bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Y-junction laser arrays
Authors: Welch David F. , Streifer William , Cross Peter , Scifres Donald R.
Published: February 2023

Y-junction laser arrays, grown by metal-organic chemical vapor deposition, have been shown to couple effectively the adjacent emitters inphase. The inphase radiation pattern emits symmetrical to the normal of the cleaved facet, and the number of radiating lobes is determined by the emitter width and separation. The index guided arrays of emitters have been fabricated using both buried heterostructure waveguides and inverted channeled substrate planar waveguides. These guiding structures minimize the evanescent coupling between the guides, which would normally tend to enhance the out-of-phase radiation mode. Stable far-field patterns characteristic of the inphase mode were observed up to 400 mW. In this case the radiation pattern contained three lobes. By flaring the waveguides prior to the facet the near-field fill factor was increased to >80% resulting in near-single-lobe emission. Theoretical analysis of the Y-junction array indicates that the lowest-order spatial mode is dominant and that the near-field radiation pattern is nearly uniform with only the outermost stripes decreased in intensity by ½. The uniform near field uses the injected charges more efficiently than an evanescently coupled array. Thus the modal discrimination is greater even at the higher-power levels.
Telescope systems for x-ray astronomy
Authors: Holt Stephen S.
Published: February 2023

Because of the opacity of the atmosphere, x-ray astronomy must be conducted from space. Twenty-five years ago, the first detections of nonsolar x rays were made with simple proportional counters from sounding rockets. Collimated counters aboard rockets and satellites were used to follow up these discoveries, and more recently true x-ray telescopes have been used for the study of x rays from the cosmos. There are now thousands of cataloged x-ray sources ranging from nearby stars to distant quasars. The primary advantages afforded by telescopes for x-ray astronomy are twofold: direct imagery allows finer angular resolution than otherwise possible, and it also betters the sensitivity of the x-ray detectors via the minimization of nonsource background. The primary disadvantages are associated with the necessary grazing-incidence geometry: the effective focal length is limited by the actual telescope length, and the short-wavelength response is, therefore, sharply limited by the shallowness of the grazing angle. Examples are presented of important astronomical results that have been obtained from x-ray telescopes in space. Also presented are conceptual designs (and prototypical test results) from three different types of next-generation telescope for x-ray astronomy.
Volume holography in flowing liquids
Authors: Aqui Juna C. , Hesselink Lambertus
Published: February 2023

The volume holography process in a sensitized fluid is studied. The object of the research is to use forced Rayleigh scattering methods in the measurement of velocity gradients in fluids. The process is divided into three major steps: writing of the hologram; evolution of the hologram under the effect of fluid motion; and reading of the hologram by optical means. The last two steps are discussed with special emphasis on the effects of convection and diffusion as they relate to the hologram deformation and decay.
Second harmonic generation in the positive P-representation
Authors: Holliday G. S. , Singh Surendra
Published: February 2023

Equation of motion for the density operator of the field in the process of second harmonic generation is converted into a Fokker-Planck equation by using the positive P-representation of the density operator. This Fokker-Planck equation is replaced by a set of four coupled stochastic differential equations using the Ito interpretation. The statistics of the light field are studied by numerically solving these stochastic equations. For long interaction times substantial antibunching and squeezing are possible in principle.
Optical spatial correlator using two bar code systems
Authors: Li Yajun
Published: February 2023

Light flux passing through two superimposed transmitting screens on which bars and spaces are encoded is sensitive to their lateral displacement. This property of bar code systems provides the possibility of fixing an absolute reference mark in the measuring operations of optoelectronic transducers for length or angle measurements. Attention is concentrated on the problem of how to increase the contrast of the main autocorrelation peak above the rest of the correlation signal.
Acceleration of a fast atom beam by laser radiation pressure
Authors: Riis Erling , Poulsen Ove
Published: February 2023

The resolution obtainable in classical as well as modern spectroscopy has always been limited by the finite velocity distribution of atoms. Even in experiments using nonlinear first-order Doppler-free techniques it plays an important and limiting role through second-order Doppler broadening and transit time broadening. Successful demonstrations of cooling and even stopping of thermal atomic beams have recently been reported using the radiation pressure of laser beams. This technique can also be used for cooling fast ion beams stored in heavy ion storage rings. In the present experiment a 4-m long beamline limits the interaction time of a 100-keV Ne beam with a collinear resonant laser beam to 4 μs. This only allows scattering of the order of 100 photons on each atom, corresponding to an acceleration of <0.5 eV. However, with the vast increase in interaction time in going from the present single-pass scheme to experiments on stored ions a dramatic increase in the influence and capability of the laser cooling is achieved. Laser cooling of heavy stored ions is thus predicted to lead to crystallization of the beam.
Optical advantages of a moire topographic model of a living body
Authors: Cao Xiang-Qun , Yuan Yu-Lin , Huang Wei-Shi , Lu Jian-Ming
Published: February 2023

