bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonimaging optics and the Liouville theorem in the XUV region
Authors: Jannson Tomasz , Ng Joel
Published: February 2023

In general, Liouville's theorem holds for any time-reversible Hamiltonian system including the geometrical optics (both imaging and nonimaging1,2) model of monochromatic rays, where, in Hamiltonian formulation,2 the z-coordinate is treated as a parameter equivalent to the time variable in statistical classical mechanics. Thus the so-called ideal nonimaging optical elements, well known in the IR/VIS/UV region,1,3 can also be introduced to the collimation and concentration of XUV electromagnetic radiation (1–100 nm). Contrary to the IR/VIS/UV region, where the nonimagng elements are based on either metallic reflection or dielectric total internal reflection, the XUV concentrators/collimators are based on grazing incidence total external reflection, since the refractive index of all optical materials is smaller than 1 in the XUV region.
Holographic wavelength-division multiplexers with low cross-coupling
Authors: Jannson Joanna , Jannson Tomasz , Yeung Peter C.
Published: February 2023

Fiber-optic multichannel wavelength-division multiplexers (WDMs) with extremely low cross-coupling losses (< −60 dB), based on high optical density (OD) holographic filters, are proposed. The basic architecture of multimode holographic WDMs consists of a cascade of high OD Lippmann-Bragg holograms in waveguide geometry. Based on the optical performance of high-efficiency holographic technology1 developed in the near-UV, visible, and near-IR regions, the intrinsic losses per channel can be as small as 0.05 dB. The number of channels in both multiplexing and demultiplexing modes can exceed 10 with channel separation being 10–15 nm. Multichannel WDMs with low intrinsic and cross-coupling losses are particularly desirable in the next-generation fiber-optic local area network applications.
Speckle reduction in SAR imagery
Authors: Harvey E. , April G.
Published: February 2023

The high resolution in synthetic aperture radar (SAR) systems is reduced by the speckle appearing in SAR images. This speckle noise is generated by the coherent processing of radar signals and is similar to optical speckle. This multiplicative noise in radar images may be reduced by computer spatial processing: noise smoothing algorithms are developed based on local homomorphic processing of the images. The algorithms applied to the SAR images suppress the speckle noise without deterioration of the edges and fine details.
Optoelectronic design using detector signal simulation
Authors: Howard Timothy L.
Published: February 2023

The design of high-accuracy optical position sensors requires detailed knowledge of detector signal responses. An optical design method has been developed which combines features of traditional ray tracing with a pixel-based image model to calculate idealized output signals for solid-state detectors. The method uses masking grids to generate a weighted-pixel image. Pixel intensities are then summed to signal channels appropriate to the particular detector geometry under study. The value of this method lies in its utility as a design tool; comparative evaluations of various optical trains and detector geometries may be performed prior to optical breadboard and test. The method is easily realized as an array-based computer program. Features of the program and its implementation are discussed including optical system modeling, mask generation and pixel weighting, and signal summation. An application of the method to the design of a high-accuracy electronic autocollimator is reviewed and shown to compare closely to experimental results. Extensions of the method and its uses in other applications are discussed.
Computer synthesized diffraction patterns
Authors: Rayces Juan L. , Lebich Lan
Published: February 2023

An efficient algorithm for the computation of monochromatic and polychromatic diffraction in the region of the focus of a converging wavefront has been devised for the Perkin-Elmer RAY-GODE optical design computer program. The algorithm generates a digitized map of intensity over an area defined by the user. With this map energy distribution can be integrated in different ways. Also, the program plots an analog map which closely resembles photographs of so-called aerial images of artificial stars observed under a microscope.
Magnitude of chromatic variation of magnification on the human fovea
Authors: Simonet Pierre , Campbell Melanie C. W. , Harrison Elaine M.
Published: February 2023

Dispersion of the refracting elements in the eye gives rise to chromatic aberration. A difference of refraction in red and blue light of ~1 diopter is due to longitudinal chromatic aberration. At an angle to the optical axis, a variation of magnification with wavelength (also termed transverse or lateral chromatic aberration) is introduced. The chromatic difference of magnification for targets illuminated by 650- and 490-nm wavelengths was measured by having subjects align Vernier targets in a split field. The subject’s measured longitudinal chromatic aberration was compensated for during the experiment. Preliminary measurements indicate that the chromatic difference of magnification is no more than 30 sec of arc, much less than the value (≃60 s) calculated for a centered schematic eye model incorporating a pupil. It is postulated that nasal decentration of the pupil of 0.25 mm dramatically reduces the amount of this aberration present on the fovea, as discussed by Bennett and Rabbetts.1
Frequency-hopped spread spectrum optical processor
Authors: Javidi Bahram
Published: February 2023

