bluuebunny/crossref_metadata_2025 huggingface dataset:
Refractive and dimensional development of the crystalline lens in childhood
Authors: Mutti Donald O. , Zadnik Karla , Adams Anthony J.
Published: February 2023

Classical models of emmetropization involve axial length increases accompanied by compensatory, coordinated decreases in crystalline lens power. The underlying mechanisms of this coordination are as yet unclear. We have begun the Orinda Longitudinal Study of Myopia to evaluate the development of the ocular components of refraction in schoolchildren, measuring cycloplegic refraction (Canon R-1 autorefractor), corneal curvature (photokeratoscope), axial dimensions (Humphrey model 820 ultrasound), and crystalline lens curvatures (video-based comparison Ophthalmophakometer). Initial cross sectional results on 240 children, 82 first (mean age 6.6 years), 92 third (8.5 years), and 66 sixth graders (11.6 years) indicate that the crystalline lens thins during development as its curvatures flatten. The mean lens thickness values (±s.d.) for the three groups respectively are: 3.58 ± 0.15 mm, 3.46 ± 0.16 mm, and 3.44 ± 0.13 mm. Adjusted multiple regression y-intercepts for refractive index are 1.417, 1.354, and 1.357 for the three age groups.
Reducing complexity
Authors: Fuller Tim
Published: February 2023

Many organizations have become clogged with excess complexity, extra activities that are required because of builtin flaws in the system thus leaving little time for real work or those activities that are necessary to produce the product or service and the activities the customer cares about. Since this excess complexity has been with us for so long, most people do not realize how much there is and that it can be measured and reduced.
Enhanced nonlinear recording using a thermoplastic plate and its use in holographic associative memories
Authors: Paek Eung Gi , Jung E. C. , Silberberg Y. , Ravi T. S.
Published: February 2023

We describe a new way of enhancing arbitrary higher-order diffraction using a thermoplastic plate. Such an enhanced diffraction efficiency is obtained by adjusting the angle between the two recording beams that the diffraction angle of the desired order is tuned to the angle at which a thermoplastic plate gives the maximum frequency response and optimizes the exposure time. Using the method, any order can be selectively enhanced with a diffraction efficiency comparable with that of maximum attainable first order.
Ion beam figuring of steep optical surfaces
Authors: Wilson S. R. , McNeil J. R.
Published: February 2023

Ion beam figuring is a noncontact technique for the final shaping of precision optical components. Its use has in the past been primarily restricted to planar and near planar surfaces. To extend the application of ion beam figuring to steeply curved surfaces and surfaces with large saggital depth requires further development of the theoretical model. In this paper, the propagation and sputtering properties of the ion beam produced by a common ion source are modeled. The effects accounted for include: (1) beam current loss during transit from the ion source to the surface, (2) divergence of the ion beam during transit, and (3) influence of the beam/surface geometry on the sputter yield and the material removal profile. The model is then tested experimentally by performing ion beam milling tests on optical components in configurations that are inexpensive, easy to test, and yet strongly exhibit the effects of steep surface geometries.
Computer simulation and optimization of stressed-lap polishing
Authors: Burge J. H.
Published: February 2023

Computer controlled stressed-lap polishing, developed at the Steward Observatory Mirror Laboratory, promises to be an effective method for figuring large, fast aspheric mirrors. Stressed- lap polishing uses a large stiff circular polishing tool that is actively deformed under computer control so that it continually fits the aspheric mirror surface. As the lap is translated across the rotating mirror, the lap’s horizontal speed and rotation rate, the total force on the lap, and applied moments to the lap are all dynamically controlled. To fully take advantage of these many degrees of freedom, computer simulation and optimization software has been developed. The simulation is based on Preston’s equation (local removal rate proportional to pressure and relative velocity) but allows the inclusion of nonlinear effects based on comparison to measured results. The optimization of polishing parameters is accomplished by a damped least-squares optimization algorithm which varies the polishing parameters to obtain a desired simulated removal profile.
Stimulated emission in optically pumped zinc vapor
Authors: Zhang Pei-Lin , Wu Xiao-Guang , Zhao Shuo-Yan
Published: February 2023

Stimulated emission on the transitions, 53S1-43PJ: 481.05, 472.22, 468.10 nm, 43D-43P
J
:334.50, 330.27, 328.23 nm and 41D2-41P1 636.24 nm is observed following pulsed laser excitation on 41S0-43P1 resonance at 307.59 nm (peak intensity ~100 MW/cm2). To understand the mechanism we have performed the following experiments: excitation spectra of stimulated emission lines; side direction fluorescence (twenty-seven lines total, corresponding to triplet transitions from high-lying atomic states and two lines of zinc ion ZnII4p2P
J
- 4s2S1/2) and ion probe measurements; dependence of the stimulated emission intensity on Zn density and pump laser power; quenching of Zn43P1 by a small admixture of H2 in Ar buffer gas; and energy transfer between 41D and 44D states. The above experiments show the pump laser pulses efficiently photoionize the Zn vapor (1-photon resonance 3-photon ionization). Population of the upper levels result from two processes: (1) recombination of laser produced plasma and subsequent processes; (2) electron- impact collision. The energy defect of 43P1-53S1 21 131 cm-1 is approximately equal to an excess photoelectron energy of 21 1737 cm-1 from 3- photon ionization. Depletion of the lower level 43P1 results from the collision quenching of this Zn atom with other atoms and especially with H2 molecule: Zn(43P1) + H2 - → ZnH(X2∑+) + H with a cross section ~20 Å2.
Infinite resolution of holographic Fourier transform spectroscopy
Authors: Shan Zijuan , Li Zhengzhi
Published: February 2023

