bluuebunny/crossref_metadata_2025 huggingface dataset:
Balancing of aberrations by using computer-generated holograms
Authors: Tang Yaw-Tzong , Chang Ming-Wen
Published: February 2023

The primary purpose of this paper is to discuss the use of the computer-generated hologram (CGH) to improve the image formation of an optical element or system. Seidel aberrations may be detected either during the image-evaluation stage of an optical design or during optical testing. The CGH is designed and constructed according to the kinds and quantities of aberrations that exist in the element or system and the position of the CGH within the system. If the reconstructed complex-conjugate term is put into the system appropriately, the aberrations should be balanced. In our presentation we will provide a theoretical analysis and give the results of our experiments dealing with optical design and testing as well as and CGH construction. Our conclusion is that image formation is greatly improved through the use of our method.
Near-field diffraction analysis for binary optical elements
Authors: Piliavin Michael A. , Herman B. J. , Gal G.
Published: February 2023

The analysis of the performance of a binary optical element requires a physical optics calculation because of the diffractive nature of such elements. We have developed a number of software tools for this analysis, which are based on the Kirchhoff-Fresnel diffraction integral. These tools allow investigation of results of diffraction both in and out of the focal plane. The programs take a given (nonbinary) element, convert it to a binary element with prescribed etching resolutions and etching depths, and perform the diffractive calculation. The diffraction is calculated by a number of means (direct numerical integration, Fresnel approximation, evaluation of analytic formulas). The software also computes quantitative measures of performance, such as blur spot sizes, diffraction efficiencies, and wavelength separation (for dispersive elements). We discuss the abilities and limitations of the codes and present sample calculations.
Nonperiodic binary phase grating design for spot array generation
Authors: Southwell William H.
Published: February 2023

It has been discovered that a phase grating producing multiple spot patterns can also have the focusing property of a lens designed into it. Such gratings are nonperiodic. Consequently, the entire structure must be designed as a unit (except for possible reflection symmetry), as opposed to Dammann gratings wherein only the structure within each periodic unit needs to be designed as a unit. Non-periodic gratings are readily designed by flip-flop optimization of a single-quantity merit function. A suitable merit function specifies the position and relative intensity of each spot. The aperture plane is subdivided into a large number of incremental cells, each having either zero or radians phase shift. The merit function is evaluated from an initial random state. Each cell is then "flipped" to its opposite state and remains there if the merit function is improved. Unlike Dammann or other periodic gratings, these flip-flop designs can generally achieve spots of arbitrary intensity and position. Furthermore, the flip-flop approach can be used in conjunction with a lens to produce a uniform spot array (providing an alternative method for designing Dammann gratings) as well as spots with arbitrary intensities and almost arbitrary positions. The lens seems to force a reflection symmetry on the generated spot array.
Optical memory disk spatial light modulators
Authors: Rilum John H. , Tanguay Armand R.
Published: February 2023

Spatial light modulators are essential (and often the limiting) elements in optical information processing and computing system architectures. Recent advances have demonstrated that optical memory disk technology, in combination with image-based recording and an appropriate parallel readout scheme of the high-resolution optical disk medium, presents a very competitive alternative for spatial light modulation.1, 2 Not only can this technology perform a wide variety of traditional spatial light modulator (SLM) functions, but it also makes implementation of multilayered neural networks and ultrahigh-data-rate scrolling input transducers possible by using the rotational motion characteristic of the optical-disk driver. A parallel optical-readout scheme that has an inherently high signal-to-noise-ratio, has high transfer function linearity, and can be used with a variety of recording layer principles can be achieved by employing a differential (or shearing) interferometric approach.1 In this readout scheme, two spatially coherent orthogonally polarized images of the optical disk are created and are interfered differentially by introducing a shift of one-half of the minimum bit pitch along the direction of the tracks. In the output image, only local differences in phase (height) and/or reflectivity of the recording layer will be detected.
Optical disk implementations of neural networks
Authors: Psaltis D.
Published: February 2023

Summary not available at press time.
1990 update on high-power diode-array-pumped lasers
Authors: Dube George
Published: February 2023

The goal of this presentation is to report the progress and current status of our continuing development efforts on high-power laser diode-array-pumped dielectric solid-state lasers. Efficient diode-array-pumped Nd lasers, both Q-switched and long pulse, have recently exceeded 30 Watts average power.
High-power AlGaAs/GaAs single quantum-well 45°-beam-deflecting surface-emitting lasers
Authors: Kim J.-H. , Lang R. J. , Lee L. R. , Narayanan A. A.
Published: February 2023

We report on high-power AlGaAs/GaAs single quantum-well surface-emitting lasers (SELs) with etched vertical mirrors and integrated 45°-beam deflectors fabricated by a 30°-tilt ion-beam etching technique. Our results show the highest power and external differential quantum efficiency reported to date for the 45°-beam-deflecting SELs.
Applications of surface-emitting lasers to coherent communication systems
Authors: Carlson N. W. , Evans G. A. , Bour D. P. , Liew S. K.
Published: February 2023

