bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration of geometrical and physical optics concepts in optical modeling
Authors: Lawrence George N.
Published: February 2023

Geometrical optics, in spite of its relatively simple treatment of the properties of light, has proved to be extraordinarily useful for many types of system. Physical optics analysis using a complex amplitude description of the wavefront can, in principle, more accurately calculate the properties of many types of system. The greater power comes with greater complexity and increased cost of calculation. By artfully including paraxial and exact geometrical principles, physical optics calculations can more readily be applied to a variety of simple and complex optical systems. The series of diffraction operations needed to propagate through an optical train can be associated with the paraxial properties plus the addition of aberration. Conventional lenses and mirrors as well as unconventional elements such as GRIN elements may be treated in this fashion. The concepts of optical path lengths and reduced distances also play an important role in characterizing diffraction effects.
Diffractive analysis of optical systems in the nonparaxial/nonuniformly polarized regime
Authors: Gamiz Victor , Alleva Mario , Marshall Rhonda , Silva Antoinette
Published: February 2023

The diffractive analysis code oasis (optical analysis software for interactive systems) has recently been enhanced to treat optical systems in the nonparaxial and the nonuniformly polarized regimes. Incorporation of capabilities to model truly 3-D optical beam trains via exact ray tracing, allows the analyst the ability to assess the optical performance of exotic mirror geometries.
Double-passage analysis using the multiscale solutions for the high frequency random propagators
Authors: Mazar Reuven , Bronshtein Alexander
Published: February 2023

In location and remote sensing experiments there arises a number of effects related to the double passage of the backscattered field through the same random inhomogeneities as the incident one. To account for the correlation of the forward-backward propagating events, there is need of a measure in which the random information along the propagation path is preserved. For generation of the even statistical moments, the relevant measure is the two-point random function (TPRF) defined in the recently formulated stochastic geometrical theory of diffraction (SGTD). From this function, all even statistical moments can be generated. Here, we present approximate analytical solutions for the high frequency propagators based on the multiscale expansion asymptotic procedure applied to the stochastic partial differential equation governing the propagation of the TPRF. As a canonical double passage problem, it serves the case of a point source and a point scatterer. Together with the reciprocity conditions it allows the choice of an appropriate propagator and its application to arbitrary source-reflector configurations.
Recovery of turbulence-scattering distorted light by using phase conjugation
Authors: Tarng J. H. , Yang C.C.
Published: February 2023

A phase conjugate mirror can be used for correcting phase distortions of a wave field because it reverses the phase front of an incoming wave. However, if the phase distortions evolve into amplitude modulations of the wave, the recovery of the wave becomes difficult. In this paper we investigate the recovery of light which is distorted by turbulence scattering. When this scattering is weak, random phase modulations can be canceled when the light is returned from a phase conjugate mirror. However, when the turbulence scattering becomes strong the random phase modulations will evolve into random amplitude fluctuations. In this situation, the incident light on the random medium cannot be recovered. The standard deviation of a wave field, which has propagated through a turbulent medium, reflected by a phase conjugate mirror, and again passed through the same turbulent medium, is evaluated. A zero or small standard deviation implies good recovery of the light.
Optical disk-based neural network
Authors: Lu Taiwei , Choi Kyusun , Wu Shudong , Xu Xin , Yu Francis T. S.
Published: February 2023

The rapid growth of optical disk storage techniques provides an advantage for optics in large capacity information storage and processing. Here we propose an optical disk-based neural network architecture for high speed and large capacity associative processing. The interpattern association (IPA) neural network model is used to generate the tristate interconnection weight matrices (IWMs). Each IWM is stored in two blocks (i.e., positive and negative matrices) on the disk, and read out in parallel by separate pulse laser beams. The two readout beams are encoded in perpendicular polarizations and then directed to a parallel optical matrix-vector processor, which consists of a lenslet array, an input SLM, and two photodetector arrays. Parallel buffers and a postprocessing circuit would be used to alleviate the electronic bottleneck to some extent.
Injection locking of a 5-W Nd:YAG ring laser
Authors: Nabors C. D. , Farinas A. D. , Day T. , Gustafson E. K. , Byer R. L. , Yang S. T.
Published: February 2023

We have used injection locking to force a 5-W lamp-pumped cw Nd:YAG ring laser at 1.064 µm to run in a single axial mode and with essentially the same spectral quality as the 40-mW diode laser-pumped Nd:YAG master oscillator.1 The Pound-Drever rf sideband technique was used to servo control the slave laser cavity length to maintain the injection locking condition. The locking range was measured as a function of master/slave power ratio and was in good agreement with theory. To protect the master oscillator the slave laser was forced to run in a single direction with an intracavity Faraday rotator, although unidirectional operation of the slave laser could be obtained by injection locking. We measured the rms phase noise of the locked system compared to the master laser to be 0.3 rad in a 10-kHz bandwidth.
Complex colloidal suspensions for enhancement and frequency tuning of the nonlinear response
Authors: Schuster P. R. , Viands C. A. , Potember R. S.
Published: February 2023

