bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing particle indistinguishability in quantum statistics by optical interferometry and diffraction
Authors: De Martini Francesco
Published: February 2023

We have discovered from Michelson and Young interferometry experiments, carried out with the use of an argon laser (working at λ = 5145 Å, with intracavity etalon, cw, 1-W power) that the standard application of quantum electrodynamics (QED) to this problem is incorrect. Photons belonging to a chaotic mixture of |n〉 states behave as Bose-Einstein (BE) particles showing a large reduction of the interference-fringe visibility

V
(

n
¯

)
=

(

I

max

−

I

min

)

/

(

I

max

+

I

min

)

for increasing average photon number per radiation mode

〈
n
〉
=

n
¯

, where

I
(

n
¯

)

is the photodetected intensity. This effect, never investigated or anticipated before, is a manifestation of the quantum interparticle correlations inherent BE statistics. Photons belonging to a superimposition of coherent, Glauber, |α〉 states (i.e., a laser beam) follow Maxwell-Boltzmann (MB) statistics leading to

V
(

n
¯

)
=
1

for any

n
¯

, owing to absence of interparticie correlations.
Models for the arrangement of long and medium wavelength cones in the central fovea
Authors: Ahumada Al
Published: February 2023

Rules for assigning cones to the two-wavelength sensitivity classes long (L) and medium (M) have been added to the close-packing model for foveolar cone positions. The packing model places each cone tightly against two other cones already in place, so it is natural to consider schemes which assign each cone on the basis of the assignments of the two cones with which it is being placed in contact. The simplest deterministic assignment with reasonable properties is to assign the new cone to the opposite class if the two are the same and to make the assignment L if they are different. This rule generates a proportion of ~62% L and 38% M, not exactly the 2 to 1 rule that has been proposed, but fairly close. The rule has the important feature that it does not depend on the assumption of exact hexagonal (triangular) packing for its implementation. The aliasing properties of retinas generated by this rule and by random assignment with corresponding proportions are demonstrated for chromatic gratings and for luminance gratings in the case that one class is desensitized.
Quality of location information
Authors: Pavel M. , Cunningham H. A.
Published: February 2023

Theoretical and empirical characterization of changes in performance with eccentricity is used to assess the availability of location information in the human visual system. We first examine conditions in which a single scaling function can be used to describe performance at various eccentricities. We then consider performance on two types of task: (1) detection of presence/absence of stimuli, and (2) Vernier acuity and discrimination of length.
Stark spectroscopy and Autler-Townes interactions in four-level cesium atoms
Authors: Wessel John , Cooper Donald
Published: February 2023

Scalar and tensor polarizabilities of cesium 5f and 7d states were measured by three-color multiphoton excitation techniques. The low field results were quadratic and were in good agrement with calculated values. At higher electric fields, we clearly resolved Autler-Townes avoided crossings between 5f levels and dressed 7d states. The observed doublet component separations scaled linearly with Rabi frequency for the 7d—5f transitions, supporting a two-level model for the four-level experiment. The results are interesting because the observed spectra were independent of Rabi frequencies for the 6s—6p and 6p—7d transitions. Angular momentum forbidden transitions from 7d, J
z
= 1/2 to 5f, J
z
= 5/2 were observed at higher dc fields. These are attributed to dc field-induced mixing between nearly degenerate 5f and 5g states.
Collisional effects on xenon 6p fluorescence
Authors: Rankin Michael B. , Davis Jon P. , Giranda C. , Bobb Lloyd C.
Published: February 2023

We describe collision studies on the two-photon excitation and fluorescence of the xenon 6p[1/2,0] excited state. Molecular nitrogen is the major collision partner. The 250-nm second harmonic of a line-narrowed Hansch-type dye laser excites the 6p state of xenon by two-photon absorption. Sample mixtures contain xenon at a partial pressure of 1 Torr and nitrogen at partial pressures of up to several hundred Torr. Time-resolved and time-integrated measurements of the intensity of the 828-nm 6p[1/2,0]—6s[3/2,1] allowed transition are obtained with photomultipliers, a transient digitizer, and a computerized data acquisition system. We extract pressure-dependent and pressure-independent components of the fluorescence lifetime and fluorescence yield from measurements over a range of nitrogen pressures. When the excitation power density is of the order of 104 W/cm2, the excited xenon atoms decay spontaneously. For spontaneous fluorescence, we obtain an inelastic (quenching) collision cross section of ~10–14 cm2 for xenon-nitrogen collisions, and a pressure-broadening coefficient of ~3 × 107 Hz/(Torr N2) for the two-photon transition rate. For excitation intensities above 2.6 × 106 W/cm2, the xenon atoms radiate cooperatively in a subnanosecond pulse. The fluorescence yield of this cooperative emission increases with nitrogen pressure rather than decreasing as in the spontaneous case. Mechanisms are discussed.
New high resolution VUV spectroscopic facility at SURF II
Authors: Ginter Marshall L. , Brown Charles M.
Published: February 2023

