bluuebunny/crossref_metadata_2025 huggingface dataset:
Picosecond degenerate four-wave mixing in polymer films doped with an organic dye
Authors: O'neill Claire , Galarneau Pierre , Roberge Marguerite-Marie Denariez
Published: February 2023

Organic dyes embedded in polymer matrix form an important class of optical materials. They have been of interest because of their possibility of generating phase conjugated waves by DFWM using cw lasers and their use as optical memories in optical computing. Our aim is to study these recording media using pulse laser radiation and find large nonlinear susceptibilities associated with fast response time. We report picosecond phase conjugation of 532nm laser radiation by DFWM in polyvinyl alcohol (PVA) films doped with rhodamine 6G. The temporal behavior of the nonlinearity is investigated and our results indicate a fast response time (<30 ps). We have also studied the influence of the dye concentration within the polymer matrix and the influence of pump intensity on the phase conjugated signal.
How to improve the optical characteristics of a cylindrical lens
Authors: Zheng Le Nian
Published: February 2023

No summary was available at press time.
Zernike decomposition of the time-dependent thermal blooming-induced phase variation
Authors: Lee Myung Hun
Published: February 2023

A ground-based high energy laser system is prevented from achieving diffraction-limited irradiance profiles at a distant target due to the degrading effect of thermal blooming-induced phase distortions. This difficulty can often be corrected by use of an adaptive optical system which corrects classical aberrations such as tilt, defocus, astigmatism, and coma by applying the proper amount of each correcting mode to the entire aperture. These correcting modes are represented by Zernike polynomials. Assuming a uniform subsonic wind across the aperture, in the isobaric approximation with near field heating, we present an analytic solution of the linearized hydrodynamic equation for the density variation and resulting phase profiles. In this approximation, the time-dependent phase variation is the sum of the phase generated at the current time, plus a wind-transported contribution from the previous phase. For the case of a uniform circular irradiance profile, we obtain a closed form expression, which we expand in Zernike polynomials. The results agree with the previously evaluated steady state limit in the long time limit, i.e., when the time is larger than the wind-clearing time.
Experiments of a DBM broadband communication system
Authors: Tian R. S. , Ih Charles S.
Published: February 2023

An optical communication system by which broadband analog and high speed digital information is transmitted simultaneously can be implemented using radio frequency (rf) or microwave subcarrier multiplexing (SCM). This system can also be used for general broadband communications if we can use subcarriers of tens of gigahertz.1 Therefore we call this system MDM (microwave division multiplexing). However, because of the nonlinearity of laser modulation, serious intermodulation occurs especially in the high frequency range. Double-beam modulation (DBM) has been suggested and demonstrated using a standing wave acoustooptic modulator (SWAOM) to 1.2 GHz. Compared with intensity modulation, the DBM system induces less harmonic distortion and intermodulation. The DBM can be implemented in many forms.
Quantum noise squeezing at microwave frequencies
Authors: Movshovich R. , Yurke B. , Kaminsky P. G. , Smith A. D. , Silver A. H. , Simon R. W.
Published: February 2023

We report the observation of zero-point noise squeezing by means of a Josephson- junction parametric amplifier, which has been used previously to squeeze 4.2 K thermal noise1. To observe quantum noise squeezing, a number of improvements were made on the apparatus; these include the in stallation of two low-noise cryogenic high- electron-mobility-transistor (HEMT) amplifiers, which boosted the detector sensitivity an order of magnitude to 215 K. The Josephson- junction parametric amplifier was cooled to 30 mK and was operated in the degenerate mode with the signal carrier frequency at 19.16 GHz. At this frequency the vacuum noise floor is hv/2k = 0.46 K. In the deamplified quadrature a drop in the noise of 0.223 K was observed relative to the pump-off noise floor. The pump-off noise floor was established to be within 3.4 + 2.0% of the vacuum noise floor by varying the temperature of the cold termination at the parametric amplifier's input from 30 mK to 1K. A probe signal at the input of the first HEMT amplifier was used to establish that the detector system saturation was less than 7 × 10−4 dB. We have thus observed squeezing 47% ± 8% below the vacuum noise floor.
Higher-order squeezing properties of two-mode squeezed states
Authors: Gong J. J. , Aravind P. K.
Published: February 2023

We have investigated the properties of two-mode squeezed states of various kinds: squeezed coherent states, squeezed number states, squeezed thermal states, and squeezed number-thermal states. The properties studied include characteristic functions, photon number distributions, and high-order moments. We show that a two-mode squeezed coherent state appears in either of its modes as a Glauber-Lachs superposition of a coherent signal with thermal noise; this generalizes the well-known thermofield result that a two-mode squeezed vacuum state behaves like a pure thermal state in either of its modes. We investigate the higher-order squeezing (in the sense of Hong and Mandel) of squeezed coherent-thermal and squeezed number-thermal states. Although the squeezing is found to increase with order in both cases, there are nevertheless interesting differences that can be traced to the fact that the Wigner function has a Gaussian form for the former but not for the latter.
Advances in quantitative imaging diagnostics of reacting flows
Authors: Long Marshall S.
Published: February 2023

