral resolution of better than 1 nm are capable of resolving the interference effects in substrates with thicknesses of <100 µm. The absolute reflection accessory that uses the John Strong VW method measures the product of the reflection or transmission at two different locations on the sample. The spectra of a silicon wafer polished on both sides showed some unusual and unexpected interference effects. Other thin substrates of glass and polyester films also showed unusual effects. Computer calculations were made to investigate the nature of the interference effects when two thicknesses are used in a calculation of the reflection or transmission squared.
High-sensitivity detection of ultraweak spontaneous chemiluminescence of macrophage
Authors: Hishinuma K. , Kobayashi M. , Mashiko S. , Inaba H. , Kimura S. , Yoda B.
Published: February 2023

Macrophages are known to release active oxygen species during phagocytosis or in response to triggering with opsonized zymosan or phorbol myristate acetate. Chemiluminescence intensity from such active species is so low that it has been detected previously by utilizing luminol or lucigenin as a photoamplifier. Using a highly sensitive photon counting system developed recently by our group, we detected very weak chemiluminescence from mouse peritoneal macrophages without use of luminol or lucigenin.