bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous optical pulse compression and wing reduction
Authors: Halas N. J. , Grisch-Kowsky Daniel L.
Published: February 2023

In the optical fiber pulse compressor, the intensity-dependent refractive index n2 in the fiber provides the necessary self-phase modulation for subsequent temporal compression in the dispersive delay line. One drawback of using this compressor to obtain subpicosecond pulses is that compared with the pulses obtained directly from mode-locked lasers, the compressed pulses have proportionately more extensive wings. Another effect in optical fibers arising from the same third-order nonresonant nonlinear susceptibility is the intensity-dependent polarization rotation. On propagation through an optical fiber, the higher intensity portion of the pulse will acquire a different polarization than the low-intensity pulse wings. This effect has previously been used in intensity discrimination and nonlinear pulse reshaping. In this presentation we report the successful combination of both self-phase modulation and polarization rotation in a modified optical pulse compressor to achieve pulse compression with a significant reduction in the wings of the compressed pulse. An important feature of this combination is our ability to adjust the strength of the polarization rotation independent of the degree of self-phase modulation. With this situation, compression ratios of typically 20 are achieved with pulse shapes comparable with those obtained directly from mode-locked lasers.
The institutional contribution: what the Optical Society of America can do
Authors: Wilson Jack M.
Published: February 2023

In recent years, the American Association of Physics Teachers has developed several programs for working with primary and secondary school teachers. A number of these involve summer workshops with active interaction with one teacher. These programs provide one type of institutional model for professional society contribution to early science education.
Solar blind UV forward scatterometer
Authors: Trakhovsky Eli
Published: February 2023

The solar blind UV forward scatterometer system will participate in the AFGL atmospheric aerosols research program. The experimental system is designed to provide high angular resolution radiance measurements around a point mercury lamp source at the wavelength of 2537 Å. The principal advantage of operating in the solar blind spectral region is the lack of the background radiation due to absorption of the solar radiation by the stratospheric ozone layer. Therefore the system may be operational in varying atmospheric conditions both day and night. Measured radiances will be inverted to deduce the aerosol size distributions in the 0.2–10-µm radii range. It is emphasized that angular scattering in the aureole region (0.5-10°) is due to the diffraction effect mainly and is therefore relatively insensitive to the unknown aerosol refractive index and particle shape. The receiver system consists of a solar blind radiometer, angular scanning device, and personal computer. It features hand-free data acquisition, high sensitivity, low noise, and wide dynamic range. The system is photon-noise-limited. Preliminary results are presented.
Gaussian reflectivity mirror in a Cassegrain resonator
Authors: McCarthy Nathalie , Lavigne Pierre
Published: February 2023

Gaussian modes of arbitrary large section have been experimentally produced by using Gaussian reflectivity mirrors in unstable resonators. The Cassegrain configuration has appeared particularly attractive because it produced a collimated output beam and improved the far-field brightness.1 The transverse energy distributions of the beam inside the cavity in the near field and in the far field have been investigated. The introduction of a hard aperture in the cavity did not significantly deteriorate the optical quality of the beam as long as the aperture diameter was > 1.4 times the beam diameter (at 1/e of the central intensity). With smaller apertures, the far-field pattern broadened, remaining free from secondary rings. With a large enough gain section, it has been observed that a misalignment of a cavity mirror did not affect the width or the Gaussian form of both the intracavity and the far-field energy distributions.
Design and characterization of complementary Gaussian reflectivity mirrors
Authors: Lavigne Pierre , McCarthy Nathalie , Demers Jean-Guy
Published: February 2023

Reflectors with a Gaussian reflectivity profile can be used to reduce the detrimental effects of edge diffraction in unstable optical resonators. Efficient energy extraction can then be obtained only if the energy which is not reflected by the mirror is recovered as useful output.
Optical pumping of infrared lasers using an axicon geometry
Authors: Couture M. , Piche M.
Published: February 2023

Conical lenses, often named axicons, produce a smooth focus which is highly suited for optical pumping of infrared lasers. The combination of a converging and a diverging axicon geometrically isolates the pump beam from the infrared laser cavity. We have used this geometry to pump the 12.1-and 12.8-µm lines of an NH3 laser with a low-power TEA CO2 laser; conversion efficiency is improved compared to previous studies done at the same power level with other geometries. We present the results obtained with a high-power (5-J) single-mode TEA CO2 pump beam. A proposal for an optically pumped, unidirectional ring laser based on the axicon geometry is also discussed.
Physics of Lippmann (holographic/multilayer) Bragg structures
Authors: Jannson T. , Jannson J. , Yu H.
Published: February 2023