A moire topographic model of a living body has been successfully used in clinical studies. This model has three optical advantages: its sensitivity can be adjusted; the measurable depth is very large (~150 mm); smooth grating lines with outfocusing eliminate the noise. This moire topographic method has demonstrated an 88% conformation with x-ray diagnoses. The forward bending test was also used, and a conformation rate of 64% was obtained. (About 5000 children were examined.)
Optical information processing method for increasing the measuring sensitivity of moire topography
Authors: Wu Ji-Zhong , Fu Wei-Qiao , Ma De-Liang
Published: February 2023

Having a good measuring range and requiring only simple equipment and working conditions, moire topography has been widely used in measuring 3-D objects of large area and out-of-plane deformations of objects. It is limited, however, in its more accurate measurements because of the lower measuring sensitivity which is inversely proportional to its measuring depth, especially in measuring dynamic deformations of objects. An optical information processing method solving this problem is proposed.
New laser method using a ferroelectric crystal to measure specific heat
Authors: Zhuang Zhou Wen
Published: February 2023

Specific heat is an important physical parameter of matter, but its precise measurement requires great experimental skill. There are two reasons: (1) We have to measure the change of temperature precisely. (2) It is difficult to avoid (and compensate for) the unwanted heat transfer between the sample and its surroundings.
Computer simulation of optical design including holographic optical elements
Authors: Ih Charles S. , Zhuang B. H. , Shen Yan , Lu Keqian
Published: February 2023

Personal computers can now be used for serious optical design. Currently there is much good optical design software available for the IBM PC, Macintosh, and their compatibles. This software can provide high-resolution graphics, design optimizations, tolerance analyses, and image evaluations. The HOEs are now being considered for serious optical designs in which HOEs are intermixed with conventional optics. To the authors’ knowledge, none of the commercially available optical design software can analyze a generally defined HOE. Most of the software can only deal with simple holograms generated by two-point sources. Since a complete analysis and optimization are an important and necessary part of an optical design procedure and since, unfortunately, these processes are laborious and difficult, one naturally wants to take advantage of the software's capability as much as possible to perform these tasks.
Reversible optical fiber damage induced by ultraviolet radiation
Authors: Hall Gregory , Garmire Elsa
Published: February 2023

Optical damage resulting from color center formation in fused silica fibers has been investigated at 193 nm. The observance of optical bleaching to reverse the induced absorption is reported for the first time for UV-irradiated fibers. A maximum recovery of 70% initial transmission was obtained when samples damaged by ArF radiation were bleached with 13 J/cm2 of XeF light. A simple mathematical model, based on the kinetics of color center growth, correlates well with the observed induced absorption curves. Two quantities, the absorption saturation limit and the damage rate constant, characterize the fiber’s performance in specified experimental conditions. Their dependence on input fluence, fiber length, and manufacturer is documented. A color center damage threshold near 2 mj/cm2 is identified.
Brillouin scattering spectra for oxide and halide glasses: intrinsic Brillouin linewidths and stimulated Brillouin gain
Authors: Schroeder John , Hwa L. G. , Chyong M. D. , Thompson D. A.
Published: February 2023

Brillouin scattering measurements on various multicomponent halide and oxide glass compositions were done as a function of composition, lattice temperature, and configurational temperature. The intrinsic Brillouin linewidth measurements, Brillouin intensities, and Brillouin frequency shifts allowed the calculation of phonon attenuations, the Pockels elastooptic coefficients, and the stimulated Brillouin scattering gain coefficients. From the parameters obtained in the above measurements we are able to calculate the threshold energy for the onset of stimulated Brillouin scattering in halide and oxide glasses. Results show that the threshold power for stimulated Brillouin scattering is larger in some of the halide glass compositions than some of the silica-based glasses. This finding has important ramifications as a selection criteria for halide-based glasses vs oxide based glasses in their use as possible single-mode waveguide materials. The phonon attenuation values of some of the halide glasses, as measured from the linewidth data, had magnitudes that correspond more to a liquid than a solid. These anomalous phonon attenuation findings are discussed in light of existing theories.
Optical architecture for an acoustooptic correlator
Authors: Yu Francis T. S. , Nagata Toshio
Published: February 2023

Acoustooptic devices have been used in a variety of applications, such as laser beam deflectors, modulators, tunable optical filters, and signal processors. This paper discusses an architecture for an acoustooptic correlator. Two parallel on-plane acoustooptic cells are employed to convert electrical signals into acoustic strain fields which modulate incident laser light. The Fourier transforms of the acoustic fields are produced with a lens on the input plane of a liquid crystal light valve. The inverse Fourier transform of the readout beam of the liquid crystal light valve provides the cross-correlation of two input signals. Since two acoustooptic cells are in the same plane, the proposed architecture can be minimized and implemented in a compact system. This architecture can be easily extended to the system which yields more than two cross-correlations by adding an adequate number of acoustooptic cells in the input plane. This feature is useful for digital communications in which different waveforms are used to represent different messages. Due to the wide bandwidth of acoustooptic cells, this correlator can process broadband communication signals such as frequency-hopping signals.
Laser radiation pressure
Authors: Ashkin Arthur
Published: February 2023