The complex diffraction grating is formed when we use a light source with a different wavelength to record a spectral hologram. Meantime, the sinusoidal gratings with two different spatial frequencies will form the beat frequency.
The 1S → 2S two-photon transition rate in atomic hydrogen
Authors: Li Shifang , Fry Edward S.
Published: February 2023

Theoretical calculations for the 1S → 2S two- photon transition rate in atomic hydrogen are reviewed. They are compared with two experiments via the saturation effects that are observed when three-photon ionization is enhanced by two- photon resonance with the metastable 2S state. There is a significant disagreement between theoretical and experimental results. The disagreement is illustrated by determining the transition rate as a function of intensity for experimental laser profiles: (1) using parameters that give rates in agreement with experimental data, and (2) using theoretical values for the parameters. Finally, experiments that would involve direct observation of the 2S metastable state are considered. It is shown that single-longitudinal-mode laser experiments would provide an accurate measurement of the Rabi frequency for this transition and yield a definitive value for the rate. A Monte Carlo simulation method is used to consider practical effects associated with such an experiment, for example, chirp and ASE noise in the laser. Also, simulations of the multiphoton ionization process in multimode and wide band laser fields are presented.
Nd:YAG nonplanar ring lasers for microwave and fiber sensor applications
Authors: Williams K. J. , Kersey A. D.
Published: February 2023

Nd:YAG nonplanar ring lasers have been found to be useful in applications requiring the distribution of microwave signals with light and fiber-optic interferometric sensing. Nd:YAG lasers based on the nonplanar ring cavity operating at 1319 nm have the advantages of very low phase noise, inherently good frequency stability, frequency modulation of the laser at rates to 1 MHz, and single-mode operation with output powers >100 mW. By electronic feedback offset phase- locking, the lasers become mutually coherent with an offset frequency that is tunable from dc to >40 GHz, making the device an attractive source of spectrally narrow optically transmitted microwaves. The source can then be used in such applications as optical feeds for phased array microwave antennas and generation and transmission of high frequency microwave signals with light for use in testing of microwave photodiodes and for injection into microwave oscillators or transistors. The phase-lock loop method offers advantages over direct or external modulation, such as reduced harmonic distortion and higher frequency operation. Interferometric fiber sensors have been extensively researched for a wide range of measurands including acoustic, acceleration, magnetic fields, and electric fields. Semiconductor diode lasers provide a compact, reliable source of optical radiation with coherence lengths of several meters; however, they exhibit significant low frequency phase noise or frequency jitter which limits the phase shift detectability in most present-day diode laser-based interferometric sensor systems. Sensor systems using the Nd:YAG ring laser can benefit from its very low phase noise. This, combined with the FM modulation of the laser, allows the replacement of the diode laser with the Nd:YAG laser for uses requiring detection of very small phase shifts as well as systems where long measurement paths with no compensating paths are required.
Linewidth measurement of a single-mode Ti:AI2O3 ring laser
Authors: Yoon Tai Hyun , Suh Ho Suhng , Jo Jae Heung , Kim Yong-Pyung
Published: February 2023

A linewidth of 80 kHz and a frequency jitter of 900 kHz of a free-running single-mode Ti:Al2O3 ring laser was measured by using optical homodyne and heterodyne measurement methods. A single-mode 1km optical fiber was used for a 5-μs optical phase delay at 780 nm. Single-mode output of the home-made Ti:Al2O3 ring laser could be tuned between 730-820 nm and the average output power was 300 mW. In the homodyne optical spectrum a oscillation with period of 1/τ (=190 kHz), where τ is the delay time by the optical fiber, was observed on the beat spectrum like the result in the laser diode experiment with subcoherence delay time.1 We have obtained the 80-kHz linewidth by comparing the homodyne beat spectrum with theoretical calculations. A 80-MHz acoustooptic modulator was employed in one arm of the homodyne setup to shift the optical frequency for heterodyne measurement. A 900-kHz frequency jitter from the time varying heterodyne beat signal on the rf spectrum analyzer was obtained, which is about two times better than the Schulz’s result of 2MHz.2
High power limits of ridge waveguide laser structures
Authors: Graff Volker
Published: February 2023

Ridge waveguide lasers are simple to fabricate and offer high yield and low cost. High power limits are discussed and compared to more complicated structures.
High-power high-radiance 2-D collimated diode array stack
Authors: Reichert P. , Snyder J. J. , Benett W. J.
Published: February 2023

