bluuebunny/crossref_metadata_2025 huggingface dataset:
Octave-wide channels and their relation to natural images
Authors: Field David J.
Published: February 2023

One of the parameters that describes the spatial properties of cells in the mammalian visual cortex is the spatial-frequency bandwidth. Although there is some variation in the range of tuning (0.5–2.5 octaves), the physiological evidence supports the notion that the bandwidths of cortical cells increase as the peak sensitivity increases in spatial frequency; the bandwidths are roughly constant (in octaves) on a log-frequency axis. This study looks into the possible reasons for this type of representation in the mammalian system. One suggestion is that octave-wide bandwidths allow for an equal distribution of activity throughout the sensors of the code. This can be shown to be true for channels with equal peak sensitivities and images with amplitude spectra of 1/f-However, there are a number of ways to produce this equal distribution other than by octave-wide codes. In this study, a second possibility was explored. By using a Gabor-like code and a variety of calibrated natural scenes, statistical properties were described in terms of a space versus frequency representation. In such a representation, features in natural images (local regions where the phases are correlated) become spatially smaller and broader in spatial frequency with increasing frequency. This is not a necessary property of scenes in general, and some images will be described that do not show this property. Such images may be more effectively represented by codes that do not show octave-wide bandwidths.
Dark surface waves
Authors: Skinner Steven R. , Andersen David R.
Published: February 2023

We obtain analytic TE dark-surface-wave solutions to the nonlinear Helmholtz equation for the geometry of an interface between two dissimilar defocusing Kerr media. Solutions are derived in two dimensions and are in the form of eigenmodes of each of the respective nonlinear media; propagation constants are obtained by applying appropriate boundary conditions at the interface. The results show the range of independent and dependent parameters that will permit the existence of dark-surface-wave solutions, and they indicate that it should be possible to observe propagation of the surface waves with currently available experimental apparatus and materials. Novel applications of our results are foreseen in the areas of nonlinear optical switching and commimications.
Optimum condition of second-harmonic generation in a medium with the second- and third-order nonlinear susceptibilities
Authors: Choe Wonha , Caimi Frank , Banerjee Partha P.
Published: February 2023

Second-harmonic generation is investigated for a medium with second-and third-order nonlinear susceptibilities. All possible solutions assuming zero initial value for the second harmonic are obtained. Based on the analysis, the optimal condition for second-harmonic generation is deduced. A theoretical 100% conversion from the fundamental to the second harmonic is expected when the condition for phase optimization is met. Even when the condition is not satisfied, a possible best efficiency can be sought by estimating a figure of merit ΔT = (½|P|)|Δk/R–QR|, where R is the field intensity of input beam, Δk is the phase mismatch, and B and Q are combinations of the second- and third-order nonlinear susceptibilities, which depend on the angles between the optic axis and the input beam. Generally, as ΔT is reduced, a higher efficiency can be obtained. Hence, the concept of phase matching should be modified to that of phase optimization when the term QR is comparable with Δk/R. A higher efficiency will be obtained if the medium has higher B (i.e., the second-order nonlinearity) or if | Δk/R–QR | is minimized.
Novel polarization switching and beam-amplification effects in biréfringent nonlinear media
Authors: Khoo I. C. , Liang Yu
Published: February 2023

We present a detailed analysis of the parametric interaction between a strong and a weak coherent beam with a varying mixture of extraordinary and ordinary rays in nonlinear birefringent media, such as liquid crystals and photorefractive crystals. Through the induced refractive-index changes associated with scalar parameters, such as temperature and space-charge density, the e- and o-rays are energetically coupled, leading to beam amplification and polarization-switching effects. We present the explicit conditions for observing these effects and a detailed analysis of the feasibility of doing so based on experimental data on liquid crystals.
Zernike decomposition of the thermal blooming-induced phase variation for a Gaussian beam
Authors: Lee Myung H.
Published: February 2023

Thermal blooming is the critical phase-distortion degrading factor preventing a ground-based high-energy laser system from achieving a diffraction-limited irradiance profile at a distant target. Adaptive optical systems have been used to correct thermal-blooming-induced phase variation by applying the proper amount of each correcting mode (tilt, defocus, astigmatism, and coma) to the entire aperture. I have developed the analytical expression for these correcting modes,1 which are represented by Zernike polynomials for a uniform beam, and I have also explored the Zernike decomposition of phase variation for the Gaussian beam. In this paper, I present the analytic expression for the phase-variation decomposition for the Gaussian beam in the infinite and truncated cases. As a result, the expressions are reduced to error functions in terms of beam diameter, beam waist, and wind velocity. I compare these results with those of the uniform-beam case and obtain the steady-state limit, i.e., when the elapsed time is longer than the wind-clearing time.
Fast speed monocentric relay system
Authors: Shafer David
Published: February 2023

