bluuebunny/crossref_metadata_2025 huggingface dataset:
Classical and quantum-mechanical dynamics of the quasiclassical state of the hydrogen atom
Authors: Gaeta Z. Dacic , Stroud C. R.
Published: February 2023

We study the dynamics of a circular-orbit wave packet1 and find that it has both classical and quantum features. A circular-orbit wave packet consists of aligned, standard hydrogenic eigenstates of maximum angular momentum (l = in = n − 1), superimposed with a Gaussian weighting function. We calculate the uncertainty products in all three degrees of freedom and find that, as the quantum numbers of the constituent eigenstates increase, the uncertainty products tend toward h/2. The classical aspect of the dynamics displays itself during revivals, when a well-localized wave packet travels along a Kepler orbit, obeying the classical equations of motion. Spreading and revivals (including fractional revivals2) of the wave packet, which are manifestations of its quantum nature, are related to the nonlinearity of the hydrogen atom Hamiltonian. We study fractional revivals of the wavepacket in detail.
Wave packets in strong magnetic fields
Authors: Mallalieu Mark , Stroud Carlos R.
Published: February 2023

A numerical study of electronic wave packets for the hydrogen atom in strong magnetic fields is discussed. The energy eigenvalues and eigenstates used for the wave packet propagation are found with the group-theoretic techniques espoused by Delande and Gay.1 However, unlike the band matrix techniques used by them, we adopted sparse matrix techniques to minimize the storage requirements for the large number of states involved. Previous work on this problem has centered on spectroscopic information, such as energy level distributions for different magnetic field strengths. Recently, experiments by Yeazell et al.2 have demonstrated that it is possible to study highly excited states of Rydberg atoms in a different way by exciting localized wave packets with short laser pulses. In this way, the measurement of wave packets excited by the pump probe method of earlier experiments may be modelled in terms of the magnetic field problem. We will discuss the resulting wave packet behavior, such as localization and periodicity, and we will compare this method and a classical mechanics analysis.
First observation of phase-matched intrinsic second-harmonic generation in optical fibers
Authors: Kashyap Raman , Davey S. T. , Williams D. L.
Published: February 2023

Ever since Osterberg and Margulis1 reported the growth of second-harmonic generation in optical fibres, and the observation by Stolen and Tom,2 the question has remained: how is the initial frequency doubled light generated? In particular Stolen and Tom observed that pumping the fibre with 4.8 kW peak of 1064 nm radiation, the frequency doubled light grew in the LP2
ω
11 mode from the fundamental wavelength LP2
ω
01 mode. They noted that symmetry has to be broken by the nonlinearity for the even
ω
mode to odd2
ω
mode interaction to be observed. We have investigated the intrinsic nonlinearity in optical fibres by using phase-matched fibres and low optical powers. We postulated that the assymmetry of the nonlinearity which allows the observation of the LP2
ω
11 mode, will also allow the observation all the higher modes of the same order. It is practically impossible to fabricate a fibre which is phase-matched for the interaction, LP
ω
01 → LP2
ω
11. We therefore fabricated a fibre which was phase matched for the higher mode-interaction, LP
ω
01 →LP2
ω
12, and another for LP
ω
01 →LP2
ω
13. It has been demonstrated for the first time that the fibres frequency double 10's of milliwatts of CW 1064 nm radiation into the LP2
ω
12, and the LP2
ω
13 modes with no prior preparation of the fibre. These observations indicate that there is indeed an intrinsic χ(2) nonlinearity in the fibre, theoretically studied by Terhune and Weinberger3 which must therefore act as the source of the initial sh radiation.
Quasi-phase-matched second-harmonic generation in bulk germansosilicate fiber preforms
Authors: Lawandy N. M. , Selker M. D.
Published: February 2023

We have performed seeded preparation experiments on bulk Ge (3%) and P (0.5%) doped fiber preforms with a core region 1.5 mm in diameter. The experiments revealed no measurable changes in the second-harmonic background until the IR average power reached a peak intensity of ~9.5 GW/cm2 at the focal spot in the preform. This critical-intensity behavior has also been observed in highly controlled preparation experiments on fibers. This threshold behavior has been explained in fibers in terms of an optical delocalization mechanism.1 Sidelight studies on the preform revealed a sharp increase in the second harmonic over a 1 mm region, giving further evidence for the existence of a threshold. Using the effective length contributing to phase-matched SHG in the preform and a conversion efficiency of 2 10-7, we find an effective (2) 5 10-16 m/V.
Magnetic field effects in self-organized second-harmonic generation in germanosilicate optical fibers
Authors: Lawandy N. M.
Published: February 2023

One of the most striking experimental signatures of the efficient second-harmonic generation (SHG) effect in modified chemical-vapor deposition (MOCVD) germanosilicate glass is its critical dependence on the intrafiber IR intensity used for preparation. Previous work has shown that this threshold is extremely well defined in the fiber as well as in the bulk MOCVD material and is of the order of 10 GW/cm2. This critical behavior and the process of SHG have been explained in terms of an optically induced charge delocalization transition.1,2
Laser-induced etched grating on InP: thin-cell configuration
Authors: Grebel H. , Iskandar B. , Sheppard K.
Published: February 2023