Laser diodes are efficient and compact sources of light with a high radiance. Although the radiance of a high-power diode bar with an aperture measuring 1 μm by 1 cm has a radiance (brightness) of 2.5 × 106 Wcn-2sr-1, the radiance of a 2-D stack consisting of the same laser diode bars is substantially less.1
Raman microprobe studies of AlGaAs quantum well laser facets
Authors: Tang W. C. , Rosen H. J. , Vettiger P. , Webb D. J.
Published: February 2023

Facet temperature rise is believed to play an important role in the degradation of semiconductor lasers. In this paper the facet temperature and output power of uncoated AlGaAs single quantum well lasers operated at constant current were measured as a function of time until catastrophic breakdown. The temperature rise is observed to consist of two regimes: an initial linear temperature rise accompanied by a gradual power degradation followed by a rapid nonlinear temperature rise at what appears to be a critical temperature leading to catastrophic optical damage (COD).
Image decomposition in human vision
Authors: Watson Andrew B.
Published: February 2023

Of the stream of visual information that meets the eye, some is retained and some is thrown away. That which is retained could in principle be represented in many ways, but the brain has chosen a particular representation that emphasizes the parameters of scale, location, orientation, motion, luminance, and two color coordinates. This representation may be visualized as a partition of the image stream into various bands in the spatiotemporal frequency domain. I discuss how this partition may be visualized, how it may be represented mathematically, how it may be implemented by simple neural operations, what purpose it may serve in the visual process, and how it may be exploited in the design of digital video systems.
Effect of cueing on object and part comparisons
Authors: Ankrum Corlene , Palmer John
Published: February 2023

The role of objects in perception can be examined by comparing judgments of objects and parts. In our task, observers viewed two figures sequentially, and made same-different judgments. The comparisons were either between two whole objects or between a whole object and a part. A whole advantage was found. Observers were faster and more accurate on whole comparisons than on partial comparisons. We investigated three hypotheses that may account for this effect. One hypothesis is that the whole advantage is because of an encoding strategy that favors a representation of the whole over representations of the parts. This encoding hypothesis can be contrasted with a second hypothesis that postulates no favoritism in representation but an advantage in retrieval for whole objects over their parts. The third alternative is that the whole advantage may occur due to emergent features present in the whole object that are disturbed in partial comparisons.
Decomposition of natural images by principal components as a design consideration for the visual system
Authors: Buchsbaum G. , Derrico J. B.
Published: February 2023

The advantages of representing a signal by principal components can be briefly summarized as follows, (i) The basis functions of the representation are orthogonal and have uncorrelated coefficients, (ii) The expected square coefficients are minimum compared with other generalized Fourier representations. These properties make principal components attractive for efficient image coding and representation, because uncorrelatedness reduced redundancy and smaller coefficients require smaller dynamic ranges. Principal components computed for natural color images are comprised of basis functions with various spatial profiles and color responses. These principal components are similar to certain visual system image operations in space and in color, including the color opponent transformation and a variety of spatially organized receptive field filters with different color responses. This similarity suggests that units in the visual system are tuned to features which are principal components of natural images, thereby efficiently coding and representing the image.
Macroscopic quantum states generated by twin-beam systems
Authors: Reid M. D. , Munro W. , Sanders B.
Published: February 2023

Nondegenerate parametric oscillation and four-wave mixing generate correlated twin-beams that exhibit squeezing in the intensity difference fluctuations. Using a simple theoretical model for parametric amplification we predict that the twin-beam devices generate macroscopic states that violate Bell’s inequality. In four-wave mixing, or parametric oscillation with an amplitude-squeezed pump, the twin-beams may also exhibit squeezing in the intensity of each beam. We predict that the use of these intensity-squeezed devices is advantageous in the preparation of the macroscopic quantum states. It is also possible to use nondegenerate systems to generate macroscopic superposition (Schrodinger cat) states.
Direct detection of photon bunching
Authors: Qu Yujiang , Singh Surendra
Published: February 2023

Second-harmonic generation (SHG) has been predicted to be very sensitive to photon bunching. Because of its two-photon nature SHG would be more efficient with bunched than with random or antibunched photon sequences of the same mean intensity. We use this phenomenon to demonstrate the bunching of photons in time. The fundamental beam, derived from a laser operating near threshold, was focused into a 90° temperature phase matched nonlinear crystal. The operating point of the laser was varied in the neighborhood of threshold, and a feedback loop stabilized its intensity at each operating point. It is well known that the character of laser light changes in passing the threshold of laser action. Underlying photon sequences are bunched below threshold and random above threshold.
Flame temperature measurements employing the Doppler width of ro-vibrational transitions
Authors: Dayton D. C. , Sausa R. C. , Kotlar A. J. , Miziolek A. W.
Published: February 2023