A real-time optical processor that can detect spread spectrum signals transmitted by the frequency-hopping method is presented. The system can generate the 2-D correlation distribution between the reference data and the input data at the output plane of the optical processor. The 1-D spread spectrum data in the time domain are converted to 2-D code patterns in the space domain suitable for optical signal processing. The codes are then processed to yield the 2-D correlation between the reference signal and input signal. The architecture of this optical processor is such that the conversion and processing of the data are carried out in real time. The system employs acoustooptic Bragg cells, 2-D spatial light modulators, and the electronics interface. The effect of the acoustooptic cell’s nonideal behavior on the system performance is studied.
Heat transport in titanium-doped sapphire rods
Authors: Farrukh Usamah O. , Buoncristiani A. M. , Byvik C. E.
Published: February 2023

The measured thermal properties of titanium-doped sapphire crystals have been incorporated into a mathematical model for the transport of heat in finite laser rods. The crystals have a nominal titanium concentration of 0.09% by weight of the oxide. Measured values (at 23°C) are 0.219 cal/g K for the specific heat and 0.358 and 0.386 W/cm K for the anisotropic thermal conductivity perpendicular to the parallel and to the c axis, respectively. Orthonormal radial and longitudinal eigenfunctions were obtained, and the time evolution of the temperature distribution in the rod was calculated for end pumping configurations assuming radiative boundary conditions at all surfaces. Computed effective decay times of heat dissipation within the modeled crystals indicated the need for active cooling if a repetitive pulsed operation is desired.
Stimulated emission in indirect AlxGa1-xAs
Authors: Kalt H. , Norwood D. P. , Boggess Thomas F. , Smirl Arthur L.
Published: February 2023

In Al
x
Ga1-
x
As close to the direct-to-indirect band gap semiconductor crossover composition (x
c
≃ 0.43), alloy disorder mixes the wave functions of states in the Γ- and the X-conduction bands. This allows bimolecular recombination of electrons in the indirect bands without phonon participation (quasidirect transitions). At appropriate carrier densities stimulated emission out of the X valleys is observed for indirect Al
x
Ga1-
x
As with Al concentrations up to x = 0.52. In Al0.45Ga0.55As a population inversion for the T band is achieved for carrier densitiies at which the distribution in this band is strongly nondegenerate. This is due to the easily obtainable high degeneracy in the valence band. Simultaneous stimulated emission out of the Γ and X bands is then observed.
Modulation instability induced by cross-phase modulation in optical fibers
Authors: Agrawal Govind P.
Published: February 2023

Modulation instability refers to a process in which weak perturbations from the steady state grow exponentially as a result of an interplay between the nonlinearity and the group-velocity dispersion. In the context of optical fibers modulation instability requires anomalous dispersion and manifests as breakup of the cw or quasi-cw radiation into a train of ultrashort pulses.1 This paper shows that a new kind of modulation instability can occur even in the normal dispersion regime when more than one optical field copropagates inside the fiber. The physical mechanism behind this novel phenomenon is cross-phase modulation that invariably accompanies the nonlinearity-induced self-phase modulation. The modulation-instability-induced gain and the frequency range over which the gain occurs are studied by including the effect of group-velocity mismatch. Numerical results are presented for the realistic case of propagation around 0.53 μm.
Amplification of 1-μm ps pulses in GaAs by transient energy transfer
Authors: Dubard J. , Smirl Arthur L. , Cui A. G. , Boggess Thomas F. , Valley George C.
Published: February 2023

Large amplification of 1-μm ps pulses is achieved by two-beam mixing in GaAs. Here two 28-ps (FWHM) pulses are spatially and temporally coincident in an undoped semi-insulating sample of GaAs with an angle 2θ between the two beams. The energy transferred between the two beams is measured as a function of fluence, crystal orientation, pump–probe ratio, and time delay between pump and probe. The two-photon absorption of the two interferring pulses produces a spatially periodic distribution of electron-hole pairs. The sign of the Drude-Lorentz index change associated with these free carriers is negative, and the magnitude is proportional to the carrier density. Thus this tree-carrier index grating is spatially shifted by one-half a period (or π) with respect to the incident irradiance pattern. It is well known that such an index grating cannot transfer energy in two-beam coupling experiments in steady state or for equal beams. During picosecond two-beam mixing experiments, however, significant energy transfer is expected because of the highly transient nature of the grating formation. This process is called transient energy transfer, and for fluences larger than ~5 mJ/cm2, it is observed to dominate the twobeam mixing process. At fluences of 25 mJ/cm2, weak beam gains >10 are measured at room temperature. Similar gains were recently reported in Si1 at energy densities of ~100 mJ/cm2.
Optical coatings made by plasma chemical vapor deposition
Authors: Boling Norman
Published: February 2023