Monolithic, surface-emitting laser array technology is an attractive approach for producing the high-power coherent sources required for free-space coherent optical communications. Recent developments will be reviewed, and conceptual array designs for communication systems will be described.
Soft-x-ray astronomy: results and future missions
Authors: Golub Leon
Published: February 2023

Softx-ray astronomy began with detection of x-rays from the sun in the late 1940s and continues to have strong ties to study of the solar emission. Because it is intrinsically interesting and is the strongest x-ray source, studies of the sun remain the testing ground for new techniques and the development of new instrumentation, such as multilayer coatings for near-normal incidence imaging and high resolution electronic array detectors. The continued development of grazing incidence techniques and associated instrumental recording devices, combined with improvements in sensitivity and resolution, have allowed x-ray astronomy to detect and study a large variety of "normal" astronomical features in addition to the rare and unusual objects which were first detected. Current missions in the soft x-ray and XUV are carrying out extensive mainstream studies in all areas of astronomy, and future missions call for studies directed at the most fundamental cosmological questions.
Many-body analyses of spontaneous and stimulated emission in highly-excited GaAs
Authors: Bardyszewski Witold , Yevick David
Published: February 2023

We discuss our previous work on the computation of gain spectra and nonradiative Auger transition rates in highly excited III-V bulk semiconductors. This work was motivated by the well-documented deviation of experimental measurements of emission spectra from standard one-particle model predictions. In particular, theoretical errors arise from the large effects of the spatial correlation of the recombining particles on the line shape and on the associated deviations from the k-selection rule. We accordingly developed a nonequilibrium Green's function theory for radiative recombination in highly excited semiconductors that properly incorporates the k.p conduction and valence band structure, many-body effects associated with the electronhole interaction, and the scattering of carriers by collective excitations of the lattice. We find good agreement with the experimentally observed gain spectra as well as with the semiconductor laser linewidth broadening factor. Finally, we summarize our work on nonradiative Auger processes and contrast our results to experimental data.
Homodyne statistics
Authors: Braunstein Samuel L.
Published: February 2023

The balanced homodyne detector is the paradigm of phase-sensitive detection schemes in quantum optics. We study the effects of a quantum local oscillator in a coherent state for this detector when it is coupled to a single signal mode. We calculate explicit general expressions for the output statistics of the difference current of this detector (applicable even to non-classical states), and compare them to the statistics of the so-called quadrature-phase amplitude. We show that the naive condition that the number of quanta in the local oscillator be much larger than the number in the signal is not sufficient to ensure that the homodyne detector approximates an ideal detectorof the quadrature-phase amplitude, further, we derive explicit conditions for this approximation to be achieved when the signal is a coherent state or a superposition of coherent states.
Multibeam gain competition deduced from intensity statistics of amplified spontaneous emission
Authors: Alman Gregory M. , Abraham Neal B.
Published: February 2023

The univariate and bivariate intensity statistics of amplified spontaneous emission (ASE) from continuously excited HeNe and HeXe gas discharges have been measured for the purpose of characterizing the dependence of ASE fluctuations on gain length and degree of homogeneous broadening. Comparison with theoretical results from a model for intensity fluctuations in heavily saturated multimode systems confirms that increasing the homogeneous broadening lowers the number of competing "modes" in the system. Intrinsic to this simple coupled-intensity model are unique combinations of cumulants that are independent of the number of modes and the strength of their coupling. These combinations have been measured, and they are independent of the degree of homogeneous broadening and are constant as the discharge length is increased. The normalized cumulants and cross-correlations for coprapogating and counterpropagating orthogonal, circularly polarized beams in a HeXe homogeneously broadened medium are consistently smaller in magnitude than those for orthogonal, linearly polarized beams. Comparison of results for neon and xenon discharges will distinguish whether this is the result of back-reflections or is a property of the counterpropagating beams quasiresonant with these noble-gas transitions, which differ in their upper- and lowerstate angular momenta.
Intensity dependence of fluorescence lifetimes and quantum yields from doxycycline using picosecond excitation
Authors: Pradhan Asima , Hasan T. , Gillies R. , Alfano R. R.
Published: February 2023

The excitation-intensity dependence of the fluorescence lifetimes of doxycycline in a buffered saline solution investigated with 353 nm picosecond excitation. The excitation intensity ranges was 107109 W/cm2. The fluorescence lifetimes did not change over this range. The fluorescence profile was fitted to a double exponential with about a 100 ps fast component and a 400 psslow component. The relative-fluorescence quantum-yield measurements in the excitation intensity range of 51014 photons/cm2 to 61016 photons/cm2 displayed a linear dependence on the incident intensity up to 51015 photons/cm2, and after this intensity the quantum yield decreased monotonically. These preliminary results agree with the model of excited-state absorption at high excitation intensities. This process will affect the doxycycline photosensitization of cancer cells using picosecond pulsed excitation.
Undetected luminance steps displace edges
Authors: Naiman Avi , Makous Walter
Published: February 2023