Recently developed nonintrusive laser-based spectroscopic techniques for combustion diagnostics are providing important results that serve as stringent tests for present and developing flame models. Laser-induced fluorescence (LIF) and resonance enhanced multiphoton ionization, in particular, have the high sensitivity, spatial resolution, and species selectivity needed to measure spatially resolved species concentration and temperature profiles in flames. In propellantlike flames in which NO2 is the primary oxidizer, however, these techniques are severely restricted since NO2 is photolyzed at wavelengths <405 nm. This affects the local flame temperature and species concentrations measured.
Analysis of binary mixtures of spherical macromolecules in quasielastic scattering experiments for low intensity levels
Authors: Gonzalez F. , Saiz J. M. , Moreno F. , Valle P. J.
Published: February 2023

Analysis of mixtures of particles in solution by QELS experiments are often reported. Photon correlation spectroscopy (PCS) constitutes the usual method used by authors to obtain hydrodynamic properties of particles. When the level of scattered light is very low, the signal to noise ratio is very small, and the use of PCS [in particular the measurement of the second-order correlation function, g(2)(τ)] requires a long time of measurement. For this kind of situation, an alternative technique has been proposed recently, based on the measurement of the Laplace transform of the time interval probability between consecutive photons Q(s).
Two-mirror reflecting microscope for soft x-ray uses
Authors: Shealy David L. , Wang Cheng , Jiang Wu , Hoover Richard B.
Published: February 2023

During the past several years, we have analyzed many aspects of spherical and aspherical two-mirror soft x-ray microscopes. These results are summarized and used to project the performance capabilities of a multilayer two-mirror microscope operating within the water window. As a result of the technological developments associated with NASA soft x-ray solar physics projects that have used one- and two-mirror telescopes operating at various wavelengths from 4.4 nm to 33.5 nm, a project has been initiated to fabricate and test a two-mirror microscope initially operating at 13 nm and then, after some developmental work, within the water window where an ultimate spatial resolution of <10 nm seems possible.
Gravitational wave detection via an optical parametric oscillator
Authors: Wong N. C.
Published: February 2023

An active gravity-wave detector based on a solid-state two-arm optical parametric oscillator (OPO) is proposed. The signal and idler waves of a nearly degenerate OPO are internally separated so that the signal beam propagates along one arm of the OPO and the idler beam along the orthogonal arm. The signal–idler beat frequency is monitored to yield a sensitive measure of the path displacement in the two arms of this OPO cavity-interferometer. The beat frequency can be chosen to lie in a low-noise spectral region to minimize the effects of technical noise, such as l/f noise.
Fresnel diffraction with small apertures
Authors: Struckhoff A. D. , Carlsten J. L. , Kraus Hal G.
Published: February 2023

Fresnel diffraction experiments were conducted with small apertures and a spatially filtered He-Ne beam. The beam was left uncollimated so that a diverging wave was incident on the aperture. This allowed the input radius of curvature to have an effect in determining the location of the Fresnel patterns. The diffraction patterns were magnified onto a 1-in. linear photodiode array of 1024 elements. The imaging system was composed of a 3.8 - mm focal length microscope objective and a 1-m lens. The diffraction-limited entrance f/No.
Chromatic and achromatic afterimages
Authors: Martinez-Uriegas Eugenio , Kelly D. H.
Published: February 2023

Three experimental techniques show that the contrast of chromatic and achromatic negative afterimages of stabilized gratings depends linearly on the conditioning contrast over a wide range (0-90%), and that both types of afterimage have similar gains across spatial frequency. They also have similar time-courses of buildup and decay along exponential curves with a (1/e) time constant between 4 and 8 sec. Both chromatic and achromatic afterimages greatly increase the detection threshold of a grating briefly flashed upon the afterimage if the flashed grating is chromatic and isoluminant; however, if the flashed grating is achromatic, its threshold is practically unaffected by either type of afterimage.
Contrast sensitivity as a function of area for circular gratings
Authors: Luntinen Olavi , Rovamo Jyrki , Nasanen Risto
Published: February 2023

Using circular gratings, where luminance L=Lo [1 + m sin(2πfE + ø)] was modulated as a function of eccentricity E in angular degrees of the visual field, we measured Michelson contrast sensitivity as a function of relative grating size, calculated as Af2 and expressed in terms of the number of square cycles. As with linear gratings (e.g., vertical bars and horizontal luminance modulation), the increase of contrast sensitivity with Af2 was similar at all spatial frequencies studied and saturated between 100-200 square cycles irrespective of spatial frequency. In addition, contrast sensitivities for a linear and circular grating were similar irrespective of spatial frequency (f) or grating area (A).
Stimulated pair annihilation and a positronium annihilation laser
Authors: Luna L. Carlos A.
Published: February 2023

I studied stimulated pair annihilation, and its probability is obtained according to Feynman rules. I also noted how this effect tested the nolocality of quantum mechanics. SPA is used to propose a positronium annihilation laser by using relativistic electrons and positrons and a periodical static magnet to produce the stimulating radiation and secure the coherence. Since the magnet period is practically limited to 5 × 10–3 m the minimum required energy is 109eV, which produces a frequency of 1030 Hz. Also, this kind of laser is tunable and an attempt is made to calculate gain that is not inversely proportional to frequency like free electron lasers. Finally, I also propose a tunable gamma-ray source using SPA.
Feasibility of x-ray third-harmonic generation in plasmas
Authors: Shkolnikov P. L. , Kaplan A. E.
Published: February 2023