The Burch design of two concentric spherical mirrors is a simple relay system that is often used in the infrared region. It is corrected for third-order spherical aberration, coma, and astigmatism. For really fast speeds, however, its performance is limited by higher-order spherical aberration. This makes the design unsuitable for use in the deep ultraviolet, in which the fast-speed performance would not be diffraction limited. Permitting the two mirrors depart from concentricity can give much better performance on axis, but it introduces coma and greatly reduces the useful field size. This paper describes a new version of the Burch design, with two additional elements. The resulting catadioptric system is completely concentric and is corrected for third-, fifth-, seventh-, and ninth-order spherical aberration. A design for use in the deep ultraviolet, with a numerical aperture of 0.70, will be shown.
Teaching the behavior of lenses for finite ray heights and angles
Authors: Walther A.
Published: February 2023

Most undergraduate texts on optics suggest that a perfect lens would realize the Gaussian ray patterns for finite ray heights and angles. Maxwell, however, has already proven that this suggestion contradicts Fermat's principle. In this paper I show how students can be helped to develop a sense of the nature of real lenses by having them write short simulation programs that are valid for finite ray heights and angles. General-purpose programming languages, such as Pascal, C, and FORTRAN, can be used, as well as symbolic-mathematics software, such as Macsyma or Mathematica. These exercises are not time consuming; not more than a few dozen lines of code are needed. Several specific examples will be shown.
Photonic neural-network architecture based on incoherent-coherent holographic interconnections
Authors: Jenkins B. K. , Tanguay A. R. , Piazzolla S. , Petrisor G. C. , Asthana P.
Published: February 2023

An adaptive neural-network architecture is presented that incorporates (1) a simultaneous incoherent/coherent holographic recording and reconstruction technique that permits simultaneous updates of all weights in a multiplexed volume holographic interconnection during each iteration of a neural learning algorithm1; (2) a double-angle multiplexing arrangement in which each pixel of the object-beam spatial light modulator (SLM) is illuminated by a set of mutually incoherent beams, each at a different angle; and (3) optoelectronic SLM's for the neural input and training planes, each with dualchannel inputs and outputs.2 The architecture incorporates modularity; capability for lateral, feedforward, and feedback interconnections in a multilayer network; effectively bipolar signals and weights; and capacity to implement a variety of network models and supervised or unsupervised learning algorithms. Results of computer simulations and laboratory experiments on selected aspects of the architecture will also be presented.
Four-dimensional neural network architecture
Authors: Henshaw Philip D.
Published: February 2023

This paper describes a four-dimensional (4-D) optical-interconnect architecture that has the potential to provide much larger numbers of interconnects than can be achieved with electronics. Many applications require more interconnections than can be realized by using electronics (approximately equal to those of a stupid honeybee). For example, vision applications, including infrared search and track, may require more than 1010 interconnects and 1013 interconnects per second. This interconnect architecture makes use of holographic interconnects stored in spectral-hole-burning (SHB) materials. The use of holography and spectral selectivity provides access to the fundamental capacity of the material to achieve a large storage capacity of interconnect values. In addition to the three spatial dimensions available with volume holographic techniques, a fourth independent dimension, laser frequency, is available. Information can be stored and read independently at many laser wavelengths in SHB materials. Our 4-D interconnect concept provides a way to fold the access to the four spectral and spatial dimensions into a compact package. The use of four independent dimensions allows implementation of a completely general 2-D-to-2-D interconnect, which makes optimum use of the space-bandwidth product of the spatial light modulators that supply the input and training patterns.
Compact six-port optical reflectometer
Authors: Zhang Y. , Colef G. , Eichmann G. , Li Y.
Published: February 2023

A novel six-port optical reflectometer is proposed and demonstrated to measure the complex reflection coefficients of an optical component, such as an optical waveguide or a phase-conjugate mirror. This simple reflectometer architecture is composed of two cascaded Michelson interferometers. By using a scattering-matrix representation, it is found that the reflection coefficients to be measured must satisfy the three-cycle (performance) equations. For an optical implementation, adjustable high-quality mirrors mounted on microtranslation stages are needed to obtain a suitable phase relationship between two Michelson interferometers. A system calibration is also needed before a measurement, to determine the performance-equation parameters. After this calibration, by simply measuring the output optical power at the various reflectometer ports, the reflection coefficients of unknown optical components can be computed. In our experiment, two λ/10 (λ = 633 nm) mirrors were mounted on computer-controlled micropositioners and were placed at two of the six reflectometer ports. A λ/2 phase shift between the two interferometers was selected. Detailed descriptions of the reflectometer's model, its optical implementation, and preliminary experimental results will be presented.
Comparison of error diffusion methods for computer-generated holograms
Authors: Eschbach Reiner
Published: February 2023