Although an edge is defined by an abrupt change of luminance, the luminance profile of its retinal image affects its perceived location. We measured the trade-off between luminance and perceived location of an edge by interposing a thin, uniform strip of variable luminance between the black (0.7 nit) and white (70 nits) sides of a sharp edge and having observers make vernier adjustments of an uncomplicated sharp edge, so that the two edges appeared to be aligned. We found that the perceived location of the contour depended on the luminance of the strip, even when the strip was not detectable. The relation between perceived location and luminance was linear for strips 1 ft. (30.4 cm) wide or less but nonlinear for wider strips. Transfer of information was maximum at 1.4 ft. (42.7 cm), the widest strip that could not be detected at any luminance. A model involving three stages of spatial filtering and an interposed nonlinearity described the data from strips that could not be seen, with no free parameters. With the optimum strip width, 1.4 ft. (42.7 cm), the model had errors of prediction and residual variance that were half of those produced by models based on the assumption of linearity.
Pump-coupled micromasers
Authors: Bergou Janos , Hillery Mark
Published: February 2023

The traditional way to induce coherence between two lasers is to inject part of the output of one into the other. Here we wish to discuss a different coupling method which we shall consider in the context of two micromasers. In this case the coupling of the two masers will be through the pump and not through their fields.
Phase jump and intensity instabilities in a homogeneously broadened ring laser with backscattering
Authors: Cheng F. C.
Published: February 2023

The equations of motion of a single-frequency homogeneously broadened bidirectional ring laser with optical backscattering have been investigated numerically by using Monte Carlo simulation. Studies of the coupled, third-order equations of motion, with additive and multiplicative noise terms, show that under some conditions of backscattering the laser has two regions of operation. When the magnitude of the backscattering coefficient, R, is less than a critical value, Rc, which depends on the pump parameter, the laser exhibits the usual noise-induced spontaneous intensity switching. When R is larger than Rc, the two modes exhibit steady-state anticorrelated oscillations. The simulations demonstrate that the relative phase of the two propagating waves can experience sudden phase jumps of in both switching and oscillation regions. Noise-induced transitions from one region to another can be observed when R is close to Rc.
Resolution of large ground-based telescopes at infrared wavelengths
Authors: McKechnie T. Stewart
Published: February 2023

A recent prediction that existing large ground-based telescopes can achieve 0.050.1 arc sec resolution at infrared wavelengths by means of direct-imaging techniques has been experimentally confirmed. The 0.1 arc sec resolution actually obtained (during 1.5 arc-second seeing in the visible spectrum) is at odds with conventional theory, which predicts only marginal resolution improvement at infrared wavelengths. Conventional theory is based on the assumption that the outer scale limit Lo is much larger than any existing telescope and may possibly be many kilometers. However, much of the large-scale turbulence attributed to the atmosphere is simply the result of telescope oscillations and tracking errors. The new predictions are based on a much smaller Lo value of about 20 cm.
Backscatter enhancement of reflected laser beams propagating through random media
Authors: Frehlich R. G.
Published: February 2023

The propagation of reflected waves in random media produces an enhancement of irradiance at the transmitter plane that is centered on the propagation axis. The behavior of this enhancement is described by the mutual coherence or second moment of the backscattered field. Because the transmitted and reflected waves pass through the same random media, the second moment becomes a fourth moment when expressed as a one-way propagation problem. The leading-order behavior of the backscatter enhancement of a Gaussian laser beam that is reflected from various ideal targets (mirror, diffuse surface, aerosol target, retro-reflector) is determined by using path-integral methods to generate a series solutions for the general fourth moment. The scale of the irradiance enhancement and the scale of the field coherence are related to the physical scales of the one-way propagation problem in the various parameter regimes of the phenomena. The many characteristics of backscatter enhancement may provide new methods for remote sensing of winds, the parameters of the turbulence spectrum, and the boundary-layer energy budget (e.g., heat and momentum fluxes). A surprising consequence of the backscatter enhancement is that turbulence increases system performance for certain laser-radar applications.
A photorefractive model of second-harmonic generation in glass fibers
Authors: Leskova T. , Agranovich V. M. , Stegeman G. I.
Published: February 2023

A photorefractive model of the efficient second-harmonic generation of light in single-mode glass optical fibers is presented. In this model the photoinduced charge redistribution gives rise to an internal dc electric field, which acts on the χ(3) of the glass, resulting in an effective χ(2) Phase matching is due to the interference of the radiation-driven field and the second-harmonic field.
Throughput enhancement of an electronic multiprocessor by the coupling of an optical coprocessor
Authors: Pinkston T. M. , Efron U. , Nash J. G.
Published: February 2023

