bluuebunny/crossref_metadata_2025 huggingface dataset:
Optoelectronic system for distributed computing
Authors: Kiamilev F. , Esener S.
Published: February 2023

The performance of a large parallel processing system can become limited by the serial nature of synchronization.1 For example, divide-and-conquer parallel search algorithms partition work into separate processes that must all halt when a solution is found. This process requires synchronization of all the participating processors. However, when each processor has only one input and output port, such operations can only proceed serially; this represents a bottleneck in the performance. Previously, we have designed an optoelectronic multistage interconnection network for communication and parallel computing.2,3 In this paper, we extend this design to add distributed processing capability within the network.
Perceptions of rigidity with rotating ellipses
Authors: Mulligan Jeffrey B. , Shiffrar Maggie
Published: February 2023

We have investigated the perceived rigidity of rotating ellipses in a variety of conditions, following Wallach et al. (1956), who observed that rigidity is seen only when the eccentricity or aspect ratio is large. We measured the degree of rigidity as a function of aspect ratio, and found that a number of factors besides aspect ratio can have a profound effect on the percept. For example, a single rotating ellipse is often perceived to be more rigid than a family of concentric ellipses of the same aspect ratio. In a similar finding, we have observed that an asymmetric Gaussian blob with elliptical contours is seen to be more rigid than a single ellipse, suggesting that low-frequency content may be important for rigidity.
Using ideas from biology to solve the self-motion estimation problem
Authors: Perrone John A.
Published: February 2023

Attempts to derive 3-D self-motion information from 2-D image sequences have been hampered by the difficult problem of reliably measuring the 2-D image motion. The small size of the motion sensors relative to the length of many of the contours in the scene results in measurements of the normal component of the velocity vectors, not the correct image velocity (the aperture problem). This is problematical for many self-motion estimation algorithms, especially those that rely on vector differences to decompose the translational and rotational components of the flowfield. Current techniques for solving the aperture problem are not readily applicable to the type of image motion generated during observer motion. We know however that the normal component of the image motion is constrained to lie within ±90° of the true direction. Motion sensitive cells, such as those in the area MT of the primate brain, often have direction bandwidths of this size.
Disparity averaging across spatial scales
Authors: Smallman Harvey S. , MacLeod Donald I. A.
Published: February 2023

We have investigated disparity averaging using a novel stimulus which yields two spatially coextensive disparity signals carried by different spatial scales at each point in a random dot stereogram. This was accomplished by sinusoidally modulating the luminance of dots carrying various disparities with phase differences between the two eyes’ views that were equal to or different from the dot disparity. In a 2AFC task observers judged the relative depths of two panels in a random dot stereogram. A reference panel carried equal texture and sinusoid disparities; the second panel carried a different texture disparity and a sinusoid of variable phase. Near the horopter, transparency was the norm. However, with larger disparity offsets from the horopter, disparity averaging occurred, even when the texture and sinusoid disparities differed by over 10 min arc. Either two disparity estimates are extracted and then averaged at each point, or else the tradeoff between fine and coarse scales occurs at the input to the disparity sensing mechanism. We have considered two schemes of the latter kind. An explanation based on low-pass monocular filtering and windowed cross-correlation fails to model the results. A more successful scheme postulates a disparity code involving the ratio of excitation of coarsely tuned mechanisms away from the horopter.
Polarization-encoded optical shadow-casting: arithmetic logic unit design: separate output generation
Authors: Ahmed Jamal U. , Awwal Abdul Ahad S.
Published: February 2023

A polarization-encoded optical shadow-casting (POSC) system1 processes 2-D coded input in parallel. Light emitting diodes (LEDs) shift and overlap the shadow of the overlapped input pattern from which a decoding mask spatially filters and detects the output. Our current work involves designing an arithmetic logic unit (ALU) which is the heart of general purpose computing. For an ALU, sixteen logical operations of two variables and addition/subtraction result of three binary variables need to be generated. To simplify the design process, the result of three binary variables need to be generated. To simplify the design process, the resulting ALU truth table with twenty-four entries, is partitioned2 into smaller sections, so that each section can be realized with smaller pixel inputs. In the sectional arrangement, inputs A and B are controlled by the third input pixel C to generate both arithmetic and logical output, separately, similar to a single instruction multiple data flow machine. The application of truth table partitioning results in a smaller pixel size, only two pixel subcells for each input. The input coding and source LED pattern are also provided.
Optical phase conjugation in polyacetylene
Authors: Shen T. P. , Rogovin D.
Published: February 2023