Laser-induced photoelectrochemical (PEC) etching of semiconductor compounds offers the possibility of a maskless, simple-surface patterning process.1 The thin reaction cell configuration offers some advantages over bulk cells, among which are its ease of use and the potential for a true holographic etching process. In this configuration, an electrolyte layer of about 50 m is held by capillary action between a semiconductor wafer and a microscope cover glass. The cover glass face that is in contact with the electrolyte may be coated with a transparent conductor (such as indium tin oxide) to form one of the biasing electrodes. In previous works2,3 we have suggested that a nonlinear diffusion process governs the PEC reaction; oxide is built and then dissolves during the reaction. We now present findings on light diffraction from an etched pattern in a thin-film cell configuration. We suggest that indirect monitoring of the reaction process, such as light diffraction, be carefully interpreted owing to interfering parameters such as the existence of a reaction product layer.
Spectral changes produced in Young’s interference experiment
Authors: Wolf Emil , James Daniel F. V.
Published: February 2023

As was first predicted theoretically by Zernike in a classic paper1 and later verified experimentally by Thompson and Wolf,2 the fringes formed in Young's interference experiment reveal some of the spatial coherence properties of the light incident on the two pinholes. More recently, it was found that Young's interference experiment also provides information about its spectral-coherence properties.3-5 Conversely, the degree of spectral coherence of the incident light affects the spectrum of the light in the fringe pattern. However, a detailed study of the changes in the spectrum produced on super-posing two partially coherent beams does not appear to have been carried out. Our paper is concerned with this problem. We find that although only small changes take place with narrow-band light, drastic modifications in the spectrum can take place when the bandwidth of the incident light is sufficiently broad. Our analysis clearly distinguishes between the contribution due to diffraction and the contribution due to the state of coherence of the light incident on the pinholes.
Energy conservation in partially coherent fields
Authors: Gamliel Avshalom , Wolf Emil
Published: February 2023

Recent developments in coherence theory have shown that the spectrum of the field produced by a partially coherent source depends not only on the source spectrum but also on the spatial correlations of the source fluctuations.1 In particular, it has been found that some correlations may give rise to frequency shifts of spectral lines.2 Questions have been raised concerning energy conservation in such situations. In this paper we first discuss energy conservation laws pertaining to fields generated by sources of any state of coherence, and we use these fields to demonstrate that conservation laws are not violated when source correlations produce spectral changes in the emitted radiation. We also show that spectral shifts may be generated by isotropic sources, without violating energy conservation.
Power dissipation in lossy dielectric gratings
Authors: Kok Yon-Lin
Published: February 2023

The rigorous, coupled-wave approach is adopted to solve the electromagnetic scattering problem associated with a lossy-dielectric surface-relief grating. The general solution model describes both electromagnetic diffraction and power dissipation in the grating materials. I will present computer simulation results for gratings with rectangular and tri-angular groove profiles in which various values of grating material conductivity are assumed. As a limiting case of zero conductivity, the solution converges for lossless-di-electric gratings to the previously published result. I will show that the power conservation law is strictly observed when the individual diffraction efficiencies and the power dissipations in the lossy material are summed. This may be used to verify the convergence of the numerical calculations. Furthermore, the optical absorption coefficient (or penetration depth) was found to be a strong function of the incident wavelength. My results thus introduce a new kind of grating anomaly in light scattering by periodic structures.
Grain-size considerations for programmable optoelectronic multiprocessor interconnection networks
Authors: Kiamilev F. , Krishnamoorthy A. , Urquhart K. S. , Marchand P. , Esener S. , Lee S. H.
Published: February 2023

Programmable optoelectronic multiprocessor (POEM) architecture is based on wafer-scale integration of optoelectronic processing elements (PEs) and free-space optical interconnects.1 The strength of POEM machines comes from their efficient implementation of interconnections and the large degree of parallelism that is inherent in free-space optical interconnections. An important architectural feature of such a parallel computer is its interconnection network. An interconnection network is a system of optoelectronic PE switches and free-space optical links that interconnect processors in a parallel computing system. The complexity of the PE switch determines the tradeoff between electronic and optical interconnects. Previously, we have designed a POEM perfect-shuffle interconnection network using 22 PE switches and have compared its performance with a VLSI-based perfect shuffle.2 In this paper we extend our comparison to include larger PE switches (e.g., 44,1616, etc.), as well as and 22 PE switches realized by using optical gates, as is done in symbolic substitution. The basis of our comparison include system speed, volume, footprint area, and power consumption. In addition, we determine the optimal PE switch size for given optoelectronic technology parameters.
Vector-wave calculation of photonic band structures
Authors: Leung K. M. , Liu Y. F.
Published: February 2023