This summary presents results of a study aimed at assessing the relative enhancement of an electronic multiprocessor system by the addition of an optical co-processor. An analytical performance comparison of optical and electronic processing paradigms is being conducted using image processing/vision operations as benchmark tasks. These tasks range from low-level operations such as matrix-matrix multiples to high-level operations such as position and scale invariant pattern recognition. Three specific multiprocessors developed by Hughes were used in the comparisons: the Image Understanding Architecture (IUA), the 3-D Computer, and the Systolic/Cellular System multiprocessor.
Solid-state lasers pumped by advanced diode laser sources
Authors: Fan T. Y.
Published: February 2023

Diode laser sources are inherently continuous-wave devices because their output is peak-power limited. Thus, for average power performance, more effective use of the pump diode lasers is obtained in high-repetition- rate, as opposed to low-repetition-rate, operation; the latter requires more diode to achieve a given average power. I report on a Nd:YAG laser pumped by high repetitionrate, two-dimensional arrays and on the use of a strained layer in InGaAs quantum-well diode lasers as pump sources for solid-state lasers. Two-dimensional rack-and-stack arrays have been limited to relatively low repetition rates and low duty cycles because of difficulties in heat removal; planar geometries cooled by microchannel heat sinks allow higher duty cycles. Average output power of 11 W from a Nd:YAG slab laser has been demonstrated with no evidence of adverse thermal effects in the pump lasers. The development of strain-layer InGaAs diode lasers opens new possibilities for diode-pumped lasers; the main application of these diode lasers has been for pumping Er3+ fiber amplifiers. The use of these diode lasers to pump bulk lasers such as Nd3+, Yb3+, and Er3+ will be discussed.
A compact optical dilation multistage interconnection network
Authors: Huang Kung-Shiuh , Peir Jih-Kwon
Published: February 2023

Conventional multistage interconnection networks (MINs), such as omega networks, have space-variant interconnections. In this paper, we describe the designs of optical three-dimensional MINs based on different dilation structures of interconnection. The dilation interconnection preserves the spatial-invariant property. Such space-invariant interconnections are easy to implement in optics because they can he realized by simple space-invariant optical systems. Two basic parameters, degree and distance, can be used to precisely define a dilation structure. Degree represents the number of destinations to be connected, while distances indicate which neighboring nodes, in terms of physical distances, are to be linked. Optical three-dimensional MINs use three-dimensional free-space interconnections between nodes in a two-dimensional array. It is convenient to organize the two-dimensional array of nodes into rectangular (or square) mesh such that it can easily match a conventional rectangular coordinate system. A rectangular-dilation MIN for N nodes requires degree-9 dilation interconnections to maintain the log N routing stages, ranging from 0 to (log N - 1). The dilation distance in the kth stage is k. The destination-address bits are used for the routing in the corresponding stage as in the two-dimensional environment.
Optimal paritioning of very large-scale optoelectronic computing systems
Authors: Ozaktas Haldun M. , Goodman Joseph W.
Published: February 2023

Based on wiring-space and heat removal consideration, we predict how many optically interconnected chips a set of N gates must be partitioned into for minimum system delay.
Acousto-optical spectrometers
Authors: Pustovoit V. I.
Published: February 2023

We describe an acousto-optical spectrometer consisting of a Bragg cell made of singlecrystal quartz. Spectral range of 420-780 nm and resolution of 0.2 nm is achieved. Applications in the monitoring of plasma-assisted material treatment are described.
Parametric study of refractory metal films by laser-induced deposition
Authors: Xu J. , Lu X. M. , Lou Q. H.
Published: February 2023

Thin films of W and Mn on quartz and Pyrex substrates were deposited by photodissociation of respective carbonyls W(CO)6 and Mn2(CO)10 with a XeCl laser at 308 nm. The UV laser beam at 10 Hz was focused into a Pyrex cell containing carbonyl gas and was perpendicularly incident on a quartz or Pyrex substrate.
Hyperfine spectroscopy of krypton-81
Authors: Cannon B. D.
Published: February 2023

The hyperfine constants of krypton-81 and its isotope shifts relative to the stable krypton isotopes were measured for several transitions from the 5s [3/2] J = 2 metastable state. These measurements used continuous-wave single-frequency lasers for Doppler-free two-photon and saturated absorption spectroscopy. These measurements and the implications of the measured splittings for proposed ultratrace detection of krypton-81 for dating ancient ground water and glaciers will be discussed.
Rotationally resolved electronic spectra of 1- and 2-methylnaphthalene
Authors: Tan X.-Q. , Pratt D. W.
Published: February 2023

High-resolution fluorescence-excitation spectra of the S1S0 transitions of 1- and 2-methylnaphthalene have been obtained in the collision-free environment of a molecular beam. Each spectrum is composed of two sets of spectral lines that can be fit to different rotational Hamiltonians. The two sets of lines belong to the ground torsional levels A and E, respectively. The A lines can be fit to a rigid-rotor rotational Hamiltonian; the E lines, however, are perturbed by a coupling between the torsional motion of the methyl group and the overall rotation of the molecule. The first-order and second-order perturbation coefficients can be obtained from the fit of both A and E lines, thus allowing us to determine the torsional barriers of both electronic states. The values obtained, which depend significantly on the position of methyl substitution as well as on both the vibrational and electronic state of the molecule, will be interpreted within the framework of molecular orbital theory.
Hyperfine structure of the 648 nm mixed forbidden transition in Bi2O9
Authors: Wood David R. , Hou Lifang
Published: February 2023

