bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrared-to-visible image conversion using a silicon liquid crystal light valve
Authors: Wu S. T. , Efron U. , Hsu T. Y.
Published: February 2023

Near-IR-to-visible image conversion using a Hughes silicon liquid crystal light valve1 (LCLV) was demonstrated. An input 1.06-μm laser A, intensity of ~100 μW/cm2 was used to activate the 125-μm thick silicon photoconductor. The photoactivated current generated in the silicon by the 1.06-μm input beam results in a spatial voltage pattern which is transferred to the high impedance liquid crystal layer. This electric field causes molecular reorientation to occur in the liquid crystal film; since the liquid crystal film is birefringent, this reorientation causes the polarization of the visible projection beam (λ2 = 0.633 μm) to be rotated.
Microchannel spatial light modulator as an array of binary logic gates
Authors: Fisher Arthur D. , Wu M. H. , Suzuki Y. , Hara T. , Mukohzaka N.
Published: February 2023

In the microchannel spatial light modulator (MSLM),1 a photocathode converts a 2-D addressing-light pattern into an electron image, which then passes through a 2-D microchannel plate (MCP) electron amplifier onto a mirror deposited on a LiNbO3 electrooptic crystal. A readout light beam enters the opposite side of the crystal and reflects off the mirror to form a modulated output beam. The electron image stores on the crystal for months, but a grid between the MCP and crystal allows electron removal by secondary emission. By exploiting the secondary emission dynamics, the MSLM can intrinsically be operated in a binary hard-clip thresholding mode.1,2
Radiometric and imaging experiments on Gaussian Schell-model sources
Authors: Turunen Jari , He Qingsheng , Friberg Ari T.
Published: February 2023

We report results from experimental studies dealing with the effects of partial coherence on the radiometric and imaging properties of beams generated by Gaussian Schell-model sources. The variable-coherence sources, represented by Gaussian distributions of optical intensity and spatial coherence, are realized by an optical system analogous to one introduced earlier.1 The source coherence properties and those of the beam it produces are measured with a wavefront-folding interferometer. On changing the degree of coherence, the beams span the range from full coherence (laser beam) to full incoherence (geometrical optics). The quantities studied include the radiation pattern, an associated equivalence theorem, and the evolution of optical coherence on propagation. In imaging of Gaussian Schell-model sources, the invariant ratio of coherence length to beamwidth is examined. In addition, measurements are carried out on the coherence-dependent focal shift and magnification in focusing. Results are compared to theoretical predictions.2
Instabilities and chaos in a multimode standing-wave cw dye laser
Authors: McMackin I. , Radzewicz C. , Raymer M. G.
Published: February 2023

Experimental and theoretical investigations of a multimode standing-wave cw dye laser have been carried out. For a three-mirror cavity the laser spectrum is found to evolve by discrete transitions, with increasing pump power, between spectra composed of three stable modes to spectra composed of many modes whose amplitudes fluctuate strongly. At low powers there are three stable modes, separated by 2 GHz (8 cavity mode spacings). When the pump power is raised, the separation suddenly jumps to 4 GHz. After a range of power in which the spectrum is unstable, three stable modes again appear, now with a spacing of 8 GHz. A further increase of pump power leads eventually to a quasicontinuous spectrum, with a spectral width corresponding to about 100 cavity mode spacings. The behavior at low powers is caused by the simultaneous presence of spatial hole burning and an extremely weak etalon which arises spuriously from diffuse backscatter from the folding mirror. In a regime corresponding to unstable spectra, we find experimental evidence for deterministic chaos. We also have carried out numerical simulations of this type of laser using realistic parameters and find qualitative agreement with experiment, including the decrease of mode-intensity correlation time with increasing pump Power.
Effective medium theory of nonlinear optical properties of composites of semiconductor microstallites
Authors: Sung C. C. , Li Y. Q. , Ingura R.
Published: February 2023

Nonlinear optical properties of microstructures immersed in a linear dielectric are investigated. The microstructures are assumed to be composed of simple saturable two-level atoms. The local field corrections are included in a self-consistent manner leading to multiple solutions for the absorptive part of the dielectric constant of the microstructure as noted earlier by Chemla and Miller.1 For a given structure we use the effective medium theory and average over the random positions of the grains to obtain the effective medium dielectric constant in the quasistatic limit (λ ≪ grain size) as a function of the volume fraction of the grains. The results exhibit sharp hysteresis effects. However, in the study of the propagation in the medium these effects are modified considerably. While defined switches are observed in the mean field at certain points in the medium where the absorption jumps from the upper to lower branch, the optical intensity undergoes only a change of slope.
Longitudinal and transverse inhomogeneities in a nonlinear oscillator
Authors: Haus Joseph W. , Scalora M. , Wang L. , Bowden C. M.
Published: February 2023