Plasma chemical vapor deposition (PCVD) is not commonly used in the optical coating industry, despite the fact that it can often offer significant advantages over the more conventional optical coating processes. Among these advantages are: (1) Very high coating rates: In intense plasmas high-quality coatings can be deposited locally at 106 Å/min and globally at several g/min in relatively simple equipment. (2) Ease of coevaporation or doping: High efficiency of deposition of any constituent in the plasma allows multiconstituent films through simple mixing of input gases, leading to greater control over important film characteristics such as stress, adhesion, and resistance to chemical attack. (3) Films with very low absorption: High-purity starting materials and equipment without electron guns, electrodes, etc., reduce absorbing contaminant levels well below those practical with sputtering or thermal evaporation.
Reactive ion plating deposition for sui generis optical coatings
Authors: Pulker H. K. , Buhler M. , Hora R. , Guenther K. H.
Published: February 2023

Edge filter double-halfwave narrowband transmission filters and broadband antireflection coatings have been deposited employing a reactive ion plating process. Reactive ion plating is distinctly different from other ion-assisted deposition techniques in that a high-current low-voltage plasma arc burns into the vapor source rather than a low-current medium-to-high energy ion beam irradiating the substrate and growing film surface. The vapor sources are melts of metals or suboxides produced by a modified standard electron-beam gun. The optical substrates when coated by reactive ion plating are in contact with the plasma and attain a self-bias potential of –5 to –60 V, which accelerates the vapor atoms/molecules ionized by the plasma arc toward the substrate surface. The resulting coatings have a very dense microstructure as apparent from high-resolution transmission electron micrographs, obtained by direct sectioning of the coatings perpendicular to their surface with a microtome, and by replicating fractured edges with a platinum/carbon preshadowed carbon film.
Effect of ion-assisted deposition on the surface roughness
Authors: Jin Mike S. , Smith Douglas J.
Published: February 2023

A number of studies report higher packing densities of various thin-film materials utilizing the ion-assisted vapor deposition technique,1,2 but its impact on the surface roughness and scattering has not been studied extensively. This report presents the experimental results from a study on the surface roughness and scattering characteristics of several amorphous, polycrystalline, and crystalline materials. The results compare thin films deposited with various ion energy and ion current density with thin films deposited without any ion assist. The roughness measurements of the samples were made on a total integrated scatterometer and a stylus profilometer. The structural comparison made with an x-ray diffractometer and a transmission electron microscope, and some of the possible mechanisms responsible for the observed changes are also presented.
Application of coherent-mode representation to inverse propagation problems
Authors: Wolf Emil , Habashy Tarek
Published: February 2023

A new mathematical technique for obtaining solutions to certain types of inverse propagation problem is presented. Specifically, propagation from a planar secondary source of any state of coherence is considered. It is shown how, in circumstances when contributions from evanescent waves may be neglected, the cross-spectral density function in the source plane may be determined from measurements of the cross-spectral density in any plane parallel to the source. The method, which is based on the coherent-mode propagation in spatially bandlimited wave fields,1 is illustrated by results obtained from computer simulation. The method appears to be particularly suited to determining the mode structure of a source, e.g., a laser, from correlation measurements made at an arbitrary distance from it.
Interaction of two evanescent waves traveling in opposite directions
Authors: Yu L. , Yu L. S.
Published: February 2023

Two evanescent waves are generated by division of a laser beam by total internal reflection. Two separated rectangular prisms are used to form a narrow gap of the order of 1 wavelength. The gap width is modulated by two plate piezoelectric transducers with a resonance frequency of ~10 MHz. A third prism is used to change the direction of one beam, and as a result the two beams reaching the separated surfaces from opposite sides form two evanescent waves that propagate in parallel but opposite directions. At first one of the beams is turned off, and we measure the tunneling intensity of the other one. Matched evanescent waves interact with each other to form a propagating wave, so that as the previously extinguished beam is turned on, there is an interaction between the two evanescent waves that may change the tunneling intensities of both beams, which are also modulated by transducers. A plate with varying thickness is inserted into one beam to adjust the relative phase between the two waves.
Holographic associative memory switching system
Authors: Healey Peter , Smith David W.
Published: February 2023

An N × N optical space switch is described which uses holographic associative memory techniques to store switch states. The switch states are stored as follows: Light from one input port is spatially expanded and then phase-front encoded by a spatial light modulator and directed onto a phase volume holographic recording material. Light corresponding to the available output ports is allowed to fall, in turn, to the same region of the holographic medium. By using a unique phase-front code on the input (reference) wave as it is stored in association with each output (object) wave, a multiplexed phase volume hologram with associative recall properties is created. This process is repeated for all N input ports. Crosstalk can be minimized and efficiency maximized by selecting a suitable orthogonal set of reference wave codes and by maximizing the angular separation between the object point sources so that the Bragg extinction angle is exceeded. The main advantage of this type of optical switching system is that all switch states are preprogrammed and may be tailored to particular needs.
CFF depends on color appearance
Authors: Larimer James , Piantanida Tom , Arend Lawrence , Varner Denise
Published: February 2023