We describe a new spectroscopic facility at SURF II (Gaithersburg, MD) established for use in high resolution (Δλ < 0.004 Å at 800 Å) research requiring light from an electron storage ring. The project is a joint effort by the University of Maryland, the National Science Foundation, the Naval Research Laboratory, and the National Bureau of Standards which involved (a) the conversion of a 6.65-m off-plane Eagle spectrograph to a focal- plane scanning spectrometer, (b) the construction of a beam line with a polarization-enhancing optical system and differential pumping capability, (c) the acquisition and testing of a new generation of ruled concave gratings (4800 lines/mm), and (d) the installation of items (a)-(c) into a spectroscopic facility within the existing experimental halls at SURF II. Discussion includes details about the facility and the current experimental programs at the facility.
Quantum jumps in atomic systems
Authors: Zoller P. , Marte M. , Walls D. F.
Published: February 2023

We present a microscopic model for the so-called quantum jumps in three-level atoms with one transition between two levels being strongly driven and the third level being metastable. Our model is based on calculating the elementary probability density P(0,t)(t1, … , t
n
) which gives the probability density that exactly n photons are emitted at times t1, … , t
n
by the atom in the time interval (0, t) on the strong transition. This enables us to calculate the conditional probabilities

c
˜

(
τ
)

that given a photon has emitted at τ = 0 the next photon emission occurs at time τ. This quantity is shown to be the sum of two exponentials which for sufficient differetial in the time scales describe the periods of light and darkness. Using this conditional probability it is possible to numerically simulate the individual photon emissions.
Coherent CO2 DIAL laser remote sensing of toxic and hazardous gases
Authors: Grant William B.
Published: February 2023

The MAPM, an acronym for Mobile Atmospheric Pollutant Mapping System, is a CO2 DIAL lidar using heterodyne detection. The MAPM is distinguished from previous CO2 DIAL lidar systems in that it employs a pair of CO2 lasers with PRFs up to 150 Hz which should increase the measurement accuracy and reduce the measurement time required. The MAPM is mounted in a semitrailer and has a scan mirror above the roof. We discuss the system design, as well as results of demonstration measurements on organic solvents in a sample chamber and system performance characteristics, with an emphasis on factors limiting performance such as speckle, aerosol spectral properties, and interfering molecular species.
Measurement of asteroid diameter and albedos with a laser pulse
Authors: Vetter Alan A.
Published: February 2023

Illumination of asteroids with a pulsed laser provides a model-independent measurement of asteroid diameters. Due to the depth from the subearth point to the limb of the asteroid, the return pulse is spread in time. The signal duration is twice the maximum depth along the earth asteroid line divided by the speed of light. The range and depth are determined from temporal measurements alone. Therefore, only timing, not spatial resolution of the asteroid with the laser beam, is required to measure the depth. The depth measurement is possible because there is little or no limb darkening at optical wavelengths for most asteroids. The normal albedo is determined from the height of the initial portion of the return. The geometric albedo is determined from the integral of the return signal.
Optical polynomial processing based on the bilinear transform
Authors: Lin Shing-Hong , Krile Thomas F. , Walkup John F.
Published: February 2023

With the motivation to extend linear/bilinear operators to a more general class of nonlinear operators via a Volterra series (polynomial) approximation, we look into optical polynomial implementations using a factored representation so that presently known bilinear techniques can be employed. Since there are two inputs and one kernel in the generalized bilinear transform, the two inputs act as polynomial input variables and the elements in the kernel represent coefficients of the quadratic polynomial. Thus higher polynomial processing can be realized by iterating the bilinear transform. A dual-LCLV system is proposed to form such a quadratic polynomial. With electronic or optical feedback, a general optical polynomial processor is achievable. The work has been extended to perform bipolar complex analog and binary digital polynomial operations. The analog operations are performed by using separate parallel channels for real/imaginary and positive/negative numbers and making use of triple matrix-matrix product processing. Systolic and wavefront processors and a triple product processor are used to implement binary digital polynomial processing.
Ultrafast dynamics of dyes using 10-fs pulses
Authors: Fork R. L. , Brito Cruz C. H. , Knox W. H. , Shank Charles V.
Published: February 2023

We report on the dynamics of nonequilibrium distributions of dye molecules, such as, Nile Blue, Cresyl Violet, sulforhodamine 640, and rhodamine B, excited by pump pulses of 65-fs duration and probed by pulses compressed to durations of 10 fs. We examine a spectral region centered at the pump wavelength, 618 nm, and ranging from 570 to 670 nm. Differential absorption spectra are taken at intervals of 25 fs following the initial excitation of the dye. We observe optically induced changes which reach equilibrium within a few hundred femtoseconds following excitation. Of special interest is hole burning at the pump wave-length as well as bleaching of replica holes at energies shifted from the pump energy by a vibrational quantum energy. We also observe transient excited state absorption in near-infrared dyes due to pump-induced nonequilibrium population of the vibrational levels of the upper electronic state and transient-induced transmission in dyes such as rhodamine B where our 618-nm pump pulse lies below the absorption edge of the dye. We discuss the relationship of these optically induced dynamics with ultrashort pulse formation in lasers.
Orientation-selectivity in large-scale localization
Authors: Burbeck Christina A.
Published: February 2023