We consider a nonlinear medium whose polarization P is described by a nonlinear oscillator equation.1,2 The steady-state fields are analytically solved for plane waves in a slowly varying envelope approximation. We find the conditions for the appearance of a boundary in the medium separating a high-polarization branch of stationary solutions from a low-polarization branch. We show how this boundary can be probed by the reflected intensity and by degenerate four-wave mixing spectroscopy, and results are given for these cases. We also use a numerical procedure to solve the steady-state equations which include one transverse dimension. There is an interesting change in the on-axis behavior related to the self-focusing effects for Fresnel numbers of order unity.
Design and use of optical compare-and-exchange units
Authors: Stirk Charles W. , Athale Ravindra A. , Friedlander Carl B.
Published: February 2023

Networks of compare-and-exchange (C&E) units can perform many useful functions including sorting, selecting, merging, packet switching, and the logical set operations. The throughput of these functions is critical to the performance of parallel operations for relational data bases and interconnection networks for telecommunications and parallel processors. Optics is well suited for the implementation of C&E since the simple units are hardwired, and they must be globally connected in multistage networks to perform the desired operations. Thus we present designs for C&E modules based on a variety of optical technology. The designs are evaluated in terms of their potential performance on the above applications.
X-ray narrow line transition radiation due to excitation of inner-shell electrons in atoms
Authors: Kaplan A. E. , Law C. T.
Published: February 2023

We develop a theory of a new effect, whereby x-ray radiation with narrow spectral lines is generated by an electron beam passing through a multilayer solid-state structure using a method proposed earlier by Kaplan and Datta. These lines are attributed to the extremely narrow resonances of dielectric constants of materials in the vicinity of the atomic absorption edges. The available data for atomic scattering factor f for all elements in the periodic table show that only K, L, and M absorption edges have sharp resonances and, therefore, are suitable for the effect discussed. The power of the transition radiation is proportional to |Δϵ(λ)|2, where Δϵ is the difference between dielectric constants ϵ of two materials forming a multilayer structure. Conventionally, ϵ is represented as ϵ = 1 − f1reλ2NA/π, where re = e2/mc2 is a classical electron radius, NA is the atomic density of material, and f1 is a real part of the atomic scattering factor f. We have found that for most of the atomic shells and elements, the factor f1 at the absorption edge can be written as f1 = Z− AS + BS[fS(ω/ωS) − 1], where Z is the atomic number, S labels the type of shell, and ωS is the lowest transition frequency for the particular shell S.
Photoabsorption and electron scattering in x-ray transition radiation in a solid-state superlattice
Authors: Law C. T. , Kaplan A. E.
Published: February 2023

Fast electrons traversing the interface of two media with different dielectric constants generate the so-called transition radiation. In a multilayer structure with many interfaces, the radiation is greatly enhanced and concentrates conically around some resonant angle. It was recently shown1 that multilayer solid-state structures with a spatial period as thin as 10-100 Å (which can be readily fabricated with the present technologies) can be used to generate x-ray radiation with a subrelativistic electron beam. However, the losses due to photoabsorption, bremsstrahlung radiation, and electron scattering cannot be neglected in a solid-state structure.
Amplitude and phase modulation in GaAs/GaAlAs multiple quantum well-based spatial light modulators
Authors: Hsu T. Y. , Wu Wei-Yu , Efron Uzi , Schulman J. N. , Chang Y. C.
Published: February 2023

Multiple quantum well (MQW) structures have shown relatively efficient (low-field) electrooptical modulation at extremely high speed1 and can be used in 2-D spatial light modulators with relatively high resolution. Experimental and theoretical studies of MQW-based SLMs are presented.
Spatial and temporal tuning differences between broadband and opponent cells in monkey lateral geniculate nucleus
Authors: Young Richard A. , Von Blanckensee Hans , Marrocco Richard T. , De Valois Russell
Published: February 2023

The responses of macaque monkey lateral geniculate neurons to full-field temporal achromatic flicker and drifting sine-wave gratings (mean luminance 17 cd/m2) were studied using single-unit recording methods. Cells were also classified into spectrally opponent or broadband on the basis of their responses to diffuse narrowband spectral luminance increments, using principal-component analysis1 and cross-point techniques. The results showed that the mean peak temporal frequency response of broadband cells (10.8 ± 3.2 Hz, n = 12) was significantly greater than that of opponent cells (4.0 ± 0.3 Hz, n = 36) regardless of stimulus modulation level, electrode depth, or whether a cell was the on-or off-center type. Also, the mean response amplitude to the optimum temporal frequency stimulus was significantly larger for broadband cells than opponent cells, again for all conditions tested. Finally, broadband cells responded to lower spatial frequencies of drifting gratings than did opponent cells at all stimulus modulations (e.g., 1.1 ± 0.1 cycles/deg, n = 14 for broadband cells; 1.9 ± 0.2 cycles/deg, n = 45 for opponent cells, 95% stimulus modulation). These spatiotemporal differences between opponent and broadband cell groups in the monkey LGN are consistent with differences between opponent and broadband chromatic channels as inferred from human psychophysical studies.
Invariance of MDB matches across variations in edge blur
Authors: Lindsey Delwin T. , Teller Davida Y.
Published: February 2023