By stabilizing the image of a green adapting field on the retina and surrounding it with a yellow annulus whose outer boundary is unstabilized on the retina, we were able to use filling-in to change the apparent color of the green disk to the color of the annulus. By reversing the colors of the annulus and field we changed the filled-in color to green. This color change only occurs with retinal image stabilization. Using this method, we examined whether the apparent color of the adapting field influences the CFF of a superimposed test spot. The test spot consisted of counterphase-flickering tritan metamers at various contrasts, which generated time-varying signals exclusively in the short-wavelength cone pathway. We found that for our conditions, CFF depends on the perceived color of the adapting field independent of the spectral distribution of its retinal image. These results indicate that CFF can be influenced by a chromatically coded neural site that is itself influenced by the filling-in process.
New approach to inverse synthetic aperture radar imaging
Authors: Hudson Scott , Psaltis Demetri
Published: February 2023

Inverse synthetic aperture radar (ISAR) imaging is an extension of synthetic aperture radar (SAR) imaging to cases where the synthetic aperture is produced by target motion (trajectory), as opposed to radar motion, and hence unknown a priori. In SAR knowledge of the motion is used to produce the image; lack of this knowledge causes the ISAR imaging problem to be underdetermined. Additional constraints are needed to obtain a solution. The typical constraint used, to assume that the target is effectively rotating at a constant angular velocity, can faithfully image the target only in those cases where the real trajectory is accurately described by this assumption. We show that ISAR imaging can be extended to include much more general trajectories by putting constraints on the image produced rather than on the trajectory. The work we present includes (1) a theoretical analysis of ISAR image formation with arbitrary trajectories, (2) computer verification of this analysis and simulation of our method, (3) sonar imaging of simple objects, and (4) an optical implementation of our method.
Comparison of optical processing techniques for synthetic aperture radar
Authors: Haney Michael W. , Athale Ravindra A. , Psaltis Demetri
Published: February 2023

Synthetic aperture radar (SAR) is widely known as one of the most successful applications of optical processing techniques. However, as use of SAR has expanded to include more and varied applications, optics has not continued to play a central role in the processing architectures. This has been due to technological limitations and restrictions inherent in the original coherent processing technique. In recent years several hybrid optical SAR processing approaches have been proposed which address the new processing issues while still exploiting the processing power of optics. These techniques fall into three groups: space-integrating, where the image is formed via a 2-D spatial integration of light after a frame of data has been received; time-integrating, where the image is formed with a temporal integration of light along each coordinate axis; and time-and-space-integrating, in which a 1-D spatial integration is performed after each line of data is received and the results are temporally integrated along the other dimension to complete the imaging process. We compare the fundamental limitations of these approaches in key performance aspects such as resolution, dynamic range, real-time operation, and flexibility. The results provide guidelines in matching the various hybrid architectures with the diverse SAR applications.
Evaluating color vision with moving stimuli
Authors: Cavanaugh Patrick
Published: February 2023

The contribution of color to motion can be measured by finding the equivalent luminance contrast of color stimuli: the contrast of a moving luminance grating required to just null the notion of an equiluminous color grating, of the same spatial and temporal frequency, moving in the opposite direction. The equivalent contrast of color stimuli was highest at low temporal and spatial frequencies and was highest for red/green stimuli, intermediate for yellow/blue, and lowest for green/purple falling on the tritanopic confusion line. This new measure provided an excellent basis for identifying color-defective observers, since, unlike normals, they required little or no luminance contrast to null the motion of a chromatic stimulus, whether it was red/green, which they discriminate less well than normals, or blue/yellow, which they discriminate as well as normals. Additional tests showed that neither long-range motion processes, interneuron variability in equiluminance, phase lag, nor second harmonic distortion in the response contributed significantly to the motion perception. The contribution of color to motion appears to derive, at least in part, from an opponent-color input to direction-selection units. This input is absent for color-defective individuals.
Chromatic-achromatic interactions in pattern vision
Authors: De Valois Karen K. , Switkes Eugene
Published: February 2023

Using a simultaneous masking paradigm and a variety of chromatic axes, we have examined the spatial frequency selectivity and orientation bandwidth of mechanisms which respond to isoluminant chromatic gratings. We find similar selectivity along both dimensions to that seen for isochromatic luminance gratings, differing only in that bandwidths for color patterns are often somewhat broader. Furthermore, the contrast dependence of color–color masking is similar to that seen for luminance when mask contrasts are normalized on a multiples-of-threshold metric. When chromatic and luminance patterns are mixed in a masking experiment, chromatic mask gratings significantly impede the detection of luminance gratings when the mask contrast is above its own threshold. The frequency selectivity of this interaction is similar to that seen for luminance–luminance masking. Facilitation is never seen for the combination of a chromatic mask and a luminance test. Luminance masks, however, facilitate the detection of a chromatic test for a wide range of suprathreshold mask contrasts and across a broad range of mask/test frequencies. Only when mask contrast is very high is the detectability of a chromatic test reduced. In all cases, mixed chromatic-luminance masking results are independent of the relative pattern phase at which the mask and test patterns are used.
Guided TE waves in a multilayer planar waveguide surrounded by nonlinear media
Authors: Li Yi-Fan , Lit John W. Y.
Published: February 2023