Error diffusion (ED) is a powerful tool for the generation of binary computer-generated holograms (CGH's). Several modifications of the original ED algorithm have been proposed to incorporate the special requirements and assumptions present in CGH's. Examples are the method of Hauck et al., the method of Barnard, and the edge-enhanced error-diffusion algorithm. The different versions of the algorithm are compared for their application to computer-generated holography with respect to reconstruction errors and the overall brightness of the reconstruction.
Three-dimensional optical Fourier transforms
Authors: Pattison John H.
Published: February 2023

The optical Fourier transform need not be restricted to the praxial case; it maybe generalized to describe large-angle diffraction from weakly scattering space-filling objects. The three-dimensional optical transform is based on the geometry of the Ewald–Laue construction: (1) The object is illuminated by a plane wave k; (2) each plane-wave component k' of scattered light is focused at the point Mk' with respect to the object-space origin (M is a dimensional factor scaling the wave vector into a displacement vector); (3) the image at the focal sphere is translated by–Mk; and (4) steps 1–3 are continued while k is scanned through all directions. The resulting image contains the product of the object function's Fourier transform and fixed geometric factors. A simple optomechanical apparatus produces visible transforms by means of limited k scanning above the ocular flicker rate; the demonstration is pedagogically potent. Applications include mapping of diffraction data into reciprocal space without electronic processing of data. Current research invokes Fourier-plane holography to form tomographic images from diffractometric data entirely through optical processing.
New masks for complementary source-pupil filtering
Authors: van der Gracht J. , Rhodes William T.
Published: February 2023

Rhodes and Koizumi1 introduced the complementary source-pupil filtering system, which performed contrast and edge enhancement and exhibited good immunity to coherent artifact noise. In addition, some simple spatial filtering was demonstrated. Their system is partially coherent, and the nonlinear equations describing its behavior do not provide much insight. We introduce two useful classes of masks for use in complementary source-pupil filtering systems that have simple analytical models. The first class of pupil masks is a random array of dark spots on a clear background. Low-contrast objects illuminated by the complementary source yield high-contrast images with no sign of speckle noise. The system can be approximated as a high-pass coherent spatial filter followed by an incoherent system in which the optical transfer function is determined by the pupil mask. The width of the individual dark spots determines the width of the stop band of the high-pass coherent system. The second class of pupil masks is a regular array of dark spots on a clear background. The complementary source produces images with reduced contrast and removes square-wave terms with a spatial frequency determined by the spacing of the dark spots. The system can be modeled as a coherent system designed to notch a particular spatial frequency followed by a clear-aperture incoherent system.
Diode laser arrays
Authors: Scifres Donald
Published: February 2023

High-power laser-diode arrays have now become commercially available at cw power levels of 10 W and at quasi-cw power levels of as great as 250 W. This tutorial will address the operation and limitations of high-power laser diodes, including physics of operation, lasing wavelength, reliability, power limits, and modulation rates. New technologies, such as two-dimensional surface emitters and coherent laser arrays, will also be described, as will prospects for future developments and improvements.
Investigation of the diffusion processes during the waveguide fabrication by ion exchange in glass
Authors: Giebler K. H. , Rauch F. , Wagner W. , Singer C. , Fabricius N.
Published: February 2023

For exact modeling of integrated-optical devices by the beam-propagation method, for example, an accurate knowledge of the refractive index profile is necessary. Especially in the case of single-mode waveguides, optical measuring methods fail because their spatial resolution is too low.
Spectrometric investigation of the human ocular fundus
Authors: Schweitzer D. , Klein S.
Published: February 2023

A neu trend in ophthalmological diagnosis and therapeutic control is the spectrometric examination of the human ocular fundus. In collaboration with Carl Zeiss Jena an experimental ophthalmo- spectrometer was developed at the Department of Ophthalmology of the Friedrich Schiller University, Jena.
Evidence for an Electroretinogram Source at the Optic Disc
Authors: Sutter E.E. , Tran D. , Wu S.
Published: February 2023

A new recording technique for the electroretinogram is used to study the distribution of pattern electroretinogram components within the central 23° of the visual field. The main focus is on the first slice of the second order binary kernel (response to pattern reversal between consecutive stimulus frames). Its topography shows great nasal/temporal asymmetry in amplitude as well as wave form within the central 15°. The asymmetry is not seen in the local luminance response and there is no known anatomical or histological correlate. A two component hypothesis provides a plausible explanation. Both components have a relatively symmetrical distribution in amplitude and wave shape. However, the second component shows increased latencies that correlate with the length of the fiber bundle to the optic nerve head. This finding suggests a signal source in the area where myelination begins. The latency shifts are attributed to propagation delays in the unmyelinated nerve fiber layer. This hypothesis finds further support in the topographies of the two components. While the first component can be attributed to nonlinearities of the luminance response in the outer retinal layers, the second component shows further enhancement of the central response due to the increase in the ganglion cell to receptor ratio.
Quantum Correlation Between the Junction Voltage Fluctuation and the Photon Number Fluctuation in a Semiconductor Laser
Authors: Richardson W.H. , Yamamoto Y.
Published: February 2023