Interest has increased for the development of materials with large third-order nonlinear optical characteristics. Spatially isotropic materials, such as colloidal suspensions, have demonstrated that their dominant nonlinear response arises from third-order terms in nonlinear susceptibility. Measurements of this nonlinear behavior have been made for many different colloidal materials suspended within a dielectric matrix. Conductive particles and semiconductor microcrystallites show a strong and fast nonlinear response when irradiated with energy near the surface plasma resonance. Due to this frequency dependent behavior, these suspensions are limited in terms of their bandwidth. Suspensions of dielectric spheres (index of refraction different from the matrix material) have also shown nonlinear optical behavior, but the mechanism is entirely different. Movement of the spheres results from the radiation force generated by the incident energy. These colloidal suspensions are broadband, however, their response time is orders of magnitude longer than that seen with the conductive particles. The research to be presented involves the development of a suspension comprised of different colloidal materials (including organometallics). This complex suspension must maintain the critical optical properties of each component, while combining them with one system.
Gain and noise characteristics of a Brillouin amplifier
Authors: Scott A. M. , Tapster P. , Watkins D. E.
Published: February 2023

We have studied the gain and noise characteristics of a Brillouin amplifier, both when it is used to amplify weak signals and when it is used for phase conjugation. The amplifier consists of a 20-cm long cell filled with TiCl4 which is pumped by a 25-ns pulse from a near diffraction-limited injection seeded Nd:YAG laser. The Brillouin gain is given by G
B
= exp(gIpL), where I
p
is the input pump intensity; and gains in excess of 109 have been measured for signals of 500 fJ. The observed signal-to-noise ratio is 85:1; within a factor of 16 of the theoretical limit. In the absence of a signal, the output noise is observed to vary as Nout = N
o
G
B
/g, where N
o
is a spontaneous scattering term equivalent to an input noise signal. When an aberrator is placed in front of the beam, the intensity of noise which is conjugate to the pump beam is enhanced by a factor J > 2, i.e., Nout pc = N
o
G
J
/Jg. The enhancement factor depends on the speckle in the pump beam, and observed values of J > 3 are larger than predicted by theory.
Transverse instabilities for counterpropagation in Kerr media
Authors: Firth W. J. , Fitzgerald A. , Pare C.
Published: February 2023

In a Kerr medium with instantaneous response, pure counterpropagation of scalar plane waves is dynamically stable because of conservation laws. Inclusion of diffraction provides extra degrees of freedom, and both plane waves and Gaussian beams become unstable against transverse modulation when counterpropagating in a Kerr medium, even with no explicit feedback. The spontaneous spatial patterns which emerge may be dynamic or static but are frequently metastable, often persisting for hundreds of transit times before changing. Stability analysis leads to an interpretation as a generalization of phase conjugate oscillation to the Raman-Nath regime, in which formed and backward four-wave mixing terms are important, and can lead to lower thresholds than in the Bragg regime. Thresholds are also often lower than for the plane wave instabilities found when, e.g., finite response time or field polarization are incorporated, so that these theories will often be incomplete without transverse effects. Some existing experimental observations may be ascribable to transverse instabilities, even in more complex configurations such as resonators.
Real time optical 2-D array logic operation using two-wave mixing in photorefractive crystals
Authors: Xu Huai Fang
Published: February 2023

When coherent optical beams cross in a photorefractive crystal such as BaTiO3, SBN, there is an automatic 90° phase shift between beams A and B at the place of maximum refractive index of the photorefractive grating, because there is a 90° phase shift between the grating and the interference pattern of two beams A, B (A, B also indicate the amplitude of beams A, B). Because of the energy conservation law there is a 90° phase difference between A
t
and A
d
, Bt and B
d
(beams A and B will be divided into transmitted beam A
t
, B
t
and diffractive beam A
d
, B
d
, respectively).
Critical flicker frequency as a function of photopic luminous flux across the human visual field
Authors: Raninen Antti , Franssila Rauli , Rovamo Jyrki
Published: February 2023

Using the method of adjustment and a panel of 256 LEDs (dominant wavelength 640 nm) mounted in a solid, black enclosure and covered with a white diffusion screen, we measured CFF to cone stimuli (sinusoidal luminance modulation of 30%) across the temporal visual field at three different levels of retinal illuminance (1970,123, and 25.0 phot, td) produced by inserting neutral density filters (Lee) in front of the panel. Retinal illuminance was constant at all eccentricities studied because retinal area per one solid degree of visual field and effective pupillary area decrease similarly when eccentricity increases from 0° to 80°. The stimuli were M-scaled1 to keep the number of ganglion cells stimulated at various eccentricities approximately constant (4400 cells). M-scaling was obtained by reducing the viewing distance in inverse proportion to the sampling density of ganglion cell receptive fields across the retina. CFF was found to increase monotonically with eccentricity but the increase was the steeper the higher the level of retinal illuminance, in agreement with our previous results.2 However, when plotted in double logarithmic coordinates, CFF was found to increase as a single linear function of photopic luminous flux (F) collected by retinal ganglion cells: CFF = 18 × F0.22 (r2 = 0.945). Flux was calculated by multiplying retinal illuminance with Ricco's area that provides an estimate for the average area of the human ganglion cell receptive field center at various retinal locations.
Performance limitations of IR detector materials: a technology comparison
Authors: Kinch Michael A.
Published: February 2023