The effects of edge blur on minimally distinct border (MDB) judgments were investigated using a computerized color video system. A single observer made MDB matches of the red, green, and blue primaries and fixed-ratio binary mixtures of the primaries to a 30-townsend (TD) standard white. The method of adjustment was used. The monitor was 260 cm from the observer and viewed through a Powell achromatizing lens. The stimuli were 1° 30′h × 40′V and were presented with a 4-s on duty/0.25-s off duty cycle. The edge separating test and standard stimuli were formed either by appropriate step functions for each of the three monitor guns or by functions computed by spatial convolution of the appropriate sharp edges with Gaussian blur functions having standard deviations of 1, 2, 4, or 8 min of arc. Within the range of spatial and chromatic parameters explored, the spectral sensitivity, precision, and additivity of the MDB matches were all essentially unaffected by the introduction of edge blur. The results suggest that the sharpness of a border is less important than has been assumed in determining the characteristics of MDB matches.
Modified Coulomb scattering in intense high-frequency laser fields
Authors: Gavrila M. , Kaminski J. Z. , Van De Ree V.
Published: February 2023

A nonperturbative theory was recently developed to describe electron-atom scattering in high-frequency laser fields.1 It applies at frequencies already available from excimer lasers in the VUV but extends beyond into the x-ray range. It was shown1 that, for monochromatic radiation, in the high-frequency limit the time-dependent Schrodinger equation describing the scattering reduces to a time-independent Schrodinger equation containing a dressed potential V0(α0. r). where α0 = I1/2ω-2 a.u. (I = intensity, ω = frequency). Consequently, in this limit only elastic scattering can occur (multiphoton free-free transitions are quenched).
Structure of atomic hydrogen in high-intensity high-frequency laser fields
Authors: Gavrila M. , Offerhaus M. J. , Pont M. , Walet N. , McCurdy C. W.
Published: February 2023

Substantial effort is now being invested in the development of high-frequency lasers operated at high intensities. A nonperturbative theory was developed to deal with atoms placed in such fields.1,2 We present here first a highly accurate calculation of the structure of atomic hydrogen placed in a monochromatic high-frequency ω laser field of linear polarization and arbitrary intensity l. It has been shown1,2 that in these circumstances the time-dependent Schrodinger equation reduces in the high-frequency limit to a time-independent Schrodinger equation containing a dressed potential V0lin(α0, r), where α0= I1/2ω−2 a.u.
Ozone measurement using tunable diode laser heterodyne spectrometery
Authors: McElroy C. T. , Goldman A. , Murcray David G.
Published: February 2023

Tunable diode laser heterodyne spectrophotometry (TDLHS) has been used to make extremely high-resolution (0.0005-cm−1) solar spectra in the 9.6-μm ozone band. Observations have shown that a SNR of 120:1 for an integration time of ⅛ s can be achieved at a resolution of 0.0016 wave numbers. The measured SNR at 0.0016-cm−1 resolution is ~30% of that theoretically obtain able. The spectral data have been inverted to yield a total column amount of ozone of 311-m-atm-cm compared to a value of 355-m-atm-cm obtained at the nearby National Oceanographic & Atmospheric Administration ozone monitoring facility in Boulder, CO. Line positions are reported for several ozone lines in the 996-997-cm−1 spectral region.
Solgel method for producing lens quality radial gradient-index glass
Authors: Caldwell J. Brian , Diana John , Moore Duncan T.
Published: February 2023

High-quality radial gradient-index glass based on the TiO2-SiO2 and ZrO2-SiO2 systems has been prepared using solgel techniques. The use of additional components such as AI2O3, B2O3, and GeO2 helps to eliminate the problems of gel fracture, bloating, and crystallization. In all cases, the precursor gels are prepared from metal alkoxides, water, alcohol, and a small amount of acid catalyst. The refractive-index gradient is created by selectively leaching the TiO2 or ZrO2 component from the precursor gel by placing the gel in an aqueous acid solution. The leaching process is halted by placing the gel in methanol. The gel is then dried in an oven and then sintered into glass by heating to temperatures as high as 1500°C. Plane-faced gradient-index lenses have been made with diameters >8 mm and index changes >0.02.
Cascade Raman soliton 1.34-1.65-μm fiber lasers
Authors: Gouveia-Neto A. S. , Gomes A. S. L. , Taylor J. R.
Published: February 2023

Exploitation of highly efficient stimulated Raman scattering in optical fibers has given rise through a soliton shaping mechanism to a simple source of femtosecond high-power pulses from simple fiber ring laser systems, synchronously pumped by the 100-ps pulses from a cw mode-locked Nd:YAG laser at 1.32 μm.1 Principally, the operation has been limited to the first Stokes band around 1.4 μm (Ar 440 cm-1). The soliton pulse shaping mechanism giving rise to pulses of 100 fs, which as a result of the short interaction length is unable to generate efficiently the higher Raman orders in cascade. By using a dispersion shifted fiber, so that the first Stokes band and the fundamental are in the positive group velocity dispersion regime, highly efficient Raman generation (>50%) is possible in fiber spans 100s of meters. This technique then permits efficient generation of the second Stokes component (centered around 1.5 μm), which if in the region of negative group velocity dispersion can undergo a solitonlike pulse compression.2 In a dispersion shifted fiber ring laser geometry, pulses as short as 170 fs with peak powers of ~4 kW around 1.5 μm have been generated. Further cascade into the third Stokes per mitted similar operation with pulses of ~200 fs.
Investigation of efficient second harmonic generation in glass fibers
Authors: Mizrahi Victor , Osterberg U. , Stegeman George I. , Sipe John E.
Published: February 2023