A number of transitions between levels of the ground (6p3) configuration of Bi2O9 are a mixture of electric-quadrupole and magnetic-dipole radiation. The degree of mixture is described by the ratio of the radial parts of the transition probability integrals E and M. The 648 nm transition includes 12 mixed magnetic-dipoleelectric-quadrupole components plus a number of weaker electric quadrupole (F = 2) components. These components comprise six groups of two or three closely spaced components each. This suggested the use of high-resolution grating spectrometer which is able to separate the groups, as a cross-disperser for a Fabry–Perot interferometer. Interferograms were recorded photographically on 103a-F spectroscopic plates with exposures of up to 12 h. A microdensitometer was then used to determine densities, which were converted to intensities by means of our plate calibration curves. We observed all 14 components already described in the literature plus two new F = −2 components. The ratio of electric quadrupole to total line strength was determined from the four electric quadrupole component intensities compared to total intensities and inversely weighted by the known angular portions of the transition probability integrals. Our results show an electric quadrupole contribution of 30 5% to this mixed transition, compared to previously reported values of about 20%.
External-cavity semiconductor laser using a grazing-incidence diffraction grating
Authors: Harvey K. C.
Published: February 2023

An external-cavity semiconductor laser has been developed that uses a diffraction grating at grazing incidence for wavelength selection and output coupling. The laser cavity consists of an objective-lens beam expander, grazing-incidence diffraction grating, and end mirror. The output is coupled out through the zero-order reflection from the diffraction grating. One end of the cavity is the rear facet of the diode laser, and the other is the mirror that reflects the first-order reflection of the diffraction grating. This arrangement is similar to the Littman configuration for pulsed dye lasers.
Reaction dynamics of the OH–Ar complex
Authors: Lester Marsha I.
Published: February 2023

Recent experiments performed in this laboratory have provided a detailed picture of the intermolecular potential between the open-shell hydroxyl radical and an argon atom. The interaction potentials between Ar (1S0) and OH in the ground

X

 
2

II

3
2

and excited A 2Σ+ electronic states have been probed through spectroscopic measurements and half-collision studies of the weakly bound OH-Arvan der Waals (vdW) complex. Vibrational excitation of the OH subunit induces dissociation of the complex, providing a means to examine the dynamics taking place on these potential energy surfaces. Our results show striking differences, in both the potentials and dynamics, between the ground and excited electronic states. The rate of dissociation is at least five orders of magnitude slower in the ground electronic state than in the excited state. The dissociation dynamics for OH-Ar complexes correlating with changes with initial vdW state selection. The product rotational distribution reflects the bending wave function of the complex, while the rate of dissociation depends on the number of quanta of excitation in the vdW stretching coordinate. The rate becomes faster as the excitation in the vdW stretch is decreased.
Implementation of high-bandwidth fiber optic data communications networks: proposed public standards
Authors: Baldwin Christopher
Published: February 2023

Data communications networks have become ubiquitous and vital facilities in the modern office. The networks must be inexpensive, support many different hardware platforms and must be easy to install and maintain. System integrators and component designers have worked together to develop standards that define the requirements for data communications networks with these desired properties. The standards describe the requirements that an implemented system must meet, and thus provide a common development point for fiber optic component manufacturers and system integrators. The ANSI X3T9.5 fiber distributed data interface (FDDI) is an example of a network standard that is imminently reaching completion while the ANSI X3T9.3 fiber channel standard is an example of developing fiber optic standard. The presentation will review the technical requirements of these standards to show how they implement the required physical connections.
Spatial vision by the isolated short-wave-sensitive (blue) cones
Authors: Wilson Hugh
Published: February 2023

As the short-wave-sensitive (SWS) cones comprise a small percentage of the total cone population, it has been suggested that they only function to provide an additional dimension to color space. However, we have recently shown that the SWS cones do contribute to a variety of spatial information processing tasks. In these studies SWS cone responses were isolated by superimposing blue test stimuli on an intense yellow adapting field. Masking studies under these conditions show that the SWS cones contribute to two or three spatial mechanisms that are tuned to low spatial frequencies and are orientation selective. The SWS cones were next shown to be capable of both spatial frequency discrimination and vernier acuity, although thresholds were higher than for the luminance system in both cases. Other studies have shown that the SWS cones also contribute to both stereopsis and motion processing. All of these results suggest that the SWS cones contribute to all forms of spatial information processing as effectively as possible given their sparse sampling distribution in the retina.
Excitonic nonlinearity in quantum confined CuCI glass composites
Authors: Justus B. L. , Seaver M. E. , Ruller J. A. , Friebele E. J. , Campillo A. J.
Published: February 2023