No summary was available at press time.
Photoinduced absorption spectroscopy as a probe of electronic states in high Tc material systems
Authors: McCall R. P. , Ginder J. M. , Leng J. M. , Ye H. J. , Epstein Arthur J. , Farneth W. E. , McCarron E. M. , Shah S. I.
Published: February 2023

Optical and infrared absorption and photoinduced absorption studies of the high T
c
families of materials give insight into the types of charged excitation existing in these materials, as well as the nature of their ground states and mechanisms for superconductivity. Near steady state photoinduced optical absorption spectra on thin films and pressed KBr pellets of YBa2- CU3O7-δ for δ ~ 0.7 show two absorption peaks below ~1.5 eV and a crossover to photoinduced bleaching at higher energies. Photoinduced infrared spectra reveal several absorption and bleaching modes and a broad electronic transition centered at ~1000 cm-1. The photoinduced bleaching modes correspond to direct absorption modes of the semiconducting YBa2Cu3O6.3 material. The photoinduced absorption modes correspond to direct absorption modes of the superconducting YBa2Cu3O7 material. The presence of the photoinduced IR modes and the higher lying absorptions and bleachings shows that long-lived, stable electronic defect states lying within the energy gap are created.
Nonlinear systems based optical neural net architectures
Authors: Liu Hua-Kuang , Barhen Jacob , Farhat Nabil H.
Published: February 2023

To increase the storage capacity of the Hopfield-type neural network, the spurious states need to be reduced or eliminated. Recently, a new type of attractor called a terminal attractor, which represents singular solutions of a neural dynamic system, has been introduced1 for the elimination of spurious states in associative memory. These terminal attractors are characterized by having finite relaxation times, no spurious states, and infinite stability. They provide a means of real time high density associative memory applications and potential solutions of learning and global optimization problems. The original terminal attractor model assumed continuous variable representation of neural states in the neural dynamic equations. Also, sigmoidal thresholding functions are assumed. These assumptions present difficulties for optical implementations. To implement the terminal attractor model, we have made modifications to incorporate this model to the associative memory system.
Analyses of optoelectronic heterodyne detection
Authors: Ih Charles S. , Du X. C.
Published: February 2023

The use of APD for optoelectronic heterodyne detection (OEHD) for a rf modulated lightwave has been reported.1 In OEHD, the APD is used both as an optical detector and frequency downconverter (mixer). Since the gain of the APD is a nonlinear function of the bias voltage, the inclusion of a rf local oscillator with dc bias will convert the incoming rf modulated optical signal directly into an electrical IF current. We call this method electronic injection. We have also investigated the OEHD using a rf modulated optical beam injection or simple optical injection. The strong local rf modulated optical beam will cause the effective bias of the APD to vary with the local rf, thus achieving OEHD.
Femtosecond time-resolved studies of desorption from a surface
Authors: Budde F. , Heinz T. F. , Loy M. M. T. , Misewich J. A. , Smith B. D.
Published: February 2023

Desorption induced by pulses of visible light of 200-fs duration has been investigated for the model system of nitric oxide (NO) molecules absorbed on a Pd(lll) surface. The nature of the desorption process has been examined through characterization of the final-state energy distributions (rotational, vibrational, and translational) of the desorbed NO molecules.1 Important observations include the high desorption yield and its strong nonlinear dependence on laser intensity, as well as the high degree of vibrational excitation of the desorbed NO molecules. These results indicate that the desorption process cannot be either a conventional thermal or a photochemical mechanism. Recently, direct time-domain investigations of the desorption process have been undertaken. These measurements are accomplished by a correlation technique in which the total desorption yield is recorded as a function of the separation in time between two equivalent excitation pulses. In this manner, a subpicosecond relaxation time is inferred. This finding is compatible with an electron mechanism for desorption but appears to preclude a desorption process based on vibrational excitation of the substrate. The nature of the desorption process will be discussed in terms of calculations of the electronic and lattice temperature of the Pd substrate induced by the laser radiation.
Color reflection holography of eight Munsell chips: theoretical and experimental treatment of the fidelity of color reproduction
Authors: Hubei P. M. , Solymar L.
Published: February 2023

We present a theoretical model that predicts the color of images in a color hologram recorded by three laser lights and replayed in white light. Effects of bandwidth and replay scatter noise are included in the model. The model is used to generate spectral power distributions, which are transformed into points on the 1976 Commission Internationale de l'Eclairage (CIE) diagram. Eight color-display holograms were recorded1 at the following combinations of wavelengths: 458, 488 nm (blue), 514,529 nm (green), 633,647 nm (red). The object used was an array of Munsell color chips, including the eight recommended by the CIE.2 The holograms were reconstructed with a standard white-light source and were measured with a telespectrophotometer. Measured spectral power distributions of each Munsell-chip image were used to calculate points on the CIE diagram.
RGB upconversion laser pumped by single IR pump
Authors: McFarlane R. A.
Published: February 2023