The discovery of efficient second harmonic generation in phosphorous-doped glass optical fibers1 has prompted considerable interest, as this is normally a dipole forbidden process. The two main questions are, first, by what mechanism is the second harmonic generated, and, second, how is the process phase-matched. A model which ad dresses these questions has recently been proposed.2,3 We present the results of experiments designed to test the model and further elucidate the mechanism responsible for this effect.
Feasibility of solitons near the zero dispersion point of optical fiber
Authors: Wai P. K. A. , Menyuk C. R. , Chen H. H. , Lee Y. C.
Published: February 2023

Recently,1 we proposed the use of solitons at the zero dispersion point for long-haul communication, a scheme that combines the low-power requirement of propagation at the zero dispersion point with the robustness of the soliton approach. Important issues, such as the variation of the zero dispersion point along the fiber length, were not considered. In a fiber, the zero dispersion point along the fiber length was not considered. In a fiber, the zero dispersion point fluctuates due to variations in the fiber core size. By using a multi ple-length scale expansion, we are able to show analytically that if the correlation length of the axial inhomogeneities is much smaller than both the second-order and third-order dispersion length, solitons propagate in this regime even if the magnitude of the fluctuations is large. Physically, the variations are so fast that the pulse cannot respond to them. The analysis is supported by results of numerical simulations. We have also investigated the effect of Raman downshift, which affects solitons by shifting the carrier wavelength away from the zero dispersion point.
Use of optical techniques in the consistent labeling problem
Authors: Haney M. W. , Athale R. A. , Geesey R. A.
Published: February 2023

Many artificial intelligence problems are formulated as backtracking tree searches. In general, these problems have exponential time complexity, and many researchers have concentrated on developing practical tree-pruning techniques to improve the efficiency of the search algorithm. Consistent labeling (CL) techniques (variously known as constraint satisfaction and forward checking techniques) use the relational constraints of the problem in local graph operations to reduce the complexity of the search tree. The appropriate data structures for some CL operations are Boolean tables which can be manipulated by Boolean matrix algebraic techniques.1 For some problems, their implementation on sequential machines may be impractical.
Symbolic substitution and patterns
Authors: Johnson John L.
Published: February 2023

The interrelationships among symbolic substitution, neural nets, optical correlators, the permutation group S
N
, and digital computers are discussed. An example is given showing how these apply to the design of a full binary adder. Arithmetic rules are transformed into two pattern replacement rules which are implemented by neural networks. These are combined to form the N-bit adder. A functionally equivalent system design using optical correlation techniques is discussed. The group aspect is discussed. Since every group is isomorphic to a subgroup of S
N
the interrelationships imply access to a powerful mathematical base for optical nets. A binary Grossberg model leads to a characterization of S
N
in terms of the number of nodes and input connections.
High-resolution shaping and encoding of femtosecond pulses
Authors: Weiner A. M. , Heritage J. P. , Salehi J. A.
Published: February 2023

We previously reported the synthesis of arbitrarily shaped picosecond pulses by spatial filtering in a fiber and grating pulse compressor.1 Here we describe high-resolution shaping and encoding of femotsecond pulses using a modified nondispersive grating apparatus. Elementary examples include the femtosecond odd pulse (a pulse doublet abruptly phase shifted by π at t = 0)1 and high-frequency femtosecond tone bursts with beat frequencies as high as 2.6 THz. To illustrate further the high degree of complexity which may be incorporated into the shaped waveforms, we discuss frequency domain phase coding of femtosecond pulses. Pseudorandom binary phase masks, fabricated according to the optimal m-sequence codes,2 are utilized to scramble the phases of the various optical frequency components; In this way, intense femtosecond pulses are encoded into picosecond duration pseudonoise bursts. Subsequent unscrambling of the spectral phases (decoding) allows the original femtosecond pulse to be restored without broadening. We anticipate that high-resolution pulse shaping will have important applications in coherent time domain spectroscopy and optical communications; as one example we discuss a proposed optical spread spectrum communications switch based on encryption and decoding of ultrashort pulses.
Monochromatic aberrations of the model eye
Authors: Blaker J. Warren , Poutous M. K. , Rosenblum William G.
Published: February 2023

The young mature eye model with a gradient-index crystalline lens can easily be scaled to examine its properties at various levels of accommodation. We examined this model with both spherical and aspherical lens surfaces for spherical aberration and astigmatism at various accommodative levels. The results are compared with those of the other eye models and clinical experimental results. Good agreement with the clinical results has been obtained.
Noninvasive visual assessment: (1) wavelength effects relating to the moon illusion, and (2) tracking recovery from systemic arterial sclerosis
Authors: Mcleod Roger D.
Published: February 2023