Plasma is a natural medium for x-ray third-harmonic generation (THG): the interaction of x-ray laser (XRL) radiation with plasma is similar to that of optical laser radiation with gas or vapor, unless the energy of x-ray quanta E is higher than the ionization potential of the plasma. We consider x-ray THG for couples XRL line-plasma satisfying the following conditions: (i) 2E almost coincides with the energy El of some ion level l which is optically inaccessible from the ground level, and (ii) E
l
+ E is approximately equal to the energy of another level with the large rate of the radiative decay to the ground level. Although the selection of the available XRL lines and the known energy levels of ions is limited, we find and consider (including some propagation conditions) a number of such couples with plasmas of alkalilike ions.
Measurement of ultralow losses in an optical interferometer
Authors: Thompson R. J. , Rempe G. , Kimble H. J. , Lalezari R.
Published: February 2023

Ultralow-loss high-reflectivity mirrors are important for a variety of uses in optical physics. In this paper we report measurements of cavity decay times for a spherical mirror cavity over the wavelength range 790–880 nm. Total losses (transmission plus absorption and scatter) as low as 1.7 ppm per mirror are observed. The resonator used in this study consists of two dielectric-coated mirrors of 17.5-cm radius of cuivature separated by 4 mm. A tunable Ti:sapphire laser excites the cavity as the length of the resonator is slowly scanned using a piezoelectric transducer.
High temporal and spatial resolution via fluctuating pulses
Authors: Finkelstein V. , Berman P. R. , Bouchene A. , Débarre A. , Keller J.-C. , Le Gouët J. L. , Tchenio P.
Published: February 2023

If two strong cross-correlated fluctuating laser pulses having a relative time delay t
d
interact with a three-level atom, they can modify the atomic response to a third probing pulse in a manner that varies dramatically on a time scale δt
d
which is much smaller than the correlation time of the pulses τ
c
. It is found that δt
d
decreases with increasing strength of the pulses.
Stimulated Brillouin scattering of chirped optical pulses
Authors: Miller Edward J. , Boyd Robert W. , Harter Donald J.
Published: February 2023

Stimulated Brillouin scattering (SBS) has become well known for its ability to remove phase distortions imposed on a laser beam. However, to date, most SBS experiments have been performed using nanosecond laser pulses, so that the incident laser pulse duration exceeds the phonon lifetime of the SBS active medium. When the incident pulse is shorter in duration than the phonon lifetime, the SBS process becomes transient, and the gain is dramatically reduced. Therefore, higher input laser intensities are required to reach threshold. Very often, these intensities exceed those required to observe competing effects such as stimulated Raman scattering or optical breakdown. Cumulative SBS has been shown to reduce the SBS threshold for short optical pulses. In this technique, several pulses, separated by less than the phonon lifetime of the SBS medium, are used to excite SBS. In this way, the phonon field gradually grows from several incident pulses. Chirped pulse amplification has become a standard technique for obtaining high peak-power optical pulses. Therefore, it is desirable to develop a technique to generate efficient SBS using chirped optical pulses. In this study, we have shown that cumulative SBS can efficiently generate SBS using multiple, chirped optical pulses. Using N2 as a SBS active medium, we observed reflectivities exceeding 60% when the SBS process was excited using broadband, chirped laser pulses. The incident pulses were ~120 ps in duration and possessed a 1-nm bandwidth. We also observed that the SBS process preserves the linear chirp of the applied field and that the reflected pulse could be compressed to streak camera-limited resolution of 8 ps upon double passing a dispersive grating pair.
Quadratic optical pulse compressor
Authors: Stone Thomas W.
Published: February 2023

The phase delay function of grating-pair pulse compressors can be expanded in a Taylor series in terms of powers (ω - ω0), where ω is the frequency of spectral components of the pulse and ω0 is the central frequency of the pulse. The quadratic term in this expansion corresponds to a linear path variation with frequency, and to the ideal compression of a linearly chirped pulse. Higher-order terms in this phase delay function are often undesirable, particularly for broad-spectrum input pulses. Using the concept of shaped volume transmission gratings,1 grating-pair pulse compressors are described in which all phase delay function terms higher than second order are eliminated. This is accomplished by solving for the grating shape that provides the phase delay described by the truncated Taylor series. Similarly, selected quantities of higher-order terms may be added to better match the compressor to input pulses having deviations from an ideal linear chirp. Specific solutions for tailored pulse compressors are presented, including the purely quadratic case (no higher-order terms).
Recent advances in antiguided diode laser arrays
Authors: Mawst L. J. , Botez D. , Jansen M. , Peterson S. , Ou S. S. , Sergant M. , Roth T. J. , Mutz C. Z.
Published: February 2023

Resonant-optical-waveguide (ROW) arrays are monolithic devices capable of radiating in a diffraction-limited beam to high output power levels. These devices are attractive for many applications because they are one wire devices with no active phase control required, that is, the internal structure of the array both controls and locks the phase of each emitter. In effect, the ROW array operates as lateral DFB for spatial modes.
Thermal focusing effects in gain-guided diode laser arrays
Authors: Osinski Marek , Cherng Chung-Pin
Published: February 2023