Using a cw Ti3+:sapphire laser operating near 800 nm, to pump Er:YLiF4 and EnBaY2F8 laser crystals, we have obtained laser oscillation from upper levels 4I13/2,4I11/2, 4I9/2, 4S3/2, 2H9/2,4G11/2, and 2P3/2 of the Er3+ ion. We will summarize the observations to date, covering 0. 47-2.7 µm. Five of the upper laser levels are above the pumped level and therefore must require that cooperative energy sharing processes be occurring or involve a sequential absorption of two, three, or more pump photons, or both. To our knowledge, the laser at 470 nm is the first blue laser to be excited with a single IR pump. Previous reports of blue operation have required either a pair of yellow pump photons or a combination of a visible and a near-IR pump to achieve a cascade absorption pumping pathway. An examination has been reported by Xie and Rand1 of the appearance of instabilities that occur under conditions of nonlinear coupling between the several state populations. It appears likely from our observations, that for many of the above systems, an accurate description of the laser behavior will need this complex nonlinear analysis.
Canonical quantum theory of nonlinear optics
Authors: Drummond Peter D.
Published: February 2023

The classical theory of nonlinear optics is well established, owing to the seminal work of Bloembergen and others. In this theory, nonlinear coefficients are used to express dielectric properties in a unified way. A quantum-mechanical theory of this type is obviously desirable, allowing the calculation of quantum effects, without requiring a detailed electronic and molecular model of the dielectric. In current research that encompasses such effects as squeezing and photon antibunching, a coherent quantum theory is essential. This should include nonlinearities, inhomogeneity, and dispersion to be relevant to physical dielectric media.
Amplitude squeezing in second-harmonic generation
Authors: Bowler D. P. , Liu J. M.
Published: February 2023

A new method of amplitude squeezing a second-harmonic signal with negative feedback will be discussed. Negative feedback is known to produce amplitude squeezing in diode lasers.1 Previous studies of second-harmonic squeezing that did not include negative feedback predicted no squeezing to the sixth order in the low-conversion-efficiency limit2 and 3 dB squeezing in the limit of 100- conversion efficiency.3 By employing negative feedback, substantial squeezing is possible in the low-conversion-efficiency regime. Amplitude noise reductions in excess of 10 dB are possible. This approach does not require a resonant cavity to enhance amplitude squeezing. The squeezing dependence on key system parameters, such as second- harmonic photon number, will be discussed.
Transparency, depth, color, and contour
Authors: Nakayama Ken
Published: February 2023

I present a series of stereoscopic demonstrations to show that the perception of transparency is closely related to luminance, contour, and depth. An image region is seen as transparent if it is of intermediate luminance relative to adjacent image regions, if it is perceived to be in front of another region, and if it has a border that provides information indicating that a surface is visible through this region. Yet transparency is not a passive end product of these required conditions. If transparency is seen, a number of seemingly more elemental perceptual primitives such as color, contour, and depth, can be radically altered. Thus, with the perception of transparency, neon-color spreading becomes apparent, contours can disappear, and depth can be profoundly altered.
Refractive-index distribution within the crystalline lens of the rock bass and its variation with age
Authors: Campbell Melanie C. W. , Harrison Elaine M.
Published: February 2023

It has been postulated that the refractive- index distribution within the crystalline lens of the eye of the fish contains a core of constant refractive index. However, Campbell and Sands have shown that this would be inconsistent with the excellent image quality of the lens in the eye of a visual species of fish.
Enhancement of chiral assmmetry by multiple light reflection
Authors: Silverman M. P. , Badoz J.
Published: February 2023

The asymmetric response of a gyrotropic medium to left and right circularly polarized light, as manifested in specular reflection, provides (1) a sensitive test of the electrodynamics of chiral media and (2) a novel spectroscopic method particularly suitable for nontransparent chiral materials in microquanitites. The differential reflection of circularly polarized light, d = (IL-IR)/(IL+IR) (where IL and IR is the reflected-light flux of specialized polarizations), is ordinarily linearly proportional to the chiral parameter(s) and is of the order 105-10-6 for many materials. However, for total reflection near critical angle, d is a nonlinear function of the chiral parameter(s) and can exceed the above range by several orders of magnitude.1 This enhancement can be further increased by multiple reflection. For N passes at the critical angle from a weakly absorbing chiral sample, d is approximately N times greater than for a single pass. The enhancement factor is smaller than N to the extent that the incident angle departs from critical angle or N exceeds an optimal value. For sufficiently high N, the angular range of enhancement becomes too narrow to be of practical utility.
Methyl rotors in large molecules: probes of intramolecular vibrational relaxation and electronic structure
Authors: Pratt David W.
Published: February 2023

A methyl (CH3) group that is attached to a large molecule by a covalent bond adopts a preferred conformation with respect to nearby bonds and exhibits large-amplitude torsional motion. Both the preferred conformations and torsional motions are influenced by the local electronic environment. Additionally, the low-frequency torsional modes may couple to other molecular vibrational modes, providing a mechanism for intramolecular vibrational energy redistribution (IVR).
Cavity-enhanced emission in microdroplets
Authors: Campillo A. J. , Eversole J. D. , Lin H.-B.
Published: February 2023