A spatial frequency model for vision requires that the diffraction pattern representations of the Fourier transformed equivalent of object information, as electric-field amplitude representations at the focal surfaces of two quasimonochromatic wavelength intervals, are coincident with rod and cone outer receptive segments.1 A focal length and wavelength interdependency are linked to the accommodation necessary to achieve coincidence of the particular wavelength intervals with the retina. The correct magnitude of the horizon effect is quantifiable as 10% by measuring the horizontal cross sections of the apparently equal top and bottom parts of an appropriately selected numeral 8. A 1.55 times enhancement was previously established psychophysically as the ratio of apparent diameters of the zenith and horizon moons.
Visual mechanisms and visual illusions
Authors: Adelson Edward H.
Published: February 2023

Many perceptual phenomena and visual illusions can be understood-in terms of mechanisms that extract different kinds of energy. Photoreceptors are tuned for spectral energy, and cells in cortex can be considered to be tuned for local pattern energy corresponding to texture, scale, orientation, motion, and so on. Even though the tuning tends to be broad, exquisite sensitivity can be achieved by comparing the outputs of such cells. Thus we can discriminate colors that differ by a single nanometer or lines that are offset by a fraction of a cone width. Comparison mechanisms also lead to a wide range of remarkable illusions and aftereffects in the domains of color, brightness, motion, and form.
Optical image processing: what future?
Authors: Rhodes William T.
Published: February 2023

No summary of this tutorial or biographical information was available at press time.
Optical properties of fractal clusters
Authors: Sheng Ping , Chen Zhe , Weitz D. A. , Lindsay M. , Lin M. , Meakin P.
Published: February 2023

The optical properties of fractal aggregates and effects of multiple scattering are studied using computer-generated clusters whose structures are known. We show that the dominant effect of multiple scattering is reflected in the mean-field index of refraction of the clusters. By contrast, multiple scattering does not mask the q dependence of the scattering, even when the polarizability of each particle is large, and when d
f
> 2, so that the cluster is geometrically opaque. In addition, we show that, in spite of the aggregates’ generally low density, the connected structure necessarily imposes significant high-order multipole interactions between each particle and its nearest neighbors. For metal particles, this results both in the appearance of a second red-shifted absorption peak as distinct from the single-particle Mie resonance as well as strong depolarized scattering.
Diffuser radiation patterns over a large dynamic range
Authors: Shirley Lyle G. , George Nicholas
Published: February 2023

A previous publication shows that two classes of radiation pattern result from diffusers having a normally distributed surface profile and an rms phase delay much greater than 1 rad.1 The functional form of the radiation pattern depends on the behavior of the autocorrelation function of the surface profile for small offsets. If the autocorrelation function is cone shaped near the origin, the shape of the radiation pattern depends on the parameter w/S2, where w is the correlation length and S is the rms phase delay of the diffuser. However, if the correlation function is rounded at the origin, i.e., parabolic, the shape of the radiation pattern depends on w/S.
Zeeman spectroscopy on deep double donors in Si: the solid-state analog of the helium atom
Authors: Peale R. E. , Muro K. , Sievers A. J. , Ham F. S.
Published: February 2023

Since double donors in silicon are the solid-state analog of the helium atom, one expects the existence of spin-triplet levels along with the singlet levels commonly observed in IR spectra. In our diffusion-doped Si:Se0 samples, a weak line was observed at 2146.38 cm−1, near the expected zero-stress position of the forbidden 1s(3T2) transition inferred by Bergman et al.1 but too sharp to have been observed in their 1-cm−1 resolution zero-stress spectra. We have studied the Zeeman splitting and polarization components of this new IR absorption line in Si:Se0 and of the corresponding feature in Si:Te0 in both the Faraday and Voigt geometries in fields up to 4 T directed along the three principal crystallographic directions. The isotropic splitting into two σ components and one central π component demonstrates the threefold multiplcity of these levels and g values of 1.0 and 1.3 for the Se and Te lines, respectively, agree well with the simple theory of Lande g factors with an orbital g factor of zero.
Nanometer digital control for a grating ruling engine
Authors: Loewen Erwin G. , Portas Geoff
Published: February 2023

The MIT-B 400-mm grating ruling engine has been partially rebuilt mechanically and equipped with a new interferometer displacement measuring system using a He-Ne frequency stabilized laser, polarization beam splitters, and four-phase silicon detector systems. Both translation and rotation are measured and used in feedback correction loops to compensate for lead screw and residual yaw error of the grating carriageways. The signals are digitized with a bit size of 0.088 nm and processed with a high-speed microprocessor designed to handle all control functions, including the cumulative effects of basometric pressure changes on wavelength. All motions are driven by high-efficiency dc servo motors equipped with tachometer feedback and high-resolution angular encoders. The grating carriage is driven at a nominally constant speed, and the diamond carriage motion is retarded or speeded up to compensate for any residual mechanical errors. Digital input provides for all conceivable groove frequencies 20-2000/mm, including programmable variations. Echelle rulings have demonstrated a resolution of over 106 and periodic errors of <1 nm.
Analysis of particle field holograms on movable stage during reconstruction
Authors: Vikram Chandra S. , Billet Michael L.
Published: February 2023