Quantum correlation between two observables are of fundamental importance in the measurement of quantum mechanical systems. We introduce here a new type of quantum correlation, that between the junction voltage fluctuation

v
^

n

and the external field amplitude fluctuation

Δ

r
^

, in a semiconductor laser. A measure of the correlation, which originates in the dipole interaction between the internal field and the electron-hole system, is given by

C

v
r

=

〈

(

v
^

n

Δ

r
^

†

)

s
y
m

〉

/

(

〈

v
^

n

2

〉

〈

Δ

r
^

2

〉

)

1
/
2

. At the pump rate required to produce a beam at the standard quantum limit (SQL), C
vr
is

−
1
/

2

, while classically the correlation is abscent. In the experiment, the amplified a.c junction voltage was combined with the voltage associated with the photocurrent, due to the output field, at a wideband 180° hybrid. Seperate measurement of the spectral densities of the sum and difference of the amplitude

S

v
n

±

g
r

Δ
r
=

(

〈

v
^

n

±

g
r

Δ

r
^

〉

2

)

taken from the respective ports of the hybrid TEE confirm, for the first time, that the correlation is negative. The relative electrical gain is denoted by g
r
. Additionally

S

v
n

+

g
r

Δ
r

was less than

(

〈

v
^

n

2

〉

+

g
r
2

〈

Δ

r
^

2

〉

)

. This is indicative of a quantum correlation, since the laser amplitude noise was already below the SQL. Furthermore

S

v
n

+

g
r

Δ
r

was less than

g
r

2

S

Δ
r

, indicating that the correlation already in the quantum regime has crossed the so called second threshold. The optimum measured C
vr
was −0.40 ±.02.
Optical Amplification in a Nonlinear Fiber Interferometer
Authors: Marhic M.E. , Hsia S.-H. , Jeong J.-M.
Published: February 2023

Optical amplification in optical fibers by means of degenerate four-wave mixing (DFWM) is studied by classical equations. A balanced interferometer is used to mix and separate the signal and the pump. Exact solutions are obtained even with pump depletion. If the cross-phase modulation is small, the signal power gain varies as the square of the pump self-phase shift. This gain can be sizable for moderate fiber lengths and laser powers, before the onset of stimulated Raman scattering. We have experimentally verified these calculations with a Sagnac interferometer, comprising a 300 m long polarization-preserving fiber, emitting pulses with 100-200 W peak power and 100-200 nsec duration. We have measured a signal power gain of 22 (13.3 dB); this value correlated well with a pump self-phase shift of 3π/2 measured in a separate two-wavelength experiment. This system can be used for squeezing fluctuations of the signal quadrature which is not amplified. We have performed a classical derivation of squeezing, based upon a geometrical study of the transformation of the signal phasor. The results are in agreement with those of more elaborate quantum-mechanical derivations.
Multiple Quantum Well Electron Transfer GaAs/AlGaAs Waveguide Modulator
Authors: Blum O. , Zucker J. E. , Chang T. Y. , Sauer N. J. , Divino M. , Jones K. L. , Gustafson T. K.
Published: February 2023

Recently a novel multiple quantum well heterostructure that uses bandfilling for intensity modulation has been demonstrated in which applied voltage transfers electrons from a reservoir into a quantum well. In this paper we report the first GaAs/AIGaAs waveguide modulator based on this concept. These modulators have high speed potential and are well suited to applications using high power AlGaAs lasers near 860 nm, such as optical data storage and pumping of miniature Nd:YAG lasers. The n-i-n waveguide consists of AlGaAs cladding layers enclosing five periods of the electron transfer structure and is cleaved to 490 pm. At 10V, the quantum well is empty and the waveguide is highly absorbing. As applied voltage decreases, the waveguide becomes more transmitting, as a result of both reduction in the quantum confined Stark effect (QCSE) and bandfilling due to electrons flooding the quantum well. The QCSE becomes prominent again at -10V consequently reducing the transmission. Bandfilling produces the most efficient modulation of 75:1 at 864.5 nm for a voltage swing -5V to 10V. The above phenomena are successfully interpreted in terms of the calculated energy band diagrams and the photocurrent spectra. Our calculations also indicate clear ways to improve the structure and enhance the performance.
A Model for Second-Harmonic Generation in Fibers Based on Anisotropic Photoexcitation of Defect Electrons
Authors: Anderson Dana Z. , Mizrahi Victor , Sipe John E.
Published: February 2023

We present a self-consistent model of anomalous second-harmonic generation in glass fibers. The model involves the interference of photoionization amplitudes arising from optical fields having frequencies ω and 2ω. The photoelectrons are emitted anisotropically with a dependence on the relative phase of the two optical fields. The simplest case is an interference between one-photon ionization at 2ω and two-photon ionization at ω. Fermi’s Golden Rule gives the rates,