It was shown that Kogelnik's coupling constant,1 proportional to the product of refractive-index modulation and number of layers can be a useful parameter in comparative analysis of diffraction efficiency and bandwidth of different Bragg-Lippmann structures including holographic Lippmann reflection filters,2,3 dielectric multilayers, rugate filters, etc. In particular, in the case of dielectric multilayers, the refractive-index modulation is relatively high while the number of layers is relatively low, while for Lippmann holograms, the situation is exactly opposite (number of layers even up to 500). In this paper the basic parameters of Bragg-Lippmann structures such as diffraction efficiency, bandwidth, spectral characteristics profile, refractive-index profile, Bragg wavelength range, and Bragg wavelength nonuniformity are discussed from the point of view of material effects including material scattering/absorption, local defects, and scattering on interfaces. The analysis results are used to verify possible broadband and narrowband energy-related applications. Also, the possible hybrid systems are considered.
Contrast perception in the peripheral visual field
Authors: Cannon Mark W.
Published: February 2023

Peripheral contrast thresholds have been measured in many stimulus conditions, and the effect of the cortical magnification factor on sine wave grating detection thresholds is well known. Very little, however, has been done to determine the behavior of suprathreshold contrast perception in the periphery. In the experiments described here, perceived contrast functions were determined for 2° sine wave grating patches of 2,4, 8, and 16 cycles-/deg at the fovea and at four peripheral locations using the method of magnitude estimation. The peripheral locations were distributed over the range of eccentricities for which each stimulus was visible (e.g., 0-40° at 4 cycles/deg and 0-10° at 16 cycles/deg). Experimental results demonstrate two main points: (1) When perceived contrast values at a given spatial frequency are combined across eccentricities, the data are well fitted (R2 ≃ 0.9) by a single power function of contrast minus threshold with an exponent near 0.5. This same equation describes the data, at all spatial frequencies studied, implying that similar mechanisms mediate contrast perception in fovea and periphery at both low and high spatial frequencies. (2) While suprathreshold behavior of the 2° grating patches remains remarkably uniform in the fovea and periphery, thresholds increase dramatically with eccentricity. This implies that contrast perception and contrast detection may be mediated by different mechanisms.
Use of a reflective neutral-density wedge for the measurement of saturation discrimination
Authors: Higgins Kent E. , Knoblauch Kenneth , De Monasterio Francisco M. , Coletta Nancy J.
Published: February 2023

The psychophysical measurement of saturation discrimination can be time-consuming, since maintaining constant luminance of a mixture of white plus monochromatic light while varying only its colorimetric purity is difficult without providing separate controls for the independent variation of the luminance of the two components. The necessity of adjusting two controls not only complicates the task for the subject but also extends testing time. We describe an apparatus which provides a relatively rapid means of measuring saturation discrimination. Subsequent to an initial measurement of the photopic luminosity function with heterochromatic flicker photometry, the observer only needs to turn a single control to vary the colorimetric purity of a test field relative to a constant white-light reference field to determine the saturation threshold at each wavelength. This is made possible by the use of a variable beam splitter to combine (mix) the white and monochromatic channels of the test field. The variable beam splitter is a standard reflective neutral-density wedge placed within the optical system at an oblique angle relative to the orthogonal beams being mixed. Preliminary results show that this provides a relatively rapid and reliable means of measuring saturation discrimination in a laboratory or clinical setting and yields results in normal subjects similar to those described by previous researchers.
Framework for color constancy
Authors: Worthey James A.
Published: February 2023

The eye can discount some features of an illuminant substitution but not others. Sorting out which features are discounted helps to organize constancy data, while avoiding possible overstatement of what the visual system can do. In outline form: (1) The eye cannot undo a breakdown of metamerism. (2) The eye discounts illuminant effects on object luminance well, whether (a) the light changes in intensity only, or (b) it changes in color as well. (3) The eye tends to discount the color of the illuminant, but (a) blue-yellow shifts are discounted better than (b) red-green shifts.1 (4) The eye tends not to discount illuminant effects on color contrast as quantified by (a) the red-green contrast parameter

t
^

or (b) the blue-yellow contrast parameter

d
^

.2 The poster reviews supporting data.
Electrooptical computer for Fourier transform power spectral density measurements
Authors: Bryant F. D. , Reeve C. D. , Collins P.
Published: February 2023

The optical deconvolution system previously described by Hayden and Reeve requires an electrooptical computing system which can measure the power spectral densities of pulsed signals applied to an acoustooptical cell. A system is described in this work wherein the optical computing section consists of a He–Ne laser beam which is modulated using an acoustooptical modulator, and the Fourier transform is performed by a simple lens. The power spectral density is measured by a linear photodiode array interfaced to a British Broadcasting Corporation microcomputer. This system is evaluated using common signal waveforms, such as a chirp. The ability to measure signals of arbitrary shape is explored, and applications of this system to deconvolution problems are discussed.
Applications of holography to x-ray Imaging
Authors: Howells Malcolm R.
Published: February 2023