The nonlinear optical properties of size quantized excitons within semiconductor microcrystallites are the subject of much current interest. When embedded in glass, quantization of the exciton translational motion occurs in CuCI, leading to quantum size effects such as enhancement of the oscillator strength and the nonlinear refractive index. We report the measurement of the nonlinear refractive index, n2, at the Z3 exciton resonance for CuCI quantum dots in borosilicate glass. The optical nonlinearity is measured using a single beam absorption saturation technique. The glass samples were studied at 77K with an excimer pumped dye laser operating from 370 nm to 388 nm. Absorption spectra were obtained as a function of incident laser intensity. At the highest incident intensities the transitions were completely bleached. The nonlinear refractive index is calculated from the saturated absorption spectra using the Kramers–Kronig transformation. Significant enhancement of the nonlinearity over that of bulk CuCI is observed. In addition, a microcrystallite size dependence of the nonlinearity is observed.
Iterative processing using a cavity with a phase conjugate error
Authors: Lo Kanwai Peter , Indebetouw Guy
Published: February 2023

Iterative algorithms have become increasingly important for solving signal recovery/restoration as well as for solving recognition/selection problems. The optical implementation of iterative algorithms using a conventional feedback system is limited by the losses and by the accumulation of phase error at each round trip. A cavity that utilizes a phase conjugate mirror (PCM) offers a means to overcome these limitations. A PCM with gain can compensate for the cavity losses and restore the phase of the wave-front after each pair of round trips. It thus provides a regenerative feedback without accumulation of phase errors. Many image recovery schemes are equivalent to an equalization of the eigenvalues distribution. This process requires either a negative feedback, which is generally not possible to achieve in a cavity with a PCM, or a positive feedback with complementary operators in the feedback loop. A typical example of the latter is the Gerchberg algorithm. An optical system was built to implement the Gerchberg algorithm using an externally pumped BaTiO3 crystal as a PCM, and using complementary masks in the feedback loop. The recovery of simple band-limited images is demonstrated, and some of the limitations of the system are discussed.
Edge enhancement by hybrid optical rotating kernel min-max transformation
Authors: Lee Yim-Kul , Rhodes William T.
Published: February 2023

Hybrid optical implementation of a rotating kernel min-max transformation is discussed and applied to optical edge detection and enhancement. An input image is convolved with a short, narrow 2-D kernel that is rotated, either continuously or discretely, through 360°. As the kernel rotates, the convolution output is monitored, and the maximum [= Max(x,y)] and minimum [ = Min(x,y)] values at each point (x,y) are stored. Since the kernel used is typically real and non-negative, the convolution operation can be performed using an incoherent spatial filtering system. Using an asymmetric kernel, two different types of edge images are obtained: (1) a gray-scale edge image and (2) a binary edge image.
Measurement of molecular reorientational relaxation time by incoherent light with optical Kerr shutter
Authors: Yu Yi-Zhong , Ning Ji-Ping , Yao Jian-Quan
Published: February 2023

We report, the first time to our knowledge, the measurement of reorientational relaxation time T of dye molecules dissolved in solution using incoherent light. In the experiment, an AO Q-switched and frequency doubled YAG laser with pulse width 150 ns long compared with the Tor was used, the measured dye molecules were Rh6G and RhB dissolved in different solvents. The transmitted intensity of the probe light was measured by changing the delay time t between the probe light pulse and pumping pulse. The resolution time was governed only by the coherence time tc of the laser light. A combined time constant T (1/T = 1/T1 + 1/Tor, T is the first excited state lifetime) was employed.
IR electronic spectroscopy: triplet C3 and PtH
Authors: Bernath P. , Engleman R. , Jarman C. , Amano T. , Sasada H.
Published: February 2023

A new triplet band system of C3 was discovered near 6500 cm−1 in absorption using distributed feedback diode lasers as radiation sources. The band system was also found in emission from a microwave discharge of CH4 in He. High-resolution infrared emission spectra of the PtH molecule have also been observed with the Kitt Peak Fourier transform spectrometer. The source was a platinum hollow cathode operating with argon containing a trace of hydrogen. It was possible to assign some weak lines around 8300 cm−1 to (0,0) and (1,1) bands of a 3/2-3/2 transition. The lower 3/2 state was previously known and is about 4000 cm−1 above the X2Δ5/2 ground state.
Quantum-confinement effects in rf-magnetron sputtered CdTe:glass composite thin films
Authors: Potter B. G. , Simmons J. H.
Published: February 2023