Micrometer-sized transparent droplets act as natural high-Q cavities to visible light, and this paper shows them to exhibit strongly enhanced dye emission owing to cavity quantum-electrodynamic effects. A vibrating-orifice aerosol generator1 was used to produce a linear stream of virtually identical (less than 2 parts in 105 diameter variation) falling droplets 14 μm diameter, 10-5 M solution of Rhodamine 6G in ethanol; the droplets were excited by a cw argon-ion laser. Droplet emission was examined with a double 1 m Spex spectrograph and a photomultiplier. Recent development of elastic-scattering-size spectroscopy1,2 allowed identification of the various cavity modes contributing to the emission. This was necessary because of the different Q values and spatial properties of the resonant modes. Q values were calculated from Lorenz-Mie theory and were found to be consistent with observed fluorescence linewidths for the experimentally resolvable fourth-order modes. It was experimentally determined that Q's of only 103 were sufficient to observe sizable enhancements in the A coefficient. Lasing was observed to occur at reduced thresholds, e.g., 400 W/cm2 for fourth order modes having Q's of 2 × 103. This corresponds to a cavity induced enhancement in the B coefficient of 103.
Simulation of an optical diffraction grating with spontaneous emission
Authors: Tan Sze M. , Walls Daniel F.
Published: February 2023

The propagation of an atomic beam through a beam splitter or atomic interferometer involves solving the generalized Bloch equations for the motion of the atoms within an electromagnetic field. We describe a method for obtaining numerical solutions that include the effects of spontaneous emission and detuning during the period of interaction with the electromagnetic field and also during the free propagation between interaction regions. Results from the simulations will be presented.
Theory of atomic interferometers
Authors: Wright S. M. , Glasgow S. , Meystre P.
Published: February 2023

The deflection of a stream of two-level atoms by a standing-wave light field has been studied extensively, both experimentally and theoretically, because of its potential application in the building an atomic interferometer. Such an interferometer would have the atom de Broglie wavelength as its resolution limit rather than the light wavelength, as in conventional interferometers.
Focusing of cold neutral atoms: a Fresnel zone plate
Authors: Bigelow N. P. , Prentiss M. C. , Tennant D. , Bjorkholm J. E. , O'Malley M.
Published: February 2023

We have fabricated a free-standing transmission Fresnel zone plate for the focusing of long-thermal-wavelength neutral atoms. The zone plate was fabricated from a 0.7μm thick boron-doped silicon membrane. The pattern was formed by means of electron-beam lithography, and the final grating was generated by reactive ion etching. The zone plate is composed of 100 zones, the diameter of the outermost zone is approximately 80 μm. The zone plate is designed to focus incident atoms having a thermal wavelength of 17 Å into a 2000 Å spot at a focal length of about 1 cm. A maximum of 8% of the incident flux will be transmitted and focused into the primary spot with this design. The use of diffraction optics for the focusing of an atomic beam is novel in that it does not rely on any electromagnetic forces for achieving focusing. As a result, this approach can be used to focus any particle with a long thermal de Broglie wavelength.
Electron–hole competition in photorefractive materials with shallow traps
Authors: Tayebati Parviz
Published: February 2023

We present a steady-state solution of a model of the photorefractive that which includes donor shallow traps and deep traps with electrons and holes as charge carriers. Both electrons and holes are assumed to be photoexcitable from the deep traps. Holes may recombine only to the deep traps, whereas electrons may recombine to the ionized shallow traps or to the deep traps. Electrons trapped in the shallow traps may be re-excited thermally and optically. The grating in the shallow traps is in phase with the illumination pattern at low intensities and is out of phase with it at higher intensities. The intensity at which the switching occurs is determined in terms of material parameters and grating spacing. The phase of the charge grating in the deep traps is not a function of intensity but is only a function of the dominant charge carrier. These charge gratings do not vanish as grating spacing becomes infinitely large, although the sum of them vanishes thereby leading to no space-charge field. We will discuss the consequence of the intensity dependence of the phase of the shallow traps' charge grating on the value of the space-charge field in various regimes.
Photonic ring counter using cascaded symmetric self-electro-optic-effect devices
Authors: Lentine A. L. , Chirovsky L. M. F. , D'Asaro L. A.
Published: February 2023

We describe a photonic ring counter that demonstrates cascadability of symmetric self-electro-optic-effect (S-SEEDs) devices1,2at a bit rate of 12.5 Mb/s for conventional operation and at a bit rate of 27 Mb/s when the devices are operated as optical signal-sense amplifiers. In each of these two experiments, the average laser-diode power incident on each device was less than 650μW. The system switching speeds, which agree well with speeds calculated by using the measured switching energies of the devices, were limited by the laser power incident on the devices. However, saturation of the quantum-well material, which results in reduced contrast ratio and bistability width, prevented more laser power from being used. In spite of this, we expect that switching speeds of optical-processing systems using SEEDs will continue to improve.
Generalized exclusive-OR modules as a natural basis for fiber logic systems
Authors: Islam M. N. , Sauer J. R.
Published: February 2023