Laser imaging techniques have developed considerably over the past few years and are Increasingly becoming productive diagnostic tools for studying turbulent reacting and nonreacting flows. Two-dimensional measurements of scalar quantities, such as temperature, species concentration, and density, have been demonstrated by means of Lorenz—Mie, Rayleigh, fluorescence, and Raman scattering. New developments in detectors, lasers, and computers have reduced the complexity and cost of some of the basic two-dimensional measurements and thus have increased their applicability. In addition, the use of more sophisticated experimental configurations has allowed laser imaging techniques to be extended considerably. One area of advancement is the ability to make measurements rapidly enough to follow the temporal evolution of flow structures. Developments in high-speed quantitative imaging techniques will be presented along with results from turbulent premixed flames.
Positive pulse switching in coupled, nonlinear Fabry-Perot cavities
Authors: Ho Kuongchoi Caisy , Indebetouw Guy
Published: February 2023

Conventional bistable Fabry-Perot cavities are switched off by interrupting a bias. This is dissipative and thus, in principle, is not conducive of high speed. Positive-pulse switching has been demonstrated in systems in which two different mechanisms were responsible for the up and down switching and also in devices using a transient phenomenon.
Crystalline organic semiconductor thin-film optical waveguides
Authors: Zany D. V. , Shi Y. O. , So F. F. , Forrest S. R. , Steier W. H.
Published: February 2023

Recently, crystalline organic semiconductors have been of interest because of their excellent electronic and optical properties. One crystalline organic semiconductor, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), is of particular importance owing to its usefulness in optoelectronic integrated circuits based on PTCDA-inorganic semiconductor heterojunction structures.
New side-chain polymers with large stable electro-optic effects
Authors: Shi Y. Q. , Steiery W. H. , Devine R. , Yu L. P. , Chen M. , Dalton L. R.
Published: February 2023

Polymer materials with large second-order nonlinearities can potentially be used to fabricate low-cost, high-performance electrooptic and nonlinear optical devices for photonic switching. The important physical properties for these applications are large nonlinearity, long-term stability, and simplicity of device fabrication. We have synthesized and characterized a promising new class of polymers with disperse red side chains. The second-order nonlinear optical properties have been characterized by means of second-harmonic generation. With the corona-poling method, large resonance enhanced second-order nonlinear coefficients of 590 pm/V for polyester-disperse red and 280 pm/V for copolyester-disperse red, were observed at 532 nm. Using a simple two-level model, we have conservatively extrapolated these values to 800 nm, where the films are transparent, and have obtained χ(2) values of 112 pm/V and 84 pm/V. The near-infrared electro-optic coefficients(r33) calculated from χ(2) are 26 pm/V and 24 pm/V, respectively. The χ(2) values are stable at 70-80% of their maximum values for at least several hundred hours. These are among the largest stable second-order coefficients reported. We have also studied the linear optical properties of these polymers under ultraviolet and short- wavelength visible light illumination. A significant refractive-index decrease from chromophore bleaching has been observed. The large index change makes it possible to use available photolithographic methods in device fabrication.
Linear model of color transparency
Authors: Mulligan Jeffrey B.
Published: February 2023

When two lights are combined additively, the color that results can be determined from the colors of the two component lights without knowledge of the nature of the actual spectra. This is not the case for a subtractive mixture, which occurs with color transparencies and colored shadows, because the spectrum of the resultant is the product of the two component spectra. Because the actual spectra cannot be known solely from colorimetric data, prediction of the subtractive mixture is an ill-posed problem. Concrete predictions can be made by adopting one of the assumptions of Maloney and Wandell's theory of color constancy (JOSA A, 1986), namely, that all naturally occurring reflectance/transmis- sion spectra can be described as a linear combination of three spectral basis functions. Under this assumption, a subtractive color mixture can be represented by a bilinear operator acting on pairs of tristimulus values. Although the detailed predictions depend to a degree on the choice of the basis functions, certain algebraic properties are obeyed by all models of this type. The model generates predictions of perceptual transparency that are analogous to those made for achromatic displays by the theories of Metelli (Scientific American, 1974) and others.
Optical zone of the cornea
Authors: Koester Charles J. , Roberts Calvin W.
Published: February 2023

Surgical modification of the cornea for the correction of ametropia has received increasing attention, particularly with the introduction of radial keratotomy and, more recently, excimer-laser photorefractive keratectomy. The goal is to produce an optical zone that is centered on the pupil and within which the corneal curvature is modified to a constant, predetermined value. There are medical reasons for making the optical zone relatively small.
Noise mechanisms in optical fiber systems and their effects on communication systems
Authors: Yariv Amnon
Published: February 2023