X-ray holography has failed for many years to fulfill its initial promise. This has been due mainly to the poor coherence property of available x-ray sources. We believe this is changing: the opportunity now exists for effective use of x rays in the 23-45-Å region in 3-D imaging of biological material. We outline the theoretical basis of x-ray imaging in general and describe the issues involved in designing an optical system for x-ray holographic microscopy. We report progress in experimental realization of ideas in forming x-ray holograms using synchrotron radiation and in reconstructing with visible light.
Multilayer reflectors for the extreme ultraviolet
Authors: Scott Marion L. , Arendt Paul , Springer Robert , Cordi Richard , Cameron Bernard , Windt David , Cash Webster
Published: February 2023

Multilayer reflectors for short wavelengths, such as the soft x-ray region, have been fabricated using materials such as tungsten and carbon.1-3 More recently, a normal incidence reflector at 170 Å was fabricated by Barbee using molybdenum and silicon.4 The normal incidence reflectors described in this work were designed to operate in the EUV. The choice of materials for this effort will be discussed. We analyzed these coatings using Auger depth profiling to determine whether the correct profile was obtained. We also measured the total physical thickness of the coatings on a witness sample. The reflectance of the coatings was measured vs angle of incidence. One of our conclusions is that Auger depth profiling of layers as thin as the ones in this study can be misleading if the ion-etch rates of the two thin-film materials are significantly different. The data and conclusions from these measurements are presented.
Optically activated gallium arsenide guided-wave modulators
Authors: Carson Richard F. , Batchman Ted E.
Published: February 2023

New integrated optical modulator designs are presented that are based on a GaAs-clad dielectric waveguide technology. These devices exhibit unique features that arise due to the periodic coupling between the propagating lossless guided modes of a dielectric optical waveguide and the lossy modes supported by a semiconductor cladding layer. An incident light beam that propagates with a photon energy above the band gap of the GaAs introduces carriers that shift the absorption of the GaAs cladding. The carriers induce shifts in the periodic interaction between the modes of the dielectric portion of the waveguide and those of the GaAs cladding. Depending on the cladding thickness and material absorptions that are used, the induced shifts can modulate either the amplitude or phase of a guided lightwave that propagates at a photon energy near the band gap of the GaAs. The coupling properties of the clad-waveguide structure and the effects of shifts in the GaAs cladding permittivities are evaluated analytically. Proposed device structures will allow the use of a dielectric waveguide and a thin isolated GaAs layer with a GaAs substrate so the modulator will be fully integrable with other guided-wave devices.
Novel phase-integral equation for the computation of the exact number of guided modes in a graded-index waveguide
Authors: Griffel G. , Ruschin S. , Croitoru N.
Published: February 2023

We have recently reported a closed-form formalism that furnishes an expression for the exact number of guided electromagnetic TE and TM modes in a multilayered dielectric waveguide structure.1 This formalism is developed further here to give the exact number of guided modes for any case of graded-index dielectric waveguide. The computation of the number of modes is made by solving a first-order nonlinear phase integral equation (PIE). The PIE is actually an extension of the well-known WKB formula, and besides being exact, it has the advantage of taking into account not only the surface of the index profile but also its slope. In this way, the slope has no smoothness limitation relative to the wavelength. Another problem which is overcome here is that of the turning point boundary matching, since the integral is carried on the edge of the profile [i.e., β = K0n(∞)]. Moreover, we have also shown that for every case the result of the computation comes out to be ϕ∞ = (m + 1/2)π, where m stands for the number of guided modes. Numerical calculations and curve plottings were made for various profile shapes, such as exponential, Gaussian, inverse square cosh, etc.
Optical guiding in single-crystal LiNbO3 sputtered films
Authors: Griffel G. , Ruschin S. , Croitoru N.
Published: February 2023

The use of sputtering techniques in order to obtain single crystal film has attracted wide interest recently due to the relative simplicity of the process and of the systems involved. Nevertheless, the quality of the film has a strong dependence on the parameters related to the deposition process. We have studied the influence of the main parameters, namely, the substrate temperature, the rf sputtering power, the total gas pressure, and the oxygen/argon ratio. LiNbO3 was deposited on three types of substrate: Corning glass, quartz, and sapphire. We also examined the influence of postsputtering annealing. The analyses included reflected electron diffraction, Auger electron spectroscopy, and laser beam coupling. It was found that the substrate temperature plays a main role for all three substrates. Its variation enabled the control of the crystalline structure, which was random polycrystalline film on the Corning glass, oriented polycrystalline on the quartz substrate, and single crystal on the sapphire. Optimal fabrication parameters for the last case are reported. Annealing of the substrate improved the results further, and sharp electron diffraction dots of LiNbO3 with the c axis parallel to the substrate surface were observed. A He-Ne laser beam was coupled into the layers via a prism coupler, and guided light mode attenuation was measured.
Excitation of surface-plasmon modes along thin metal films
Authors: Tamir T. , Burke J. J. , Stegeman George I.
Published: February 2023