A generalized-exclusive-OR (GEO) module is a logical representation of ultrafast all-optical soliton-dragging gates that can be used for design purposes. We show that a GEO module is Boolean and connectivity-complete for a time-division-multiplexed system. Two GEO modules, can be interconnected as NOR and AND gates or broadcast and routing switches. A bit serial counter can be implemented with four GEO modules, and a time slot interchanger can be devised with two or three modules. Because GEO modules lead to minimal component implementation of some basic functions, they may be the natural basis for designing fiber-based logic systems.
Comparison between holographic and guided-wave interconnects for VLSI multiprocessor systems
Authors: Camp Jean , Morris James , Feldman Michael R.
Published: February 2023

The performance of guided-wave and holographic optical interconnects are compared to each other and to conventional electrical interconnects for use in high-performance very-large-scale integration (VLSI) parallel computing systems. The comparison is based on chip-to-chip communication within and between VLSI thermal-conduction multichip modules. The interconnects are evaluated in terms of maximum data transmission rate, power dissipation, crosstalk, and connection density as a function of the number of processors in the system. Previous comparisons between optical and electrical interconnects1 for intrachip communication neglected transmission line effects. Because of the range of interconnect lengths (1–10 cm), both transmission-line and lumped RC line effects must be taken into account for electrical connections. Also, the light propagation delay for both holographic and guided-wave connections are significant. Owing to the high index of refraction of guided-wave systems, they have a longer propagation delay than do free-space systems. Advantages and disadvantages of multiplexing several signals over the optical connections have been analyzed. Detector circuit amplifiers, optimal in the sense that they minimize total power dissipation, have been designed.
Effects of contrast of test and reference stimuli on stereopsis
Authors: Siderov J. , Harwerth R. S.
Published: February 2023

The effects of differences in contrast between test and reference stimuli on stereopsis were investigated. Stereoscopic stimuli that were limited in their spatial-frequency composition were presented on a single video monitor and were viewed through synchronized liquid-crystal shutters. The test stimulus was presented in the middle of the screen with reference stimuli above and below. Binocular disparity of the test stimulus was produced by programmable delay of the horizontal sweep for the video image of one eye. The first experiment measured stereoscopic thresholds for test and reference stimuli with identical spatial-frequency composition but with variable contrast. In agreement with previous reports, stereo thresholds decreased as contrast was increased. In a second experiment, the contrast of the test stimulus was fixed, and the contrast of the reference varied from zero to twice the contrast of the test. Stereo thresholds decreased until the contrast of the reference equalled that of the test, and then they became constant. In a third experiment, the binocular disparity of the reference stimuli was varied. Stereo thresholds decreased with contrast in the same way as in the first two experiments. Our results emphasize the dependence of stereoscopic vision on contrast for stimuli on or off the horopter.
Ferroelectric liquid-crystal tunable filters and displays
Authors: Sharp Gary D. , Chase Holden , Doroski David , Johnson Kristina M.
Published: February 2023

Ferroelectric liquid crystals (FLCs) are currently used in combination with fixed waveplates and polarizers to make rapidly tunable in (100 kHz to 10 MHz) optical filters. These include discretely tunable filters using bistable SmC* FLCs1 and continuously tunable filters using analog SmA* FLCs.2 Current work indicates that high-resolution, high-peak-transmission filters can be constructed with only liquid crystal cells and polarizers.
Diffraction properties of fixed gratings in photorefractive media
Authors: Gu Claire , Yeh Pochi
Published: February 2023

Although the holograms in photorefractive media can be manipulated dynamically, the stored holograms are partially erased by the reading beam each time the information is retrieved. There are situations where it is desirable to have holograms that can be fixed by physical processes. The diffraction of these fixed gratings is different from that of a simple Bragg scattering, because energy coupling between the reading beam and the scattered beam is caused by not only the fixed grating but also the photorefractive grating formed by these two beams.
Effects of a Gaussian beam on photorefractive materials
Authors: Xu Chibing , Statman David , McIver John K.
Published: February 2023

The band-transport model is used to study the effects of a cw Gaussian laser beam on photorefractive materials. Particular attention is paid to differences in behavior of the material with and without an applied electric field. In the steady state, without an applied electrical field, the effects of the light intensity, beam width and the photovoltaic term are discussed. The inclusion of the thermally excited carrier background is shown to be necessary in order to obtain reasonable physical results. When the intensity is low enough, our results agree with previous work in this area. When a de electric field is applied, the field in the illuminated area of the crystal is significantly below the applied field value. This results from the movement of the carriers under the influence of the external field. Outside of the illuminated area and near the electrodes the field is enhanced as a result of the power supply maintaining a constant potential difference between the electrodes. On the other hand, the application of an ac field amplifies the field in the illuminated region. This effect may be useful in enhancing the electro-optical effect, as well as other nonlinear optical effects.
Studies on the molecular genetics of tritanopia
Authors: Weitz C. , Miyake Y. , Shinzato K. , Montag E. , Nathans J.
Published: February 2023