Relative spatial localization of widely separated objects (>30–50 min of arc) cannot be completely accounted for by a neural representation consisting of spatial frequency channels; another, more proximal, mechanism is also required.1 Is this localization mechanism selective for orientation? Relative localization accuracy was measured as a function of orientation using two dot stimuli with a mean separation of 100 min of arc. The observer’s task was to compare the inter-dot separation on a given trial to the average separation. Accuracy varied systematically with orientation, being poorest at 0°, 45°, and 90° (vertical). This suggests that the large-scale localization mechanisms are tuned for orientation. To explore further this orientation selectivity, localization accuracy was measured again, but now one dot was displaced orthogonal to the direction of measurement by a distance that varied randomly from trial to trial.
Visual texture segmentation based on energy measures
Authors: Bergen James R. , Adelson Edward H.
Published: February 2023

Various attempts have been made to describe the human ability to use texture information to define perceptual regions. Some of these have used statistical measures of structure while others have been based on differences in occurrence of certain features. We have tried a very simple approach based on the local energy present in concentric and oriented linear receptive fields. Measures of this kind can account for a number of observed phenomena: (1) In a texture made up of randomly oriented L and + shaped elements, strong segregation is ob­served if the line segments forming the elements are of the same length. If the + elements are enlarged slightly (10–20%), the segregation be­comes much weaker. (2) If the size of the elements in a texture is reduced while the average spacing between them is kept constant, the segregation also becomes weaker.
Adaptive filter model for striate cortical processing of spatial information
Authors: Dagnelie Gislin
Published: February 2023

Since the introduction of sine wave gratings in electrophysiology [Campbell and Green, J. Physiol. 181, 573 (1965)], properties of spatial visual processing have been investigated and expressed in terms of spatial frequency channels. Such channels have also been found in human psycho­physics, leading to models of spatial vision such as that of Wilson and Bergen [Vision Res. 19, 19 (1979)]. The physiological substrate of such models in man is unknown but is generally thought to be situated early along the visual pathway. To test the nature of spatial frequency processing in striate visual cortex in primates, visually evoked potentials were recorded subdurally in alert rhesus monkeys. Two-dimensional (checkerboard) stimuli, in which spatial frequency components could be modulated independently, were presented. Our data show that neuronal responses to modulation of one spatial frequency component are highly dependent on the presence of (stationary or modulated) components with spatial frequencies at intervals up to two octaves. These interactions occur both for transient and for steady-state stimuli and are mutual, although not symmetric. They can best be modeled as mutual adaptations of localized spatial filters; a few populations of such filters, with bandwidths of 1–2 octaves, could account for the data.
Deamplification of quantum noise in a cryogenic optical fiber
Authors: Shelby R. M. , Levenson M. D. , Perlmutter S. H. , Devoe R. G.
Published: February 2023

We have clearly demonstrated the parametric deamplification of electromagnetic vacuum fluctuations in a traveling wave geometry using a single-mode optical fiber.1 The minimum detected noise level was 12.5 ± 0.5% below the noise level produced by an incandescent source at the same photocurrent. Noise levels below the standard quantum limit appeared in two 9-MHz wide frequency bands centered at 45 and 56 MHz. At other frequencies, noise due to guided acoustic wave Brillouin scattering overwhelmed the squeezing, even at 2 K. Stimulated Brillouin oscil­lation was avoided by dividing the pump wave into many frequency components with a phase modulator. The theory of squeezed state generation and detection with such a multifrequency pump is discussed as are the phenomena which limit the noise suppression by this technique.
Squeezing in three simple systems: degenerate parametric oscillation, intracavity frequency doubling, and optical bistability
Authors: Kimble H. J. , Hall J. L.
Published: February 2023

Squeezed states of light represent a manifestation of the nonclassical character of the electromagnetic field and hence are of great intrinsic interest in quantum optics. There are as well a number of applications in measurement science and optical communication associated with the possibility of sensitivity beyond the standard quan­tum limit. The experiments that we have undertaken attempt to explore the degree of achievable and detectable squeezing in three distinct physical systems. From a conceptual point of view each is in some sense ideal and should provide a large degree of squeezing. However, in practice each offers a potential set of advantages and disadvantages associated with technological constraints and with a lack of precise correspondence between experiment and existing theoretical models. The three experiments that we describe are as follows: (1) degenerate parametric oscillation in a doubly resonant cavity pumped by the frequency-doubled light from a Nd:YAG laser at 1.06 μm, (2) intracavity second harmonic generation in a doubly resonant cavity pumped at a fundamental wave­length of 515 nm with an Ar+ laser, and (3) optical bistability for a collection of two-level atoms within a high finesse interferometer of decay rate comparable to the inverse atomic lifetime.
Application of squeezed-state light to high-precision interferometry
Authors: Caves Carlton M.
Published: February 2023