A thin metal film can support two (Fano) plasmon modes, of which one exhibits a symmetric and the other an antisymmetric field with respect to the plane bisecting the film. It has recently been shown1 that, when the metal film is placed on a dielectric substrate, each of the two Fano modes evolves into two other distinct modes. However, the possible excitation of all four modes by realistic sources has not yet been explored. We therefore examine the field produced by an elementary (point or line) source placed in the film substrate geometry; any other arbitrary source can be described by a suitable superposition of such elementary sources. We then find that each of the two Fano modes along an isolated metal film accounts for a single viable mode when the film is placed on a substrate. Even though they are also solutions of the secular equation, the other two modes do not provide a distinct contribution to the total field due to an actual source. We therefore conclude that only two of the four plasmon modes may be experimentally observed in a film substrate geometry.
Power limiting and self-focusing in nonlinearly absorbing liquid crystalline media
Authors: Guha Shekhar , Mohebi M. , Van Stryland Eric W. , Soileau M. J.
Published: February 2023

Picosecond optical limiting below 10 kW was observed in five isotropic phase-shift base liquid crystals (LCs) at 532 nm using 20-ps laser pulses. The limiting power in each was about the same as that in CS2 (8 kW) at this wavelength. The nonlinear refractive index n2 for the LCs was more than five times smaller than that of CS2, and the limiting originated mainly from two-photon absorption. Two-photon absorption coefficients (β) were measured for the LC samples at 532 nm. At 1064 nm no nonlinear absorption was observed and the values of n2 for these samples were also measured at that wavelength. The well-known theory of self-focusing was extended to include two-photon absorption. This theory was used, together with the measured β and n2, to predict the power limiting performance of these materials. The theory also predicted a self-focusing effect arising from purely two-photon absorption which is at present under experimental investigation. The LCs used are similar in composition to the widely used MBBA (p-methoxy benzylidene p-n-butylanilene) but lack the oxygen atom and are isotropic at room temperature. These materials can be used in building fast nonlinear optical devices, in addition to the power limiter described here.
Laser pulse compression using volume phase transmission holograms
Authors: Ho P. P. , Yang T. Y. , Katz A. , Alfano R. R. , Ferrante R. A.
Published: February 2023

Pulse compression is a useful tool to reduce the laser pulse duration down to the bandwidth limited region. At the same time, this increases the obtainable pulse peak power. We have demonstrated the use of a high diffraction efficiency volume phase gelatin transmission grating pair to compress gigawatt femtosecond laser pulse duration down to the 85-fs bandwidth limited vale. The dispersive parameter of the transmission grating pair based on the Treacy reflection grating pair approach is a good guideline for practical adjustment.
Adaptive phased array radar, artificial neural networks, and optics
Authors: Johnson John L. , Duthie J. Graeme
Published: February 2023

The rate equation for the antenna weights and the covariance matrix of adaptive phased array radar are compared to the neural slab rate equation and the synaptic connection strength matrix of an artificial neural network model. It is shown that the mathematics are nearly identical except for a few key differences. These differences are traced to the basic goals of each system: The purpose of the radar systems to null out a given input distribution while that of the neural model is to identify and discriminate various input distributions. The second part of the paper considers some of the optical techniques appropriate for each system and discusses how they might be applied to the other. Other optical approaches are developed and shown to be compatible with adaptive phased array and/or artificial neural networks.
Brightness and flicker luminosity in sex-linked dichromacy
Authors: Knoblauch Kenneth , Laxar Kevin , Wooten Billy R.
Published: February 2023

The luminosity functions based on heterochromatic brightness matching (HBM) and 15-Hz heterochromatic flicker photometry (HFP), each on a dark background, were compared for two protanopes and one deuteranope. At wavelengths greater than each observer’s achromatic point, there was very little difference between the two methods. At short wavelengths, the two types of curve diverged with less energy needed for HBM than for HFP. Using each observer’s own color matching functions, the data were replotted to show (1) the additivity of luminosity for two wavelengths and (2) the effect of colorimetric purity on the brightness: flicker ratio. Both types of analysis indicated a superadditive effect for HBM at short wavelengths. Several simple models combining receptoral or postreceptoral outputs, linearly or nonlinearly, failed to characterize completely dichromatic HBM on a dark background. The addition of a large white adapting field produced a two-lobed HBM luminosity curve that can be modeled approximately as an interaction of opponent and nonopponent processes.
Trapping and cooling of neutral atoms by light
Authors: Ashkin A.
Published: February 2023

Radiation pressure forces have been proposed for making stable optical traps for neutral atoms and other dielectric particles. Recently introduced optodynamic or alternating beam traps based on the scattering force are compared with cw traps based on the gradient force. Trapping experiments on micron-sized dielectric particles are described which demonstrate the basic principles of alternating beam light trapping. The relationship of these traps to the optical Earnshaw theorem is considered. The implications for trapping of recently demonstrated sources of slow atoms are also discussed.
Slow atoms and stable lasers
Authors: Hall J. L. , Ertmer W. , Blatt R. , Zhu M. , Hils D. , Salmon C.
Published: February 2023

Radiative cooling using electrooptic frequency-sweep techniques prepares a gas sample at milli-kelvin temperatures. Observed interaction times and laser linewidths promise resonance widths of a dozen hertz.
Detection of surface orientation from texture
Authors: Aloimonos John (Yannis) , Chou Paul
Published: February 2023