The basic scattering and gradient forces of laser radiation pressure on atoms, dielectric particles, and biological particles are introduced, and experimental demonstrations of these forces are reviewed. As uses for radiation pressure forces, we consider the slowing, cooling, and trapping of neutral atoms at low temperatures; and the trapping and manipulation of dielectric and living biological particles in the Mie and Rayleigh size regimes.
Etalon filter applicable to optical intersatellite communications
Authors: Goto Koji , Araki Kenichi , Yasukawa Koji
Published: February 2023

We studied the etalon filter whose free spectral range equals the mode spacing of high-power laser diodes at high-speed modulation. When the sun comes into the receiver’s field of view, more than 5-dB laser power has to be applied to maintain the same bit error rate as that for no background radiation. But, in the case of using the etalon filter, only 1-dB additional laser power will be sufficient to keep the same performance.
Compound superposition array
Authors: Zinter J. Robert
Published: February 2023

Gradient-index (GRIN) arrays exist in nature as compound eyes. The two types of compound eye are the superposition and apposition eye. The purpose of this paper is to describe the design, fabrication, and testing of an array of imaging elements which is in direct analogy with the superposition compound eye. The first-order design of the array is based on the superposition imaging of two GRIN rods tilted with respect to each other; these rods are referred to as the array unit. The array unit is then replicated about a sphere to encompass theoretically 360 solid degrees, i.e., 4π sr. Placement of the array units is based on the principles of geodesic engineering. Analysis for the array’s performance was developed based on third-order aberrations.
DC electric field effect on cross-polarization four-wave mixing in GaAs
Authors: Cheng Li-Jen , Liu Duncan T. H.
Published: February 2023

Under no external electric field, GaAs crystal of the

4
¯

3
m

symmetry is optically isotropic. Thus the cross-polarization phenomenon in the beam coupling and four-wave mixing in photorefractive GaAs can be easily observed and implemented in image processing, as recently demonstrated. However, when an external electric field is applied, the situation is different. Experimental results of an investigation on the effect of the dc electric field on properties of phase conjugate beam of four-wave mixing in photorefractive GaAs crystals are presented. The GaAs crystals used were in the rectangular form of three surfaces normal to (001), (110), and

(

1

1
¯

0

)

crystal orientations. It was observed that, in the samples with electrical contacts on (110) surfaces, an applied field of 13 kV/cm not only enhanced the diffraction efficiency by 2–3 orders of magnitude, depending on the experimental condition and sample properties, but also induced a polarization rotation of the phase conjugate beam by ~80° with respect to that of no electric field. In the samples with electrical contacts on (001) surfaces, only the enhancement in diffraction efficiency was observed.
Effects of side diffraction and phase modulation on optical multiwave mixing and phase conjugation
Authors: Khoo I. C. , Zhou Y. , Michael R. R. , Lindquist R. G. , Yan P. Y. , Liu T. H.
Published: February 2023

We report several recently observed optical wave mixing effects in thin films of nonlinear materials, such as liquid crystals and silicon. Kerrlike local and nonlocal and diffusive nonlinear resonses are studied. The presence of the diffracted beam is, theoretically and experimentally, shown to have a pronounced effect on the amplification of the probe beam in pump–probe wave mixing. The diffracted beam also drastically alters the phase conjugation reflection of the probe beam, phase conjugation self-oscillation threshold, and aberration correction characteristics.
Saturable absorption and optical bistability in polymer dye etalons
Authors: Wu J. W. , Norwood R. A. , Garito A. F. , Kalyanaraman P.
Published: February 2023

Optical bistability in semiconductors such as III–V compounds has long been under intense study, first, to understand the relationships between bistable phenomena and the mediating resonant intensity-dependent index of refraction n2 and, second, to develop thin film nonlinear optical devices. Conjugated organic and polymer semiconductors and insulators are well known to exhibit unusually large nonresonant third-order nonlinear optical susceptibilities χ(3) whose origin resides in highly correlated electronic excitations. We have succeeded for the first time, we believe, in designing ultrathin polymer dye films possessing large resonant n2 values and in implementing wide-aperture Fabry-Perot polymer etalons for optical bistability studies. In addition to primary nonlinear optical properties, the design of the polymer dye etalons incorporated outstanding secondary material properties: (1) large saturable absorption with zero unsaturable background; (2) saturable absorption centered in the spectral range of operating laser diodes; (3) thin film formation; and (4) spin coatable films and high throughput fabrication. The polymer dye is composed of phthalocyanine oligomers which possess a quasi-2-D electronic structure and thereby exhibit an exceptionally large absorption (α of 1 × 105 cm–1 at 810 nm) that is easily saturable. Saturable absorption and optical bistability were studied in ultrathin films as a function of incident intensity, pulse duration (30 ps–1 s), and wavelength (800–900 nm).
Optoelectronic bistability in gallium phosphide
Authors: Choi M. S. , Hur J. H. , Gundersen Martin A.
Published: February 2023