In a previous paper,1 we presented general formulas describing field distributions, eigenvalue equations, and power flow for both TE and TM modes in multilayer slab waveguides. These formulas for TE modes are now extended to the case of multilayer slab waveguides surrounded by nonlinear media with positive nonlinear coefficients. By introducing a parameter ψ
i
(half-phase shift) for each of the two outermost layers, we found that the extended formulas are formally identical with those of the linear counterparts for eigenvalue equations and power flow and are slightly different in the outermost layers with those of the linear counterparts for field distributions. The parameter ψ
i
is constant when the layer is linear and a function of the intensity in the outermost boundary interface when the layer is nonlinear. Applying these new formulas to the three-layer case, a thin film bounded by two nonlinear media, we have obtained the results which, although different in form, agree with those derived by other authors. Also, four-layer structured and symmetrically five-layer structured waveguides with nonlinear outermost media are discussed, and some numerical results are presented.
Nonlinear optical properties of spatially distributed particle composites
Authors: Bowden Charles M.
Published: February 2023

We examine the nonlinear dielectric response of small spherical grains ϵ
m
embedded in a linear dielectric ϵ
d
. The models for the spherical grains are a Kerr medium1,2 and a two-level system.3 The expression for the dielectric function ϵ
m
is dependent of the grain size; in addition it also depends on the local electric field E
L
. This field is related to the external applied field E0 by the equation E
L
= (3ϵ
d
/ϵ
m
+ 2ϵ
d
)E0. The steady-state equation for the averaged external field is ∇2E0 + (ω2/c2)ϵ*E0 = 0, where ω is the frequency of the field, ϵ* is the dielectric function from the effective medium approximation, and it is obtained from the self-consistency relation4 〈ϵ(r) − ϵ*/ϵ(r) + 2ϵ*〉 = 0; the angular brackets denote an average taken over the ensemble of dielectric spheres distributed in a small volume. Using the slowly varying-envelope approximation we solve these equations for a distribution of grain radii and the affect this has on the effective optical nonlinearities. In particular, we show its effect on the optical bistability for these composite systems.
Advances in optical resonators
Authors: Siegman Anthony E.
Published: February 2023

No summary of this tutorial or biographical information was available at press time.
High-sensitivity transmission mode liquid crystal spatial light modulator with compound electrode
Authors: Ashley Paul R. , Davis Jack H. , Oh Tae Kwan
Published: February 2023

Spatial light modulators are a key element in coherent signal processing applications, primarily as an incoherent light converter. In this and other applications the sensitivity and spatial resolution as well as speed are important considerations which limit performance. In addition, most devices require operation in the reflection mode due to inadequate transmission of the thick photoconductor layer. Reported here is a liquid crystal modulator using a thin-film (≤1-μm) amorphous silicon photodiode in a PIN configuration. A novel electrode design is used to greatly increase the efficiency of the field switching, allowing the use of photoconductor layers thin enough to achieve good transmission. The electrode design incorporates an additional array element located between the photoconductor and the liquid crystal which enhances a horizontal component of the electric field. Spatial resolution of over 20 Ip/mm has been demonstrated. The white light sensitivity is better than 3 μW/cm2. A 2-D ac lumped element device model was developed for characterization of the modulation, spatial resolution, complete field distribution, and temporal performance. The unique electrode design combined with the capability for transmission mode operation using the twist mechanism of the nematic liquid crystal alone results in a much desired insensitivity to thickness nonuniformities.
Liquid crystal light modulator fabricated using a diffraction grating
Authors: Sakata Hajime , Nishimura Michiyo , Yamanobe Masato , Matsumoto Kazuya
Published: February 2023

We present a light modulator fabricated with a diffraction grating. Liquid crystal is filled in the grooves of the fine grating base, and it works as a phase tunable material. In the turn-off state, liquid crystal is forced to orient parallel to the grooves due to the geometry and shows an extraordinary refractive index which is different from that of the groove–grating base. In this state, we can minimize the zeroth-order diffracted light using an optimally designed groove–grating shape. When a voltage is applied to the liquid crystal in the turn-on state, the liquid crystal turns itself perpendicular to the base and shows the ordinary refractive index, which almost matches that of the groove–grating base. The incident light is fully transmitted as zeroth-order diffracted light. Forced orientation causes a fast turn-off transition. As the groove pitch is decreased, turning-on becomes slow and turning-off becomes fast. We have obtained more than 90% transmittance including surface reflection loss of the device. The extinction ratio is as muchas 100. When the switching voltage is 15 V, turn-on time is <100 μs, and turn-off time is several milliseconds.
Abbe's sine condition and readout principle of an optical disk system
Authors: Kubota Shigeo
Published: February 2023