Texture density depends on both the orientation and the depth of the textured plane in view. Previous approaches stated that because of this fact (i.e., density depends on both scaling and foreshortening), density cannot be used to recover surface orientation under perspective projection. In this paper we prove that these two effects (scaling and foreshortening) can be separated and so texture density can be used to uniquely recover surface orientation. We present algorithms that are based on strong (texels) and weak (edges) segmentation. Experimental results on natural images, based on the Gibsonian uniform density assumption, are very good; these images include grass fields, gravel paths, brick walls, aerial photographs of towns or parking lots, ocean waves, man-made artificial texture (cloth, carpet, etc.). Our algorithms first preprocess the image to find texels (and if this is not possible, to find edges) and then using the assumption that the texture-elements are uniformly distributed on the world plane (Gibson), they recover its orientation. An extension of our theory to curved surfaces is also discussed.
Enhanced bandwidth magnetostatic wave-optical diffraction
Authors: Wey C.T. , Tuan H. S. , Parekh J. , Craig A. E.
Published: February 2023

The coupling of light between orthogonally polarized dielectric waveguide modes by means of optical effects stimulated in yttrium iron garnet (YIG) films by magnetostatic waves (MSWs) has been demonstrated in a variety of ways. MSW magnetooptic Bragg diffraction has been reported1 with efficiency of 5%/W cm (rf power, interaction length) at frequencies above 3 GHz using surface waves (MSSWs) in a collinear diffraction geometry. Doppler shift of the frequency of the diffracted optical beam has been observed using forward volume waves (MSFVWs) in a transverse geometry. In recent work, the dependence of MSW dispersion characteristics on bias magnetic field strength has been exploited to extend the MSW-optical Bragg interaction bandwidth by employing a spatially gradient magnetic field. The basic character of this dependence is outlined for the particular case of MSFVW propagation perpendicular to the direction of the bias H-field variation, and theoretical results for various linear gradients are presented. Experimental observations which support predictions are presented; constant MSW propagation velocity over a broad frequency range is indicative of operation in a delimited wave number regime which can be tailored to coincide with the optical Bragg diffraction criteria. The trade-offs of decreased diffraction efficiency for increased bandwidth are discussed.
Theory for surface electromagnetic wave modulators
Authors: Begley D.L.
Published: February 2023

Previous studies have concentrated on the examination of material properties with surface electromagnetic waves (SEW) generated by both the attenuated total reflection (ATR) and the two-prism technique. The two-prism technique enables the SEW to probe properties of the material surface over relatively large distances. This technique is essentially the same technique utilized in the early work of integrated optics. The basic structure used to support the SEW is an interface (or combination of interfaces) between two (or more) media. This basic structure is much simpler than those used in integrated optics. The propagation characteristics depend on the material parameters at the supporting interface. It is possible to vary the dielectric constant and refractive index of the substrate material by applying the proper bias voltage through contacts deposited at the surface. From previous studies made in the far infrared it has been shown that the SEW can propagate over relatively large distances at GaAs-air, GaAs-metal-air, and SrTiO3-air systems. Theoretical analysis and results are presented which indicate that it is possible to construct a working SEW modulator at various semiconductor and electrooptic material interface systems.
Determination of loss mechanism in long-range surface plasmon modes
Authors: Booman Richard A. , Sarid Dror
Published: February 2023

Long-range surface plasmon (LRSP) modes have been observed on very thin metal films sandwiched between two dielectrics1 that can be excited using frustrated total internal reflection.2 The intensity profile of the light in the reflected beam contains a structure caused by interference between the light reflected from the prism base and the light being reradiated by the mode. It is possible to determine the loss coefficient of the LRSP mode from this intensity profile, and if there is an interference zero in this profile, loss coefficients caused by dissipation and reradiation can also be determined.3 A computer-controlled system that locates the plasmon resonance angle and also measures the reflectance vs angle and the intensity profile from a charge-coupled-device array was used for the data acquisition. We have measured the decay constants of several thin silver films based on the intensity profile. The results are compared with the decay constant obtained from the angular width of the plasmon resonance.
K-distributed noise from a space-time random process
Authors: Phillips Ronald L. , Andrews Larry C.
Published: February 2023

The perturbation of both the spatial and temporal behavior of an optical wave propagating through a random medium is modeled as a Gaussian fluctuating process. We assume the wave has a space-time separable correlation function. We then expand the spatial fluctuations as an orthonormal series over the receiver aperture. Each term of the series represents a single spatial mode. Each of the spatial modes can be expanded as a temporal orthonormal series over the Integration time of the detector. Since the fluctuations of the entire wave are taken to be Gaussian, the coefficients of each term in the space-time series are also Gaussian. If each function within the two series expansions is an eigenfunction of its respective correlation function, the random Gaussian coefficients of the functions are independent.
Wandering of laser beams due to a thick turbulent layer along the path
Authors: Consortia Anna , MantovanI M. , Conforti G.
Published: February 2023