Optoelectronic bistability was observed in gallium phosphide light emitting diode. Three device functions—current, optical output intensity, and optical output peak wavelength—showed bistable characteristics. The bistability is based on negative differential resistance occurring in the forward biased current–voltage characteristics. The switching voltage was ~15 V. Based on these I–V characteristics, the two stable states are (1) high impedance state in which the current is ~1 mA and the optical output has a weak-intensity yellow light with peak wavelength at 569 nm, and (2) low impedance state in which the current is ~200 mA (depending on the load resistance) and a strong-intensity (an order of magnitude stronger) green light with peak wavelength at 543 nm. We show the output–input intensity hysteresis curve obtained with an optical filter and typical optical output spectra of the bistable states of a GaP light emitting diode. The spectra show the intensity and peak wavelength differences between the two states.
Splitting images into transparent and opaque components using Markov random fields
Authors: Kersten Daniel , Bulthoff Heinrich H.
Published: February 2023

Both the perception of transparency and the estimation of reflectance, given sharp illumination edges, are problems that human observers routinely solve without apparent effort. Although the conditions leading to phenomenal transparency have been thoroughly studied, it has not been clear how to tease apart the transparent from the opaque components of an image. We have modeled the restricted case of the estimation of reflectance in Mondrian images in the presence of multiplicative illuminants with sharp (transparent overlays) or smooth edges. Our computational goal is to find the most probable opaque and transparent components conditional on the image luminance. The posterior probability is the product of three terms: the forward probability of the image conditional on the reflectance and illumination and the prior probabilities of the reflectance and illumination. The priors are modeled as intensity-based Markov random fields with coupled line processes. The landscape of the posterior probability is extremely rugged, leading to multiple stable maxima, a phenomenon human observers also experience. It is also shown that supplementing raw image data with intensity edges considerably improves the solution.
Contrast in complex images
Authors: Peli Eli
Published: February 2023

The contrast of test images such as sinusoidal gratings or a single patch of light on a uniformed background is well defined, but this is not the case for complex images. When the Michelson definition, used for sinusoidal test patterns, is applied to complex scenes the contrast of the whole picture may be defined based on only one point in the image. Human contrast sensitivity is known to be a function of the spatial frequency. Therefore, the spatial frequency content of an image should be included in the definition of contrast. We propose a definition of local bandlimited contrast in images which assigns a contrast value to every point in the image as a function of the spatial frequency band. The contrast is calculated for frequencies at one-octave intervals. For each frequency, the contrast is defined as the ratio of the bandpass filtered image at that frequency to the low-pass filtered image filtered to an octave below the same frequency.
Filter for rotationally invariant pattern recognition using radial eigenfunctions
Authors: Jouan Alexandre , Arsenault Henri H.
Published: February 2023

A new rotationally invariant matched filter has been developed. The principle is based on the extraction from the target of the information based on rotation-invariant principal components. For this purpose, the Karhunen-Loeve expansion applied to the target f(r, θ) sampled on angular radii yields its representation with a set of radial eigenfunctions ordered by decreasing eigenvalues: where Ψ
k
(θ) denotes the kth eigenvector of the angular covariance matrix. The inverse Karhunen-Loeve transform using a reduced number of radial eigenfunctions yields the synthesis of a new pseudoobject defined by The similarity between the original and the reconstructed targets depends on both the order and the number of the radial eigenfunctions used in the inverse transform. A rotationally invariant filter is then obtained by performing the circular harmonic expansion of the reconstructed pseudoobject.
Efficient optical implementation of the hypercube interconnection network
Authors: Drabik Timothy J.
Published: February 2023

If the 2
N
nodes of a binary N cube are lexicographically ordered in a 2
N/
2 × 2
N/
2 array, the total number of different spatial displacements encountered in moving from every node to all its neighbors is 2N. The interconnection graph is thus somewhat space-invariant, because the number of different displacements grows only logarithmically with the number of nodes. If one transmitter and receiver per node are time multiplexed according to the canonical communication scheme for hyper- cubes,1 it follows that no collisions occur and that the signals from the neighbors of a given node may simply be superposed at the node’s receiver. The admissibility of superposition, together with the low interconnect complexity of the graph resulting from lexicographical placement, makes a hologram-based free-space optical interconnection scheme very practical.
Direct fiber-etalon-fiber interfacing
Authors: Jin R. , Hanson C. , Khitrova G. , Chavez-Pirson A. , Gibbs Hyatt M. , Peyghambarian Nasser , Bowen T. , Junag F. Y. , Bhattacharya P. K. , Weinberger D. A.
Published: February 2023