Tritanopia differs fundamentally from other inherited anomalies of color vision. Its autosomal dominant tranmission1 implies a mechanism unlike that of protanopia or deuteranopia. Because people with tritanopis lack a measurable blue-cone electroretinographic response,2 the defect is likely localized within blue-cone photoreceptors. These findings suggest that a mutant gene product actively interferes with blue-cone function or viability. Could a mutation in the gene encoding the blue-sensitive visual pigment3 be responsible for tritanopia? To test this hypothesis we have used the polymerase chain reaction and denaturing gradient gel electrophoresis to screen for sequence variation in this gene in members of five families in which tritanopia appears in more than one generation. We have found three different single-nucleotide changes in affected members of four families that were not detected in control subjects of appropriate ancestry (p = 0.001, p = 0.003, and p = 0.003, respectively). Two of the changes encode different singleamino-acid substitutions and the third, a single-nucleotide deletion, disrupts a sequence likely to be important for proper splicing of messenger RNA. Expression studies of visual-pigment DNA constructs bearing these sequence alterations are in progress.
Optical Bistability in a MQW Etalon with Optical Half-wave Periodicity
Authors: McDaniel Donald L. , McInerney John G.
Published: February 2023

Optical bistability (OB) in passive nonlinear etalons such as those containing multiple quantum wells (MQW) of GaAs/AlGaAs is a promising alternative to other bistable optical switching mechanisms such as those which occur in semiconductor lasers and laser amplifiers [1]. Although OB in passive nonlinear etalons is somewhat slower, it is much more easily extendable to one- and two-dimensional arrays of switches. To realize this advantage, it is necessary to minimize the switching thresholds and optical absorption (and hence the power dissipation) in the MQW etalon. Following an approach which has already proven successful in reducing thresholds and increasing power efficiencies of vertical-cavity surface-emitting semiconductor lasers (VCSELs) [2], here we consider a MQW structure with several quantum wells (or closely-spaced groups of quantum wells) spaced one-half wavelength apart in the resonant cavity, positioned so that they align optimally with the antinodes of the standing wave optical field in the etalon. We have analyzed the system numerically using a wave propagation model in a thin-film matrix formalism. The spacers are assumed to have constant indices, the unsaturated QW absorption α0 follows the semi-empirical description of Chemla et al. [3], and the excitonic features saturate according to the simple rule α(I) = α0/(1 + I/Isat). In contrast to the situation where optically-pumped lasing occurs, here the spacers are non-absorbing and the input optical beam(s) for holding and switching are tuned close to the heavy-hole excitonic absorption peak in the quantum wells. As in the VCSEL, significant excitation of the quantum wells occurs primarily along the cavity axis, reducing the switching threshold. This reduction, together with the low background absorption of the structure, should enable efficient arrays of bistable optical switches to be constructed.
Diode-pumped Vertical-cavity Surface-emitting Semiconductor Lasers for Free Space Communication
Authors: McDaniel Donald L. , Li-E Li , McInerney John G.
Published: February 2023

Vertical-cavity surface-emitting semiconductor lasers (VCSELs) are potentially useful for fast optical interconnection between wafers, free-space communication and formation of coherent 2-D laser arrays. The use of resonant-periodic-gain (RPG) media, in which a series of gain regions (single quantum wells or closely-spaced groups of quantum wells) with half-wave optical periodicity is aligned with the antinodes of the optical standing-wave in the laser cavity, provides enhanced gain along the cavity axis and at the designed lasing wavelength. The result is a considerable reduction of parasitic transverse amplified spontaneous emission, and considerably improved laser thresholds and spectral behavior [1]. However, the structure is not amenable to longitudinal injection pumping, and hence alternative means of efficient pumping must be found to realize its practical advantages. For optical interconnects, transverse current injection is probably best. For high-power operation and long-distance free-space communication, however, the high electrical-to-optical power conversion efficiency (~20%) and good beam quality achievable using diode laser pumping [2] are advantageous. Here we describe the use of CW and quasi-CW 740-nm diode lasers and laser arrays to pump GaAs/GaAlAs and InGaAs/GaAlAs VCSELs. Power outputs of up to 90 mW were obtained by quasi-CW pumping of the latter devices, with pump spot diameters from 6-20 μm. Since these results were limited by the available pump power at 740 nm, improved structures optimized for 780-nm pumping will be described.
Photorefractive optical phase-sensitive detection
Authors: Woods C. L. , Khoury J. , Ryan V. , Cronin-Golomb M.
Published: February 2023

Phase-sensitive detection can be realized optically by using degenerate four-wave mixing in photorefractive materials. Phase-sensitive detectors or lock-in amplifiers use a reference-triggered phase-sensitive mixer followed by a time-integrating low-pass filter. Mixing the two signals gives sum- and difference-frequency outputs, and a low-pass filter extracts the difference frequency. The phase encoded in the photorefractive hologram relative to the reference beam provides the mixing, and the response time of photorefractive material provides the time integration. Correctly modulating only the phase of the reference beam at a period much shorter than the photorefractive response time eliminates the phase-conjugate beam. Then modulating the phase of the signal input beam in the same waveform, but at a slightly different frequency from the reference, produces an oscillating phase-conjugate intensity. When the modulation frequencies of the two beams are phase-locked, a stable phase-conjugate signal is obtained with an intensity determined by the relative phase shift. These optical phase-sensitive detection experiments agree with calculations from dynamic photorefractive theory for the phase-conjugate intensity.
Uncertainty-limited atomic position measurement using optical fields
Authors: Welch G. R. , Stokes K. D. , Schnurr C. , Gardner J. , Thomas J. E.
Published: February 2023