The effect of the position and thickness of a layer of turbulence on a laser beam wandering is theoretically investigated. Using a simple model of turbulence, the wandering of a beam and the correlation of the wandering of two parallel beams are evaluated for small fluctuations.
Transverse cusp diffraction catastrophes: pertinent wavefronts and a Pearcey approximation to the wave field
Authors: Marston Philip L.
Published: February 2023

Longitudinal cusp caustics (which unfold along the direction of propagation) are of interest when modeling the focusing produced by the passage of light through irregular media1 or reflected by curved surfaces. In the present research I model diffraction patterns characteristic of transverse cusp caustics which unfold perpendicular to the propagation direction of the most strongly focused ray. It is assumed that the amplitude exp [ik(g — ct)] in an x-y plane results from propagation (from an unfocused source) through irregularities or from reflection. If this wave is to propagate beyond the x-y plane in a homogeneous medium to produce a shear-free transverse cusp, it is sufficient to consider g = a1x2 + a2y2x + a3y2, a2 ≠ 0, with real a
j
. The Fresnel approximation of the resulting 2-D diffraction integral gives a wave field proportional to the 1-D Pearcy integral P(X, Y) or to P
*
(X, Y) depending on the sign of a1 + (2z)−1 where z is the distance beyond the x-y plane. The real parameters X, Y depend on the a
j
, z, k, and the transverse coordinates in the observation plane. Stationary-phase points of the diffraction integral locate the rays from the x-y plane to the observation point.
Joint statistics of irradiance and its duration measured in strong refractive turbulence
Authors: Hill Reginald J. , Churnside James H.
Published: February 2023

We measured the time series of irradiance from a diverged He-Ne laser using 3- and 7-mm receiver aperture sizes that simulated the day-adapted and night-adapted human pupil. The propagation range was 1 km at a height of 2 m above flat grassland. The data are within the saturation-of-scintillation regime wherein the irradiance variance decreases with further increases of propagation distance and refractive turbulence strength.
Diode-pumping for coherence and peak power
Authors: Kane Thomas J.
Published: February 2023

Laser diodes and laser diode arrays now provide significant average power. They are efficient, compact, and reliable. Laser diode-pumped solid-state lasers can be equally compact and reliable, but they operate typically at 1/3 of the efficiency of their diode pumps and are more costly. To find wide use they must have significant performance advantages.
Recent results and perspectives on coherent optical communications
Authors: Chan Vincent W. S.
Published: February 2023

We summarize recent results in coherent optical communications using semiconductor lasers. Special emphasis is placed on trade offs between system designs and characteristics of currently available devices. Projections on future system characteristics and performance are made based on trends of device and circuit developments. Examples are drawn from fiber systems as well as space systems.
Development of photoreceptor sensitivity and color vision in early infancy
Authors: Brown Angela M.
Published: February 2023

Over the course of infancy and early childhood, major changes in visual function occur. A clear understanding of these changes could lead to a more complete understanding of adult vision, because a good theory of vision must parsimoniously account for infant and adult vision and for the smooth transition between them that occurs during normal maturation. This paper summarizes what is known of rod and cone vision in human infants. We include morphology of the rods and cones, psychophysically measured absolute and increment thresholds, photosensitivities and spectral sensitivities of the receptor mechanisms, and the overall luminous efficiency function. The ability to discriminate between lights on the basis of differences in spectral composition emerges over the first three months of life. Four hypotheses are discussed concerning what critical immaturities are responsible for the poor color vision of very young infants: (1) a color vision deficiency of a recognized adult type, (2) extrafoveal detection of stimuli, (3) inadequate spatial resolution for chromatic stimuli, and (4) immaturity of chromatically opponent channels.
Polarization properties of two-beam coupling with running gratings in BSO
Authors: Marrakchi Abdellatif , Johnson R. V. , Tanguay Armand R.
Published: February 2023

Self-diffraction in bismuth silicon oxide (Bi12-SiO20 or BSO) crystals exhibits pronounced optical polarization effects due to concomitant natural optical activity and electric field-induced linear birefringence. Foote and Hall have recently studied the case wherein BSO is used in the diffusion limit (i.e., with small linear birefringence) and with a fixed grating.1 The model described herein extends these results to the case of an optically active material in which either fixed or running gratings can be present, in both the diffusion and/or drift limits. Detailed computer studies of this polarization behavior have clarified the optimum configurations for maximizing energy transfer in two-wave mixing experiments, both with and without running gratings. Experimental parameters that can be manipulated for such an optimization include the crystallographic orientation, the polarization state of the incident beams, and the externally applied electric field. When both optical activity and absorption are included in the analysis, the effective electrooptic coefficient of BSO is closer to the value measured by electrooptic techniques2 compared to previously reported photorefractive measurements.3 In addition, the large enhancement of the space–charge field by the moving grating technique gives rise to peculiar polarization properties that are commonly used to increase the signal-to-noise ratio in photorefractive devices utilizing BSO crystals.
Measured performance of a laser diode direct detection optical communication system at very low received signal energies
Authors: Davidson F. , Sun X.
Published: February 2023