Direct interfacing between single-mode optical fibers and GaAs nonlinear etalons is successfully demonstrated. The optical fibers used in our experiments are from AMP, Inc., with a core size of 10 µm. The ends of these fibers are polished and mounted in ceramic housings. The light source is a CR590 dye laser pumped by an argon-ion laser. The laser beam is modulated by an acoustooptic modulator to give pulses of several microseconds in duration. Laser light is coupled into a fiber by using a 10X microscope objective with a numerical aperture of 0.3, and the coupling loss is <3 dB. The nonlinear etalon used in the experiment is made by coating both sides of a 108-period 58-Å- 96-Å GaAs/AIGaAs multiple quantum well with 400-Å Ag, giving reflectivities of ~87 %. Optical bistability is observed when the nonlinear etalon is brought into contact with the fiber, with no lens between the output end of the fiber and etalon. A similar fiber is used to collect the output light from the etalon with an efficiency of >70%, suggesting that fiber-optic interconnects could be feasible in a digital optical processor.
Rotation-invariant pattern recognition
Authors: Arsenault Henri H.
Published: February 2023

This paper reviews recent research in rotationinvariant pattern recognition and classification methods using mostly circular harmonic matched filters. The early methods using single CHC filters are inadequate for classification of similar objects such as aircraft on cluttered backgrounds. The performance of such filters may be dramatically improved by combining several filters together in a single composite filter or by combining the results of several filters used sequentially. Methods of tuning the filters to eliminate sidelobes and clutter are presented, and implementations for real-time optical processing systems are discussed. Among the possibilities for the latter are the use of a new kind of computer-generated computer hologram for spatial light modulators with a small number of degrees of freedom, of binary phase-only CHC filters for rapid spatial light modulators, and of joint-transform Fourier-plane thresholded optical correlators. Because all the methods are based on matched filtering, they may be implemented either by purely digital means or by means of a hybrid system using an optical correlator with spatial light modulators and digital analysis of the output.
Hybrid recognition of three-dimensional targets
Authors: Sweeney D. W. , Schils George F.
Published: February 2023

A small bank of correlation filters is designed using an iterative process. The filter bank will recognize continuous views of a selected 3-D target. Filter design begins by finding orthogonal eigenimages that represent the 3-D information about the target. These eigenimages are combined to form the complex valued correlation filters. The set of coefficients used to combine the eigenimages for each filter is determined so that two constraints are simultaneously satisfied. First, each filter must contain all the eigenimages. Second, as the filters are applied to the input scene in sequence, the inner products between the filters and any potential target view must have a constant magnitude. The detection method relies on finding points of constant intensity in the correlation domain as a small bank of filters is applied in sequence.
X-ray lithography for the 1990s?
Authors: Wilson Alan D.
Published: February 2023

X-ray lithography Is a proximity printing process using ~10-Å x rays. Resolutions of 0.1 µm have been demonstrated in a number of laboratories around the world, and a large, relative to optical lithography, depth of focus has been observed as well as 100% process latitude. This process latitude is an excellent attribute and has a significant role in the apparent insensitivity of x rays to defects and excellent linewidth control achieved with x rays. X-ray lithography employs no optical elements between mask and wafer which could limit the field size as in optical lithography. Chip or field size is limited by mask defect density and overlay. Intrinsic exposing rates, determined by the ratio of x-ray power to resist sensitivity, is of the order of 10 cm2/s—a very suitable rate of exposure for manufacturing.
Comparison of three methods tor limited-view reconstruction in computer tomography
Authors: Oskoui-Fard Peyma , Stark Henry
Published: February 2023

Three new methods of image recovery in computer tomography are used to reconstruct a simulated image from a set of limited-view data: affine transformations; circular interpolation from nonuniformly based samples; and convex projections. Because the latter uses prior information in a systematic fashion, the method of convex projection gave better results than the other methods.
Large lightweight mirror for IR simulation
Authors: Janeczko Donald J.
Published: February 2023

Martin Marietta has designed and built a large-aperture large-field-of-view (FOV) dynamic thermal scene computer-controlled projector for testing infrared seekers. To achieve acceptable performance, an optical system was designed which features a 32-in. diam f/3.8 spherical mirror.
Structural analysis techniques in optical design
Authors: Gamble Michael , Viswanathan V. K.
Published: February 2023

A combination of the structural analysis code PAFEC,1 Wavefront Analysis Package (WAP), and physical optics code GLAD2 has been used successfully at Los Alamos to design and engineer optical systems, such as grazing Incidence resonators and imaging systems. The vital importance of properly designed mounts for optical elements is illustrated with several examples of trade-off analyses in the performance of the optical system. In particular, the performance characteristics of lightweight honeycomb and triangular celled optics are described.
Distortion invariance, target discrimination, and optical correlation
Authors: Gheen Gregory
Published: February 2023