A potential application of squeezed-state light is to improve the sensitivity of high-precision interferometers whose performance is generally limited by photon shot noise or photon-counting statistics. Such interferometers include passive laser gyroscopes and the very sensitive interferometers being developed to detect cosmic gravitational waves. One usually operates a high-precision interferometer in a differential mode, so that noise from the (laser) light source is in principle irrelevant. Operation in a differential mode means that there is a second, normally unused input port. Vacuum noise entering this second port is responsible for the irreducible photon shot noise at the interferometer’s output. Injecting squeezed-state light into the normally unused input port can improve the sensitivity. I discuss the use of squeezed-state light in ring interferometers, delayline Michelson interferometers, and Fabry-Perot interferometers. Included in the discussion are real degrading effects, such as losses, inefficient photodetectors, and laser noise in the presence of nonideal fringe contrast. I explore the compatibility of the squeezed-state technique with other exotic techniques for improving sensitivity, such as Drever's idea for power recycling. Sensitivity estimates for various configurations and techniques are presented.
Theoretical comparison of multiquantum well, staircase, and doped quantum well avalanche photodiodes
Authors: Brennan Kevin
Published: February 2023

A comparison of the multiquantum well, staircase, and doped quantum well avalanche photodiodes is presented based on the calculated gain and excess noise factor. The gain is determined from the electron and hole ionization probabilities per stage derived from an ensemble Monte Carlo calculation. The Monte Carlo calculation is particularly well adapted to study impact ionization in APDs since it includes the full details of the conduction and valence bonds as well as collisional broadening. Various device geometries are examined (different layer widths, dopings, and overall effective field strength) among the three different device types. In each case an optimized structure, in terms of the overall gain and excess noise factor, is presented. The results for devices made from the GalnAs/AllnAs material system indicate that the doped quantum well device gives the largest gain at the lowest excess noise factor of the three device types.
Index and dispersion of co-evaporated thin films
Authors: Southwell William H.
Published: February 2023

Using the thin layer equivalence principle, which determines the equivalent index of two very thin layers having the same total physical thickness, we argue that the index squared of co-evaporated films is given by the sum of the index squared of the constituent materials weighted by their volume fractions. This turns out to be in agreement with the Drude model. A more difficult question is: what is the wavelength dependence or dispersion of the co-evaporated thin film? To answer that, we started with the derived expression for the mixed index and applied a dispersion relation for each of the constituents. The dispersion was expressed in terms of a chromatic coordinate expansion, which assumes an ultraviolet band edge and a far-infrared cutoff. Each constituent material is characterized by a dispersion coefficient indicating how much of the chromatic coordinant is needed to express the proper index dispersion. The dispersion coefficient of the mixed layer is thus obtained in terms of the dispersion coefficients of the constituents and the volume fraction of the mixing. It is shown that it is possible to control the dispersion of thin-film coatings through co-evaporation.
Determination of the phase dispersion of a wide-band multilayer high-reflective coating using multibeam interference
Authors: Wo Minzhen , Liang Peihui , Zhang Shaofong , Wang Zhijiang
Published: February 2023

In research on a gaining ultrashort pulse using the mode-locked technique, the phase dispersion (PD) effect of the optical elements has a great influence on the pulse shape, in particular the PD second-order derivative broadens the pulse width. The PD compensation can be anticipated by an appropriate choice of coating system design and by controlling the coating manufacturing techniques.
Nonlinear coupling of modes: a new approach to all-optical guided wave devices
Authors: Silberberg Yaron , Stegeman George I.
Published: February 2023

Intensity-dependent nonlinearities in waveguide structures which support more than one guided mode can lead to coupling between these modes. We have analyzed the interaction of the two lowest- order modes in a general symmetric waveguide structure. In this analysis we assumed that the index changes are not large enough to affect the mode shapes, however, ail the wave-mixing terms are included to account for the nonlinear phase shifts and power exchange between the modes. We have found that as the power is increased the beat period between the modes increases, while power is exchanged at the same periodicity. Above a critical power the two modes are phase-locked and a relatively constant field distribution is propagating along the guide. These effects can be the basis of a number of all-optical waveguide devices. For device applications controlled excitation and extraction of the modes are required. We discuss several such configurations and their applicability for all-optical signal processing.
Numerical analysis of nonlinear semiconductor optical waveguides
Authors: Gibbons Wayne M. , Sarid Dror , Arizona U.
Published: February 2023