Thermal effects in diode laser arrays are known to be important for the array mode selection.1 Here, we examine in detail the role of active region heating, considering a uniform ten-strip GaAs/AlGaAs gain-guided array. The array is regarded as a perturbed broad-area laser whose modes are coupled via complex-permittivity perturbations induced by heating and injected carriers. Array modes are determined using the coupled-mode theory. The thermal perturbation is taken as a half-period cosine with center value of ΔT, vanishing at the lateral claddings. When heating-induced waveguide nonuniformity is small, the dominant array mode is ν = 10. Calculated temperature dependence of modal gain spectra reveals that with raising temperature, the highestgain mode shifts gradually from ν = 10 to ν = 13. Thus, thermal focusing results in sequential excitation of high-order modes with increasing pumping current. Calculated near- and far-field patterns for ΔT = 4°C are in excellent agreement with injection-seeding experiments,2 while numerical simulations2 with ΔT = 10°C give somewhat narrower near fields for ν > 10. This indicates that the active region heating may not be as severe as previously thought. Sensitivity of the high-order modes to thermal focusing can be used to establish the actual temperature increase with good accuracy.
Electron-phonon coupling in II–VI quantum dots
Authors: Persans P. D. , Tu An
Published: February 2023

The shift in electronic energy levels is the most striking effect when semiconductor particles are reduced in dimension into the quantum dot regime but there are other effects that may also be important in the use of quantum dot materials for nonlinear optics. In this paper we discuss how the interaction between electronic quasiparticles (such as excitons) and phonons is altered as particle dimensions are reduced. Phonons can be confined if the matrix for the quantum dots has no mode at the phonon energy; polaritons may also be quantized. The wavevector of both phonons and electronic quasiparticles is ill-defined to the extend of 1/d, the size of the particle. This uncertainty in wavevector should enhance the coupling between electronic states and phonons.
Logic functions using asymmetric nonlinear coupling at a fiber coupler
Authors: Yang C. C. , Wang Alex J. S.
Published: February 2023

Although nonlinear coupling at a coupler has been widely studied for all-optical ultrafast switching, use of nonlinear coupling for logic functions has not been reported. In this paper, the phenomena of asymmetric nonlinear coupling at a fiber coupler are presented. By asymmetric nonlinear coupler, we mean a coupler in which the Kerr effects in the two waveguides are different when the same power is launched into each waveguide. The difference in Kerr effect can be implemented by controlling the nonlinear constant or waveguide thickness. Although the nonlinear effect is asymmetric in such a coupler, linear coupling is still symmetric, otherwise energy cannot be conserved. It is found that, in the chosen range of coupler asymmetry, input energy tends to appear in the waveguide of larger nonlinearity at the output end of a half beat-length coupler when only one waveguide is excited. When both waveguides are excited, the energy distribution between the two output ports depend on the relative phase of the two input signals. By appropriately choosing the coupler asymmetry and the relative phase of the input signals, nor, and, or. and xor gates are implemented using a half beat-length coupler.
Steerable pyramids for image decomposition and enhancement
Authors: Freeman William T. , Adelson Edward H.
Published: February 2023

We have previously described1 the use of steerable filters, in which a small set of oriented basis filters are used to analyze images in a uniform and efficient manner. Filters of arbitrary orientation can be synthesized as linear combinations of the basis filters. We now describe a multiscale pyramid decomposition using steerable filters. The steerable pyramid breaks an image down into a set of bandpassed subimages; the subimages at a given level of the pyramid form a steerable set. The steerable pyramid is overcomplete and therefore nonorthogonal. However, it is self-inverting, meaning that the analysis functions used to build the pyramid are the same as the synthesis functions used to reconstruct. We have implemented image noise cleaning within this representation. The pyramid is used to analyze local image orientation. Neighborhoods with strong orientation are likely to represent image structure, while neighborhoods with little or no orientation are likely to represent noise. The pyramid coefficients are modified according to the likelihood that they represent image or noise. The pyramid transform is then inverted, producing a cleaned image.
Integral logarithmic transform: theory and applications
Authors: Roy Frieden B.
Published: February 2023

Mathematical properties and potential uses of a new class of integral transforms are described. Its input functions f(x) or f(x,w) must have limited support, as is true of any image. For a 1-D input f(x), the 1-D integral logarithmic transform is defined as F(y) = ∫f(xy)d(logx). For a 2-D input function f(x,w) the alternative 2-D transforms F(y,z) = ∫∫f(xy,wz)d(logx)d(logw) or G(y,z) = ∫∫fρ(yr, zθ)d(logr)dθ are defined. In the latter, function fρ (r,0) is the 1:1 polar remapping of input function f(x,w). Mathematically, it is found that transforms F(y) and F(y,z) are invariant to linear change of scale (magnification) of input coordinates x or (x,w). This is without incurring an objectionable magnification-dependent translation in the output, as is incurred by simple 1:1 log-polar mapping. Of further interest, transform G(y,z) is invariant to both magnification and rotation of the input function f(x,w). Also, the transform F(y) due to a nonlinear power-law change of scale f(x) is itself a power-law change of scale on the original F(y). Finally, the log-transforms are conveniently inverted: for example, in the 1-D case of a given F(y), the input f(x) can be computed as f(x) = (x/xo)F'(x/xo), where xO is the upper support coordinate for f(x). An optical implementation of transform F(y,z) is described.
Hermite functions maximize the spacespatial frequency uncertainty of Gaborlike functions
Authors: Klein Stanley A. , Beutter Brent
Published: February 2023