We use plane wave method that correctly treats the vector nature of the photon to calculate the photonic band structure of a medium consisting of a face-centered cubic array of spheres embedded in a host material. Results are calculated for various volume-filling fractions of spheres, f, and refractive-index ratios for both the dielectric- and air-atom cases. Variations of the effective long wavelength refractive index with f is in excellent agreement with experimental data.1 The band gaps for the air-atom case at the Land X-points in the Brillouin zone as a function of f are also in accord with experiments. In particular, we found the X-gap to go to zero for f = 0.66, which is close to the experimental value of 0.68. However, in the case of an 86% volume-filling fraction of air-atoms, we did not find a common gap, and this is in disagreement with experimental findings. The primary problem seems to be caused by symmetry, which requires the bands to be degenerate at the W-point. Extensive numerical calculations for refractive index ratios varying from 1/4 to 4 have not produced a common gap for the present model.
Maximization of the analog bandwidth of optical devices with nonlinear gain
Authors: El-Halafawy F. Z. , Abou-El-Enein A. A. , El-Halawany M. M. , Abou-Koura A.
Published: February 2023

The analog bandwidth of optical device (InGaAsP laser source ) with nonlinear gain is parametrically studied to maximize it.1 Thermal dependent optical parameters are considered.2 We have used the small signal model to investigate the steady-state optical harmonic response in order to enlarge the 3 dB point of the device. The peak at resonance, the resonance frequency, the gain crossover frequency, and the 3 dB frequency are related to the operating temperature and the injected currents simple quadratic forms. Both the optical gain and the carrier density at transparency are thermally expressed as exponential forms. The main feature of the obtained results is that as either the temperature decreases or the injected current increases, the resonance peak decreases and the above frequencies increase. The obtained theoretical variations are in good agreement with experimental work.
Soft-x-ray microscopy at the National Synchrotron Light Source
Authors: Kirz Janos
Published: February 2023

The absorption edges of important light elements (C,N,O) fall in the soft x-ray range. Consequently, with proper choice of the beam energy one can penetrate relatively thick specimens or ionize the core level of an atom on the surface. The recently commissioned soft x-ray undulator at the NSLS is a bright and tuneable source of 200800 eV radiation. Teams from the NSLS, Lawrence Berkeley Laboratory, IBM, the University of California at San Francisco, and the State University of New York-Stony Brook have been using it to develop several forms of microimaging, including scanning transmission microscopy, scanning photoemission microscopy, holography and diffraction. Coherently illuminated zone plates1 are used to form microprobes for scanning and as a source of spherical reference waves in Fourier transform holography. Three of the instruments have achieved resolutions in the 5070 nm range. Applications in biology include the study of whole cells and organelles, while work in surface science is just beginning to address the important problems of radiation-sensitive heterogeneous materials.
Raman amplifiers in a two-leg interferometer: quantum noise versus fringe visibility
Authors: Swanson R. C. , Battle P. R. , Carlsten J. L.
Published: February 2023

Quantum mechanics fundamentally requires any linear amplifier to introduce quantum noise onto the amplified signal.1 In the case of the linear Raman amplifier, the fully quantum-mechanical Raman equations give a precise prediction of how much noise is introduced.2 Understanding and testing this prediction is important not only from a practical point of view, where one might be interested in the conditions for which a signal can be amplified without distortion, but also from the fundamental point of view of understanding the quantum-mechanical Raman process. To test these predictions, we consider the specific case of a Mach-Zehnder interferometer with a Raman amplifier in each leg of the interferometer. The input signal is provided by a separate Raman generator. As the input signal is varied from a small input to a large input, the fringe visibility varies from essentially zero, indicating that the noise dominates the output pulse, to nearly unity, as the amplified input signal dominates the noise. Using the Raman equations, we find that surprisingly few photons are predicted to be necessary for the signal to dominate the noise. The present work is devoted to measuring these fringes experimentally.
Photon-photon scattering induced SHG in magnetized vacuum
Authors: Ding Y. J. , Kaplan A. E.
Published: February 2023

Photon-photon scattering in a vacuum1a is perhaps one of the most fundamental mechanisms giving rise to nonlinear optical effects.1b However, none of the previously proposed effects has been observed in the experiment.1b Recently, we have demonstrated the feasibility of new nonlinear magneto-optical effects in a vacuum that gives rise to optical second-harmonic generation (SHG) under the action of both strong dc magnetic field (Ho) and high intensity optical laser radiation available.2 Here we review practical aspects of possible experiment on the SHG in vacuum. Stipulating that signal-to-noise ratio is sufficiently high, e.g., =102, and using pulsed magnetic field H0 ~ 8 × 106 Gauss, one can obtain the least laser intensity of I1 ≃ 1014W/cm2. With such an intensity or even higher, the average number of detected photons per pulse nears unity. One can use averaging of photon counts over a few laser beam lines for a single pulse or/and over many pulses of laser. NOVA with λ1 ~ 0.35m or GEKKO XII with λ ~ 0.53 μm can provide the laser energy of 6-10 kJ/pulse in each of 10~12 beam lines. If all the beam lines are used, the probability of not observing any SHG photons can be as low as ~10-6-10-4. Using picosecond lasers, the number of pulses required to observe the effect is ~106-107. SHG from the plasma of the ionized residual gas becomes negligible compared with vacuum contribution when the vacuum pressure is < 10-5 torr.
Maximum-likelihood statistics of multiple quantum phase measurements
Authors: Braunstein Samuel L. , Caves Carlton M. , Lane A. S.
Published: February 2023