The analytic solutions to the wave equation for linear optical waveguides are well established and understood. When one or more of the waveguide media is nonlinear, the solution to the wave equation is complex and requires more approximations. Several analytic solutions have been formalized for Kerr-type nonlinearities in the substrate and/or cover of a slab waveguide. Semiconductor waveguides are desired for some integrated optics applications. Important effects in semiconductor materials and waveguides that are neglected by the Kerr model are absorption, frequency dependence, and saturation of the nonlinearity, carrier diffusion, and surface recombination. Accounting for one or more of these effects makes an analytic solution to the wave equation complicated. As a result, numerical solutions become more attractive. We present the results of a numerical solution to the wave equation, including the above effects, for a nonlinear semiconductor waveguide. We discuss how these results can be used to design an optimum semiconductor waveguide.
Central pathways for color vision
Authors: Lennie Peter
Published: February 2023

Psychophysical evidence suggests that signals from cones are later transformed to yield an achromatic signal and two chromatically opponent ones. Although physiological observations on the lateral geniculate nucleus (LGN) of the macaque monkey have confirmed the existence of opponent transformations, these differ in important respects from the kind inferred from psychophysical evidence. In particular, the red-green chromatic pathway appears also to carry an achromatic signal, to an extent determined by the spatial properties of the stimulus. The characteristics of the yellow-blue pathway also differ from those inferred from psychophysical observations. Although signals that arise in the LGN do not meet the requirements of the psychophysical model, a linear transformation of these signals could do the required job. Analysis of the chromatic properties of neurons in striate cortex (the recipient of information from the LGN) shows that signals from the LGN are transformed substantially, so as to resemble more closely those expected on psychophysical grounds. The second-stage mechanisms inferred from psychophysical observations therefore seem to reflect the action of at least two distinct physiological transformations.
Optimal coding of spatiochromatic information in the retina
Authors: Buchsbaum Gershon
Published: February 2023

Natural visual stimuli are multidimensional signals encompassing parameters of space, time, and color. Information in these signal dimensions is redundant because natural images exhibit some spatial, temporal, and chromatic regularities. Further, these signal dimensions are not independent. The incoming visual stimulus is processed and coded in the retina by spatially organized center-surround chromatically antagonistic receptive fields with complex temporal characteristics. The basic hypothesis is that the purpose of retinal signal processing is to reduce signal redundancy and to efficiently code visual information before transmission to higher stages of the visual system. Under this hypothesis it is shown that retinal coding is designed to obtain optimality in coding, considering the relative amount of information in each dimension, corresponding to a high bit rate in the spatial dimension and a low bit rate in the chromatic dimension. The coding in these dimensions achieves favorable image degradation minimizing sensitivity to picture-to-picture variations, considering the computational load required from the retina.
Imaging system design for estimation of partially coherent Images
Authors: Matic Roy M. , Goodman Joseph W.
Published: February 2023

An object, illuminated by partially coherent light, is composed of a signal plus a noise transmittance. The problem is to design the pupil screen of the imaging system so that the detected image of the object is the minimum mean-square error estimate of the image of the signal transmittance. This problem is not linear but is bilinear, because of the input-output relationship between input transmittance and output intensity. This problem is solved using a nonlinear parameter optimization approach where the parameters to optimize are discrete samples of the magnitude and phase of the pupil. The improvement factor, which compares system performance relative to the performance of a diffraction-limited imaging system, is defined. The design of several optimal pupil screens is presented. These designs verify the validity of our design technique and demonstrate that both the optimal pupil screen and the improvement factor are a function of the statistics of the signal and noise and a function of the coherence of the object illumination. Our results also show that preprocessing is more effective for coherent systems than for incoherent systems.
Detective quantum efficiency of Imaging systems with amplifying and scattering mechanisms
Authors: Rabbani Majid , Shaw Rodney , Vanmetter Richard
Published: February 2023

A general analysis is given of the influence of stochastic amplifying and scattering mechanisms on the transfer of signal modulation and noise in imaging processes. A moment generating function approach allows us to obtain fundamental relationships for signal and noise that connect one stage of an imaging process to the next. In this way imaging systems of any complexity can be easily described by cascading the appropriate number of elementary stages. We have used this analysis to quantify the spatial-frequency dependence of signal and noise as they propagate through a multistage imaging system. It has been shown that although signal modulation to any stage of the system must pass through the modulation transfer function of that stage, uncorrelated input photon noise does not do so. Amplification of photon noise in one stage, however, can produce a noise structure that is correlated and thereby constitutes an effective signal spectrum to subsequent stages. Thus, in general, it is necessary to cascade these two components of the noise spectrum separately at each stage, and the formalism for doing so has been presented. As an example this formalism has been used to confirm previous physical arguments used in the derivation of an overall DQE model for a radiographic screen-film system.
Correlelogram as a stereo display element: theory and computer simulations
Authors: Dallas William J.
Published: February 2023

The correlelogram is a multiple layer optical element which can be used for stereo display. This paper concentrates on extension of the theory behind the correlelogram and on computer simulations for generating images as they would appear on the display. The theoretical extensions covered in this paper are smoothing of the pixel structure; elimination of artifacts; and extension of the theory to multilayer, multiperspective displays.
Butterfly color vision: spectral properties of photoreceptors and wing patterns
Authors: Bernard Gary D.
Published: February 2023