Wavelets that are localized both in space and in spatial frequency are useful for vision modeling and image processing. For example, in image compression one would like localization in spatial frequency so that the small spatial filters are insensitive to low spatial frequencies to which the visual system is highly sensitive. One would also like spatially localized filters to reduce interference between adjacent features. Several investigators, including Gabor, asked what particular wavelet shape minimizes the joint space-spatial frequency uncertainty (the Heisenberg uncertainty). Consider the class of functions that are an nth-order polynomial times a Gaussian. Gabor proved that the nth-order Hermite polynomial produced the extremum of the Heisenberg uncertainty. He believed that the extremum he found was the minimum. We found that Gabor was partly right and partly wrong. A Hermite polynomial when multiplied by a Gaussian is indeed an extremum of the Heisenberg uncertainty for the class functions that are an nth-order polynomial times a Gaussian. The problem is that it maximizes rather than minimizes the uncertainty.
Lasers
Authors: Schawlow Arthur L.
Published: February 2023

Lasers have made possible many applications in science, technology, medicine, and the arts and have changed our concepts of the nature of light.
Bits and photons: a perspective of optics in telecommunications
Authors: Kogelnik Herwig
Published: February 2023

The demonstration of the first laser (1960), the first low-loss optical fiber (1970), and a string of associated breakthroughs, have started a revolution in telecommunications technology. The Chicago field trial (1977) saw an early incorporation of this lightwave technology in the telephone network. An early large-scale deployment was the installation of the Northeast Corridor system in the United States (1983).
Seventy-five years of the United States optical industry
Authors: Shannon Robert R.
Published: February 2023

The American optical industry has grown even more rapidly and extensively than the Optical Society has over the past seventy-five years. Originally limited to the production of lenses and a small catalog of scientific instruments, the optical industry now encompasses many areas of imaging, electronics, data communication, and industrial processing. Optical techniques have permeated most of the basic industries in the country, and the optical industry has traditionally been a leader in the introduction of new technology.
Introduction to wavelets and considerations for optical implementation
Authors: Freeman Mark O. , Duell Ken A. , Bock Brett , Fedor Adam S.
Published: February 2023

Wavelets have gained the attention of the signal processing community for their usefulness in analyzing nonstationary signals, for their mathematical elegance, and for their relative ease of computation. This paper is intended to introduce the audience to the basic principles of wavelet analysis and to consider where optical techniques can be applied advantageously. A signal is decomposed on a set of basis functions created by scaling and shifting a single fundamental wavelet. The space and frequency localization of the resulting wavelet transform, spanning the range from pure Nyquist sampling (no frequency localization) to Fourier transforms (no spatial localization), is determined by the choice of this fundamental wavelet. A common choice for the fundamental wavelet has compact support in the signal domain and bandpass-like behavior in the frequency domain. With this choice, rapidly varying information is well localized in the signal domain while slowly varying information is well localized in the frequency domain. We will discuss what constitutes an allowed fundamental wavelet, orthogonal and nonorthogonal wavelet bases, and the choice of sampling intervals in shift and scale. We will also discuss some of our theoretical results on filtering noise from nonstationary signals by using the wavelet transform for nonstationary spectrum estimation. In considering the use of optical techniques for wavelet computations, it is important to be aware of the digital competition. One reason for the popularity of wavelets is that O(N) algorithms exist for their digital computation. This is stiff competition for an optical system if the only advantage that can be claimed is speed. We will discuss the possible advantages of optical systems related to continuous rather than discretely sampled shift coordinates and the ease of implementing arbitrary scaling factors and nonseparable 2D wavelet functions. Finally, we will present an optical system for computing 2D wavelet transforms.
Accelerator techniques for multiphoton spectroscopy of simple atoms
Authors: Mackerrow E. P. , Donahue J. B. , Quick C. R. , Tiee J. J. , Bryant H. C. , Halka M. , Mohagheghi A. H. , Tang C. Y.
Published: February 2023

Using crossed laser-relativistic ion beam (800 MeV) techniques, we have measured two- and three-photon detachments of the 0.75 eV bound electron in H_ as a function of CO2 laser photon energy, intensity, and polarization. The threshold region for photodetachment rose much faster for linear polarization than for circular polarization. Intensity scans of the H- two- and three-photon detachments show a slight departure from the general power law. Two-photon, bound-bound, transitions in H°(n=4) → H°(n = 11) were also observed. Intensity scans for these transitions show a rate approximately ∝ I1.25. Photon energy scans of this transition show a broadening with increasing laser intensity.
Defining perceptual objects
Authors: Burbeck Christina A.
Published: February 2023