ρ
˙

+

and

ρ
˙

−

, of electron emission in the positive and negative directions: where g(ω) is a lineshape factor, k and K|µ2|2 are the 1- and 2-photon rate constants. The photocurrent generated by the anisotropic ionization develops a space-charge field: where e
0
is 105 - 106 V/cm, depending on material parameters. The space charge field, in conjunction with χ(3) for the glass, produces a properly phase-matched χ(2). Energy considerations suggest that the interference is between higher order ionization processes; these also lead to a suitable χ(2). In the slowly varying envelope approximation the intensity of the second-harmonic field grows as a saturating exponential: The small signal gain G
0
is estimated to be on the order of 10dB/cm-consistent with the experimentally observed 0.1 to 6dB/cm.
Selection of optimal angles in ellipsometry and reflectometry
Authors: Weedon W.H. , McKnight S.M. , Devaney A.J.
Published: February 2023

Multiple angles of incidence (MAI) have been employed in both ellipsometry and reflectometry as a means of obtaining several independent measurements where multiparameter estimation of optical constants is involved. However, there exists no systematic investigation into the determination of a set of incidence angles and polarizations that are optimal in terms of reducing both random and systematic errors and minimizing correlations among the measurements. Several researchers have found configurations that give good results for certain problems using physical arguments, but a general procedure that applies to all cases has not been developed. We demonstrate that the multi-dimensional Cramer-Rao (CR) bound of maximum likelihood estimation theory gives a quantitative measure of the random and systematic errors and correlations in one canonical expression; hence it is an ideal candidate for selecting an optimal experimental configuration in both MAI ellipsometry and reflectometry. Maximum likelihood (ML) estimation theory is used for the inversion problem because the estimation error is known to approach the CR bounds asymptotically. Numerical examples are given to demonstrate the procedure and illustrate how the effect of both random and systematic errors on the material estimates may be reduced.
Dynamics of stimulated Brillouin scattering in an optical fiber
Authors: Gaeta Alexander L. , Boyd Robert W.
Published: February 2023

The temporal behavior of stimulated Brillouin scattering (SBS) in an optical fiber under continuous-wave excitation is studied. In the absence of any feedback, the temporal evolution of the Stokes light for laser intensities well above SBS threshold is extremely noisy with nearly 100% fluctuations. The origin of these fluctuations is the spontaneous initiation of the SBS process. The experimental results agree with a theoretical analysis that includes the stochastic density fluctuations in the material. In the presence of a small amount of feedback, such as from the fiber endfaces, the Stokes light exhibits a transition to deterministic behavior in which the output either can be free of any fluctuations or can oscillate at harmonics of the round-trip time of the fiber.
How to design a lens for manufacturing
Authors: Kreitzer Melvyn H.
Published: February 2023

The design of an objective for 35 mm photography is used to illustrate how manufacturing considerations determine the final forms of high volume consumer optics.
How to design optical systems using cost-effective manufacturing technologies
Authors: Broome Barry G.
Published: February 2023

The advantages and limitations of several potentially cost-effective manufacturing technologies are discussed. Design features unique to the various technologies and their relevant materials are identified, the application of optical design programs to desensitize manufacturing tolerances is demonstrated, and specific examples are described. The design process, from the specification through tolerancing and component testing, is considered. The emphasis of this discussion will be on the application of cost-effective manufacturing technologies to the design of optical systems. Hybrid glass/plastic machine-vision objective lenses, photofabricated lens arrays for imaging and energy transport systems, and diamond-turned null reflectors for interferometric testing are cited as examples of competitive optical systems design.
Quality function deployment: designing a world class product
Authors: Smythe R.
Published: February 2023

Worldwide competition has redefined the requirements for total product quality. Today's markets demand products that simultaneously meet customer requirements, are developed at an ever-quickening pace, and are produced at ever-decreasing costs. Achieving goals that were once conflicting demands a thorough understanding of the process of product development. Quality function deployment (QFD) is a systematized process of product development. It draws together the entire cross-functional product development team at the beginning of a project. Manufacturing, marketing, research and development, and engineering all work together to understand the customers' wants expressed in the customers' language. The team then uses a matrix approach to correlate the customers' wants with how the new product will meet these wants. This simple, though at times tedious, process forces cross-functional groups to communicate during product creation. In formulating the product definition, we have considered performance, manufacturability, critical components and tolerances, and, most important, the customers' requirements.
Beyond just-in-time
Authors: Bell J.
Published: February 2023

I will discuss briefly the evolution of CalComp's journey to World Class Manufacturing. The primary emphasis will be on why and how JIT was implemented, our success and failures, results to date, and where we are going in the future.
Decade of continuous improvements with Xerox that led to improved market performance and the Malcolm Baldrige National Quality Award
Authors: Bebb Barry
Published: February 2023