Studies of butterfly mating behavior have shown that colored wing patterns provide important signals for detection and recognition of a proper mate. Butterfly retinas contain three or four spectral types of photoreceptor, but the spectral locations of peak sensitivity for the types differ greatly among the species. Relative abundance also varies greatly. The goal of this study is to relate the spectral properties of receptor systems to those of wing patterns. Spectral sensitivity functions of each spectral type of receptor are measured optophysiologically. Reflectance spectra of wing patches are measured microspectrophotometrically. Comparing color-image data with receptor data indicates which wing features provide the strongest signals. For example, butterflies of the famous Monarch/Viceroy mimicry complex look very similar to us but not to each other. Monarchs have receptors peaking at ~360, 450, and 550 nm. Viceroys, on the other hand, do not possess the 550-nm type but have instead a receptor type that peaks at only 515 nm. Thus, Viceroys are much less sensitive at long wavelengths than Monarchs. Furthermore, whitish wing spots of the two species have quite different spectra. Calculated tristimulus values indicate that these spots are important signals for species discrimination.
Color spectra and the dimensionality of positive frequency-limited functions
Authors: Buchsbaum Gershon
Published: February 2023

In an earlier paper1 the properties of color spectra as a collection of frequency-limited functions were considered in relation to trichromacy. A well-known formula which proposes that the number of significant degrees of freedom of a frequency-limited distribution (with frequency limit F) in an interval of limited extent (E) is N = [2EF] + 1 was applied ([x] being the nearest integer smaller than x). The relation between trichromacy (N = 3) and the visual spectrum (E = 400–700 nm) was investigated and it was concluded that the visual system can sufficiently represent with three degrees of freedom a collection of signals with a frequency limit of 0.005 cycles/nm.
Measurements of stimulated Brillouin scattering phase conjugation fidelity
Authors: Suni Paul , Falk Joel
Published: February 2023

We have used a novel method to measure the fidelity of a stimulated Brillouin scattering phase conjugator. A 40-μm period phase grating splits a 532-nm beam into multiple orders. The conjugator returns the beams to the grating where they are recombined. The output energy in each of the grating orders allows us to infer the accuracy of the conjugation process. In preliminary experiments we blocked all but two incident orders and used a computer-based data logging system to measure the energies in four orders returned through the grating. The energies in two of these orders determine the relative gains seen by the incident beams while the energies in the other two orders essentially measure coherent addition and subtraction of the two beams returned from the conjugator. We have found that the energies measured in the latter two orders are inconsistent with perfect conjugation of both incident beams. The discrepancies can be attributed to the finite frequency shift of the Stokes beam and to the incomplete spatial reproduction of the returned orders.
Spatial coherence of a phase conjugate wave generated by stimulated Brillouin scattering
Authors: Gosnell Timothy R. , Watkins David E.
Published: February 2023

We have measured the spatial coherence of an initially fully spatially coherent pump laser beam following stimulated Brillouin scattering (SBS) in SF6 gas at 15 atm. Using a simple interferometric technique, we find that the fraction of the diameter of the scattered beam which is spatially coherent decreases with increasing f/No. of the incident 308-nm pump beam. Surprisingly, we also find that the spatial coherence of the scattered beam increases with decreasing pump energy. To our knowledge, these measurements are the first to address the issue of spatial coherence in SBS and point toward an important measure of the fidelity of phase conjugation produced by SBS. The influence of a weak seed beam on the coherence of the phase conjugate beam is also discussed.
Enhanced stimulated Brillouin scattering
Authors: Rogovin D.
Published: February 2023

It is well known that the amplitude of a laser radiation field in the vicinity of a metallic microparticle can be dramatically amplified at the surface plasma frequency. This feature of microparticle electrodynamics arises from a resonant coupling of the laser radiation field to the electronic plasma mode and has been utilized as a means to greatly enhance a variety of nonlinear processes. These are (1) second harmonic generation, (2) nondegenerate four-wave mixing, (3) phase conjugation, and (4) Raman scattering. Here, we show that stimulated Brillouin scattering can also be enhanced by surface mediated effects. In particular, since the amplitude of the electric field outside a microparticle is enhanced by resonant surface plasmon effects the laser-induced electrostrictive forces which give rise to stimulated Brillouin scattering in a liquid will be increased in the vicinity of the microparticle. Thus, if an appropriate liquid media such as CS2 is seeded with metallic microparticles, the Brillouin gain coefficient can be measurably enhanced if the laser fields are resonant with the microparticle surface plasmon mode.
Quantum behavior of four-wave mixers under strong pump depletion
Authors: Yurke Bernard , Stoler David
Published: February 2023