Of all the lasers in use today, it is only the semiconductor laser where the quantum noise, inevitable in all lasers, is of major practical concern. This is due to two reasons. The first one is that since semiconductor lasers have a very small physical volume, the cavity quality factor is very small, which results, according the the Schalow-Townes formula, in a large spectral width of the laser output. The second reason is that due to the widespread application of semiconductor lasers in real-life optical fiber comunications systems, the noise aspects are of real concern. The basic physical mechanism of this noise is the addition of spontaneous emission power to the laser field. This effect is compounded and amplified by coupling between intensity and phase fluctuations, which are characteristic of semiconductor lasers. In the talk we will review those physical effects and show some possible ways of reducing the laser linewidth. These ways include the use of large external cavity and/or coupling of frequency dependent loss mechanism into the laser oscillators. The effect of spontaneous emission is also a limiting factor in optical fiber amplifier systems, which are assuming major practical importance. In this case the major noise mechanism is beating between the signal propagating in the fiber and the background amplified spontaneous emission power. The basic limitation on signal to noise ratio in a practical system because of this mechanism will be reviewed. Experiments performed in various laboratories will be discussed and compared to the theory. A limiting noise behavior of the optical amplifier fiber system is shown to consist of a transmission system with uniformly distributed gain along the whole length of the fiber. The penalty factors for using other schemes of optical fiber amplification compared to the ideal system will be discussed. The last mechanism to be discussed will be that of double Rayleigh scattering in fibers. This converts phase noise to intensity noise. The resulting limiting RIN will be discussed and compared with new experiments.
Atomic scattering in quantum fields: standing wave versus traveling waves
Authors: Meystrel P. , Shore B. W. , Stenholm S.
Published: February 2023

Atoms undergo two types of momentum changes as they pass across a near-resonant standing wave. First, their transverse momentum spreads. Second, if the atoms cross the field at an angle, they undergo Bragg scattering from the periodic structure provided by the wave. Classically, this behavior can be understood in terms of traveling waves: the atom catalyzes the transfer of momentum from one traveling wave to the other, thereby changing its own transverse momentum. In the quantum regime, however, there is an essential difference between scattering by two running waves and by a standing wave. With running waves, we can in principle know which of the two waves has exchanged a unit of momentum with the atom. In contrast, a standing wave is an inseparable quantum unit whose average momentum remains zero at all times. This unity is imposed by the fixed mirrors that establish the standing wave. These act as infinite sinks of momentum. Quantum mechanics forbids one even in principle to determine, via a field measurement from which traveling wave the atom picked up its momentum. To demonstrate this point, we discuss the diffraction and deflection of an atom in both a standing wave and a superposition of two counter-propagating running waves.
Large beam coupling gain in lnP:Fe using Franz–Keldysh electrorefractive photorefraction
Authors: Millerd James , Koehler Steffen , Garmire Elsa , Partovi Afshin
Published: February 2023

A beam-coupling gain of 19.1 cm−1 in InP:Fe has been achieved using near band edge photorefractive techniques. The conventional electro-optic photorefractive (EOPR) effect in semiconductors may be combined with the Franz–Keldysh electrorefractive photorefractive (ERPR) effect to produce large beam coupling gain coefficients. We have examined the effects using a tuneable Ti:sapphire laser in a pump/probe configuration and an applied electric field. Conventional EOPR creates a sinusoidal space-charge field (Esc) through carrier drift and diffusion, and the applied field (Edc) increases the magnitude of the applied space charge (Etot = Esc + Edc), as well as affecting the phase shift of Δn with respect to the intensity pattern. With appropriate temperature stabilization and ERPR, this phase shift can be maintained near ±90°, depending on the sign of Edc, determining the direction of energy transfer. We have characterized beam coupling gain, Γ, as a function of wavelength, intensity, temperature, grating spacing, and applied electric field and achieved a maximum Γ = 19.1 cm−1 at λ = 970 nm, T = 17 °C, Λ (grating wavelength) = 8.5 μm, IPump = 141 mW/cm2, and β (pump/probe ratio) ≈ 1000. Still higher gains have been seen using a moving grating technique, and the results will be presented at the conference.
Control of mode width and depth profiles in optical channel waveguides by lateral channel tapering
Authors: Thurston R. N. , Kapon Eli , Shahar Arie , Deri R. J.
Published: February 2023

In fiber-optic communication systems, such functions as signal generation, switching, modulation, filtering, and multiplexing will likely be done in a "planar" geometry, consistent with planar photolithographic fabrication methods. The mismatch between the fiber and the typically smaller semiconductor waveguide mode of the planar photonic device can result in substantial insertion loss. Mode matching can be accomplished by tapering the waveguide cross-section. Although modem fabrication methods allow a waveguide cross-section to be tapered in both width and thickness, fabrication is simpler if only the width is tapered. We have shown that, with an appropriate layer structure of the waveguide, control over both transverse dimensions of the mode can be achieved by tapering only the rib width of a rib waveguide. The concept is illustrated with waveguide parameters corresponding to GaAs/AlGaAs waveguides at 1.52 μm wavelength. Calculations of mode shapes based on the Gauss–Seidel finite-difference iteration strategy indicate that such waveguide tapers can reduce coupling losses of single-mode optical fiber-to-semiconductor channel waveguides to the range of 1.0–1.5 dB, as compared with 3 dB or more in coupling directly from the fiber to the tighter guide. Preliminary experiments indicate that the tapers do indeed produce a large change in the near-field spot size.
Analysis of interchannel cross talk and throughput efficiency in highly multiplexed fan-out-fan-in holographic interconnections
Authors: Asthana P. , Nordin G. , Piazzolla S. , Tanguay A. R. , Jenkins B. K.
Published: February 2023