Semiconductor laser diodes, although far from ideal laser sources, are attractive candidates as transmitters in free space satellite-to-satellite optical communication systems. Both average and peak output power limitations of these devices make low alphabet size optical pulse position modulation (PPM) an attractive signal format for direct detection systems.
Development of spatial contrast sensitivity in human infants
Authors: Hainline Louise , Camenzuli Cheryl , Abramov Israel
Published: February 2023

Spatial contrast sensitivity functions (CSFs) were obtained from a large sample of infants grouped in 1-month intervals from 1 to 6 months. Only infants who passed a photorefractive screening were included in the study. The response measure was derived from the infants’ eye movements recorded by an infrared, TV-based eye tracker. Infants viewed vertical sinusoidal gratings, drifting horizontally at 7 deg/s across a large (38 × 29 deg) oscilloscope screen; direction of movement (left or right) was randomized. The output of the eye tracker was presented in real time to a blind experimenter who voted on the direction of grating movement based on the infant’s eye movements; for any grating, contrast was reduced until the experimenter made an error. With these methods, good estimates of threshold can be obtained for 3–6 spatial frequencies in <20 min. The mean infants’ CSFs, at all ages, show considerably greater sensitivity than data previously reported from other behavioral techniques. At all ages, the CSFs are maximal at some intermediate spatial frequency; with increasing age there is a tendency for this maximum to shift to higher frequencies. There is also an overall increase in sensitivity with age, particularly at higher frequencies. By 6 months, the CSF is still below that of adults tested in the same fashion. The behavioral procedures were validated using adult observers who also provided CSFs measured with more traditional psychophysical techniques. From these control experiments, infants’ higher sensitivities with this method can be attributed in part to the use of a large screen and drifting gratings viewed centrally.)
Infrared laser radiation by a passive Q-switch medium in the Q-switching process
Authors: Lin Yuan-Qi , Yang Bao-Cheng , Li Yong-Fang , Zhen Yi-Shan
Published: February 2023

The techniques of Q-switching and mode locking, using saturated-absorption media, are widely utilized in modern laser instruments. Taking account of this fact, we regarded the laser active and passive Q-switch media in a laser system as a combination of two coupled four-level subsystems and analyzed the behavior in terms of rate equations for these systems. The passive Q-switch media also act as a laser active media while they work as Q-switches. Some numerical solutions of the equations for several different sets of parameters were obtained, and the relationship between the output powers of both subsystems was discussed.
White light 3-D image plane holography
Authors: Gerhart Grant R.
Published: February 2023

We present a technique for recording and reconstructing an image plane hologram of a 3-D object using a white light source. A diffraction grating is placed in the image plane of a lens in intimate contact with the holographic emulsion. The grating structure is multiplied onto the recorded negative image of the object to serve as a spatial frequency carrier for the holographic image. The substitution of a diffraction grating in place of an external reference beam drastically reduces the temporal coherence requirements for this type of image plane holography. The spatial and temporal coherence requirements are calculated and shown to be consistent with a wide variety of holographic applications involving large 3-D objects. The holographic image reconstruction is accomplished by spatial filtering the optical Fourier transform of the original recorded hologram. The zero spatial frequency diffraction order produces a negative image of the original object while the nonzero diffraction orders produce a positive holographic image which exhibits parallax effects.
Modulation transfer function of an inhomogeneous and layered random medium using the small-angle approximation
Authors: Kuga Yasuo , Ishimaru Akira
Published: February 2023

Image transmission through an inhomogeneous and layered random medium is important in many areas. For example, clouds and fog are inhomogeneously distributed and often have a layered structure, imaging through a homogeneous random medium has been studied using the small-angle approximation of the radiative transfer theory.
Recognition of elementary geometric figures using rotationally invariant correlation filters
Authors: Schils George F. , Sweeney Donald W.
Published: February 2023

Sophisticated machine vision systems will require a high-speed front end that can compress the massive information present in visual data. These machine vision systems require as input the locations of basic geometric features, such as lines, arcs, and corners. Objects such as lines maintain their shape when viewed from any perspective, but they still must be recognized from an arbitrary rotation angle.
Relating the parameters of the I-K distribution to strength of turbulence parameters
Authors: Andrews Larry C. , Phillips Ronald L.
Published: February 2023

In weak scattering regimes the I-K distribution1,2 is consistent wth the assumptions of the Born approximation coupled with the further assumption of a compound or doubly stochastic field of the electromagnetic wave. Based on a pure power-law Kolmogorov spectrum and well-known results from the Born approximation for plane waves propagating through a turbulent medium, a relationship is established between the two parameters α and ρ of the I-K distribution and the strength of turbulence parameter