In optical disk systems, when a spot scans a pitted spiral track, the orders diffracted by the pits interfere with one another on the detector, causing it to generate a signal. The signal can be approximated by a convolution of the pits with a line spread function. Since aberration degrades the line spread, it causes waveform distortion in the signal. This is particularly harmful to the digital signal, in which the length of the pits should be reproduced precisely. Experimentally, the largest waveform distortion is observed in the presence of coma. The next largest cause is spherical aberration. Consequently, an optical disk system must be aplanatic to reproduce a distortion-free signal.
Measurement of mixing fluid flows with optical tomography
Authors: Snyder Ray , Hesselink Lambertus
Published: February 2023

Optical tomography offers advantages over conventional techniques for visualizing complicated mixing fluid flows. We have developed a system for acquiring 3-D measurements of concentration nonintrusively in a turbulent mixing coflowing jet. Holographic interferograms simultaneously record views from 36 different angles of the jet in 300 μs. The interferograms are processed tomographically to yield the index of refraction at all points in the jet. We show measurements of a 6-m/s helium jet mixing with air. The temporal resolution, spatial resolution, and SNR are very good.
Scaling law and spectral invariance with 3-D quasihomogeneous primary sources
Authors: Foley John T. , Wolf Emil
Published: February 2023

A sufficiency condition was recently derived for a planar secondary source to generate light whose normalized spectrum is the same throughout the far zone and across the source plane.1 This condition is known as the scaling law because it implies certain invariance properties of the degree of spectral coherence of the source under scaling with wavelength. We derive a corresponding condition for light produced by 3-D primary quasihomogeneous sources. While the corresponding 3-D version of the scaling law is found to be a sufficiency condition for the normalized spectrum of the emitted light to be the same throughout the far zone, it has quite a different implication, which is discussed, regarding the relationship between the spectrum of the far field and the source spectrum.
Relationship between quantum states at the input and output of a beam splitter
Authors: Hong C. K. , Ou Z. Y. , Mandel Leonard
Published: February 2023

By making use of the diagonal coherent state representation of an optical field, together with the operator relations between dynamic variables at the input and output of a beam splitter, we have derived a general relation between density operators of input and output states. As an illustration of the general procedure we consider two orthogonally polarized photons at the beam splitter input and derive the output state. We show that in the special case in which the reflectivities and transmissivities of the beam splitter are equal, this state exhibits certain features of the well-known singlet state for orthogonally polarized photons.
Bounds on sub-Poissonian statistics in the Jaynes-Cummings model
Authors: Hillery Mark , Mlodinow Leonard D.
Published: February 2023

There is a conservation law present in the Jaynes-Cummings model which restricts its dynamics. This means that from a given initial state only a subset of all possible states of the system can be reached. This allows one to place bounds on the expectation values of observables of the system. Using this procedure bounds are found on the extent to which the field statistics can become sub-Poissonian for an initial coherent state. Mandel’s Q parameter, which measures the extent to which the statistics are sub-Poissonian, is shown to be a decreasing function of the initial field amplitude. For an initial thermal field it is found that there is a temperature (which depends on the field frequency) above which the field never becomes sub-Poissonian. These methods can be extended to multiatom systems, and results for such systems are presented.
Longitudinal periodicities of quasihomogeneous fields
Authors: Ojeda-Castaneda J. , Andres P.
Published: February 2023

On free propagation the cross-spectral density function obeys two Helmholtz equations. We show that under the paraxial approximation, both equations can conveniently be written as a single differential equation in terms of the sum and difference coordinates. Furthermore, we indicate that the formal solution to this single differential equation can be written as a differential operator, which converts the cross-spectral density function at the object plane into the cross-spectral density function at any other plane. This formalism is applied to give a coherence theory of the Lau effect at finite distances when using quasihomogeneous fields.
Caustic merit function for optical design
Authors: Al-Ahdali Issam H. , Shealy David L.
Published: February 2023

A caustic merit function, which measures the spread of the caustic surfaces from an ideal image point, has been defined for use in minimizing all orders of the monochromatic aberrations of an optical system. Evaluation of this function requires a few rays to be traced through the optical system. For a triplet lens the caustic merit function, which is subject to the constraint that the total power of the lens remain constant, has been used to optimize several lenses. The rms blur circle radius for the optimized systems has been evaluated and compared with that of the original systems. Since the caustic merit function describes all order of image aberrations, the present results suggest that the caustic merit function could be used in designing arbitrary optical systems and could have wide use in the area of computer automated optical design.
OTF and MTF of a tessar photolens treated as a cascade linear system
Authors: Calvo Maria Luisa , Lakshminarayanan Vasudevan
Published: February 2023