The general image analysis of particle field holograms is described with the movable hologram on the translation stage during reconstruction. The general case of noncollimated recording and reconstruction beams with fixed observation plane is considered. Relationships for volume and transverse magnification are determined for complete quantitative analysis in particle field holography.
Image plane holographic method for displaying spatial inhomogeneities of a phase object
Authors: Tian Zhiwei , Li Zhengzhi , Wei Gaoyao
Published: February 2023

We present a double-exposure image plane holographic method which can be used to study the spatial inhomogeneities of a phase object. The crossed grating or holographic lens grating divides the incident coherent beam into multiparallel beams which illuminate the phase object in various directions. The essence of the image plane holographic method is that a double-exposure hologram is recorded by multidirectional illumination of the phase object, and micromovements of the holographic plate are made between exposures. The multiobject beams appear during the process of holographic reconstruction. One lens is set behind the hologram, and the needed reconstruction beam may be achieved by spatial filtering in the back focal plane. When the spatial filtering position changes, the phase gradient distribution in various directions is obtained. The midplanes of the object and hologram are optically conjugated, and this system ensures the visualization of any cross section of transparent objects of various forms at a certain focusing depth.
Effects of absorption, pump depletion, and nonlinear refraction on thermal degenerate four-wave mixing
Authors: Guha Shekhar , Chen Wenpeng , Conner Philip
Published: February 2023

Degenerate four-wave mixing, arising from the thermal grating effect or other mechanisms such as the Kerr or photorefractive effect, can be described by a set of four coupled differential equations involving the four fields. Analytical solutions to these equations have been presented for cases where either the pump depletion or the effects of absorption were ignored.1 When both the pump depletion and absorption effects were included, a numerical result involving an iterative solution of the differential equations was presented.2 We present here a solution of the coupled-wave equations in which absorption as well as pump depletion effects are taken into account along with nonlinear refraction. The DFWM reflectivity is reduced to a quadrature using a method proposed by Kessel and Musin.3 For special cases of small absorption and no pump depletion, the solution reduces to the expressions presented earlier.4 The method of solution does not involve finding first integrals of the set of differential equations and can be extended to the description of DFWM using other physical mechanisms.
Dammann gratings as array generators
Authors: Jahns J. , Prise M.E. , Downs M.M. , Walker S.J. , Streibl N.
Published: February 2023

Dammann gratings are binary phase gratings which can be used for producing an array of spots of equal intensity.1 These gratings are of interest, e.g., for providing power supply beams for a 2-D array of logic devices in an optical digital computer. Dammann gratings are computer generated using nonlinear optimization techniques. For producing a 1-D array of N spots, N transitions between +1 and − 1 in the grating have to be computed. The computed data are used to write a binary amplitude mask with an electron-beam machine. Finally, a phase grating is fabricated using reactive ion etching in quartz glass. We present efficient ways to compute Dammann gratings and investigate their performance depending on resolution and other fabrication parameters.
Rotation-invariant pattern recognition using the coordinates of the proper centers of multiple circular harmonic filters
Authors: Sheng Yunlong , Arsenault Henri H.
Published: February 2023

A rotation-invariant single circular harmonic filter does not in general yield a maximum center autocorrelation peak. A new method for predicting the level and position of the center correlation and of sidelobes as a function of the expansion center of the circular harmonic filter was recently developed.1 The proper expansion center that ensures the maximum peak correlation can be easily found by this method. The position of the correlation peak corresponds to the expansion center for the maximum energy of the circular harmonic component. The positions of the correlation peaks of different circular harmonic filters constitute a feature pattern of the object that can be used for rotation-invariant detection of the object against sidelobes yielded by noisy background and parasite objects in a complex scene. The discrimination ability is much improved by the use of multiple circular harmonic components. Only intensity thresholding, clustering, and matching of the simple point patterns are needed for the output of the filters. The procedure is faster and easier than the other methods.
Binary phase-only filters: implications of bandwidth and uniqueness on performance
Authors: Dickey Fred M. , Stalker K. Terry
Published: February 2023

The use of binary phase-only filter (BPOF) concepts in conjunction with recently developed spatial light modulator technology offers the potential for real-time image processing.1 Thus BPOFs have been suggested as a replacement for matched filters in pattern recognition problems.2 However, there are several design issues to be explored in using the BPOF. First, the standard BPOF design approach does not explicitly define the BPOF bandwidth. We define a figure of merit for BPOFs which references the signal-to-noise performance of matched filters and investigates the relationship of BPOF resolution and noise performance as a function of filter bandwidth. Second, since the standard BPOF is equivalent to a phase-only filter (POF) matched to only the even part of the reference image, its response is not unique. We discuss the consequences of image positivity on uniqueness and BPOF filter design. We develop a relationship between a two-channel configuration (to match both the even and odd parts of the reference) and the POF. We show that the two-channel configuration effectively reduces the uniqueness problem to that for POFs.
Irregular sampling and grating detection
Authors: Ahumada Albert J. , Yellott John I.
Published: February 2023