Holographic optical interconnections have often been suggested for meeting the demanding requirements for high-density, independent weighted fan-out/fan-in interconnections imposed by advanced optical computing systems, such as neural networks. In this paper we consider the capabilities of a wide variety of previously proposed holographic interconnection schemes, as well as those of a recently proposed double angularly multiplexed incoherent/coherent architecture1 to perform the desired interconnection functions. Based on numerical simulations that use the optical beam propagation method and on experimental verification of selected aspects, we present results that compare the degree of interchannel crosstalk, the independence and accuracy of weighted outputs, the throughput efficiency, and the practicality of real-time reconfigurability. We show that fan-out/fan-in interconnection systems with single-reference-beam multiplexing suffer from significant crosstalk that is caused by a k-vector degeneracy in the beams fanned in to a given output node. This beam-degeneracy crosstalk, which is distinct from the grating-degeneracy crosstalk discussed previously,2 adversely affects the fidelity of the desired reconstructed weighted beams upon readout, even in the low-exposure (low-diffraction-efficiency) limit. We also verify, as is generally recognized, that fully coherent simultaneous recording introduces large weight distortions in the reconstructed output for both the coherent and incoherent readout cases. In comparison, however, we demonstrate that the double angularly multiplexed incoherent/coherent approach yields low weight distortion, allows simultaneous weight initiation and updates without coherent recording crosstalk effects, and permits incoherent summation at the output nodes with no incoherent fan-in loss.
Integration of motion information over space
Authors: Pavel M. , Shiffrar Maggie
Published: February 2023

Assumptions of local rigidity and smoothness have been used to explain how the visual system reconstructs a representation of physical objects and their motion from spatially sampled images. Using moving stimuli of limited complexity, viewed through several spatially separated apertures, we investigated the effectiveness of various constraints on the reconstruction process. These constraints are essential when the image within each aperture does not permit a unique determination of local optical flow. Our results indicate that, when the image contains sufficient information, translation motion is perceived vertically and can be effectively integrated over large spatial separations. For example, a translating hidden corner viewed through two rectangular apertures is perceived as a single rigid object. In contrast, pure rotation of smooth contours is perceived with strong biases. In addition, observers are generally not able to integrate pure, uniform rotational motion information from different, nonoverlapping apertures. We found that these results are affected by the complexity of the object motion. Objects are more likely to be perceived correctly when the motion is more complex, e.g., has nonuniform velocity or consists of a combination of translation and rotation. We propose a simple statistical framework for describing these results.
Molecular genetics of red-green color vision
Authors: Neitz Maureen
Published: February 2023

Genes encoding cone pigments sensitive to middle-to-long wavelengths lie in a head-to-tail tandem array on the X-chromosome. Although two X-encoded genes, one for long-wavelength-sensitive pigments and one for middle-wavelength-sensitive pigments, are sufficient to serve trichromatic color vision, most people have more than two such genes. The arrangement, location, and degree of homology of the pigment genes promote recombination within the tandem arrays. Such recombination events produce pigment-gene complements that differ in the number and sequences of individual genes and in the interrelationships between genes. The accumulation of recombination-generated changes over the span of evolutionary time has culminated in a large number of X-encoded photopigment gene complements in the human population. It is, thus, not surprising that there are widespread variations in human color vision.
Deuteranomalous trichromacy in a subject revealing only an L-cone pigment gene
Authors: Sanocki E. , Lindsey D. T. , Deeb S. , Motulsky A.
Published: February 2023

A 19-year-old male was shown to have a deutan defect when he was examined with the FM-100 hue test (186 errors). The subject's performance on the Nagel anomaloscope was consistent with that of a person with deuteranomalous trichromacy: His match point was broad and shifted towards the green end of the red/green scale (10-40). However, southern blot analysis of the subject's DNA by means of probes for the X-linked photopigment genes revealed an absence of the restriction fragments characteristic of M-cone pigment genes. By this analysis, the subject should have deuteranopia. The differences between the psychophysical and molecular genetic results cannot be accounted for by rod intrusion into the subject's color matches: The quantal match predicted by rod and L-cone pigments falls outside the subject's anomaloscope match range. These results suggest that there are M-cone photopigment genes that are missed by conventional molecular genetic analysis.
Single Probe optical Turbulence Profile Measurement System
Authors: Walters D.L. , Weitekamp M.R. , Beland R.B. , Good R.E. , Murphy E. , Vaucher C.A.
Published: February 2023