σ
1
2

=
1.23

C
n
2

k

7
/
6

L

11
/
6

, where

C
n
2

is the refractive-index structure parameter, k is the wavenumber of the electromagnetic wave, and L is the propagation path length. A second independent relation for α in terms of

σ
1
2

is developed by using relations from the asymptotic theory for strong turbulence regimes. Combining these results, we obtain expressions for α and ρ that appear to be valid for all conditions of turbulence. By generalizing the power spectral density of the refractive index to include the effects of the inner scale of turbulence I0, we then develop new expressions for α and ρ that also depend on I0. The normalized variance of the irradiance

σ
I
2

as predicted by the I-K distribution is calculated as a function of

σ
1
2

and I0. Comparisons of

σ
I
2

with that of plane wave data show a very good fit when inner scale corrections are introduced. Further comparisons of the normalized irradiance moments of the I-K distribution with experimental data obtained by propagating a collimated laser beam through a phase screen also show a remarkably good fit.
New results for observable characteristics and the nature of instabilities of the Lorenz model for single-mode laser dynamics
Authors: Abraham Neal B. , Lippi G. L. , Mello T.
Published: February 2023

The five eigenvalues of the linear stability analysis of the single-mode laser model have been monitored as functions of laser detuning and laser excitation. With sufficient detuning there are two pairs of complex conjugate eigenvalues corresponding to two different kinds of eigenvector. For large detunings and high excitations, these pairs of eigenvalue may collide below the instability threshold. For detunings below the critical value for the collision, one pair of eigenvalues is responsible for the instability. For detunings above the critical value for collision, the other pair of eigenvalues is responsible for the instability. As one pair arises in resonance purely from amplitudes and the other pair corresponds to evolution of the relative phases of the field and polarization, we have investigated the eigenvectors in the detuned case and the time evolution of the solutions for evidence of qualitative changes in the nature of the instabilities near the steady-state solutions or in the long-term pulsing solutions. The collision of the eigenvalues appears to have little to do with the presence or absence of small amplitude oscillations near the instability threshold but does seem to provide information on the stability of the relative phase of the solutions.
Probability distributions of the light intensity in a dye laser
Authors: Gage Edward C. , Lett Paul D. , Mandel Leonard
Published: February 2023

With the help of a fast digitizer, the probability distribution of the light intensity of a single-mode dye laser has been measured photoelectrically, for various working points of the laser, from well-below to well-above threshold. In the region below threshold the laser exhibits short spiking and a double-peaked probability distribution with large value at zero intensity. A plot of most probable vs mean light intensity shows a discontinuity suggestive of a first-order phase transition. The experimental results are compared with Monte Carlo solutions of the equations of motion, with both additive spontaneous emission noise and multiplicative Ornstein-Uhlenbeck pump noise, and reasonable agreement is found.
High-performance laser frequency stabilization using an external electrooptic phase shifter
Authors: Wong N. C. , Hall John L.
Published: February 2023

A simple and effective laser frequency stabilization technique uses a high finesse optical cavity (5-MHz FWHM) as the frequency discriminator and an external ADP phase modulator to supply the necessary high-speed laser frequency correction. This is supplemented by a lightweight laser PZT for mid- and low-frequency corrections. The fast frequency servo has a unity gain frequency near 2 MHz, while its low-frequency gain rolls off below 50 kHz where the PZT loop becomes dominant. The FM noise spectrum of our single-mode argonion laser output extends up to 300 kHz but is dominated by water-induced fluctuation of 1.8-MHz rms frequency excursion at 600 Hz. In closed loop operation, the high-frequency noise is suppressed down to the measurement noise level, i.e., the frequency servo error point shows an apparent noise level well below the shot noise level. This is the key achievement toward obtaining an ultranarrow laser linewidth. The present residual linewidth of 70-kHz rms is due to insufficient gain at low frequencies to suppress the water-induced FM noise at 600 Hz. We believe this can be readily corrected by increasing the low-frequency gain with a region of steeper gain slope vs frequency in the PZT channel. Alternatively, adding an acoustooptic modulator as a fast frequency shifter1 will certainly provide the needed bandwidth. An argon laser linewidth of just a few kilohertz is expected.
Comparison of laser phase and suppression of noise
Authors: Yang Xuan-Min , Yi Ming , Huan Zong-Hua
Published: February 2023

The sensitivity and accuracy of the usual methods for comparing the phases of two beams of light are affected by the intensity noise of environment and light source, although they can be improved by a lock-in circuit only for a periodic signal.
Artificially generated ultrasonic holograms
Authors: Hildebrand B. Percy , Bossi R. H.
Published: February 2023

In the course of research on synthetic aperture ultrasonic holography, some interesting experiments with artificial holograms were performed. The general idea was to synthesize one dimension of the hologram aperture by frequency control. Thus, a hologram was made by sweeping the frequency of the transducer at each position of a linear scan. When the frequency sweep was linear, the result was much like a Fourier.transform hologram in that linear fringes were obtained. When the frequency was swept quadratically, the familiar Fresnel zone patterns were generated.