Recent theoretical studies have considered various possibilities for experimental measurements of phase using quantum states of a finite mean number of photons. Currently, the most experimentally accessible of these possibilities is an interferometric phase measurement using a squeezed state that has minimum variance for the phase quadrature; this possibility can yield, in principle, a phase measurement with uncertainty of order l/(mean number of photons). Shapiro, Shepard, and Wong1 (SSW) have proposed another possibility. They maximize the peak likelihood in an abstract measurement of the Susskind-Glogower phase operator, and they claim a phase sensitivity that goes as l/(mean number of photons).2 The SSW phase probability distribution consists of an extremely narrow peak sitting on a broad base that covers the entire 2 radians of phase; as a result, a single SSW phase measurement has poor sensitivity. Shapiro, Shepard, and Wong argue that their claimed sensitivity can be achieved in a sequence of measurements. We study the statistics of the maximum-likelihood estimator in a sequence of SSW phase measurements, and we report how the uncertainty in the estimator scales with the mean number of photons used in the entire sequence.
Visual classification of degree of vessel stenosis
Authors: Judy Philip F. , Nawfel Richard , Swensson Richard G.
Published: February 2023

This experiment measured human observers' ability to classify vessels with four degrees of stenosis that were rendered on film. The noisy image data simulated a radiologic image. One rendering linearly mapped the image data into optical density. With a second rendering, a threshold of 25% of maximum vessel contrast was applied before the mapping. The observers' classification responses were analyzed by an extension of the standard receiver-operating-characteristic procedure.1 The statistical efficiency of the observers was 0.55 (0.05 standard error) relative to a computer classification procedure on the same image data and 0.059 (0.023) relative to an optimum calculation. The observers' efficiency was higher with the threshold-rendered images and decreased only slightly as the displayed vessel contrast decreased by a factor of 64. Observers' classification of stenosis may be based primarily on the vessel's edge location, because the display manipulation that degraded gray-scale information (while sharpening edges) increased the observers' efficiency.
Spatial-frequency discrimination after pattern adaptation
Authors: Thomas James P. , Greenlee Mark W.
Published: February 2023

We explored the human observer's ability to discriminate changes in the spatial frequency of Gaussian-truncated sinewave gratings before and after adaptation to high-contrast gratings. The Weber fraction for spatial-frequency discrimination (f/f) was measured for one reference frequency (5 c/deg) as a function of contrast (0.020.32) at a photopic (270 cd/m2) luminance level. Thresholds were estimated before and after adaptation by means of a maximum-likelihood procedure (the BestPEST). Adaptation was for 200 s, with 15 s readaptation after each trial. As was found in earlier studies, f/f decreases monotonically with increasing contrast and approaches an asymptote at contrast levels of 0.030.05 in the unadapted state. After adaptation to a 5 c/deg, high contrast (0.7), counterphase flickered (5 Hz) grating, the function relating f/f to log-contrast shifts to higher contrasts, but the shape of the function and the asymptotic value of f/f do not change. Adaptation to gratings of other spatial frequencies produces smaller shifts. These findings are in line with recent results by Sclar et al.1 on the effects of adaptation on V1 cells in the macaque.
Femtosecond Optical parametric oscillator
Authors: Edelstein D. C. , Wachman E. S. , Tang C. L.
Published: February 2023

We discuss our new femtosecond laser source which is tunable from the deep red to the mid-infrared.1 This is the first cw-modelocked singly resonant optical parametric oscillator and, we believe, the most broadly tunable femtosecond (or cw) laser in existence. It is based on parametric conversion in KTiOPO4 in a singly resonant, dispersion-compensated, and actively-stabilized cavity2 which is sync-pumped intracavity by a standard CPM dye laser. The desire for broad tunability, cw operation, and femtosecond pulses dictates the use of a thin crystal with a singly resonant cavity and, therefore, pumping with very high-peak intensities such as exist in a CPM cavity. This adds complexity, but results in a device which should be tunable over its complete phasematching bandwidth of 3.5 × 1014 Hz(720-4.5μm). This source provides ca. 100 fs pulses continuously at 108 Hz and mW average powers, diffraction-limited beams, and 3% rms noise; thus it is highly suited to typical pump-probe type measurements in condensed matter. Data characterizing the performance will be presented along with brief mention of the theory, design, alignment, and evaluation of alternative possibilities. Our first experimental results using this source for tunable ultrafast measurements of hot carrier dynamics in InGaAs and other compound semiconductors will be presented. A very broad range of semiconductors, color centers, and molecular systems may be accessed with this laser for both ultrafast and cw measurements.
Statistical theory of the multistable external cavity laser
Authors: Lenstra Daan
Published: February 2023