Polyacetylene is a long linear, chainlike material whose optical properties at visible wavelengths arise from the motion of the π-electrons along the bonds that connect the sites. The nonlinear optical properties of polyacetylene materialize from two anharmonic electronic interactions: (1) the π-electrons interact with the phonons and (2) they interact with each other through their Coulomb repulsion. The motion of the π-electrons driven by an optical field were described within a classical framework and the third-order optical susceptibility associated with phase conjugation was determined. The wavelength (λ) has dependence on the nonlinear optical susceptibility; two peaks coincide with a resonant response. A low frequency peak in the vicinity of 1.2 µm reflects a two-photon resonance process and arises from the Coulomb repulsion. A high frequency peak at 0.6 µm is the single photon resonance and arises from both the Coulomb repulsion and the electron phonon coupling.
New linear electrooptic measurement technique for second-order nonlinear thin films
Authors: Yankelevich D. R. , Knoesen A.
Published: February 2023

A reflection-mode polymeric interference modulator is used to measure the linear electrooptic (EO) coefficients of a second-order nonlinear polymeric film. The reflection-mode interference modulator is a stratified structure consisting of a partial reflecting conducting layer, an EO layer, and a highly reflecting conducting layer. At resonance, the reflected light intensity is modulated through the linear EO effect by a modulating voltage applied across the conducting layers. The linear and modulated reflectance characteristics are modeled by anisotropic stratified transfer matrix methods with a high degree of accuracy. From reflectance and modulated reflectance measurements as a function of the angle in incidence, both the linear and nonlinear properties of the nonlinear film can be determined. Using this technique dispersion measurements of the nonlinear EO coefficients can be performed using a broadband incoherent source. This measurement technique is used to characterize the linear EO coefficients of poled polymeric thin films.
History and physical principles of Lode Star technology
Authors: Hutchin Richard A.
Published: February 2023

Lode Star research began in 1979 with a concept called the ray-method suitable for MWIR imaging technology. After field experiments at the Verona test range, the concept evolved into the A-method which some years later was called laser guide star in the open literature. Considerable work was done assessing optimal processing techniques for combining multiple guide stars leading to two effective approaches called stitching and merging. The technology was augmented by the S-method and sodium resonance scatter which generated multialtitude, multisource estimators for high-order wavefront correction. Detailed wave propagation simulations and photometric analysis supported the viability of these techniques which led to successful field experiments.
Ultrafast measurements of energy flow, geminate recombination, and fast structural rearrangements in photoexcited heme proteins
Authors: Zhu Huiping , Xu Xiaobing , Lingle Robert , Hopkins J. B.
Published: February 2023

Two-color picosecond transient Raman spectroscopy is used to study the ultrafast ligand binding reaction of O2 with hemoglobin. Oxyhemoglobin is photodissociated and the subsequent geminate recombination reaction investigated by vibrational spectroscopy. For ultrafast reaction in solution it is often difficult to separate the dynamics of chemical change from simple relaxation of the internal energy. We have used Stokes and anti-Stokes transient Raman spectroscopy to measure both structural changes in the heme and vibrational energy relaxation. Rates of energy relaxation have been measured in both deoxy and oxyhemoglobin. These results provide detailed information about the coupling between the heme and the protein. For oxyhemoglobin the rate of geminate recombination is faster than the vibrational cooling rate.
Ferroelectric liquid crystal tunable polarization filter
Authors: Sharp G. D. , Stockley J. E. , Doroski D. , Johnson K. M.
Published: February 2023

Ferroelectric liquid crystals (FLCs) have been used in discrete and continuous polarization interference filters.1-3 Birefringent filters have been mechanically tuned by rotating an achromatic half-wave plate, that reflects the desired center wavelength to coincide with the analyzing polarizer axis.4 Smectic A
*
FLCs are essentially fixed retarders, which are analog rotatable, and fast switching (100 kHz–1 MHz), with the application of an electric field. However, a single element cannot yet achieve the 45° of analog tilt required to tune through a free-spectral range. In addition, the elements are not achromatic. In this paper, we present a method for combining two or more FLC switching elements and compensate for FLC chromaticity effects.
Optical memory element for an integrated-optical computer
Authors: Parker M. A. , Swanson P. D.
Published: February 2023

Logic and memory devices consisting of lasers, waveguides, saturable absorbers, and detectors have been integrated onto a wafer of GaAs-AlGaAs multiquantum well heterostructure. The laser-based memory element to be integrated uses laser quenching for the reset operation and the saturation of absorption in multiquantum well material for the set operation. The monolithic development of this device should serve as a key component for optical computing in future Air Force technology.
Fisher information and the complex nature of the Schrodinger (or Helmholtz) wave equation
Authors: Frieden B. Roy
Published: February 2023

The principle of minimum Fisher information (MFI) provides a basis for deriving most of the laws of physics.1 The Fisher I is defined as (mean-squares error)-1 in the efficient determination of the classical position θ of a particle. For a one-component pdf p(x) = q2(x), the Fisher information is a one-term functional I = 4 ʃdx[q’(x)]2. Thus, I decreases as q(x) becomes smoother, or as disorder increases, consistent with the second law of thermodynamics. In the above, p(x) was specifically assumed to have a single component q2(x). Then MFI gives a real-only wave equation. Here we consider multicomponent cases p(x) = q12(x) + … + qN2(x), where the qn(x) are independent degrees of freedom. We seek the Fisher I for the case N = 2 of nonrelativistic quantum mechanics or of scalar optics. A benchmark statistical situation arises when the N components of qn(x) do not overlap. Then their informations add, and the resulting mean-squares error value is efficient, i.e. an absolute minimum.
Fisher information and error complimentarity
Authors: Frieden B. Roy
Published: February 2023