Silicate glass films containing CdTe have been produced using an rf-magnetron sputtering technique in which a fused silica substrate is alternately exposed to each of two sputtering sources holding targets of Pyrex 7740 glass and high purity CdTe. This process represents a highly versatile fabrication technique for the production of semiconductor-doped glass materials. We report the successful deposition of CdTe-doped glass films containing as much as 30 vol % semiconductor with average crystallite sizes ranging from 46 to 158 Å. Planar-view transmission electron microscopy has shown the isolated crystals of CdTe to possess a circular morphology and a zincblende crystal structure. Room temperature optical absorption measurements exhibit a clear blue-shift in the fundamental absorption edge as the average semiconductor crystal size is reduced, indicative of a substantial quantum confinement effect. Analysis of the behavior shows it to be governed by an effective mass term which is intermediate between the translational and reduced masses of the bulk CdTe Wannier exciton.1 Failure of the data to exhibit a reduced mass behavior in the absorption edge shift with crystal size suggests that a substantial Coulomb interaction between the photoexcited electron and hole still exists even at crystal sizes 0.3 times the Bohr diameter of the bulk CdTe exciton.
Pressure-tuned phase transitions in CdSe:glass composites
Authors: Zhao Xue-Shu , Silvestri Markus , Schroeder John
Published: February 2023

The phase transition properties of CdSe microcrystals embedded in glass were studied by Raman scattering and photoluminescence under pressure in a diamond anvil pressure cell. From careful measurement of Raman intensity versus pressure, a complete phase transition from wurtzite to rocksalt phase of the CdSe particles in the glass composite was observed above 70 kbar in contrast to approximately 30 kbar in bulk CdSe. During the phase transition there was no observed sudden color change which shows that the phase transition in small crystallites does not induce a large number of defects. From photoluminescence measurements we conclude that in the small particle system, after the phase transition there is not a sudden absorption edge drop which was observed in bulk materials. We also suggest from photoluminescence measurements of CdSe in the rocksalt phase that the bandgap of CdSe is indirect and about 2.02 eV.
Selectively low emittance of beryllium oxide and the effects of contamination
Authors: Ribbing Carl G. , Chibuye Teddy , Lidström Erik , Wäckelgård Ewa
Published: February 2023

Beryllium oxide has a strong Restsrahlen band in the wavelength interval 9–15µm. This feature makes the material selectively low emitting in the primary atmospheric window 8–13µm, which reduces radiative cooling through a clear skye. It has been suggested to use BeO for condensation and frost prevention in situations when metalic or electrically conducting materials cannot be used, e.g., on ceramic high voltage insulators.1 In this contribution, spectral emittance data are presented which agree with the previously known bulk reflectance results. Detailed structures observed in the reflectance and emittance spectra are explained as the effect of details in the phonon dispersion relation. The effect of simulated soot contamination upon the surface of BeO has been studied. It is found that even heavy contamination in an industrial atmosphere leaves at least 50% of the emittance reduction intact and consequently there are good prospects that the condensation prevention effect would prevail even after long time exposure to atmospheric contamination.
Nonclassical fourth-order interference experiment
Authors: Zou X. Y. , Ou Z. Y. , Wang L. J. , Mandel L.
Published: February 2023

A new fourth-order interference experiment based on detecting photon pairs in coincidence has been carried out. A Mach-Zehnder type of interferometer is used, with the two photons generated simultaneously in the process of down-conversion as inputs and two photon counting detectors at the two outputs. The optical path difference can be varied piezoelectrically. It is found that the coincidence counting rate, after subtraction of accidentals, exhibits a sinusoidal variation with the optical path difference as predicted by quantum mechanics, but in violation of the laws of classical optics. This is another non-classical interference effeet. By contrast, two light beams derived from a He:Ne laser used as inputs to the interferometer, do not produce any fourth order interference.
Pattern cohesiveness around isoluminance
Authors: de Weert Charles M. , Troost Jim M.
Published: February 2023

One of the peculiar phenomena occurring in two color pictures is a severe loss of cohesiveness when figure(s) and ground become isoluminous, whereas when both luminance and color differences exist between figures and background grouping of similarly colored parts is just a very dominating effect. In this paper we will present a quantitative method to measure this effect quantitatively. In a four-alternative-forced choice procedure pictures, disturbed by noise are presented. We will also discuss the possibility to use this method for measuring combined color and brightness differences.
Cone contrast comparison of luminance and chromatic sensitivities for movement, flicker, and flashes
Authors: Eskew Rhea T. , Stromeyer Charles F. , Kronauer Richard E.
Published: February 2023

Expressing visual stimuli in terms of the contrast they produce in the different cone classes approximately accounts for (1) the highly overlapping cone spectra and (2) (von Kries) adaptation, allowing meaningful comparisons of post-receptoral sensitivities to color and luminance. This paper reviews this comparison for lights that stimulate only the L and N cones (ca. 3 log Td adapt). For low to medium temporal and spatial frequencies, chromatic sensitivity is as much as 9× luminance sensitivity. For example, for 1° flickering spots chromatic sensitivity is higher than luminance sensitivity below 15 Hz. Experiments using moving 1 cpd gratings reveal two spectrally-opponent (L–M) mechanisms and a luminance mechanism. The color detection mechanism is 5 × more sensitive than the luminance mechanism at 1°/s, while the spectrally-opponent motion mechanism (which apparently does not signal color) is 3× more sensitive than the luminance mechanism. Greater temporal integration in spectrally opponent mechanisms may partly account for their greater sensitivity. With 1° flashes, the luminance and chromatic critical durations are about 40 and 100 ms, respectively. However, even for the briefest flashes, chromatic sensitivity is 3× luminance sensitivity. Part of this 3× could be due to the differencing operation reducing noise in opponent mechanisms; however, this hypothesis requires considerable correlated noise in the L and M cones.
1000-Fold improvement in the measured antiproton mass
Authors: Gabrielse G.
Published: February 2023