We develop a statistical theory for laser operation with external optical feedback. The theory is applicable to a broad class of singlemode lasers including gas lasers and semiconductor lasers. We introduce a characteristic potential function in which each minimum corresponds to a possible mode frequency, while the corresponding second derivative is an immediate measure for the linewidth. The minima in this potential are shifted in position with respect to the power maxima by an amount mainly determined by the amplitudephase coupling or linewidth enhancement parameter. This explains why in highly dispersive lasers the preferred and most stable mode is not the one with highest power. A diffusion model is developed in which the spontaneous emission related quantum fluctuations are the driving noise forces. This leads to a Fokker-Pianck equation for the phase probability distribution function, which is the key equation for investigating dynamical stability, lifetimes and switching times. We determine the stationary probability distribution and calculate external mode lifetimes and hopping rates.
Remarks on special relativity
Authors: Kauderer Mark
Published: February 2023

The canonical-operator approach to Fourieroptics1 has led to a new integral representation of special relativity that is different from either the Clifford algebra or spinor approach. An arbitrary Lorentz transformation can be decomposed into a rotation, a boost, and a translation. In my paper, the explicit forms of these parameters are derived, and some three-dimensional relativistic effects are discussed. In particular, it is shown that previous solutions of the Doppler effect have made unwarranted assumptions, have solved only an approximate equation, and/or have solved the problem implicitly instead of explicitly. The exact solution of the Doppler effect can be derived in a straightforward manner and generalizes the Wigner rotation to arbitrary velocities. It also provides a lower bound on the speed of the signal sent between source and receiver.
Theory for the dynamics of photosensitive gratings in optical fibers
Authors: An Sunghyuck , Sipe J. E.
Published: February 2023

Since the first discovery of the photosensitive phenomena in optical fibers by Hill et al.,1 there have been considerable efforts, both experimentally and theoretically, to understand the governing physical mechanism. The microscopic description of the formation of the photosensitive grating is still unclear. However, the experimental data appear consistent with the assumption that two-photon absorption leads to a modification in the growth of the grating. In this paper we study the dynamics of grating formation, taking into account the effects of boundary conditions at both ends of the fiber. The analysis is based on the coupled-mode equations for the interaction of two, oppositely propagating waves inside the fiber and the assumption that the dielectric constant changes owing to two-photon absorption. We solve the coupled, nonlinear partial differential equations analytically for various special cases of boundary conditions and discuss both the overall growth of the grating and oscillations in the reflectivity that appear as it develops. Our results are compared with numerical simulations.
Photoactivated refraction and oxide glass spatial light modulators
Authors: de Rochemont L. Pierre , Woods C. L.
Published: February 2023

It has recently been shown that amorphous solids can be used as volume holographic recording media by means of sufficiently intense write beams of the correct wavelength. Photoactivated alkali-ion migration has been found to be responsible for permanent grating formation in doped silicate and phosphate glasses. These experimental measurements1 used an argon laser for writing and a HeNe laser for reading, detecting both transient and permanent gratings. In GeO[2]-doped silicate glass,2 however, a UV absorption band was bleached with an excimer-pumped dye laser, resulting in prism effects and permanent grating formation that was observable at infrared wavelengths.
Changes in the peripheral pattern electroretinogram and visually evoked cortical potential with refractive error
Authors: Quinn Daniel F. , Armington John C.
Published: February 2023

We simultaneously recorded PERG and VECP responses from the visual periphery generated by an alternating checkerboard (0.3 checks, 89% contrast) under both steady state and transient conditions. Subjects viewed the stimulus through trial lenses of varying powers. The best-fit straight lines through the right sides of the amplitude versus dioptric-error plots had a slope of about 0.15 V/diopter for both the PERG and the VECP. These slopes can be compared to data from the center,1 where the PERG slope had about the same fall-off rate, but where the VECP slope was much greater at about 2.0 V/diopter. Thus, we find that the peripheral VECP is much less sensitive to blur than is the central VECP. This is consistent with results from psychophysical acuity experiments. When a stimulus to the fovea is blurred, acuity decreases very rapidly. On the other hand, in the periphery it does not matter whether refractive error is present or nob acuity is the same.2 This peripheral insensitivity to blur is now shown in the VECP.
Contrast sensitivity and contrast discrimination in human infants
Authors: Brown Angela M.
Published: February 2023

Poor contrast sensitivity is probably responsible for the poor color vision of infants. But, why is their contrast sensitivity poor? Is the deficit sensory, or is it due to perceptual and cognitive immaturities? Or, is it a methodological artifact?
Simulation of enhanced backscatter through a random phase screen
Authors: Welch Gisele , Phillips Ronald L.
Published: February 2023