The Cramer-Rao (CR) inequality e2I ≥ 1 represents complimentarity between (i) the size of mean-squares error e2 in estimation of a parameter θ from an observation y where y = θ + x, and (ii) the Fisher information I due to pdf p(x). In application to quantum mechanics, θ is the classical position of a particle, and I becomes the mean-squares momentum spread for the particle. Thus, the CR inequality becomes the Heisenberg uncertainty principle. The latter is, then, but one example of a general principle of error complimentarity. As applied to optical diffraction, θ is now the unknown centroid of a diffraction pattern. Here the CR inequality becomes e2z2 ≥ (λf/4π)2, where z2 is the mean-squares photon position in the lens pupil, λ is the light wavelength, and f is the focal length. Interestingly, here the uncertainty product can be made arbitrarily small. Another use is in the case of a nonideal gas kept at a constant temperature T. The gas is inside a container of unknown drift velocity θ. If p(x) defines the probability law on velocity x for particles of the gas, the CR inequality attains a minimum for the uncertainty product e2I when p(x) is Gaussian, i.e., when p(x) is a Boltzmann law. This describes the ideal gas scenario and gives it a new significance.
Visual motion and stereo signals for a 3-D shape
Authors: Lappin Joseph S. , Craft Warren D. , Tschantz Steven T. , Sun Changnian
Published: February 2023

Spatial derivatives of moving and/or stereoscopic images constitute information about the differential structure of surfaces in 3-D. To investigate the role of such image properties, we have evaluated the visibility of spatial differential structure in both moving and stereoscopic images. The general method involves examining the effects of rapid random transformations of the 2-D images (translations, dilations, and 2-D and 3-D rotations) on detections and discriminations of 3-D surface structure. In stereoacuity experiments such transformations have been applied independently to the monocular half-images prior to binocular combination. Results of experiments on both structure from motion and stereoacuity indicate that (a) vision is very sensitive to the image deformations that carry information about surface shape, and (b) these deformation components can be visually distinguished from other differential components that have the same effects on the image motions and binocular disparities of both individual points and pairs of points. Thus, vision seems to be sensitive to the local differential structure of moving images—a four-parameter property, supported by relations among at least five neighboring image points.
Dynamics of a single-longitudinal-mode laser inhomogeneous broadening and transverse effects
Authors: Hunter L. W. , Bandy D. K.
Published: February 2023

We consider the dynamics of an inhomogeneously broadened unidirectional ring laser formulated in the traditional Maxwell-Bloch configuration of a two-level atom with transverse modes. We numerically analyze the model for a single-longitudinal mode in the paraxial approximation, using the uniform field limit with cylindrical symmetry and a Gaussian profile for inhomogeneous broadening. Several domains of solutions are found for the resonant case in the good cavity limit. The laser threshold is found to be dependent on the mode spacing as well as on the gain and scaled Doppler broadening. Hysteresis between stable and unstable solutions is obtained in realistic operating conditions for both increasing (decreasing) gain and increasing (decreasing) mode spacing (i.e., for changes in the initial conditions).
Spatio–temporal instabilities in far infrared Raman lasers
Authors: Rai Suranjana , Rai Jagdish , Izatt J. R.
Published: February 2023

Raman lasers operating in the far infrared are well described by the three- and four-level molecular systems. The theoretical analysis of these lasers is based on a density matrix treatment. Steady-state and time dynamics of these systems has been studied extensively. However, their spatial aspects involving propagation are not well understood. In this paper, we study the spatial and temporal dynamics of these lasers based on a density matrix analysis for the four-level molecular systems. The full set of Maxwell-Bloch equation consists of sixteen equations. We obtain the numerical solutions for this system and analyze regions of phase space where the laser fields show chaotic behavior.
Design challenges for chip lithography lenses
Authors: Shafer David
Published: February 2023

Lithographic lenses provide a phenomenal amount of image pixels in combination with amazingly small amounts of distortion and departure from field flatness. These difficult achievements require about twenty lens elements in today’s state-of-the-art designs. Their evolution from simpler versions is as haphazard as the birth of Topsey—they just grew. What is needed today is a more rational approach to lens design that would allow a controlled attack on the design of such systems. This should involve two efforts. The first is the settling, through theoretical research and experimentation, of several questions about what is the optimum way to achieve certain design goals, for example, what is the best balance between relaxation and strain in a design. Controlled amounts of the latter may be required for correction of seventh-order distortion and field curvature, but this limits field coverage due to bad ninth- and higher-orders. The other effort required is the further development of the design technique described elsewhere1 that allows one to build a design from scratch with the correction of the most difficult higher-order aberrations being built in from the beginning. This needs to be expanded to give seventh-order control early in the design evolution.
Relationship between the decay rate of second-order optical properties in poled glassy polymers and structural relaxation
Authors: Rolsma P. B. , Sprague R. W. , Lee J. N.
Published: February 2023