What constitutes a perceptual object? A lamp is seen as a lamp only because we have learned the relationship between the base and the shade, but the base might be seen as a perceptual unit without prior knowledge. I suggest that separating perceptual objects from learned objects, or at least creating some continuum along this dimension, can advance our understanding of object perception by identifying the underlying sources of information. As a first step toward this, I propose that the accuracy with which the size of a region can be judged in a brief presentation serves as an objective measure of the perceptual "objectness" of the region. This measure is robust across scale and insensitive to such features as fine surface structure, supra threshold contrast, and contrast polarity, but it depends on the relationship between the elements defining the region of interest and those defining the background. I will relate the results of some previous findings on size judgments to this measure and will report the results of new experiments that further the idea.
Architectural designs of space multiplexed optical multistage networks
Authors: Cheng L. , Miller A. S. , Wang J. M. , Sawchuk A. A.
Published: February 2023

The hardware for both shuffling and switching in a volume shuffle/exchange network with N channels must be duplicated log2N times to make the network full access. We discuss two space multiplexed optical feedback systems that use a single stage of optics for the shuffles and have a simplified arrangement of the bypass/exchange switches. One method interlaces channels from all stages with space invariant optics and has locally connected switches. The other method uses shift variant optics and is based on our earlier one-copy algorithm1; it divides channels at each stage into four quadrants that are interlaced so that outputs appear in distinct blocks. Experimental results will be presented.
Packaging and fabrication of substrate-mode holographic interconnects
Authors: Kostuk Raymond K. , Fink Mark , Battiato James , Richard Fred
Published: February 2023

Substrate-mode holographic optical elements have previously been suggested as a means of reducing many of the problems associated with free-space holographic interconnects. These elements have been formed either in volume materials or as surface relief diffractive (binary) gratings. Each fabrication approach offers certain advantages and drawbacks. In addition, in order to utilize these elements in an operating system, packaging design tolerances must be established. In this presentation design tolerances for substrate mode holograms are reviewed for different classes of interconnects and are used to determine appropriate fabrication and mounting methods. The attributes of the hybrid grating for the interconnect application are also discussed. These components combine the best properties of volume and binary optic elements in a layered structure.
One step hololens recording for optical interconnections
Authors: Wang J. M.
Published: February 2023

There are many applications for lenslet arrays in optical computing and optical interconnections. A hololens array is a holographic lenslet array that functions on-axis like a refractive lenslet array or off-axis with the proper recording configuration. The general way to make a hololens array is the step and repeat exposure process,1 which is time consuming and has stability problems as the number of lenslets increases. We propose a one step method to record a hololens array by using a 4f imaging system and a lenslet array. We place the lenslet array so that its back focal plane coincides with the front focal plane of the first lens in the 4f system. This system has a unique magnification independent of the lenslet array position along the optical axis. If we put a holographic plate in the image plane of the lenslet array, a hololens array can be recorded with one exposure by introducing a reference beam. Some applications of the hololens array are presented for optical interconnections.
Efficiency of human observers relative to linear-discriminant models
Authors: Barrett Harrison H. , Yao Jie , Rolland Jannick
Published: February 2023

In another presentation at this symposium, Myers and Wagner review the use of the Bayesian ideal observer as a model for human performance and define efficiency as the ratio of squares of detectability indices for the human and the Bayesian. Though this approach has proved very useful, especially in evaluation and optimization of medical imaging systems, the kinds of problems that can be analyzed in this manner are limited because the Bayesian observer needs to know the full probability laws for the data. In practice this restricts the Bayesian to fairly simple and often unrealistic tasks. Linear discriminants, on the other hand, can be calculated from knowledge of just the first and second-order statistics of the data; thus they are often analytically tractable when the Bayesian model is not. In this paper we briefly review the principles of this approach, summarize the circumstances where it is practical, and discuss a variety of psychophysical studies that show that a particular linear discriminant, which we refer to as the Hotelling observer, correlates well with human performance. Efficiency is then redefinied in terms of the Hotelling observer.
Nondestructive thickness measurement of DCG films
Authors: Mantravadi Murty V.
Published: February 2023

Dichromated gelatin (DCG) films are coated on substrates to make holographic optical elements (HOEs) by using various techniques. It is necessary to measure the thickness of these films before and after exposure and processing. It is also necessary to estimate the variation of the thickness at different areas of the substrate. This thickness range is usually between 5 03μm and 50 μm. The principle of the method is based on the measurements on the Haidinger fringes generated by the film. For ease of observation and measurement, a commercial Fizeau type interferometer such as ZYGO has been used. The simple modification to observe the Haidinger fringes with the Fizeau type interferometer will be described. The thickness of the film is related to the diameters of the Haidinger fringes. It is possible to estimate the thickness quickly by counting the number of fringes. A more accurate estimate can be obtained by the measurement of the diameters of the fringes and by using this data in a formula that will be described. It is possible to estimate the thickness of the film to within +1 μm. The method is entirely nondestructive.