Using the general formulation for calculating the coherent transfer function (CTF) of a compound optical system working under linearity conditions in the Fresnel regime, we obtained the optical transfer function (OTF) and modulation transfer function (MTF) by performing an autocorrelation of the tessar photolens CTF. Such an analysis allows one to consider factors affecting the MTF such as the influence of the depth of field while focusing, etc. The results of this systematic procedure (which can be easily implemented on a computer) are compared with OTF functions obtained by other standard computational methods.
Impulse response of multiaperture systems comprised of 19 and 37 apertures
Authors: Watson Steven M. , Mills James P. , Rogers Steven K.
Published: February 2023

Many astrophysical observations require large diameter spaceborne optics. Because of the limited space and weight requirements for boost into orbit and manufacturing limitations, large diameter optics pose a problem. Multiaperture optical systems may provide a solution. This theoretical analysis determined that multiaperture systems with the same equivalent diameter as a single large circular optic could provide an impulse response which is superior to that of the single large optic. In addition, the diffraction patterns of these multiaperture systems contained 75% of the total irradiance of the large optic. Various numbers, sizes, and configurations of apertures (constrained by the diameter of the single large optic) were examined to find the impulse response which minimized the secondary sidelobe irradiance of the far-field diffraction pattern. The multiaperture systems, containing 19 and 37 apertures, were composed of symmetric concentric rings of circular apertures. These apertures filled the single large optic. The results of this research indicate that the central lobe width of the impulse response of the multiaperture system was equal to that of the single large optic. In addition, the secondary sidelobe irradiance maxima of the multiaperture system was 0.0148 compared with 0.0174 of the single large optic.
Real-time optical broadband pseudocolor encoder
Authors: Chao Tien-Hsin , Liu Hua-Kuang
Published: February 2023

There are many interesting applications of a pseudocoloring technique. These include image enhancement, radiographic image analysis, IR detection, and multicolor projection display.1-3 We present an innovative real-time optical broadband pseudocolor encoding technique using a liquid crystal TV spatial light modulator (LCTV SLM). This technique is able to modify the gray-scale distribution of an input image via the nematic twist of the liquid crystals in the LCTV SLM. Spatial multiplexing is obtained with a dispersive optical element for multichannel processing. Input images carried by the three spectral bands of the primary colors (i.e., red, green, and blue) are processed separately in the Fourier plane of the white light processor by varying the polarization states of each of the three analyzers. A broad range of pseudocolor mapping to a multiple of gray levels can be obtained as a result of the mixture of the three primary colors. Theoretical analyses are given, and experimental results of the pseudocoloring of both continuous-tone image and gray-scale test pattern are also demonstrated.
Intelligent control of large data files by optics
Authors: Ludman Jacques E. , Caulfield H. John
Published: February 2023

We have suggested elsewhere that the combination of page oriented holographic memories with optically addressed spatial light modulators led to the ability to assess many symptoms and many derived tentative diagnoses in parallel. Our previous work showed a general approach to avoid the necessity of an exhaustive search of memory to identify a new input. We discuss the implementation of that approach using a neural network as the controller of the total system. The result is a pattern recognition system which exhibits many useful features of the human system. In particular, it forms hypotheses, determines what measurements to make to increase the certainty of those hypotheses, makes the needed observations, and either increases the certainty of diagnosis or reduces the certainty of the initial diagnosis and oscillates to a new one.
Electrooptically tunable narrowband Fabry-Perot/Solc filter design
Authors: Weis R. S. , Gaylord Thomas K.
Published: February 2023

Tunable narrowband spectral filters are useful in many applications. A new electrooptically tunable narrowband (0.01 nm in some cases) spectral filter which combines the characteristics of a Fabry-Perot filter and a folded Sole filter, called the Fabry-Perot/Solc filter, is described. The design is based on the three-layer multiple-pass filter proposed by Williamson.1
Application of extremely high intensity light to matter
Authors: Freeman R. R.
Published: February 2023

This process—above threshold ionization (ATI)—is when an atom placed in an intense optical field absorbs s more photons than the minimum number n necessary to reach the ionization limit I0. In this process many peaks are observed in the photoelectron spectrum; and in the usual experimental conditions of a long laser pulse, the peaks are found to have relatively narrow widths and energies given by E = (n + s)ħω – I0.
Nonresonant multiphoton ionization of the noble gases at 5860-A: theory and experiment
Authors: Perry Michael D. , Szoke A. , Landen O. L. , Campbell E. M.
Published: February 2023

The nonresonant multiphoton ionization of the noble gases Ar, Kr, and Xe is investigated in the 1013–1014-W/cm2 range using a short-pulse dye laser. The experiment consists of determining the actual number of ions produced in different charge states as a function of laser intensity. Multiple ionization occurs for each species with Xe6+ being the highest charge state observed. The ion yields show no evidence of direct processes contributing to the production of multiple-ionized species.
Comparing above-threshold Ionization calculations to experiments
Authors: Bucksbaum Philip H. , Bashkansky M.
Published: February 2023