The noncentrosymmetric structure required for second-order optical nonlinearities can be induced in polymers by poling with an applied electric field. This gives any nonlinear constituents a preferred orientation in the glassy structure which is not in thermodynamic equilibrium. The slow relaxation into random orientation is of great importance in using such materials.
Poled polyimides for thermally stable electrooptic material
Authors: Wu J. W. , Valley J. F. , Stiller M. , Ermer S. , Binkley E. S. , Kenney J. T. , Lipscomb G. F. , Lytel R.
Published: February 2023

We present data indicating that polyimide is a suitable host for nonlinear optical molecules and that the resulting guest-host system, once poled, has a highly thermally stable EO response. This stability requires both poling during curing and coplanar electrodes. First, the poling electric field is applied during the cure process so that the dipole alignment is achieved before imidization and densification; second, the guest molecules are aligned in the same orientation as the conforming morphology of the host polymer. After vacuum soft-baking the spin-coated guest-dye/host-polyimide thin film (Erythrosin/L100), the films were imidized by heating to 250°C with a dc electric poling field applied. After holding the sample at 250°C for 1 h, the sample was further cured at 360°C for 0.25 h for the densification process and then cooled. The dc poling field was removed upon reaching room temperature.
Laser guide stars and adaptive optics for large astronomical telescopes
Authors: Brase James , Chocol Clifford , Friedman Herbert , Gavel Donald , Max Claire E. , Morris James , Salmon J. Thaddeus
Published: February 2023

An adaptive optics (AO) system using a high power laser tuned to the sodium resonance to make a bright guide star has been investigated and is under development. The laser for this system has been developed for the Atomic Vapor Laser Isotope Separation program and produces over a kilowatt of power with excellent beam quality, spectral control, and stability. The AO system uses a wavefront sensor based upon the Hartmann technique with an image intensified, CCD camera, wavefront reconstruction algorithm, fast steering mirror for tip-tilt control, and a deformable mirror for wavefront correction. The AO system will be applied to a 1-m class telescope located at LLNL adjacent to the AVLIS laser facility.
Artificial guide star focus anisoplanatism limitations to tilt-free resolution/antenna gain
Authors: Fried David L. , Belsher John F.
Published: February 2023

The original analysis of focus anisoplanatism1 included an effect due to the difference between turbulence-induced full-aperture wavefront tilt for the artificial guide star and for starlight. However, for short-exposure imagery tilt effects should be excluded. (For a long-exposure it should also be excluded; guide star position is so uncertain it provides no overall tilt information. That information must come from some other source, so the tilt difference should not be charged to focus anisoplanatism.) We have analyzed the focus anisoplanatism’s effect on short exposure resolution/antenna gain, generating extensive numerical results. We also analyzed the mean*-squares tilt-free focus anisoplanatism-induced wavefront error, E2, for aperture diameter D, and showed that E2 is proportional to D5/3. Writing the constant of proportionality as d
0
-5/3, so that E2 = (D/d0)5/3, we have d0 as a measure of the strength of focus anisoplanatism—a measure independent of aperture diameter. Dividing our short exposure focus anisoplanatism antenna gain results by the diffraction-limited antenna gain for an aperture diameter d0, and expressing these normalized results as a function of the normalized aperture diameter D/d0, all our results condense to a single curve, independent of wavelength, guide star altitude, zenith angle, or turbulence distribution.
VLSI electrically addressed ferroelectric liquid crystal spatial light modulators and detector arrays for optical processing systems
Authors: Turner Richard , Jared David A. , Johnson Kristina M.
Published: February 2023

The design and operation of a VLSI electrically addressed spatial light modulator (SLM) with alignment photodetectors for optical processing is presented. The electrically addressed SLM consists of a 64 × 64 array of pixels located on 40-µm centers with addressing logic around the periphery of the array. The pixel array is surrounded by a guard ring structure to reduce previously observed1 light-induced effects such as chip latch-up and shortened pixel storage time. The modulator also utilizes optical detectors located at the corners of the array for ease of insertion into optical systems. The liquid crystal material used in the device is capable of switching in 0.75 ms at operating voltages of ±3.5 V. This allows device frame rates >1.3 kHz.
Quantum-limited image restoration
Authors: Fiddy M. A.
Published: February 2023

Imaging at low-light levels relies on intensity measurements that have a signal-to-noise ratio of