Daylight single probe and differential probe

C
T
2

rawinsonde data are a factor of 10 to 100 larger than nocturnal launch data at heights of 10-15 km. Recent joint optical and balloon measurements reveal no optical counterpart coincident with the thermal probe results. It appears that the factor of 10 enhancement in daylight atmospheric profiles of

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2

is an artifact of solar heating on the measurement system. Experimental results of direct solar heating of the probe and balloon wake effects are presented along with the optical data.
Resolution of the Problem of Minkowski and Abraham
Authors: Nelson D. F.
Published: February 2023

For over eighty years the momentum density of an electromagnetic wave in a material medium has been in dispute. Minkowski proposed that it was DxB while Abraham proposed that it was ϵo E x μoH. In recent years opinion has tended, though not unanimously, toward resolution based on the Abraham result being (true) momentum density and the Minkowski result being pseudomomentum density. We differ with both of these conclusions: we find the (true) momentum density to be ϵo ExB and the pseudomomentum density to be PxB. Our results are obtained from derivations of the momentum and pseudomomentum conservation laws, the latter resulting from homogeneity of the material medium. The derivations follow from a Lagrangian formulation of an arbitrary dielectric crystal, treated non-relativistically, in Interaction with the electromagnetic field. The formulation produces all the modes of motion of the system, acoustic, optic (both Ionic and electronic), and electromagnetic, and allows for arbitrary interactions between them. This permits a physical interpretation of the difference between ϵoExB and ϵoExμoH. By obtaining the conservation laws both from the equations of motion and from the Lagrangian by Noether's theorem we are able also to interpret the difference between PxB and DxB.
Routes to Chaos in External Cavity Semiconductor Lasers
Authors: McInerney John G.
Published: February 2023

Semiconductor injection lasers are frequently operated in external cavities for purposes such as spectral narrowing and mode stabilization. However, the external cavity laser is capable of exhibiting a wide range of dynamical behavior, including self-pulsing instabilities and chaos. Currently there is limited understanding of these phenomena, particularly with respect to the crucial question of whether the behavior is stochastic (noise-driven), deterministic or a combination of both. Here we describe experimentally and theoretically the evolution of coherence collapse at low levels, and the onset of another form of coherence collapse as well as self-pulsations and chaos at high levels of feedback (> 1%). Our experiments have used GaAs/GaAlAs index-guided lasers coupled to long (10-60 cm) linear external cavities, without frequency-selective elements such as gratings or etalons. The theoretical analyses of these experiments are based on the usual rate equations for the carrier density and complex optical electric field, the latter equation having an additional time-delayed feedback term for weak external cavities and several such terms for strongly coupled cavities. Good agreement between experiment and theory has been obtained when considering low-feedback coherence collapse, as well as self-pulsations, quasiperiodicity and period doubling in strong feedback situations with tilt asymmetries. Double external cavity lasers can exhibit extreme stability but are susceptible to the same complex dynamical behavior as asymmetric single external cavity systems.
Focusing of a helium atom beam
Authors: Doak R. Bruce
Published: February 2023

A bent-crystal mirror has been used to focus an atomic-helium beam. The mirror is made from gold deposited onto a mica substrate to form a thin epitaxial film (5000 Å thick) of large single-crystal domains (domain size ~ 4000 Å). The mica sheet is then bent in situ to form a cylindrical mirror of variable radius of curvature. Measurement of scattered beam intensity and angular distribution as a function of curvature demonstrates focusing to within the mosaic spread of the surface. The reflectivity of the room temperature mirror is about 10%. Potential uses are discussed, ranging from immediate applications in intensity and resolution enhancement of helium-scattering experiments to such long-term possibilities as hypercooling of the beam or fabrication of a scanning atom microscope.
How optical computers, architectures, and algorithms impact system design
Authors: Casasent David
Published: February 2023

Optical processors can implement many functions (feature generation, correlation, logic and numeric functions, spectrum analysis, etc.) in well-engineered compact systems. The devices available generally define the optical architecture and algorithm to be used. Hybrid optical/digital and analog/digital techniques are generally workable solutions.
Spot detection in the optical-correlation plane
Authors: Scholl Marija S. , Udomkesmalee Suraphol , Shumate Michael S.
Published: February 2023

Recently, much attention has been devoted to optical correlation as a means to solve a two-dimensional object-recognition problem. Although simulation studies of such an approach demonstrated high signal-to-noise characteristics for correlation images (output signals), actual optical-correlation signals display noise characteristics that accentuate the task of locating correlation spots.
Single quantum-well inversion channel devices for OEICs
Authors: Taylor G. W.
Published: February 2023