Management and technical continuous improvement processes initiated in the late 1970s that eventually enable Xerox to recover Market Share from Japanese competitors and to win the Malcolm Baldrige National Quality Award will be presented.
Color fidelity in digital printout
Authors: Chan Eric , Wang Shen-ge , George Nicholas
Published: February 2023

Using halftone techniques and additive color mixture notions, we have implemented different ways to obtain colors matching CIE specifications from hard-copy color printing devices. We also report on our similar studies for matching colors to the Optical Society of America uniform color scales. The range of color reproduction is obtained by determining the tristimulus values of the color primaries. As long as the given color is within this color reproduction range, it can be reproduced by selecting the proper color primaries and the required amount of each primary. For colors outside the color reproduction range, we compare different ways to make the closest match. We performed experiments in which we used a thermal-wax-print color image printer that was calibrated by a precision spectrophotometer. We describe the error in matching colors quantitatively in units of "just-noticeable differences."
Chromatic discrimination thresholds measured in terms of cone excitation
Authors: Miyahara Eriko , Smith Vivianne C. , Pokorny Joel
Published: February 2023

Chromatic discriminations were measured on two critical axes: one on tritan lines where the excitation level of S-cones varied at fixed L/M cone ratios, and the other along lines radiating from the point (1, 0) in CIE coordinates, in which the L/M ratio varied at fixed S-cone excitation levels. Color discrimination thresholds were measured on a color monitor for 20 starting colors with a dark surround or with an equiluminant white or yellow surround. Discriminations on L/M cone lines were best when the color was near the L/M cone excitation balance and were not affected by S-cone excitation level. The level of L/M cone excitation had no effect on discriminations by S-cones. When the S-cone discriminations were plotted as a function of the S-cone excitation of the starting color, the curve for the dark surround showed a basic TVI template. Discrimination with the yellow or white surrounds was better than discrimination for a dark surround when the S-cone excitation level of the starting color was near that of the surround. A further experiment indicated that S-cone discrimination for the colors whose S-cone excitation level was the same as the white surround was impaired when a gap was introduced between the starting colors and the white surround.
Poled NLO polymers: progress and perspectives
Authors: Möhlmann G. R.
Published: February 2023

Optically nonlinear side chain polymers with glass transition temperatures up to 150°C appear to be attractive materials for the realization of channel waveguide polymeric integrated electro-optical devices such as monomode phase modulators, Mach-Zehnder interferometers and 2×2 directional mode coupling switches. Polymeric thin film multilayer structures, serving as the basic building elements for the devices to be made, have successfully been produced. Monomode channel waveguides have been realized in these multilayers by applying the UV-bleaching method. By selection of the proper masks for the bleaching process, the desired device type can be made. Electro-optic coefficients of the order of 30 pm/V have been induced via electric field poling of the multilayers at temperatures around the glass transition temperature of the polymers. Phase modulators, intensity modulators, and space switches have been produced, requiring driving voltages of the order of 5 volts only. Intensity modulation depths of the order of 20 dB's have been achieved for the intensity and space switching devices. Optically nonlinear polymers with improved temperature stabilities are being developed, permitting the integration with opto-electronic chips and components such as diode lasers, etc.
Fourier-transform IR characterization of molecular orientation in poled polymer glasses
Authors: Molis Steven E. , Twieg Robert J.
Published: February 2023

The electro-optical activity of organic, nonlinear optical (NLO) systems in part depends on the extent of molecular orientation of the NLO moiety. In this investigation, the technique of using infrared absorption spectroscopy to characterize molecular orientation is introduced as a means of characterizing orientational order in poled polymer glasses. A quantitative understanding of this orientation can be used in modeling the field-induced orientation of a dipole as well as for determining the polarizabilities of new NLO substituents. In this initial investigation the orientation of organic guest molecules in corona-poled guest/host systems is investigated with FTIR spectroscopy. The guest molecules include 2-methyl-4-nitroanaline and 4-aminobenzonitrile. For compatibility, we usually used polymethylmethacrylate (PMMA) as the matrix polymer, and it is interesting that some of the PMMA substituent groups also exhibit field-induced orientation. Molecular orientation parameters and relaxation behavior of these systems will be presented.
Polymers with large and stable optical nonlinearities
Authors: Twieg R. , Willson C. G. , Yoon D.
Published: February 2023

Newly emerging polymeric second order NLO materials have the potential to supplant inorganic crystals as the materials of choice for a variety of applications in modem optoelectronics technology, especially when high speed modulation and switching is involved. The main advantages forseen for the polymer based materials are their large intrinsic figures of merit and their compatibility with and tremendous advantages for fabrication of complicated structures on large substrates. Significant regular and systematic progress has been made in the design and discovery of novel nonlinear organic chromophores with large microscopic nonlinearities and additionally, significant progress has also been made in the creation of active nonlinear waveguides by polling of these dyes in a polymer matrix. Ultimately, optoelectronic applications mandate integration of the optical and electronic components and, therefore, the optical materials must meet many of the same criterion that organic electronic materials already do. For example, issues of mechanical, dielectric, and thermal stability properties must now be considered. Our efforts to identify robust dye/polymer combinations will be discussed, particularly initial approaches involving covalent attachment of chromophores to crosslinking epoxy networks.
Picosecond all-optical switching in a GaAs quantum-well waveguide coupler
Authors: Likamwa P. , Miller A. , Park C. B.
Published: February 2023