There have been various studies of a propagating beam wave passing through a random inhomogeneous medium and then being reflected back through the same medium.1 The intensity statistics in the far field display an enhancement caused by the double passage through the medium. This enhancement occurs because of single or multiple inhomogeneities, depending on the mirror's position relative to the screen's focus plane. The enhancement has been confirmed in previous theoretical and experimental work. We have developed a computer simulation of this phenomenon, which is known as enhanced backscatter. Although there are many concerns with this phase screen, the assumption made in the simulation is that the phase screen has a power-law spectrum with an 11/3 spectral index. This simulation has been tested with theoretical work2 and has provided a useful tool to study different types of reflectors, along with the general enhanced backscatter configuration.
Diffraction analysis of antireflection surface-relief gratings on lossless dielectric surfaces
Authors: Raguin Daniel H. , Morris G. Michael
Published: February 2023

Antireflective surfaces have been the subject of a great amount of research. Typically, thin-film coatings are used to reduce or eliminate reflection losses, but in certain cases design constraints limit this method's practicality. In recent years, surface-relief gratings have been shown to offer a practical alternative. In the high-frequency limit, where all orders but the zeroth order reflected and transmitted waves are evanescent, surface- relief gratings exhibit extremely low reflectivities. This discovery is useful for many applications, including the design of photodetectors, solar cells, and IR optical systems.
Modified signed-digit higher radix arithmetic for optical symbolic substitution
Authors: Awwal Abdul Ahad S. , Karim Mohammad A. , Islam Muhammad N.
Published: February 2023

Modified signed-digit binary numbers have demonstrated the promise of carry-free addition. In this method, the to-be-added pair of numbers are mapped into an intermediate pair of numbers in such a way that when the latter numbers are added, they do not result in carry generation. The corresponding recognition and substitution operations, referred to as symbolic substitution, can be performed in parallel at all digit positions; thus, the method fits elegantly with optical computing architecture. Three-step, two- step, and single step1,2 carry-free addition based on optical symbolic substitution schemes have already been worked out for the binary system. In this paper, we extend the carry-free addition and borrow-free subtraction scheme to accommodate signed-digit trinary numbers by deriving the necessary substitution rules to perform additiort/sub- traction in two steps. A number of possible sets of rules exist for addition and subtraction. The reduced minterms are derived for a possible two-or three-step holographic content addressable memory implementation.1,2
Simulation of the effective second-harmonic generation process in optical fibers
Authors: Dianov E. M. , Kazansky P. G. , Stepanov D. Yu.
Published: February 2023

In this paper we propose a dynamic mechanism of efficient second-harmonic amplification in optical fibers and explain the existence of phenomenon thresholds. We start with the assumption that the second-order susceptibility grating appears in fibers because of the strong electrostatic field caused by coherent photocurrent.1 We have obtained equations for the amplitudes and phases of this grating and second harmonic that are similar to equations describing dynamic self-diffraction of light beams. We have shown that the phase shift of the grating relative to the "interference" pattern (the pattern of coherent photocurrent oscillations) leads to an amplification of weak second-harmonic seeding. Strong exponential growth takes place when this amplification is greater than the losses. We have obtained a threshold condition connecting pump power, distance from the fiber end, and time from the beginning of fiber preparation. We have shown that the value of the length threshold and the length dependence of second-harmonic intensity are different for various seed intensities because of the dependence of photoconductivity on second-harmonic intensity. The results of numerical simulation of the phenomenon are in close agreement with known experimental results.2
Anisotropic Gaussian-Schell model sources: a canonical operator analysis
Authors: Kauderer Mark
Published: February 2023

Canonical operators are used to generalize one-dimensional Gaussian-Schell model sources1,2 to include n dimensions, misalignment, and loss or gain. The extended ABCD method1,2 is further extended to the misaligned case. The parameter of global coherence is also generalized, and it is proven that its trace is an invariant after propagation through real ABCDEF systems.
Quantum beats from separated atoms excited by correlated photons
Authors: Silverman M. P.
Published: February 2023

Entangled multiparticle quantum states cannot be expressed as a product of singleparticle states; they can give rise to correlations between separated particles unaccountable within the framework of classical physics and are of considerable interest to those concerned with the foundations of quantum mechanics. Two separated identical atoms having, for example, two excited levels with energy interval h12 are brought into an entangled linear superposition of excited states by absorption of two correlated photons. The quantum description of either atom alone shows incoherently populated excited states; the single-atom emission probability shows no quantum interference. However, the joint probability for fluorescent emission manifests, as a function of the time interval between radiative decay of both atoms, quantum beats1 at frequency 12. This quantum interference is insensitive to atomic motion and atomic density, and it can be engendered by photons whose spectral widths are smaller than the beat frequency.
Symmetries that simplify design of spot-array phase gratings
Authors: Morrison Rick L.
Published: February 2023

Dammann gratings1 are diffraction gratings that produce replicated images or arrays of spots from an incoming beam of monochromatic light. This property makes them useful for image duplication applications and spot array generation in optical computing. The process of designing an appropriate pattern typically involves an optimization procedure; therefore, the primary limitation in designing gratings that produce complex arrays is the computational resources required. Fortunately, symmetry properties can be incorporated into the grating design, significantly reducing the number of independent parameters required to describe a solution. First, we will extend the use of the translation symmetries that were introduced to produce an even-numbered spot array from binary phase gratings.2 Then we shall describe other symmetry properties that may be used to reduce the complexity of locating an optimal solution set. These symmetry properties will be generalized to cover binary phase gratings, discrete multilevel phase gratings, and continuous phase gratings.
Cascadable optical shuffle-exchange network
Authors: Haney Michael W. , Levy James J. , Athale Ravindra A.
Published: February 2023