The geometric notion of an N-dimensional linear vector space provides a useful framework in which to understand the operation and limitations of correlation techniques for pattern recognition. In general, correlators classify patterns according to a hyperplane decision surface whose orientation is determined by the filter and whose distance from the origin is determined by the threshold level that the correlation peak must exceed for an image to be classified. Thus the performance of an optical correlator depends mainly on how the reference images are distributed in this linear vector space. Using this approach, many useful conclusions can be drawn. Issues to be discussed include a simple approach toward calculating SDFs, the limitations of single-filter correlation systems, the relationship between target discrimination and distortion invariance, and the need to implement more sophisticated decision surfaces.
Shift invariant Fourier-Mellin features for pattern recognition
Authors: Sheng Yunlong , Arsenault Henri H.
Published: February 2023

The scale-invariant and rotation-invariant Fourier-Mellin transform depends on the position of the object. This limits its field of use. We propose filters of the form rs–2 exp(jmθ) with complex-valued s = v + jw. The filter contains no object information. The correlation function of the filter with an input object at every point (x', y') in the output plane is the Fourier-Mellin transform of the object developed about the origin (x', y') of a polar coordinate system. The shift-invariant features are then extracted: these are the distances between the correlation maxima from the filters with different orders s and m and the intensities of those maxima. The logpolar coordinate transform normally used for the optical Fourier-Mellin transform is not required. The method is invariant under changes of position, scale, orientation, rotation, and intensity. It also allows input containing multiple objects simultaneously. The invariant features can be used for image classification or as inputs to neural networks for invariant associative and adaptive pattern recognition.
Spontaneously generated Raman solitons
Authors: Bowden Charles M. , Englund John C.
Published: February 2023

The origin and statistical behavior of spontaneously generated Raman solitons (SGRSs) are discussed in terms of quantum fluctuations which cause quantum initiation of the Stokes field in a Raman gain medium in the presence of a strong pump field. The macroscopic temporal statistical behavior in superfluorescence, swept-gain superfluorescence, and SGRS is interpreted in terms of the amplification of quantum noise of similar origin. Predictions are presented for the observation of unique macroscopic statistical properties of SGRS as robust direct manifestations of quantum phase fluctuations.
Quantum fluctuations and soliton formation in stimulated Raman scattering
Authors: MacPherson D. C. , Swanson R. C. , Carlsten John L.
Published: February 2023

We used the Stokes output from an H2 Raman generator at 10 atm to seed a Raman amplifier. Before entering the amplifier a phase shift was electrooptically placed in the Stokes seed. Although a solitonlike pulse was regularly produced in the pump beam, its amplitude varied greatly. Subsequent studies of the Stokes seed’s power spectrum revealed large shot-to-shot fluctuations. The power spectrum normally consisted of a single near-transform-limited spike whose location jumped from shot to shot and for some shots consisted of two well-resolved spikes. Druhl found theoretically that shifting the Stokes seed slightly off resonance caused the soliton pulse to decay. These frequency fluctuations may thus explain soliton decay. It has also been predicted that solitons will be produced in the output of the Raman generator due to phase shifts resulting from the quantum noise which initiates the Stokes pulse.
Superlattice electron wave optics
Authors: Brennan Kevin F. , Gaylord Thomas K.
Published: February 2023

Starting from fundamental principles, quantitative analogies between electron waves in semiconductor materials and electromagnetic waves in dielectrics are presented. This in turn suggests a new class of electron wave optical devices such as narrowband superlattice interference filters. Phase effects associated with an electron wave are incorporated using the electron wave vector, which is proportional to the square root of the product of the effective mass and the electron kinetic energy. It is shown that the amplitude of a free electron wave is analogous to the electric field of a TE polarized electromagnetic wave in a dielectric. Amplitude effects associated with an electron wave are incorporated, using an effective amplitude refractive index that is proportional to the square root of the ratio of the kinetic energy to the effective mass. A simple expression for the critical angle for total internal reflection of an electron wave is developed. By analogy to the electromagnetic optical case, the overall electron transmissivity and reflectivity of a semiconductor superlattice are determined.
Phase waves and the statistics of Raman solitons
Authors: Englund John C. , Bowden Charles M.
Published: February 2023

When vacuum fluctuations at the Stokes frequency are amplified through the interaction of a coherent pump with a Raman medium, large phase shifts in the Stokes field may survive well into its macroscopic regime. Because the response time of the medium’s polarizability is finite, the relative phase of the polarizability and the Stokes field exhibits a peak, called a phase wave. Correspondingly, the pump reacts to a sufficiently large phase shift by briefly repleting before continuing its depletion, thus forming a solitary wave or soliton. It is possible to use the statistical properties of phase waves to predict such observables as the frequency of soliton production, the distribution of soliton amplitudes, and the soliton delay-time statistics.
Quantum initiation of stimulated Raman scattering
Authors: Swanson R. C. , MacPherson D. C. , Carlsten John L.
Published: February 2023