N

, if N photons are detected at a pixel. Usually, a simple time integration to improve the SNR is not possible because the object being imaged or the measurement system is moving; this results in a loss of high spatial frequency information and possible blur. Examples of imaging techniques are described along with the usual techniques for dealing with the photon-limited data, poor SNR, and blur. Correlation based methods (recovery from Fourier magnitude or bispectral data) provide a solution to some of these problems, in principle, and are outlined. Spectral estimation techniques to restore high spatial frequencies or missing phase information can further improve these images but are very noise sensitive in general. New methods are described that are either explicitly or implicitly regularized and permit reliable image restoration; they are based on minimum norm estimators that can incorporate prior knowledge about the object, if available. Both linear and nonlinear estimators can be defined and the role of the prior knowledge is quite different in the two cases.
Effect of detector quantum efficiency on mapping material properties using spatially resolved Raman spectroscopy
Authors: Veirs D. Kirk , Ager Joel W. , Rosenblatt Gerd M.
Published: February 2023

Spatially resolved Raman spectroscopy employing 2-D detection is used to map the chemical and physical properties of materials. Scattered light from a laser-illuminated line on the sample is projected on the entrance slit of a spectrometer and the dispersed light is collected by a 2-D detector, yielding a 2-D data matrix (up to 1024 × 1024 with x = wavelength and y = position along the illuminated line). Up to 1024 Raman spectra, each corresponding to a unique position along the line, are acquired simultaneously. Analysis of the spectra in each row of the data matrix yields a 1-D spatial profile of the property of interest. We find that fluctuations in the 1-D property profile depend linearly upon the signal-to-noise ratio (SNR) of the spectra in the data matrix. For photon-limited spectra the SNR in the data matrix varies as the square root of the quantum efficiency (QE) of the detector. A charge coupled device with QE = 50% will yield comparable quality maps to those obtained with an imaging microchannel plate photomultiplier (Mepsicron) with QE = 12% in one quarter of the time.
Effect of dead space on mean gain, excess noise factor, and avalanche breakdown voltage for Si and GaAs avalanche photodiodes
Authors: Sargeant Winslow L. , Hayat Majeed M. , Saleh Bahaa E. A.
Published: February 2023

We investigate the effect of dead space on the mean gain, the excess noise factor, and the avalanche breakdown voltage for Si and GaAs avalanche photodiodes (APDs) with nonuniform carrier-ionization coefficients. The dead space, which is a function of the electric field and position within the multiplication region, is the minimum distance that a newly generated carrier must travel to acquire sufficient energy to become capable of causing impact ionization. Recurrence relations in the form of coupled integral equations are derived to characterize the underlying avalanche multiplication process. Numerical solutions to the integral equations are obtained and the excess noise factor is plotted as function of the mean gain. We have found that, in each case, the presence of dead space results in a reduction of both the mean gain and the excess noise factor. The excess noise factor vs the mean gain curve is also lowered in comparison with the ideal case in which there is no dead space. Furthermore, dead space serves to increase the applied bias voltage at which avalanche breakdown occurs.
Polarization matrix for round-trip wave propagation in magnetooptic media
Authors: Zhao Yang , Wang Beijing , Auner Gregory W.
Published: February 2023

A polarization device can be described by the Jones polarization matrix. The difference between a magnetooptic (MO) (nonreciprocal) medium and a dielectric birefringent (reciprocal) medium must be taken into account in cases involving round-trip wave propagation through a medium. One possible way is to consider each component of the wave vector to study the net effect of round-trip propagation through a medium. This is not convenient when many polarization devices are involved, such as in a MO system. We show that the net effect of round-trip propagation can easily be obtained by using the matrices describing the forward and backward propagation through the same medium. If the Jones matrix for forward propagation is T, the matrix for backward propagation is the transpose of T. Here T is symmetric for reciprocal media and nonsymmetric for MO media.
Phase/amplitude spatial light modulators using 90° twisted nematic liquid crystal devices
Authors: Tam Eddy C. , Zhou Shaomin , Gregory Don A. , Kirsch James C.
Published: February 2023

One of the obstacles in real-time holography as well as in optical information processing is the lack of a real-time addressable spatial light modulator that can display a complex function with both amplitude and phase information. In this paper, we describe a novel method that uses two identical 90° twisted nematic liquid crystal displays to implement a continuous phase/amplitude level spatial light modulator. Phase and polarization modulation properties of the twisted nematic liquid crystal cell is due to the modulation of the tilt and the molecules in the vertical direction along the liquid crystal cell structure and the twist in the horizontal plane, respectively. By aligning the incident light to be perpendicular to the front director of the liquid crystal molecules, and inserting an analyzer (in the same direction as the incident light) immediately after the first liquid crystal cell, amplitude-only modulation can be achieved. The light amplitude coming from the first cell is then parallel to the molecular director of the second cell, and phase-only modulation can be achieved by limiting the applied voltage to be below the polarization modulation threshold. The combined modulator is then capable of modulating both amplitude and phase parameters independently by two identical spatial light modulators.
Liquid crystal infrared light modulators
Authors: Jia Yan , Chen Lixiu , Wang Liming , Zhao Jinggang
Published: February 2023