Optoelectronic integrated circuits (OEICs) are expected to perform a broad range of high-performance functions in optical interconnects, optical signal processors, and, eventually, optical computers. Performance advantages are also expected for optical switching matrices and high-speed optoelectronic repeaters. The incompatibility of electronic and optical devices usually requires additive growth techniques, which the layer structures are grown in sequence (fabrication is by selective removal), or by multiple growth techniques, in which layer sequences are grown selectively by removal of the previous sequence. We describe a new approach in which a single high precision molecular-beam epitaxial growth provides a single-quantum-well inversion-channel structure from which lasers, detectors, and transistors are formed with a single device processing sequence. In this approach the optical source detector and transistor are, in fact, the same device structure which is used differently, depending on its application. The transistor is the heterostructure field-effect transistor (HFET) and the detector is the heterostructure field-effect detector (HFED). The laser is a bistable switching device with large optical and electrical gain or is the three-terminal HFET laser. The operation and latest results on all of these devices will be presented.
Triplet-state gratings and degenerate four-wave mixing in disodium fluorescein-doped boric acid glass
Authors: Abdeldayem H. , Mago V. K. , Sekhar P. Chandra , Venkateswarlu P. , George M. C.
Published: February 2023

Degenerate four-wave mixing (DFWM) in disodium-fluorescein-doped glass revealed a large third-order susceptibility and a slow decay of the gratings that were responsible for optical phase conjugation. To understand the mechanisms for this, the following experiments were performed. The phase-conjugate signal in a DFWM setup was recorded for several concentrations of the dye in the glass. An Ar+ laser beam (488 and 457.9 nm) was used. Transient gratings were formed by turning the writing beams for the Ar+ laser on and off, and the decay was read by a He-Ne laser beam. Analysis showed that there are two exponential decays, 0.1 and 0.3 s, independent of the concentration. The possible presence of a thermal grating was eliminated by recording the decay times at 13° and 114°; we found no angular dependence. The decay time and the spectrum of the phosphorescence resulting from excitation by the Ar+ lines were recorded for the same samples. The analysis again showed two decay times, and the spectrum recorded with a double mono-chromator showed a structure having two peaks. It is therefore concluded that tripletstate gratings are responsible for the phase conjugation. However, the grating decay times were less than the phosphorescence decay times. Further investigations to understand this discrepancy are in progress.
Modeling the Stokes parameters of surfaces
Authors: Egan W. G. , Maciulaitis A.
Published: February 2023

Many data on the bidirectional reflectance properties of surfaces have been obtained by Environmental Research Institute of Michigan. The data include polarization properties represented by the bidirectional Stokes parameters. The optical properties of paints and coatings are characterized by a set of empirically derived parameters in the Maxell-ERIM surface model based on the zero-bistatic-polarization curves of these surfaces. We are in the initial stages of correlating the polarimetric optical reflectance/scattering properties of surfaces with theiractual physical properties, such as surface roughness, microstructure, and optical index of refraction. We are including the associated effects of shadowing, incident and viewing geometry, and source spatial and temporal coherence.
Perception and memory of objects and parts
Authors: Ankrum Corlene , Palmer John
Published: February 2023

What is the role of objects in shape perception? To investigate this question we studied judgments of connected two-dimensional line figures. Observers viewed two figures sequentially and made the same or different judgments. The comparisons were either between two whole objects or between a whole object and a part. These comparisons are referred to as whole and partial comparisons. A whole-comparison advantage was found; subjects were faster and more accurate on whole comparisons than on partial comparisons. This advantage occurred with several procedures and sets of stimuli. The whole advantage did not occur when the whole object was not completely connected. These findings provide evidence for the perceptual significance of objects. More specifically, they are compatible with the existence of a hierarchical representation of an object and its parts.
Computer-generated multiple-phase-level holograms using color printer techniques
Authors: Shrauger Vernon E. , Erwin Laura L. , Warde Cardinal
Published: February 2023

Current techniques for constructing multiple-phase-level structures (e.g., phase holograms) use computer-generated masks to selectively etch a glass substrate, creating discrete phase levels based on varying glass thickness (i.e., kineform). This approach requires several procedural steps and expensive photolithographic equipment. We have developed a one-step technique using color-printer technology and photographic eqipment. Colors from the printer are mapped to discrete intensity levels on photographic emulsion, and bleaching the recorded film results in discrete phase levels. We have investigated the relationship between the optical density of colors generated by our printer and the corresponding phase changes after bleaching.
Applications of optimization procedures in physical optics design
Authors: Moore Kenneth E. , Lawrence George N.
Published: February 2023

Numerical description, design, and analysis of optical systems is commonplace. As computer capabilities increase, more sophisticated analysis and design of opticval designs is possible, especially in the areas of physical optics modeling. Optimization applied to geometric analysis of lens designs is common, but relatively little work has been done in applying optimization techniques to physical optics systems. There are many potenetial applications for optimization techniques in physical optics modeling, and many of these applications would be unduly laborious to solve using other methods. For example, finding the optimum size and placement of a small aperture placed in an aberrated beam, with the constraints that transmitted energy and wavefront quality are simultaneously maximized can readily be approached through an optimization process. More complex problems such as improving outcoupled beam shape in laser cavities through the use of tilted or adaptive mirrors can be approached through contsrained optimization. The basic technique and some practical examples relevant to optical system design will be presented and discussed.
Beam propagation and the ABCD ray matrices
Authors: Belanger P. A.
Published: February 2023