In our studies of soliton formation in stimulated Raman scattering (SRS), we have discovered that a fully quantum mechanical theory predicts large shot-to-shot fluctuations in the SRS power spectrum, which leads to soliton decay. This theory, which includes a Langevin operator to simulate collision-induced fluctuations and maintain operator consistency, can be used to generate the statistics of the macroscopic SRS output. We have also studied a simpler model which uses a random vacuum field as an input to the semiclassical SRS equations. The vacuum field was numerically generated by summing a set of electromagnetic field modes that spanned the collisional Raman linewidth. Each mode was separated in frequency by less than the resolution of the system and given a random phase for each shot. Despite the lack of Langevin terms, the shot-to-shot variations and two-frequency correlation function from the simple approach were essentially indistinguishable from the fully quantum mechanical theory. This suggests that a simulation of SRS from spontaneous emission does not always require Langevin terms in the quantum noise.
Absolute extreme-ultraviolet solar spectral irradiance monitor
Authors: Smith Peter L. , Parkinson W. H. , Kuhne Michael
Published: February 2023

The solar extreme ultraviolet (EUV) flux, nominally 10–120 nm, is the principal source of energy for heating the terrestrial thermosphere. Models of this region, which are used for studying its composition and dynamic properties, require the best available input parameters. The solar radio flux at 10.7 cm (F10.7) has been used as a proxy measure of the solar EUV flux in models that determine the density of the upper atmosphere and assess the effects of atmospheric drag on spacecraft design and operations. However, F10.7 is not adequate for accurate, timely, and spatially detailed nowcasts and forecasts of atmospheric density.
Surface-relief grating structures for photodetectors for optical interconnects in VLSI
Authors: Clymer Bradley D.
Published: February 2023

The miniaturization of integrated circuit elements and the expansion of chip sizes leading to very large-scale integration (VLSI) and wafer scale integration (WSI) have created a situation in which the speed of information processing for modern computing systems has become limited by communication delays rather than gate propagation delays for logic devices. The data communication limitation on processing speed has led to considerable interest in new methods for interconnection at nearly every level of computer hierarchy. While many researchers have proposed optical solutions to interconnection and communication problems at the chip, board, and backplane levels, the integration of fast photodetectors within a chip package has yet to be accomplished. The development of such devices is crucial to the feasibility of optical interconnection at hierarchical levels below the backplane connection.
High-efficiency holographic array generators and interconnects for optical digital computing
Authors: Redmond Ian R. , Robertson Brian , Taghizadeh Mohammad R. , Walker Andrew C.
Published: February 2023

Holographic elements have been fabricated in dichromated gelatin to generate arrays of up to 56 × 56 focusing beams with over 90% diffraction efficiency. Spot diameters within 10% of the diffraction limit for f/5 lenses at visible and near-IR wavelengths have been achieved. Compensation for the aberrations introduced by the wavelength change between hologram construction and replay is achieved by forming the hologram with two optimized spherical wavefronts. These wavefronts are chosen by modeling the hologram with a ray-tracing program which includes efficiency calculations and the effects of thickness and refractive-index changes between construction and replay. These holograms can be used to illuminate arrays of optical logic gates. Holograms for interconnection of arrays have also been made as both space-variant and space-invariant devices. A hologram which provides a fanout of four to nearest neighbor pixels with an efficiency of 40% (10 ± 0.2%/beam) has been constructed. This hologram operates in the Fourier transform plane of the input pattern and is, therefore, space-invariant.
Nonlinear optical imaging in a single pass through an intervening aberrator
Authors: Martinez David R. , Alley Thomas G. , Kramer Mark A.
Published: February 2023

Nonlinear optical techniques have allowed fast practical methods of processing images. The transmitting of an image in a single pass through an intervening aberrator can be realized through the nonlinear technique of four-wave mixing. To remove optical aberrations from an intervening distortion medium via four-wave mixing, it is necessary that a reference beam have a common phase distortion as the image bearing beam by sampling the same aberration. We have used the two orthogonal polarizations of a laser to provide the reference and image bearing beams. The common phase distortions present on the two beams were removed through phase subtraction via four-wave mixing. This image distortion compensation was demonstrated with a single pass through an aberrator. Interferometric measurements of various aberrations were taken. Tilt errors of up to ten waves were corrected to better than λ/2. Aberrations severe enough to wash out images completely were accurately corrected.
Ultimate quantum limits on phase measurement
Authors: Shepard S. R. , Shapiro Jeffrey H.
Published: February 2023

In a shot-noise-limited (coherent state) phasesensing interferometer, the root-mean-square (rms) phase error is