We present results of strong field calculations of ATI in xenon and krypton by elliptically polarized laser pulses, showing how the spectra and angular distributions depend on polarization, pulse width, intensity, and wavelength. We compare these results to experiments and find that most observations are adequately explained by a simple model in which weakly bound electrons evolve in the presence of a time-varying classical potential. The induced wiggling of the electron wave function results in wave-mechanical interference, producing sharp minima in angular distributions that have been observed. Direct comparisons between theory and observations in above-threshold ionization experiments have been hampered in the past by the large spatial and temporal inhomogeneity of tightly focused pulsed laser beams. We have attempted to overcome these difficulties through direct numerical simulations of the experiments. These simulations allow us to perform quantitative tests of ATI theories despite the presence of ponderomotive scattering of the final state electrons.
Symmetry approach to coherence in spontaneous nuclear decay
Authors: Hartmann Francis X. , Rotman S. R. , Garcia K. K.
Published: February 2023

The possibility of exploiting the dynamic electron-nucleus interaction to create a nuclear population inversion in a short-lifetime excited state has been discussed,1 and work on some models incorporating nonlinear or nonperturbative approaches continues. In addition, there is also recent interest in the question of whether the superradiant effect is observable in nuclear gamma transitions from such an inversion.2 Here we examine the symmetry effect which leads to the N or N2 dependence of enhanced spontaneous emission described by Dicke in boson fields as applied to nuclear transitions. Recent laser approaches treating nuclear superradiance as a transient laser pulse involving stimulated emission do not examine that symmetry. A classification scheme based on the unitary and permutation groups is used to describe basic decay rate characteristics, spatial dependence of the cooperation number, and multilevel effects in the short-wavelength regime.
Epitaxial solar cells on upgraded metal-lurgical-grade silicon
Authors: Sastri V. D. P.
Published: February 2023

Photovoltaic characteristics of homoepitaxial solar cells on specially prepared upgraded metal lurgical-grade polysilicon substrates were measured. Good spectral responsivity values obtained in the long-wavelength region, despite poor absorption of long-wavelength radiation in the 20-μm thick epilayers, led to the inference of enhanced optical paths in the epilayers for the incident radiation. A likely mechanism for these long optical paths is surface texture often exhibited by silicon epitaxial films and seen on the samples studied. Measured minority carrier diffusion lengths of 30–40 μm and epilayer thickness of 20 μm represented conditions in which a back surface field in the substrate also contributed effectively to the performance of the cells, which, even for entirely nonoptimized fabrication parameters, yielded AM 1.5 efficiencies of the order of 7%.
Femtosecond pulse break up and soliton formation in optical fibers
Authors: Zysset Beat , Beaud P. , Hodel W. , Weber H. P.
Published: February 2023

The propagation of subpicosecond pulses in optical fibers in the vicinity of the zero dispersion wavelength is investigated. Although the input powers are sufficient to generate solitons of up to tenth order, the formation of these solitons is not observed. Instead, the input pulse breaks up temporally and spectrally after an initial stage of narrowing. Fundamental solitons are formed in this way with pulse widths of the order of 55 fs. These solitons subsequently experience the soliton self-frequency shift1 thereby increasing their wavelength and duration.
Stabilized subpicosecond pulse compression due to multiple-order stimulated Raman scattering
Authors: Heritage J. P. , Weiner A. M. , Martinez O. E.
Published: February 2023

Researchers have generally agreed that stimulated Raman scattering (SRS) must be avoided if high-quality fiber-and-grating pulse compression is to be achieved. We investigate depletion of 1.06-μm pulses by multiple-order SRS in single-mode fibers and carefully examine the implications for subseqeunt pulse compression. Intense SRS (with walk-off) clamps the pump pulse energy and steepens its rising edge; subsequent self-phase modulation results in nonsymmetric spectral broadening and a nonlinear chirp. Attempts at compression lead to asymmetric compressed pulses with broad energetic wings. As the laser power is increased, group velocity dispersion helps to linearize the frequency chirp; at powers high enough for third Stokes generation (1.9 W in our 400-m fiber), more than 80 % of the spectrum is compressible. In these conditions highly stable transform-limited pulses as short as 600 fs are obtained. We describe the evolution of the power spectrum and frequency chirp and the role of group velocity dispersion as a function of optical power in the fiber. Pulse compressibility is discussed, and stabilization due to multiple-order Raman scattering is emphasized. Finally, we discuss high-resolution picosecond pulse shaping and encoding made possible by Raman stabilized pulse compression and propose that such encoding could be utilized for an optical code-division multiple-access self-routing switch.
Comparison of Prolog and matrix-algebraic Al systems
Authors: Kiamilev F. , Jau J. , Fainman Y. , Esener S. , Lee Sing H.
Published: February 2023

A new approach for formulating Al problems in a manner suitable for parallel optical computing is being developed at UCSD. This approach is contrasted to the sequential search-based algorithms, written in the programming language Prolog, to illustrate its potential advantages. As an example, let us consider a typical Al problem where the goal is to find from whom John may steal.