We have generalized the propagation law of optical rays through an ABCD optical system by introducing a generalized radius of curvature Q such that„. The real part of the generalized radius of curvature is related to the phase of the beam, and the imaginary part to second moment of the amplitude. The beam quality factor,, recently introduced in the literature appears naturally in the definition of Q.
Numerical methods for optical modeling of laser beams and resonators
Authors: Siegman A. E.
Published: February 2023

Numerical beam-propagation methods combining geometrical and physical optics—originally developed for laser resonator calculations—may have broader applications in contemporary optical system design.
Effect of data-compression techniques on a meteorological satellite image test suite Douglas
Authors: Johnson W. , Gustafson Gary B. , Sparrow Jeanne M. , Isaacs Ronald G. , Hogan David B. , Binge Gail M. , Miettinen Kristo
Published: February 2023

We report the results of a comparative study of the effect of several lossy compression techniques on satellite-based meteorological imagery. Three algorithms, implemented by participants in this effort, were tested on a variety of satellite data products, at several compression, ratios ranging to as much as a factor of 20. The compression techniques included a scene-adaptive discrete-co-sine-transform technique, an adaptive differential pulse-code-modulation technique, and a vector quantization algorithm. A variety of quantitative measures were applied in the evaluation of these lossy image-compression algorithms. Included were the mean-square error, mean absolute error, and error histograms. We also evaluated the effect on interpretation by a meteorologist trained in the use of satellite imagery for synoptic forecasting. Finally, we applied an automated cloud-fraction-analysis routine to the data in an effort to determine its effect on performance. Additional efforts similar to these should provide useful measures of the operation of proposed image-compression techniques. In particular, additional assessment of automated-image-characterization algorithms and the inclusion of input data with more variation are expected to result in a more thorough understanding of the effects of these compression techniques.
Optoelectronic learning machine
Authors: Wunsch Donald , Caudell Tom , Falk Aaron , Capps David
Published: February 2023

Adaptive resonance is a theory of unsupervised learning in neural networks.1We propose an invention that allows parallel execution of the most computationally intensive parts of the architecture by using optical hardware. The rest of the design is carried out in electronics. The basic configuration of the electro-optical ART unit is a two-lens optical correlator. A spatial light modulatoris configured as a binary phase-only filter and contains the two-dimensional Fourier transform of the input pattern. The plane of this device is between the two lenses. The template plane is to the left of the first lens. It contains multiple templates simultaneously. The lenses are chosen such that the paraxial approximation applies, and the template Fourier transforms will overlap. On the output plane, we have a charge-coupled device (CCD) camera. This plane will have correlation peaks corresponding to templates that closely match the input image. All electronic calculations and control of the spatial light modulators are done by a microVAX. This is also used to process the CCD camera output via a frame grabber.
Rastered, uniformly separated wavelengths emitted from a two-dimensional vertical-cavity surface-emitting laser array
Authors: Chang-Hasnain C. J. , Wullert J. R. , Harbison J. P. , Florez L. T. , Stoffel N. G. , Maeda M. W.
Published: February 2023

We report the first 2-D monolithic multiple-wavelength laser array using a novel and simple technique. The lasers are surface-emitting with as-grown vertical cavities. The laser structure includes In0.2Ga0.8As strained quantum wells as the active layer and 15 and 22 pairs of p-and n-doped quarter-wave GaAs/AlAs layers as the top and bottom reflectors, respectively, grown by molecular-beam epitaxy (MBE).
Generation and characterization of picosecond optical pulses from resonant periodic gain GaAs surface-emitting lasers
Authors: Mahbobzadeh M. A. , Chu An-Shyang , Mukherjee A. , Schaus C. F. , Brueck S. R. J.
Published: February 2023

Picosecond optical pulses generated from a resonant periodic gain GaAs surface-emitting laser optically pumped by a picosecond dye laser are characterized. Pulse-width measurements from cross-correlation data, pulse spectra, and relative delay between the pump and generated pulses with a theoretical analysis are reported.
Noise reduction in experimental graded-index profile data by using simulated annealing
Authors: Hollos Stefan , Cox Hollace L. , Ashley Paul E.
Published: February 2023

Simulated annealing has been incorporated to extract the exact silver-ion concentration profile in both planar and channel silver waveguides. Planar silver waveguides were produced by using electric-field-assisted silver indiffusion techniques, and silver channel waveguides were produced by ion implantation. A scanning electron microbeam using wavelength dispersive x-ray-fluorescence analysis was used to measure the silver concentration profiles for both planar and channel waveguides.
Achromatic waveguide input-output couplers
Authors: Spaulding Kevin E. , Morris G. Michael
Published: February 2023