~
1
/

N

av

1
/
2

where Nav is the average number of detected photons. In an optimized squeezed-state interferometer, the rms phase error goes as 1/Nav. We have considered the phase measurement problem from the viewpoint of quantum estimation theory.1 In particular, for the problem of optimum phase-shift estimation from observation of a single mode of the radiation field under an average photon number constraint, we have found both the optimum quantum state and the optimum quantum measurement. The former turns out to have a truncated number-state expansion whose coefficients, out to the truncation point, fall off as 1/n. The latter turns out to be the Susskind-Glogower phase operator. More important, the resulting phase estimation performance improves as

1
/

N

av

2

.
Nonconventional joint transform correlator
Authors: Yu Francis T. S. , Zhang Chenhua , Jin Yong , Gregory Don A.
Published: February 2023

The major advantages of a joint transform correlator (JTC) must be the avoidance of matched filter synthesis, a higher space–bandwidth product, a lower carrier frequency requirement, and a higher output diffraction efficiency. However, the JTC still suffers several major drawbacks, namely, the inefficiency utilization of the light source and limited dynamic range of the square law converter. We propose a nonconventional JTC so that more efflicient utilization of the light source and the square law converter can be achieved. There is, however, an increase of spatial carrier frequency with this technique. Nevertheless, the higher carrier frequency would have some advantage in specific applications. Experimental demonstrations of the proposed JTC are provided. The results show that the spatial invariance property of the nonconventional JTC is preserved.
Hybrid method of lens optimization
Authors: Rayces J. L. , Lebich Lan
Published: February 2023

In the typical lens optimization problem there are two groups of equations. The first group which includes optomechanical constraints must be solved exactly, while the second group which includes aberrations in general admits an approximate solution. In Spencer’s method the sum of the squares of the residuals of the latter group is reduced to a minimum. If all the equations in the second group except one are eliminated, and that equation represents the norm of the vector of parameter changes, the system is a solution of Glatzel’s method. This happens automatically when the damping factor added to the diagonal in Spencer’s matrix approaches infinity. There is, therefore, a gradual transition from Spencer’s solution to Glatzel’s solution, and it is possible to combine both methods into one.
Lasers for coherent detection systems
Authors: Chan Vincent
Published: February 2023

Coherent detection offers improved sensitivities and selectabilities for communication and sensor systems. This tutorial reviews the fundamental principles of coherent detection from both the quantum mechanical and semiclassical points of view. Effects of device imperfections such as laser linewidths and mode-partition noise on the ultimate sensitivities of such detection systems are discussed. A survey of system techniques to circumvent some of these imperfections is also presented.
Laser diodes: their design and performance in coherent systems
Authors: Ikegami T.
Published: February 2023

Single-frequency and tunable laser diodes are key components in coherent systems. Single and monolithically integrated laser diodes incorporated into grating or corrugation systems are reviewed.
Applied perspective on color difference measurement
Authors: Silverstein Louis D.
Published: February 2023

Recent advances in electronic display and hard copy technology have made the use of full-color presentations feasible for a variety of applications. Color can enhance pictorial realism, increase human operator visual throughput, and facilitate performance in complex task environments. Realization of these benefits requires the specification of discriminable color sets and reliable tolerances on system visual parameters. The measurement and prediction of color differences are fundamental to these processes. This paper examines the use of existing measures of small color differences, such as CIELUV and CIELAB, for color specification problems for electronic visual displays. While small color difference formulas appear intuitively appropriate for specifying chromaticity tolerances for visual displays, their a priori applicability to large color difference problems such as color set selection would seem questionable. Nevertheless, small color difference formulas have been used for display color selection with considerable success. This success is manifest in consistent relationships between color difference estimates and a variety of visual performance measures, including color discrimination, color identification, reaction time, and visual search. Practical limitations of existing approaches to color difference measurement are discussed within the context of today’s complex color imaging devices and varied application environments.
Scaling of large color differences
Authors: Stalmeier Peep F. M. , de Weert Charles M. M.
Published: February 2023

Similarity data for very large color differences, obtained with the method of triads, are presented. The stimulus consisted of three separated fields subtending 1.06°, each field in a different color. The colors varied in hue, saturation, and luminance. Approximately 73.000 judgments are collected. The data are analyzed using the Luv 1976 color distance diagram.1 In general, the data accord satisfactorily with the Luv color space provided that weighting factors are inserted in the distance formula.
On-the-fly conversion of a modified signed digit into two’s complement binary number representation
Authors: Li Yao , Zhu Jianxin , Eichmann George
Published: February 2023

An attractive nonbinary parallel arithmetic scheme uses the so-called modified sign digit (MSD), also known as the radix-two redundantnumber system. Using the MSD, carry-free addition, subtraction, and multiplication can be performed. However, because the conventional MSD to two’s-complement-binary (TCB) conversion scheme is a serial processing technique, the overall processing speed is limited. Using a new conversion algorithm and the polarization switching technique, we propose an optical carry-free MSD to TCB conversion method. The availability of this converter will lead to a large speed increase for various proposed optical parallel MSD arithmetic processors.