The switching properties of the zero-gap directional coupler were investigated by using a picosecond mode-locked cavity-dumped Styryl-9M dye laser in a pump-probe configuration. Both pump and probe were collinear and focused onto one side of the overmoded waveguide structures. When the pump beam was completely blocked, the probe beam emerged from the one side of the coupler. When the probe pulses arrived just before (~20 ps) the pump pulses, the probe beam remained in the same side of the waveguide. However, when the probe delay was changed so that the probe pulses arrived slightly later than the pump pulses, the probe pulses were switched into the adjacent side of the output of the waveguide. The ratios of the intensities of the output spots were about 1:9 in both the switched and unswitched state. The probe delay was scanned in small steps in order to time resolve the switch times. The signal in the low channel was observed to rise while that in the other channel decreased within 1-2 ps. By scanning the probe delay over 6.7 ns, the recovery time of the nonlinear coupler was found to obey an exponential decay with a time constant of about 1 ns.
Synchronous upconversion
Authors: Zhao Xin Miao , McGraw Dan
Published: February 2023

The results of experiments with intracavity sum-frequency generation in a synchronously pumped Styryl-9 dye laser will be presented. An average power of 5 mW at 460 nm is generated by intracavity sum-frequency mixing of the 810 nm dye laser pulses and injected 1.06 μm pulses from a continuous wave mode-locked Nd:YAG laser. The sum frequency generation is done in a 5 mm long KTP crystal with 90° noncritical type II phase matching. The dye laser and sum-frequency tuning curves are presented. The double-pass 460 nm parametric gain is enhanced by introducing an adjustable intracavity dispersion. In parametric generation experiments outside the cavity, an 80% modulation of the double-pass sum-frequency gain is observed by using an adjustable dispersion. The reduced modulation observed intracavity is explained in terms of gain saturation and a dispersion-dependent cavity loss. The effect of the double-pass 810 nm parametric gain and loss on the pulse duration is observed, and the possibility of a parametric pulse compression and parametric mode locking is discussed.
What is a luminance channel?
Authors: Smith Vivianne C. , Pokorny Joel
Published: February 2023

Luminance is defined as the radiance of a source weighted by the spectral luminosity of the CIE standard observer. The definition requires the concept of linearity, formalized in psychophysics as Abney's law. Many psychophysical methods of assessing luminance obey Abney's law; the most famous are heterochromatic flicker photometry and minimally distinct border. These psychophysical functions are interpreted as summed cone activity. Implicit in this interpretation is the concept of a luminance channel, i.e., a specific neural channel, accessible by specific psychophysical techniques, encoding a sensory quality. The concept of a luminance channel has seen many uses in the visual literature. Four distinct interpretations can been differentiated: (1) A theoretical construct: a channel encoding the sensation of luminance, accessed by certain psychophysical techniques and obeying Abney's law. (2) A physiological construct: a neural channel in which specific cells encode luminance at successive levels in the nervous system. (3) An operational construct for stimulus specification: a visual stimulus that may be partitioned into separable luminous and chromatic components. (4) A psychophysical construct: a channel encoding a sensory quality, such as brightness or blackness/whiteness.
ON and OFF channels of the visual system
Authors: Schiller Peter H.
Published: February 2023

The receptors of the mammalian retina, which all hyperpolarize to light, make signconserving synapses with OFF bipolars and sign-inverting synapses with ON bipolars. Several hypotheses have been generated to explain this arrangement. To test them we applied the neurotransmitter agonist 2-amino-4-phosphonobutyrate (APB) to the retina, which selectively blocks the ON bipolars. Two kinds of experiments were carried out: In one, we examined the visual responses of single cells while reversibly inactivating the ON channel with APB. In the other, we assessed the visual capacities of monkeys before and after the ON channel was blocked. Our single-cell recordings show that the ON and OFF channels remain segregated in the geniculo-striate system until the striate cortex, where they converge. The center/surround organization of the retinal ganglion cells and the orientation and direction-selectivity of cortical cells are not produced by interaction of the ON and OFF channels but by the lateral inhibitory networks. The behavioral experiments identify two reasons for the emergence of the ON and OFF channels: (1) to make possible the central transmission of both light-incremental and light-decremental information with excitatory processes and (2) to enhance contrast sensitivity.
Physics of the magneto-optics recording and readout processes
Authors: Mansuripur Masud
Published: February 2023