A cascadable shuffle-exchange network is proposed that couples the optical folded perfect shuffle (FPS) concept1 with modulator-based exchange/bypass switches and avoids the need for optical signal regeneration at each stage. The network is based on the optically efficient version of the FPS.2 For switching, the two-dimensional array of signals is processed pairwise. Each signal passes through a polarization-switching SLM pixel; rotated polarization corresponds to the "exchange" condition for a pair of signals. Exchanged pairs are routed, via a polarizing beam splitter, to an optical arm that uses imaging lenslet arrays to perform the pairwise exchange operation by inversion of the spatial locations of the elements of the pair. These signals are then recombined with those in the "bypass" arm, via another polarizing beam splitter, and the shuffled and exchanged signals are ready for input into a subsequent stage. Each of the cascaded modules in a multistage network would be identical and potentially made from inexpensive, replicated optics.
Stiles–Crawford effect improves defocused or aberrated retinal image quality
Authors: Zhang Xiaoxiao , Ye Ming , Bradley Arthur , Thibos Larry N.
Published: February 2023

Visual sensitivity is not uniform across the pupil. Sensitivity peaks near the pupil center and is reduced at the pupil margins (Stiles–Crawford effect or SCE). Is there any functional advantage derived from this property? The SCE can be considered equivalent to apodization of the pupil, but no functional value of this apodization has been observed for well-focused images.1-3 However, the most significant effect of SCE may be to increase depth of focus.4,5 Using a wave-optics model of the human eye, we incorporate apodization by changing the pupil transmission function from a uniform function into an SCE function. We calculate the influence of SCE on the OTF with defocus error or ocular spherical aberration. Our results show that (1) Stiles–Crawford apodization significantly improves contrast for defocused images for large pupils, and (2) The Stiles-Crawford apodization is also effective at improving image quality when the eye exhibits significant spherical aberration.
Diet-responsive blood-indexed risk factor for high myopia
Authors: Lane Ben C.
Published: February 2023

Previously 1 reported highly significant depression of the chromium-to-vanadium ratio in the nape hair of patients with myopia. It is associated with depressed accommodation and elevated intraocular pressure, both of which are associated with depression of insulin potentiation of glucose uptake by ciliary-muscle insulin receptors.1,2 In this double-masked cohort-panel study, chromium (Cr) and vanadium (V) were measured in red blood cells (erythrocytes). Of the first 184 patients, 27 were myopic (3 diopters) and 14 were hyperopic (1.25 diopter). I excluded patients less than 20 years old, patients taking chromium supplements, patients taking 1 g or more of ascorbic acid per day, aphakic patients, and patients with cataracts. Erythrocytechromium/erythrocytevanadi um (ECr/EV) ratios and ECr distributions and means were significantly lower in the patients with miopia than in the patients with hyperopia: mean SD ECr/EV = 0.150 0.150 for the myopic patients versus 0.731 0.472 for the hyperopic patients (t = 4.488, p), and ECr = 70.1 53.9 ng/ml for the myopic patients and 256.7 160.0 for the hyperopic patients. Foods rich in chromium include most unprocessed naturally sweet or starchy foods. Foods rich in vanadium include chocolate, kelp, mushrooms, most U.S. chow-fed poultry, and seafood larger than herring. To my knowledge, this is the first report of this red-blood-cell-indexed effect on human refractive development.
Automatic data reduction of ronchigrams
Authors: Alcala N. , Davila A. , Langrave E.
Published: February 2023

A ronchigram is captured in the optical workshop with a charge-coupled device (CCD) camera with 256256 pixels. The image of this ronchigram is processed by a micro-computer for smoothing and fringe-peak detection.1 The resulting fringe skeleton is sampled, and the sampled data are subsequently fed into a least-squares data reduction program.2 Preliminary tests for a 15 cm, f/2.3 paraboloid showed a /10 peak to valley and a/100 RMS repeatability. The whole testing procedure takes less than 8 min.
Low quantum noise interferometer system
Authors: Shirasaki M. , Haus H. A.
Published: February 2023

A simple way of realizing a phase-sensing interferometer for quantum noise reduction is to use a squeezed vacuum for the usually unused port.1 We previously proposed a simple way to generate an approximately squeezed vacuum.2 Our method is based on degenerate forward four-wave mixing, and it is advantageous because the phase-matching condition between the signal and the pump is automatically satisfied, and the operation is broadband. We also expect that the noise of a phase-sensing interferometer following our squeezer will be reduced.
Photon statistics of a weakly driven cavity QED system
Authors: Rice P. R. , Carmichael H. J. , Brecha R. J.
Published: February 2023