Those familiar only with regular sampling theory must be somewhat surprised by recent research reports of the recognition of supra-Nyquist signals in near-peripheral vision and the detection of more peripheral sub-Nyquist signals by aliased energy.1 Although in the first case the recognition could be based on the information in sub-Nyquist aliases and in the second case subsampling at later stages is possible, both effects are also consistent with irregular sampling and different detection mechanisms for the different regions. In particular, if we assume that detection is based on sensor units with Gabor-functionlike receptive fields, we can simply include units tuned to supra-Nyquist frequencies in the near periphery but omit high-frequency sub-Nyquist units in the far periphery. This argument also requires highly irregular sampling in the far periphery to scatter aliasing noise to lower frequency units. A quantitative assessment of these arguments is based on computer simulations of signal and noise output as a function of sensor unit parameters and sampling array irregularity.
Two-tone frequency modulation with GaAIAs lasers
Authors: Wang L. G. , Riris H. , Carlisle C. B. , Gallagher T. F.
Published: February 2023

Frequency modulation (FM) spectroscopy was first demonstrated by Bjorklund1 in the visible region using a ring dye laser. The basic scheme of FM spectroscopy calls for phase modulation of the laser beam either by an external electrooptic modulator or in the case of diode lasers by modulating directly the injection current. The requirement of modulating the laser at high frequencies (several gigahertz), so that the spectral feature of interest can be probed by a single Fourier component of the laser power spectrum, introduces the need for high-speed detectors which are not always available commercially and have small and damage-sensitive surfaces.
Collisional studies involving electrons and mercury compounds
Authors: Kushawaha V. , Mahmood M.
Published: February 2023

Electron impact dissociation of HgX2 and CH3HgX (X = Cl, Br, I) has been studied in the low energy range of 1–100 eV. In each case, the emission spectrum of the B–X band system of HgX radicals (X = Cl, Br, I) has been observed along with several atomic lines of mercury. By using the most intense bandhead of the B–X system of these radicals, an attempt has been made to measure the emission cross sections at different kinetic energies of the projectile electrons. These cross sections are in general agreement with some of the previously measured1,2 cross sections. However, our measured cross sections are a factor of ~103–104 higher than those reported by Allision and Zare3 for the electron/HgX2 and electron/CH3HgX collisions, respectively.
Metrology of grazing incidence optics
Authors: Slomba A. F.
Published: February 2023

Grazing incidence optics are coming into more frequent use for the x-ray, extreme UV, and visible regions of the spectrum. These applications include astronomical telescopes, synchrotron beam handling systems, resonators for free-electron lasers, and microscopes for plasma x-ray diagnostics.
Holographic interferometer using single-mode optical fibers for the measurement of physical fields
Authors: Li Zhengzhi , Guo Bangjun , Zhu Youman , Tian Zhiwei
Published: February 2023

A holographic interferometric method applied to the measurement of physical fields through the use of fibers is presented. In this method, a hologram, carrying the information of optical elements in the object beam, is made and set behind the output end of the optical fiber. This reconstructed object wave of the hologram is used as the measuring reference wave. When part of the fiber in the object beam is put into the measured physical field, the change of some parameter in the physical field should appear in the optical wave launching from the optical fiber, called the informational object wave. The interference field is formed behind the hologram by the informational object wave, and the measuring reference wave and parametric change of the physical field are revealed by the change in the interference field intensity.
Second harmonic generation in lithium niobate fibers
Authors: Magel Gregory A. , Sudo S. , Cordovaplaza A. , Fejer M. M. , Shaw H. J. , Byer Robert L.
Published: February 2023

Guided-wave nonlinear optical interactions are attractive because of their potential for high conversion efficiency at relatively modest input powers. Achieving this potential requires excellent control over device fabrication process parameters. Interaction between lowest-order guided modes is desirable to maximize overlap integrals and provide a focusable output. Single-crystal fibers of lithium niobate are grown using the laser-heated pedestal growth technique1 in an orientation suitable for temperature-phase-matched frequency doubling of 1064-nm light. Fiber diameters are maintained to within a few tenths of a percent over tens of millimeter lengths by computer feedback growth control. The crystals are poled by thermoelectric fields generated by temperature gradients applied during or after growth.2 This poling technique may enable production of periodically alternating domains for quasiphase-matching interactions using heretofore inaccessible wavelengths or nonlinear coefficients. Magnesium indiffusion is carried out resulting in an approximately parabolic profile graded-index core which will support a 10-20-µm diam fundamental mode.
New line shape profiles in two-wave mixing
Authors: Khitrova Galina , Berman Paul , Sargent Murray
Published: February 2023

We calculate the two-level pump-probe absorption coefficient including both upper-to-lower-level decay and level decays to a still lower lying reservoir level. We carried out calculations of probe absorption profile for arbitrary ratios of natural width and detuning to the Doppler width associated with a given transition. This theory accounts for contributions from all velocity subclasses of atoms, not only those which are Doppler shifted into resonance with the laser field (Doppler limit).1 We observe and explain new line shape features based on dissimilar decays.
Programmable scanning correlator
Authors: Yu Francis T. S. , Zhou Q. H. , Zhang C. H.
Published: February 2023