Waveguide input-output couplers are key components in many integrated optical devices. Prism and grating couplers are two of the most commonly used types of waveguide couplers, but the characteristics of these components are highly wavelength-dependent. Both the coupling angle of an out-coupled beam and the coupling efficiency of an incoupled beam are strong functions of wavelength. For many applications these chromatic characteristics place tight constraints on the stability and bandwidth of the laser source that is used. In this paper a method to achromatize waveguide input-output couplers is described. The basic approach involves the use of an external diffraction grating to correct for the angular dispersion of the conventional coupler types. Two specific configurations are considered: a hybrid prism/grating coupler and a double-grating coupler. Expressions are derived for values of the grating parameters that produce achromatic coupling. It is shown that, for typical waveguide materials and performance specifications, double-grating couplers can be used to obtain an achromatic wavelength range of approximately 10 nm, and hybrid prism/grating couplers can potentially yield an achromatic range of the order of 200 nm.
Sputtered Nd: glass thin-film waveguide laser
Authors: Robertson Gordon R. J. , Jessop Paul E.
Published: February 2023

Thin-film optical waveguides were deposited on oxidized silicon substrates by rf sputtering from an Nd-doped phosphate-glass target. Planar waveguides were typically 2 μm thick and had attenuation coefficients of ~2 dB/cm, measured at a wavelength of 633 μm. When 10 μm wide rib waveguides were patterned by chemical etching, the losses were 3.5 dB/cm. Fluorescence lifetimes in the films were 100-150 μs, as compared to 337 μs for the bulk glass target material. Photoluminescence spectra also showed significant differences between the glass films and the target glass. The films had Nd concentrations approximately 30% below the target Nd concentration.
Recent results on cw tunable fluorozirconate single-mode fiber lasers
Authors: Monerie M. , Allain J. Y. , Poignant H.
Published: February 2023

The unique features of fiber lasers have stimulated interest in this new class of lasers. Rare-earth-doped fluorozirconate fibers are often superior to their silica-based counterparts owing to their multiphonon spectrum. This permits radiative transitions from levels that suffer nonradiative de-excitation in silica glasses. The potential number of lasingwave-lengths in fluoride glasses is thus large. This topic is still being studied, and many fundamental phenomena remain to be clarified. Major advances in the field have been recently published: new lasing wavelengths in erbium, holmium, thulium, neodymium, samarium, and praseodymium; Q-switched operation; diode-laser pumping; and cw-tunable operation. The upconversion laser is one of the most promising devices, and it has already been demonstrated with thulium at 480 nm and with holmium at 550 nm, for which a slope efficiency of 36% and an extracted power of more than 10 mW have been obtained at room temperature.
Limits of optical lithography
Authors: Markle David A.
Published: February 2023

The performance requirements of optical lithography equipment are driven by DRAM memory chips which require a 30% reduction in line width and a three-fold increase in resolution elements every generation. Until now semiconductor chips were small enough that arrays of them could be placed in the field of a lithography lens. This placed the emphasis on higher resolution for each new lens generation. The development of the 16-Mb DRAM has changed our priorities. The next generation of memory chips and all those to follow will require substantial increases in field sizes as well as resolution and therefore a more aggressive development pace. Within only a few short generations, conventional resolution lenses will approach 500 lb in weight and $1M in cost.
Confocal imaging of the ocular lens
Authors: Masters Barry Richard
Published: February 2023

The ocular lens is an important refractive element in the optical system of the eye; however, its three-dimensional structure has not been visualized in the in situ living eye. Laser scanning confocal light microscopy was used to image living rabbit eyes with submicrometer resolution. Optical serial sections of the in situ ocular lens were obtained in 1μm steps. The light source was a 25 mW argonion laser, and the microscope objective was a Leitz 25 ×, N.A. 0.6, water objective. The two-dimensional data sets imaged the lens capsule, the lens epithelium, and the internal structure of the lens fibrils. The two-dimensional data sets were digitally processed in several modes. The first mode created stereo pairs by tilting the angle of view of the left and right images and by using red and green glasses to fuse the images. The second mode used ray-tracing techniques to generate a three-dimensional visualization of the eye. The three-dimensional visualizations of the eye were processed as film loops with changing images showing different angles of tilt and rotation.
Ultrafast carrier-induced changes of absorption and refractive index in GaAs
Authors: Gong T. , Nighan W. L. , Gzara K. , Fauchet P. M.
Published: February 2023

We report room-temperature time-resolved pump-probe transmission (T) and reflectivity (R) measurements of a GaAs thin film with 80 fs time resolution by means of our copper-vapor laser-amplified colliding-pulse mode-locking dye laser. Ultrafast carrier-induced changes of the absorption coefficient and refractive index are then calculated from measured T and R values. Photon energies at the band edge (1.38-1.46 eV) and near the initial excited states (1.90-2.18 eV) are used, and photoexcited carrier densities are varied from 1017 to 1019 cm-3. Our results reveal the dynamics of band-gap renormalization and the importance of carrier-carrier and intervalley scattering. Mechanisms that cause an ultrafast change in refractive index are presented. The carrierdensity dependence of these hot-carrier processes are also discussed.