We present analytic results for the photon statistics of a weakly driven optical cavity containing N two-level atoms. The second-order intensity correlation function g(2)() is calculated in the weak field limit for arbitrary atomic and cavity loss rates, and cavity and atomic detunings are included. The transmitted light field may exhibit photon antibunching, sub-Poissonian photon statistics, and other novel nonclassical effects.1,2 The size of these effects depends principally on the single-atom coupling constant C1 = g2/κγ, so these effects persist with many atoms in the cavity. Our results can be interpreted via the collapse of the wave function and quantum interference of probability amplitudes. These phenomena can also be understood in terms of the self-homodyning of the driving field with squeezed polarization fluctuations.2
Electro-optically controlled waveguide grating switch
Authors: Hartman Nile F. , Twyford Elizabeth
Published: February 2023

An optical switch based on thick phase-reflective gratings and optical waveguides has been designed and tested. As a switch, the device offers both speed and high isolation. The switching mechanism relies on modulation of the grating diffraction efficiency by locally varying the average refractive index within the grating region of the waveguide. Electro-optic modulation of holographic phase gratings recorded in bulk LiNbO3 has been demonstrated previously.1 The performance of the bulk device, however, encounters severe limitations that are overcome by the waveguide design. In the waveguide configuration, gratings with thicknesses of more than 100 m can be fabricated. These gratings are capable of 100% diffraction efficiency and exhibit spectral bandwidths of only a few angstroms. The diffraction efficiency of such gratings is easily varied by addressing with a tunable narrow-spectral-bandwidth source or, alternatively, by locally varying the average refractive index within the grating region. The latter requires index differences of only 10−410−3. The experimental device described in this presentation used LiNbO3 and the linear electro-optic effect, although other active and passive mediums may be used. In addition to switching elements, modulators and grating based logic elements have also been designed.
Broadband light-intensity modulator
Authors: Ning Xiaohui
Published: February 2023

Broadband light intensity modulators are useful in a number of applications. It has been reported that by making a multilayer stack having a random thickness/index distribution an excellent broadband reflector is obtained.1 If dynamic materials, i.e, electro-optic, nonlinear-optic materials are used to construct the device, a broadband light modulator is obtained. The light modulation is achieved by varying the applied external field if electro-optic materials are used. If nonlinear-optic material is used the device is self-modulating. The configuration chosen for analysis consists of alternating layers of two different electro-optic materials and two transparent surface electrode layers. The thickness distribution is completely random. In the transmission state the indices of the two materials are equal. When an external field is applied a difference in refractive index between adjacent layers is created through the electro-optic effect. This results in a reflection of incident light over a broadband of wavelengths. The characteristics of the rejection band depend on the random distribution profile and the maximum index difference achievable. Results based on computer simulations are presented.
Dielectric films deposited with the MetaMode™ process
Authors: Hichwa B. P.
Published: February 2023

MetaMode™ is a tradename for a special form of metal-mode reactive sputtering. It is a practical and scaleable sputtering process in which the metal-deposition zone is separated from the subsequent reactive (typically oxidation) zone. Other investigators, including Schiller1,2 and Hartsough3 have suggested similar ideas. However, the MetaMode process has demonstrated the capability to make optical-quality dielectric films at metal-sputtering rates. A typical laboratory setup for this process includes a 30-in.-diameter drum, usually rotating from 50 to 150 rpm, on which the substrate is mounted. The sputter target is a 20-in. de magnetron. A similar-sized linear ion gun of OCLI design provides the reactive species. The sputtering and reaction regions are well isolated from each other with baffles and extensive vacuum pumping. In this paper we present MetaMode-deposited TiO2 film results for a variety of deposition parameters. Both the optical (n and k) and physical properties of these films were measured. The density and stoichiometry were obtained from RBS measurements and the structure information from TEM experiments. For comparison, results from titania films made with dual-ion-beam sputtering and ion-assisted evaporation will also be shown.
Optical saturation of room-temperature excitonic absorption in CdZnTe/ZnTe multiple quantum wells
Authors: Lee D. , Johnson A. M. , Zucker J. E. , Feldman R. D. , Austin R. F.
Published: February 2023

A well-defined room temperature excitonic absorption peak is a crucial property in photonic device applications of semiconductor multiple quantum wells (MQWs). Although II-VI semiconductor MQWs are potentially promising materials, especially in the bluer part of the visible spectrum, no room temperature excitonic absorption peak has been reported in these structures until recently. We present strong and well-defined room temperature n = 1, heavy-hole excitonic absorption peaks in CdZnTe/ZnTe MQWs. The temperature dependence of the excitonic absorption linewidth reveals that the homogeneous broadening, which is due to the excitonphonon interaction, is significantly smaller than that reported in a similar II-VI MQW system.1 The cw room temperature saturation intensity of the excitonic absorption peak was measured and found to be one order-of-magnitude higher than that reported in III-V MQWs. The high saturation intensity is a consequence of a smaller exciton Bohr radius, which is characteristic of wide-gap II-VI semiconductors. A high saturation intensity and well-defined room temperature excitonic absorption peak should be favorable for high power operation of electroabsorptive modulators and self electro-optic effect devices (SEEDs).