We have recently described an optically scanning correlator using a rotating grating.1 We now report a real-time programmable optical correlator using an addressable liquid crystal television (LCTV). We show that the angular orientation and spatial carrier frequency of the grating can be implemented with an LCTV controlled by a microcomputer. To alleviate the inherent carrier frequency of the LCTV, the spectra of the grating should be optically enlarged so that the spacing between the different orders is adequately separated. By varying the angular orientation and the spatial frequency of the grating, which was written into the LCTV, a mass complex spatial filter can be synthesized. Thus a real-time large capacity electronically addressable optically scanning correlator can be constructed.
Observation of a density-dependent decay rate in trapped sodium
Authors: Prentiss Mara G.
Published: February 2023

No summary was available at press time.
Quantum theory of relativistic hysteresis of a single driven electron
Authors: Kaplan A. E.
Published: February 2023

A single magnetized electron driven by the EM wave in the vicinity of the cyclotron frequency can experience hysteretic resonance1,2 caused by a tiny relativistic change of its mass. Here we develop a quantum theory of this effect considering a quantum anharmonic oscillator driven by a periodic force. Assuming the radiation relaxation and that the quantum transitions occur only between neighboring slightly nonequidistant eigenstates of the oscillator, we describe the dynamics of the system by the infinite number of coupled kinetic equations for the density matrix elements and derive a procedure for solving them.
Particle size resolution obtainable with scattered intensity measurements
Authors: Son Jung-Young
Published: February 2023

Optical single-particle counters based on scattered intensity measurements have response functions that oscillate with particle size, and the magnitudes of the oscillations limit measurement resolution. To estimate attainable resolution, the intensity scattered into a circular aperture viewing the crossing of two laser beams was calculated using the generalized Mie scattering solution for refractive indices of 1.33, 1.592, 1.7, 2.0, 2.5, and 3.0 (without an imaginary component). The particle size range considered was 0.3-6.2 μm in 0.1-μm steps for receiving lenses with f/Nos. 1, 2, and 4.
One-way complex optical field imaging through a distorting medium by conventional holography: theory and experiments
Authors: Li Zaichun , Zhang Yimo
Published: February 2023

The use of a holographic (or phase conjugate) double-pass scheme1 in image transmission applications is limited by the fact that image sending and receiving processes have to be done on the same side of the distortion. Using a phase conjugate window (PCW) one can achieve one-way complex field imaging through a thin distorting medium with no distortion.2 The effectiveness of this approach, however, is restricted by the phase mismatch between the two pump beams since the image-bearing beam is used as one of two pump beams.
Novel determination of dielectric inhomogeneity from scattered EM radiation
Authors: Hopcraft K. I. , Smith P. R. , Burge R. E.
Published: February 2023

The electromagnetic field scattered from an inhomogeneous dielectric slab is calculated by both approximate and exact methods. A novel inverse solution is found using WKB wave functions as approximations of the exact solution. The solution employs the correct EM boundary conditions and is, therefore, able to account for both surface and volume scattering effects. This enables the size and strength of the inhomogeneity to be determined. Examples of scattering from objects of variable size and strength are presented with corresponding quantitative inverse solutions. When applied to exact forward data, the inversion algorithm quantitatively reconstructs the permittivity and size of the object to an accuracy within 5 and 20 %, respectively. A comparison is made with a reconstruction based on the first Born approximation, which is found to be neither qualitatively nor quantitatively accurate.
Field correlations within fluctuating nonradiating primary sources
Authors: Kim Kisik , Wolf Emil
Published: February 2023

In a paper published not long ago, field correlations within 3-D homogeneous primary sources were studied.1 It was found that if the source is also isotropic, the degree of spectral coherence of the field has, in general, a universal form that is independent of the actual form of the source-correlation function. We present results relating to some of the special cases for which the universal form does not hold. These represent limiting cases for large dimensions of nonradiating stochastic sources.2 We consider in detail a class of large nonradiating primary sources which are Bessel-correlated, and we derive explicit expressions for their field-correlation functions. We examine some consequences of these results. We find, in particular, that with increasing separation of the source points, the field correlations decrease more slowly than the source correlations.
Generalized gauge-invariant perturbations of optical fibers
Authors: Fennelly A. J.
Published: February 2023

Review of the effects of different perturbations of optical fibers shows that their physical effects are generally identical: that usually is the transfer of the lower-order modes (as measured in the far field) to the higher-order modes of the fiber. This is so for the general classes of microbends, macrobends, pressure variations, temperature variations, and chemical changes. This means that rather than being truly different perturbations, they are physically really the same thing. Each represents a true gauge-invariant perturbation plus a piece that is merely a gauge transformation. Each perturbation is then transformable, and their apparent differences are physically trivial. We take as our points of departure the perturbed fiber discussions of Snyder and Love1 and Hill’s2 analysis of differential equations from their group invariance properties. We analyze the modal structure of unperturbed fiber in terms of the invariance group of the wave equation for the appropriate fiber geometries and boundary conditions and then show how their perturbations consist of a true physical piece and insignificant parts that are just gauge transformations of each other.