Liquid crystals have attractive properties since they exhibit a large birefringence change at low applied voltages and a good optical transparency in the IR. A parallel alignment LC cell compared with twisted or perpendicular alignment in the IR is employed for three reasons: the dark state is insensitive to wavelength; highly stable LC mixtures can be formulated with large positive εo large Δn and low viscosity; and a relatively thinner LC layer that does not seriously weaken the modulation efficiency is usable. The cell made with a pair of BaF AR-coated windows (coating In1O1 infrared conductive film) is in the polarizer-LC cell-analyzer configuration. An extended beam of a 10.6-µm Co2 laser with a few tens of µW cm2 transmitted a 10-µm LC layer of E1 driven by 2.4-3.2 V (1 kHz). An optical response time of 75 ms is achieved from this modulator utilizing the controlled birefringence effect. This time is smaller than that calculated from τ = r1d2/k11π2, because of the difference between the reorientation time and optical response time, varying by a factor of 2–4. Using the same cell with E10, the 65-ms optical response time is achieved. The smaller time is due to its better parameter of r1/k11 although Δn is a little large. The choice of LC is discussed by calculating the two important parameters of response time (τ = r1d2/k11π2) and dynamic range (δ = 2 π dΔn/λ) with r1k11 and Δn.
Perceived layering of transparent surfaces interacts with binocular disparity to determine coherent motion in moving plaid stimuli
Authors: Trueswell John C. , Hayhoe Mary M.
Published: February 2023

Certain intensity relations between neighboring regions permit the viewer to perceive transparent surfaces in a particular depth order. We explored how this transparent layering cue interacts with binocular disparity to determine whether two superimposed moving gratings appear as independently moving surfaces (component motion) or as a single plaid surface moving in a unified direction (pattern motion). Subjects stereoscopically viewed moving plaid stimuli comprised of asymmetric squarewave gratings. The narrow bars of the two gratings had different luminances, 0.8 and 78 cd/m2, whereas the intersecting regions had luminance 37 cd/m2, causing the lighter grating to appear transparent and in front of the darker grating. Disparity was manipulated to provide a depth cue that was either consistent or inconsistent with the perceived transparent layering. When both cues supported the same depth relation, only small disparity differences were required for the gratings to appear as separately moving surfaces. Conversely, when the two cues were inconsistent, much greater disparities were required. Other experiments concerning depth estimates to nonmoving stimuli suggest that perceived transparent layering and disparity cues combine to determine an estimate of depth. These results indicate that the coherence of moving plaid stimuli is determined by consistent surface interpretations emerging from the integration of information concerning motion, disparity, and intensity relations.
Color information improves motion detection and velocity discrimination
Authors: Beutter Brent R. , Kumar Tribhawn , Glaser Donald A.
Published: February 2023

The effects of chromatic information on detection and speed discrimination thresholds for particles moving in noisy environments were measured. The results show that color can be a vital cue for motion processing. Adding color to a colorless motion stimulus that conveyed no motion percept made motion detectable and also produced speed discrimination thresholds equal to the best achievable with luminance information (7%). In previous studies, attempts were made to isolate color’s contribution to motion perception by using isoluminant stimuli. To investigate the interaction of motion and color information, we used stimuli in which significant luminance contrast was present. The stimulus consisted of a particle of constant hue, saturation, and luminosity moving over a background of randomly flickering gray values. Colorless particles were undetectable in the presence of noise over a wide range of luminance values roughly equal to the standard deviation of the noise. Adding color to particles in the center of this range made the particle detectable and showed that detectability increased in proportion to the saturation of the added color. Velocity discrimination thresholds improved as saturation increased, and luminance was held constant. Finally, the improvement in velocity discrimination thresholds of colored particles produced by adding luminance information (subthreshold for gray particles) was measured.
Relative motion discrimination
Authors: Silverstein D. Amnon , Klein Stanley A.
Published: February 2023

Motion of very small amplitudes (5 sec or less) can be detected when the frequency of motion is optimal (2–4 Hz).1 Previous research has shown that in some conditions, relative motion can be discriminated whenever motion can be detected at all.2 In this experiment, we determined the range of frequencies over which this relationship holds. We used two sinusoidally oscillating dots to determine the temporal frequency response function of relative motion discrimination. The subject was presented with two dots that either oscillated inphase (the dots moved in the same direction) or in counterphase (the dots moved in opposite directions). The subject was required to discriminate between the two types of motion for a range of temporal frequencies. When the temporal frequency of the presented stimuli is optimal (~4 Hz), the visual system is remarkably adept at discrimination relative motion. However, a temporal frequency of as low as 8 Hz degrades thresholds and 12 Hz increases them by a factor of 5.33 ± 1.33.
Perceived direction of moving textures
Authors: Mast Russell D. , Wilson Hugh R.
Published: February 2023