In conditions of strong pump depletion, four-wave mixers can generate a quantum mechanical superimposition of two macroscopically distinguishable states of the electromagnetic field. We have shown with exactly solvable models1 and computer simulations that a four-wave mixer can, in conditions of strong pump depletion, generate states of the electromagnetic field which consist of a quantum mechanical superimposition of two macroscopically distinguishable states. In particular, in suitable conditions, the four-wave mixer can generate a superimposition of two coherent states of large amplitude but 180° out of phase with respect to each other. Experimentally, one can distinguish such Schrodinger catlike states from a statistical mixture by performing a measurement in which the interference between the two macroscopically distinguishable parts of the wave function is exhibited. For the cases we have considered, this interference can be exhibited as fringes in the probability distribution for the photocurrent delivered by a homodyne detector.
Propagation of quantum fluctuations through passive optical systems
Authors: Min Xiao , Kimble H. J.
Published: February 2023

By employing the input-output theory of damped quantum systems developed by Gardiner and Collett,1 we discuss the propagation of nonclassical fields through optical systems containing frequency selective elements such as Fabry-Perot interferometers. Our results are of general applicability and are expressed in terms of the linearized drift and diffusion coefficients of the generalized Fokker-Planck equation describing the intracavity field of the nonlinear source. The two nonclassical effects of photon antibunching and squeezing are treated in detail with reference to the examples of intracavity harmonic conversion and optical bistability. Not surprisingly photon antibunching can be enhanced by the suppression of the coherent part of the spectrum of intensity fluctuations with a narrow bandwidth cavity. However the enhancement is ultimately limited and the antibunching lost altogether as the amplitude of the coherent carrier is reduced to a level comparable to that of the field fluctuations (which are set by the system size). Following the suggestion of Levenson et al., 2 we investigate the use of auxiliary cavities for the control of phase and amplitude in the propagation and detection of squeezed states of light. While for a small degree of squeezing such filter cavities operate in a straightforward fashion, a mixing of field quadratures can occur as the degree of squeezing increases leading to a loss of nonclassical behavior.
Squeezing for Intracavity generated light in the master equation approach
Authors: Carmichael H. J.
Published: February 2023

Master equation methods provide useful tools for analyzing the statistics of quantum optical systems. They focus attention on a simple system of interest (a single cavity mode, for example), accounting for its interaction with its environment in parameters describing decay rates and environmental fluctuations. Intracavity systems for generating squeezed light are prime candidates for analysis by these methods. It has been shown, however, that it is important in such analysis to distinguish between the statistics of the intracavity field and the statistics of the field generated outside the cavity by transmission through the cavity mirrors.1,2 It is desirable to perform calculations with the single mode inside the cavity. Then the statistics of the multimode field outside the cavity must be related to those of the internal mode. The situation is analogous to that in resonance fluorescence, where the statistics of the fluorescent field can be calculated in terms of the source dipole operator. In this paper the field outside an optical cavity is expressed in terms of the intracavity oscillator as a source. The measurement of squeezing in the external field is then related to the correlation properties of the cavity source operator. Measurement by photon counting of homodyned light is related to the spectrum of squeezing calculated by Walls and co-workers.
Quantum theory of multiwave mixing in two-photon two-level media
Authors: Holm David A. , Sargent Murray
Published: February 2023

Multiphoton transitions are of great interest in laser spectroscopy because they permit the study of new physical phenomena and because of their potential applications. Malcuit et al.1 studied two-photon transitions in atomic sodium and showed that for appropriate phase-matching four-wave mixing can overcome the usual spontaneous decay processes. We have recently developed a quantum theory2 to treat such multiwave mixing processes in two-photon media. Because of the greater complexity of two-photon transitions, many effects arise that are absent in the one-photon case, some of which have important consequences in the generation of squeezed states. For the two-photon two-level model, the field modes have frequencies approximately one-half the frequency difference between the levels. We find that our coefficients differ from the corresponding one-photon theory in that dynamic Stark shifts have a major effect and that the pump-induced coherence between the two levels has a new term in the conjugate coupling terms, which leads to improved squeezing.
High gain–bandwidth-product avalanche photodiodes for multigigabit data rate
Authors: Campbell Joe C.
Published: February 2023

For long-wavelength (1.3- and 1.5-μm) high-bitrate (>400-Mbit/s) lightwave systems the highest receiver sensitivities have been achieved with III–V compound avalanche photodiodes with separate absorption and multiplication regions (SAM-APDs). Initial APDs of this type exhibited poor frequency response owing to charge accumulation at the heterojunction interfaces. A significant improvement in the bandwidth was achieved by introducing a transition region between the multiplication and absorption layers (SAGM-APD). Early SAGM-APDs exhibited bandwidths in the 1–3-GHz range and gain-bandwidth products as high as 18 GHz. Recently, the progression of new lightwave systems to higher and higher bit rates has stimulated efforts to further increase the bandwidth of these SAGM-APDs.
Raman gain suppression in D2
Authors: Duncan M. D. , Reintjes J. , Mahon R. , Tankersley L. L.
Published: February 2023