We are currently developing Raman-induced resonance-imaging techniques for ultrahigh-resolution position measurement and localization of moving atoms.1 We obtain transit-time-limited frequency resolution in intense spatially varying potentials, which correlate the atomic position with the Raman resonance frequency. The use of optical fields for the Raman region permits easy application to very small interaction volumes where extremely large spatially varying Zeeman shifts or light shifts (109-1012 Hz/cm) can be employed to achieve position resolution as high as 7 nm. This leads to quantum-mechanical limitations on the measurement accuracy.
Photorefractive two-beam coupling in barium strontium titanate, Ba1-xSrxTiO3
Authors: Garrett M. H. , Chang J. , Jenssen H. P. , Tuller H. L. , Warde C.
Published: February 2023

Barium titanate, BaTiCO3, has been extensively used for photorefractive applications primarily because of its large two-beam-coupling gain and self-pumped phase-conjugate reflectivity. Decreasing its response time is important for many optical information processing applications. High-temperature measurements of carrier mobilities in barium strontium titanate,1 Ba0.03Sr0.97TiO3, have shown an increase in their magnitude relative to barium titanate thus potentially reducing their response times.
Optical cross correlation for changing illumination conditions
Authors: Scholl Marija S. , Shumate Michael S. , Sloan Jeffrey A.
Published: February 2023

A semiautonomous roving vehicle is suitable for planetary exploration before the establishment of a human presence there. Such a vehicle uses cameras for acquiring visual input during daylight operations and low-light-level intensified cameras forscene input at night. It must, therefore, operate over a wide range of illumination. Solar illumination presents challenging input to the correlator because different portions of objects are illuminated, and shaded areas vary with the object-illumination angle.
InP-based opto-electronic integrated circuits for very high speed 1.5-μm laser transmitters
Authors: Lee T. P. , Lo Y. H. , Bhat R. , Grabbe P. , Bagheri M. , Iqbal M. Z.
Published: February 2023

Opto-electronic integrated circuits (OEIC's) have attracted a good deal of attention recently because they promise to have high performance, more functionality, better reliability, simpler packaging, and lower cost than discrete devices used today. Especially at speeds higher than 5 Gbit/s, monolithic integration of the semiconductor laser with the associated transistor driver becomes desirable, if not necessary, in order to reduce the parasitics due to bonding wires. In this talk, we describe the design considerations, operating chartacteristics, and performance of InP-based transmitter OEICs with very high speeds up to 10 Gbit/s. Two basic material technologies for the laser driver electronics have been investigated, namely, (1) GaAs-on-InP lattice mismatched system for GaAs MESFETs and (2) lattice-matched InGaAs/In-AlAs for MODFETs. In the former case, because of the relatively mature GaAs MESFET permormance InGaAs/InAlAs MODFET has been monolithically integrated with a λ/4-shifted DFB laser. A 3-dB modulation bandwidth of 19 GHz for the laser was measured. The transmitter OEIC can be operated at speeds as high as 10 Gbit/s. A tansmission experiment using this transmitter OEIC and a hybrid PIN-HEMT receiver achieved a distance of 29 km with a receiver sensitivity of -20.5 dBm at 5 Gbit/s. Issues concerning material and processing compatibility, performance trade-offs, and power consumption will be addressed.
Optimal twist and polarization angles for the reflective liquid-crystal light modulators
Authors: Lu Kanghua , Saleh Bahaa E. A.
Published: February 2023

On the basis of a model of the twisted nematic liquid crystal,1 we analyze the effects of the twist angle and the input polarization angle on the reflective liquid-crystal intensity modulator with a polarizing beam splitter. When the input polarization is parallel to the front molecular director of the liquid crystal, the conventionally used 45° twist has a theoretical maximum reflectance of only 81%. However, a 63.6° twist angle yields the highest efficiency (theoretical maximum reflectance of 100%). If the light source is not monochromatic and has a narrow bandwidth, the dispersion effect tends to re duce the contrast, so a tradeoff between contrast and sensitivity must be made. We show that a configuration with 65-75° twist has an efficiency close to 100%, with continuously increasing sensitivity, but decreasing contrast, as the input polarization changes from 0° to -30°.
Point response function measurements of Hughes liquid-crystal light valve
Authors: Stewart D. , Collins S. A.
Published: February 2023

We have made direct measurements of the point response function of a Hughes liquid crystal light valve. The measurements were made by illuminating the input with selected patterns and apertures and looking at the output patterns. We have also measured the overlap between two spots to find the spot separation required for uncorrelated operation.