Recently, many studies on perceived direction of motion have involved stimuli in which the bias in the perceived direction of motion is greater in the periphery than in the fovea. We have developed a stimulus for which the converse is true. Yet the results of this study can be explained by a model that also explains the results of previous work on the perception of direction of motion. The stimulus consists of a vertically moving pattern of dark and light vertical bars, that are phase shifted at regular intervals to create a texture boundary. This phase shift line can be at various orientations. In the fovea, observers perceived motion that was nearly perpendicular to the phase shift line, whereas in the periphery, the perception was much closer to the true direction of motion. For a pattern with a phase shift line at 45°, the mean bias for three subjects was 40.9° in the fovea and 20.1° in the periphery.
Particulate sorting using matched filters
Authors: Coston Scott D. , George Nicholas
Published: February 2023

We present theoretical and experimental results using matched filters to sort between two classes of spherical particles. In particular, matched filters are used to distinguish between dielectric and metal spheres. Three separate light scattering regions are compared to identify the best scattering angles; these include the forward, the near forward, and the backscatter regions. Scattering theory is used to calculate the correlation and cross-correlation peaks for the pertinent cases in the output plane of the matched filter. An interesting finding that has not appeared in the literature is that the forward scattering region is an ineffective area in which to use a matched filter for distinguishing between these particles. Of the three scattering regions, the backscatter is shown to be the most effective.
Recovery of particle size distributions by inversion of the optical transform pattern
Authors: Coston Scott D. , George Nicholas
Published: February 2023

Experiments are presented for recovering the histograms of particle size from the optical transform intensity of spherical particles. We describe a novel inversion formula, and we provide computational details for obtaining particulate sizes from the transform intensity. The intensity is given by an integral over the size distribution multiplied by an Airy function (transform intensity for a single particle). The inversion formula is derived from the intensity using Bessel-delta identities and Abel transforms. By multiplying the intensity by an appropriate kernel and integrating over the diffraction angle, recovery of the particle size distribution is obtained. In the experiments, we use chrome masks with large numbers of tiny circular apertures of disks. These have been generated with three separate distributions: the gamma, the log-normal, and the bimodal exponential.
Alternate approaches to photolithiography
Authors: Hershel Ronald S.
Published: February 2023

Until now lithography equipment has focused on IC fabrication with a current startup cost for a wafer fab estimated at $200M, nearly a tenfold increase over the past decade. The reasons for this escalation are rooted in our approach to equipment development which focuses the majority of resources to leading edge technology, leaving used and outmoded equipment to late entries into the industry. An alternative approach to optical lithography tooling is presented that avoids the high cost of startups and is therefore more attractive to the global community. A steeper tool is required that features enhanced flexibility of the substrate and mask formats, greatly improved ruggedness and environmental immunity, and precise but simple control of metrology. New mask making techniques and strategies are needed which can leverage the current high cost of electron-beam mask fabrication and drastically reduce the requirements for mask inspection and repair. New techniques in product inspection and control of critical dimensions and overlay are needed to eliminate the routine use of expensive electron microscopes, defect inspection, and x/y measuring tools.
Catadioptric lithography lenses with beam splitter elements
Authors: Rosenbluth Alan E. , Singh Rama , Doany Fuad , Chastang Jean-Claude , Wilczynski Janusz
Published: February 2023

As wavelength decreases and numerical aperture (N.A.) increases, the bandwidth of available excimer lasers can most easily be matched using lenses that are catadioptric. Beam splitters allow such lenses to maintain high N.A. without obstructing the pupil or compromising the field size. We present a compact 0.6-N.A. 248-nm design with 30-mm field diameter. The most challenging element in this system is the 170-mm SiO2 cube beamsplitter. The dichroic beam splitter coating supports alignment at 364 nm, and operates in converging light over a 36° range without introducing aberration, apodization or image displacement. The cube is a good thermal insulator, and any index gradients arising from residual absorption in the prisms or coating will be traversed in a nonrotationally symmetric way, due to the folded path. Thermal modeling and gradient-index ray-tracing suggest an absorption tolerance of 1 % for the coating and 10% m-1 for the SiO2. We have obtained material meeting these tolerances. The beam splitter prisms can be strategically cut to minimize aberrations arising from residual SiO2 index inhomogeneities, which amount to 2 ppm in the best material we have obtained. An initial study suggests that optimal positioning of the cut surfaces can meet λ/5 wavefront and 20-nm distortion tolerances in a half-scale cube. Further correction can be obtained with external compensation. Other beam splitter-related issues are vulnerability to stray light in the presence of reflective surfaces at mask, wafer, beam splitter and mirror, and the effect of polarizing beam splitter coatings of lithographic imaging.
Scanning excimer ablation system
Authors: Goodman Douglas S. , Ainsworth Tom , Bobroff Norman , Chastang Jean-Claude , Doany Fuad , Lovas Steven , Myer Richard , Rand Rick , Rosenbluth Alan E. , Singh Rama , Surovic Chris , Tibbetts Ray , Wilczynski Janusz S.
Published: February 2023