We have confirmed, for the first time to our knowledge, the nonexponential character of Raman amplification at the phase matching angle ϕ for which 2kL = ks + kA. The experiments reported here used spatially filtered pump and probe beams at 532 and 633 nm, respectively, of 30-ps duration interacting in a one-half meter cell filled with deuterium at a pressure of 600 psi. The pump and probe beams were crossed at various small angles in the cell and the gain experienced by the probe pulse was measured. At angles below 5 mrad the Stokes amplification was exponential in character and reached levels of 107. At an angle of 7 mrad, the phase matching angle for our conditions, there was no observed amplification of the Stokes pulse. At yet larger angles (~9 mrad) the gain was again exponential in character and reached levels of 107. We have also observed a double ring pattern in the anti-Stokes radiation produced in our experiment. This pattern was predicted by Bloembergen1 with the explanation that a single anti-Stokes ring is split by a region of gain suppression at the phase matching angle. We have verified that the diameter of the dark band in the anti-Stokes emission grows as the square root of the pressure, exactly as would be predicted assuming that the dark region is caused by gain suppression at phase matching.
Stimulated electronic Raman scattering in sodium vapor
Authors: Han Xiaofeng , Lu Zhenguo , Cheng Yongkang , Ma Zuguang
Published: February 2023

The observation of stimulated electronic Raman scattering (SERS) on the 3S—4S transition in sodium vapor is reported, we believe for the first time.
Transition from superfluorescence to amplified spontaneous emission in KCI : O 2 −
Authors: Malcuit Michelle S. , Maki Jeffery J. , Boyd Robert W. , Simkin David J.
Published: February 2023

We have studied the nature of the emission from a laser-excited

KCI
:

O
2
−

crystal and have observed that the emission evolves continuously from superfluorescence (SF) to amplified spontaneous emission (ASE) as the temperature of the crystal and hence the dephasing rate of the optical transition are increased. The sample is excited by a 30-ps pulse from a frequency-quadrupled Nd:YAG laser, and the 629.1-nm emission is detected using a streak camera system. At a temperature of 10 K the emission is characterized as SF with an average delay time of 200 ps and an average pulse width of 60 ps. As the temperature is increased to ~20 K, the output pulse broadens and the time delay increases to its maximum value of ~2 ns. As the temperature is increased still further, the time delay is observed to decrease, and at a temperature of 30 K the emission is characterized as ASE with a very small delay time and with an exponentially decaying time evolution. We modeled our experiment using the Maxwell-Bloch formalism and find good agreement for our measured output pulse shapes and for the dependence of delay time and pulse width on the dephasing rate.
Effect of crystal length on the correlation times of downconverted photons
Authors: Hong C. K. , Ou Z. Y. , Mandel Leonard
Published: February 2023

We have investigated the question whether time delays between signal and idler photons produced in the parametric downconversion process depend on the length of the nonlinear medium. In an ideal fission process one might expect the correlation times to be independent of this length. Experiments were therefore carried out on KDP crystals of different lengths. The distribution of time delays was measured with the help of two microchannel plate photodetectors and a time-to-digital converter. Electronic transit time spreads in the detector were determined by use of a pulsed diode laser. As a major part of the observed spread of time delays (of the order of 100 ps) is due to the photomultipliers, length-dependent effects are derivable only from the difference between rather similar distributions. The derived time delay dispersion between signal and idler photons was found to be of the order of 100 ps in an 8-cm long crystal with 400-ps transit time, and there are indications that it is slightly smaller in a 1/2-cm long crystal of 25-ps transit time. The experimental results are compared to theoretical calculations based on a parametric coupling Hamiltonian, which indicate that crystal length should play a very small role, of the order of 1 ps, and then only when the relative acceptance bandwidth Δω/ω is ~1 % or greater.
White-light signal processing based on liquid crystal television
Authors: Yu Francis T. S. , Jutamulia S. , Lin T. W.
Published: February 2023

Many applications of the liquid crystal television (LCTV) have been reported in literature. By replacing the low-quality polarizers in the LCTV and immersing the LCTV in a liquid gate, a low-cost LCTV can be applied as a spatial light modulator in a real-time optical processor. Applications of the LCTV to white-light signal processing, such as edge enhancement and spatial color encoding, were performed. Real-time pseudocolor encoding based on the birefringent effect of the liquid crystal was also investigated. A pseudocolor encoded image of an x-ray transparency was obtained using the black-and-white LCTV. The white-light noncoherent correlation technique was also studied to overcome the phase variant defect of the LCTV.
Digital programmable mask for optical processing
Authors: Goebel John H. , Jared D. , Welch J. , Matsumoto T. , Mina C.
Published: February 2023

Digital programmable masks are an enabling technology for the development of digital optical computers or processors. We have constructed a digital optical processor based on a programmable liquid crystal display (LCD). To demonstrate its capabilities we chose to use the mask as a Hadamard image encoder. We have successfully encoded images of a laser diffraction pattern (spatially asymmetric) which reproduce the details displayed in a direct photographic image. The device uses the Jaquinot advantage and would have applications in the field of sensitive imagery, e.g., astronomy. The programmable mask is considered a prototype. The possibilities of other programmable mask technologies are compared with the LCD.