Comparisons of antiproton and proton cyclotron frequencies yield the ratio of inertial masses The fractional uncertainty of 5 × 10* is 1000 times more accurate than previous measurements of this ratio using exotic atoms and is the most precise test of CPT invariance with baryons. Independent comparisons to electrons yield the mass ratios M(p)/M(e-) = 1836.152638 + 0.000083 and M(p)/M(e-) = 1836.152660 + 0.000088. For these measurements, cryogenic antiprotons (near4 K), were stored in a Penning trap for up to 2 months—much longer than antiprotons have been previously stored.
Aspheric generation for large optics
Authors: Garbarino Richard B.
Published: February 2023

Itek has developed methods to generate surfaces to high tolerances using standard numerically controlled five-axis machine tool with 0.005 in. positioning tolerance and 0.0002 in. repeatability. In this approach, the five-axis are used to keep the rotational axis of a diamond cup wheel normal to the surface at all points on the surface. This results in the entire circumference of the cup wheel performing the cutting increasing the cutting efficiencies. The method is applicable to both on and off axis spherical and aspherical surfaces, and is limited only by the size of the machine tool. This is accomplished in a two-stage process. In the first stage, the surface is cut without regards for machine-induced errors. The surface is measured on the Itek profilometer to obtain a surface normal error map. A second surfacing control file is created using this map and the surface is recut. This method has resulted in a 1.5 m parabola with a surface of 3.8-µm RMS and 2.3 m parabola with a 5-µm RMS.
Twyman effect for ULE and Zerodur–surface stresses introduced in brittle and ductile mode loose abrasive grinding
Authors: Golini Donald
Published: February 2023

The Twyman effect was evaluated for loose abrasive grinding of ULE and Zerodur. It was shown that surface stress increases dramatically in the transition from brittle to ductile mode grinding. This is believed to be the result of an increase in subsurface deformation in the ductile process. It is well known that brittle mode grinding produces surface stress in glass. The stress is thought to be caused by localized flow, occurring when individual abrasives indent the ground surface. In brittle mode, most of the grinding energy contributes to the fracture process, with small stress fields produced by localized deformation near the crack tips. In ductile mode, however, glass deformation is more extreme, resulting in a significant increase in stress. The depth of this stress varies from tens of micrometers to tenths of a micrometer, decreasing the abrasive size. In ductile mode, the thickness of the stressed layer has been seen to be as small as 22 nm. Less stress was found in ULE than in Zerodur when ground under the same conditions, however, a factor of 2 to 4 increase in stress was observed for both materials in the transition from brittle to ductile mode.
Effect of mode spacing on growth from noise in broadband stimulated Raman scattering
Authors: Hilfer Godehard , Reintjes John , Menyuk Curtis R.
Published: February 2023

The generation of Stokes light by stimulated Raman scattering with a broadband pump is usually modeled by assuming that the input Stokes signal contains the same modes as the input pump wave. In this paper we investigate the evolution of the Stokes wave when the modes of the starting signal are not related to those of the pump. If the assumed starting modes for the Stokes wave are narrowly spaced compared to the spacing of the pump modes, these calculations can serve as a model of growth from noise. Of particular interest is the case in which the pump modes are narrowly spaced compared to the Raman line width. In this situation the Stokes signal may not reproduce a series of delta function modes assumed for the pump, but may have a more uniform distribution. Evolution of the Stokes mode structure under conditions of high gain and the degree of correlation with the pump will be examined for this case and will be compared with similar results obtained for wider mode spacings.
Time-resolved linear and nonlinear absorption of femtosecond pulses in II-VI semiconductors
Authors: Fox E. C. , Canto-Said E. , Miller I. J. , van Driel H. M.
Published: February 2023

Femtosecond time-resolved excite-probe experiments have been performed in various II-VI semiconductors in transmission and reflection geometries. In particular, we have used the 100 fsec pulses from an amplified colliding-pulsed-modelocked (CPM) laser operating at a wavelength of 620 nm and with energies of 30 µJ to excite carriers in CdS, CdSe and CdSxSe1−x semiconductors. In some of these materials the bandgap energy exceeds the energy of the exciting photons and allows us to directly measure the two-photon absorption (2PA) coefficient at zero time delay. At longer delays, in all materials the excitation induced changes in the linear optical properties are measured at a variety of different wavelengths selected from a continuum. At high excitation fluences, some of these materials display modulation in the linear optical properties within the first 2 ps when probed with photons with energies which fall below the bandgap energy. We offer interpretation of our results in terms of various competing mechanisms including free-carrier absorption, interband transitions, bandgap renormalization and absorption saturation.