A large-field scanning imaging system has been developed to perform imaging ablation with a 308-nm XeCl excimer laser as the sources. A 1× Dyson-type lens with a 12-mm field images a portion of a mask onto the part to be ablated. The numerical aperture is 0.05, so patterns as small as 6 µm can be formed. A plane mirror and a roof mirror are combined so that the object and image planes are parallel and their orientations are identical. The mask and part are held on a common stage, which moves in a boustrophedonic manner to transfer the entire pattern. The stage travel allows for parts as large as 250 × 250 mm2. The illuminated region is diamond-shaped, and adjacent scans overlap by half its width to obtain uniformity. The illumination system includes a hollow four-sided kaleidoscope to provide uniformity. Scanning further increases the uniformity by averaging over the field of the lens in one direction. Alignment is performed by optically combining images of mask marks and part marks formed by two pairs of microscope objectives, one of each viewing the part and the other viewing the mask. The illumination of the mask and part alignment marks can be independently optimized. Presently, the part is illuminated in darkfield reflected light and the mask with brightfield transmitted light. Registration to 1µm has been achieved over a region of 127 × 127 mm2. Focus is found with the alignment optics, whose numerical aperture is 0.4, giving it a depth of focus much less than that of the ablation lens. The part is levelled, focused, and registered relative to the image of the mask by a motion system with 6° of freedom that is mounted on the scanning stage. The excimer laser produces 300 W at 150 shots per second.
Nonlinear optical susceptibilities for surface-enhanced plasmon modes in metallic mircoparticles
Authors: Shen T. P. , Rogovin D. , Dutton T. , Rentzepis P. M.
Published: February 2023

Metallic microparticles are endowed with electronic transitions, in particular plasmon modes, that can be resonantly excited by visible laser radiation. Once these modes have been excited, they will amplify the laser electric field in the vicinity of the microparticle. This feature of microparticle electrodynamics has been utilized as an efficient mechanism for a variety of nonlinear optical processes, such as frequency mixing, phase conjugation, and beam combination. Furthermore, the electronic nature of these excitations ensures fast optical responses, typically of the order of picoseconds. We present experimental data and theoretical calculations of two-beam coupling in metallic microparticle suspensions which suggest that efficient beam combination is achievable with such media. The specific mechanism responsible for this optical nonlinearity is the electron quantum pressure that is localized near the microparticle’s surface. On physical grounds it follows that the smaller the microparticle, the greater the quantum pressure. Since the optical nonlinearity depends strongly on the particle volume, a plot of the optical susceptibilities vs particle size will exhibit a maximum at specific particle sizes. For two-beam coupling the optimum particle size is predicted to be near 30 Å.
Efficient TEM00-mode operation of a laser diode side-pumped Nd:YAG laser
Authors: Welford D. , Rines D. M. , Dinerman B. J.
Published: February 2023

Laser diode pumped solid-state lasers with high TEM00-mode conversion efficiencies have been demonstrated using both end-pumped1 and side-pumped2 geometries. However, side-pumped systems obtain their TEM00-mode quality through the use of pumping geometries that require tens of laser diode bars. Given the high cost of quasi-cw laser diodes, side-pumped lasers operating at the tens of millijoule level are cost effective only when pumped by as few laser diode bars as possible. Single-array (up to five bars) pump sources in side-pumped geometries3-5 have been unable to demonstrate efficient TEM00-mode operation. We describe a self-imaging side-pumped geometry with efficient TEM00-mode conversion using a single, five-bar, quasi-cw laser diode array as the pump source. We have demonstrated 23% slope efficiency and 11.8 mJ energy at 1064 nm for 64 mJ cf pump energy at 808 nm. This approach should allow efficient generation of TEM00-mode quality beams at energies up to several tens of millijoules, beyond which radially pumped rod2 geometries become more effective.
How to provide an environment to stimulate creativity
Authors: Hammond Donald L.
Published: February 2023

Summary not available.
Penta prism laser polarizer
Authors: Lotem Haim , Rabinovitch K.
Published: February 2023

A novel type of polarizer is introduced. These polarizers have high extinction-ratio, high transmission, and high laser damage threshold, hence they could be used in high power laser systems. The polarizers are shaped like a regular penta prism, thus they are a device of a constant angular deviation. The polarization effects occur upon the two internal reflections in the prism. Two types of polarizer are introduced: isotropic and unisotropic. The isotropic polarizer is made of high index refraction glass, coated with dielectric multilayer thin film systems. Due to the two internal cascade reflections, both the p- and s-rays have a high extinction ratio. The unisotropic polarizer is made of a birefringent crystal where angular polarization splitting is obtained from the bireflectance (double reflection) effect. In a prism made of a biaxial crystal, fanning of a laser beam into two to eight polarized beams is possible. These polarizers can be used in the UV, visible, and IR spectral regions. Theoretical considerations and examples are introduced and discussed.