Diffraction theory of magneto-optical readout, including the effects of high-numerical aperture and polarization will be discussed and results of numerical computations presented. Emphasis will be on diffraction from sharp edges of the grooves and boundaries of the domains. Discussion of the thermomagnetic recording process will include the latest computer simulation results concerning the dynamics of magnetization reversal.
Optimizing the signal-to-noise ratio from a magneto-optic head
Authors: Dewey Anthony
Published: February 2023

In a magneto-optic head with differential detection, the light level on the data detectors is determined by the ratio γ2 of a semipolarizing beam splitter. The different noise sources in the system are analyzed, and their dependence on γ2 is determined. It is shown how to use this information to choose the value of γ2 that optimizes the SNR.
Picosecond dark spatial soliton formation in bulk semiconductors
Authors: Skinner S. R. , Allan G. R. , Andersen D. R. , Smirl A. L.
Published: February 2023

Dark spatial solitons can be are launched in bulk semiconductors by using initial conditions with either odd or even symmetry. The odd condition is produced by positioning a glass platelet in one half of the incident 30 ps pulse, so as to produce a π phase shift, and it propagates parallel to the propagation axis. The soliton also narrows with increasing bright background intensity. Such behavior agrees with that theoretically predicted for fundamental dark solitons and is consistent with previous experimental observations of temporal fundamental dark solitons propagating in optical fibers. Nevertheless, such simple tests provide only limited evidence of soliton formation. A far richer experiment, also with an analytic solution in two dimensions, is to launch pairs of dark spatial solitons by using the even initial conditions.1 For such pairs, several propagation parameters were measured and good agreement with theory was obtained. They are as follows: transverse velocity versus wire width, contrast ratio versus transverse velocity, conservation of the number of dark structures, and soliton constant versus intensity. The observed phenomenon has applications in optical switching and communications.
Pseudorecurrences in two-dimensional self-focusing
Authors: Wright E. M. , Heatley D. R. , Stegeman G. I. , Akhmediev N. N.
Published: February 2023

The nonlinear Schrodinger equation (NLSE) has been studied extensively as a universal model for self-focusing (modulation) instabilities and turbulence. In one transverse dimension, and for a Kerr-type nonlinearity, it is well known that the NLSE has exact periodic solutions that show exact recurrent behavior of the field profile. In this talk we will discuss the corresponding problem for a saturable nonlinearity, including both one and two transverse dimensions. The saturation destroys the exact recurrences and leads to pseudorecurrences in which the field profile never quite repeats itself. We shall present numerical calculations of this behavior and discuss the way in which the pseudorecurrence is destroyed, leading to apparent turbulence.
Excursion areas of intensity due to a random optical wave
Authors: Kragh Frank E. , Phillips Ronald L.
Published: February 2023

The intensity of thermal light varies randomly. A short exposure image produced by thermal light will therefore exhibit speckle, i.e. it will have bright regions corresponding to high intensity and dark regions corresponding to low intensity. A coherent image of an object whose surface is rough on the scale of the optical wavelength (true for most objects) will have speckle patterns. The intensity at each point on the image is a combination of contributions scattered from different points on the object's surface, making the intensity random and producing speckle. The expected area of these speckle regions is calculated in this study. For the purposes of calculating its area, a speckle region is defined as an excursion area of intensity over a given threshold value. The statistical analysis involves the concepts of two dimensional levels crossings and the statistics and spatial spectral properties of the intensity. The analysis is general and estimates the area of each excursion region for any gamma distributed two dimensional random process. Applications discussed include coherent imaging, conventional imaging, and damage areas on laser illuminated materials.
Generalized formulation of stellar speckle interferometry
Authors: Navarro Rafael , Pérez-Rendón Antonio F.
Published: February 2023

Joint spatial/spatial-frequency energy representations are proposed as a powerful framework, allowing a generalized formulation of stellar speckle interferometry and related imaging techniques. There are four basic functions in this scheme, which are related to each other by Fourier transforms, and all of them being able to keep both high frequency information and phase after averging: The Product Function Pi (x,δx) = i*(x– δx/2) i(x+δx/2) of the image i(x); the Wigner distribution is Wi (x,u) = FT [Pi(x,δx)δx - > u; the Spectral Product Ki(u,δu) = I*(u -δu/2) I(u + δu/2) = FT [Wi(x,u)]x- > δu and the Ambiguity function Ai (δx,δu) = FT [Ki(u, δu)]u- > δx. Within this framework, most speckle imaging techniques appear to be particular implementations of a generalized method. For instance, the Knox-Thompson method consists of taking the average (u,u) of the short exposure frames i(x), for small values of u. However, in this joint formulation it seems to be more natural and direct to take the average < Pi(x,δx) > avoiding the computation of typically hundreds or even thousands Fourier transforms. Results of a realistic computer simulation of this particular implementation of stellar speckle interferometry are included showing good reconstructions.