bluuebunny/crossref_metadata_2025 huggingface dataset:
Very high sensitivity optical receiver employing optical feedback
Authors: Methley Steven G
Published: February 2023

An extra degree of freedom is allowed by the optical feedback optical receiver design, since the normal feedback or bias resistor is eliminated from the input node. Johnson noise and resistor parasitic capacitance are thereby absent from the input. Where resistor noise was previously dominant, optical feedback can offer a considerable sensitivity improvement. The magnitude of the improvement is dependent on bit rate and is highest at the lower bit rates where resistor noise is most strongly dominant in typical receivers. This paper describes the first reported optical feedback receiver to use an avalanche photodiode paired with a PIN photodiode as the twin input photodetectors. The sensitivity of the optical feedback receiver is limited mainly by FET channel/shot noise and photodetector shot noise. For the avalanche photodiode receiver there exists an optimum value of multiplied leakage current. Currently Si devices have lower leakage current than InGaAs or Ge devices, and hence Si devices presently offer the best available performance. AT 2.048 Mbit/s primary photocurrents for a bit error rate of 10-9 were of the order of 200 pA, corresponding to 575 photons/bit and the highest reported optical receiver sensitivity of −65.6 dBm.
Color measurement using complex stimuli
Authors: Poirson Allen , Wandell Brian A.
Published: February 2023

Classic color difference measurement paradigms model observing conditions in which an observer has time to inspect a visual field and make a careful judgment. We report data collected at three color locations using a new paradigm that extends color difference measurement to conditions in which the observer must make color difference judgments quickly to targets seen within a complex spatial scene. On each trial, observers are briefly presented with a stimulus composed of many objects. One of these objects, the target, may differ in color from the others, the distractors. The observer is uncertain about the precise location of the target and distractors. The observer reports whether all the objects are the same color and d' is calculated from these responses.
Studies on determining equiluminant colors
Authors: Chan Hoover , De Valois Karen K. , Switkes Eugene
Published: February 2023

Traditionally, heterochromatic flicker photometry has been widely accepted as the method of choice for equating the relative luminance of two colors. Recently, a variety of additional methods have been used in studies of the spatial and temporal properties of chromatic mechanisms. Because of the importance of accurate luminance equation, we have compared results from flicker photometry, minimum apparent motion, and minimum contrast in the same subjects using the same equipment (a computer-generated raster graphics system). Field size (2°) and mean luminance (27.4 cd/m2) were held constant. The red and green guns of a Mitsubishi RGB monitor generated the colors to be compared. As we reported earlier,1 significant method-dependent differences are found within a given subject. The direction and magnitude of such differences are idiosyncratic. Here we present data showing that some, although not all, of the subject and method dependent variations can be attributed to temporal factors. In particular, the difference between the red-green ratios determined by heterochromatic flicker and photometry and those determined by minimum contrast sensitivity measures may be substantially reduced for some subjects by equating temporal frequency for the two methods.
Retinal image isoluminance is compromised by lateral and longitudinal chromatic aberration
Authors: Bradley Arthur , Zhang Xiao-Xiao , Thibos Larry
Published: February 2023

Although the human eye exhibits ~2 diopters of longitudinal chromatic aberration, attempts at correcting this aberration with achromatizing lenses have failed to improve visual resolution, and such corrections are rarely used in spatial vision experiments. Recently, however, it has become common practice to use achromatizing lenses when viewing color-modulated isoluminant patterns because uncorrected chromatic aberrations introduce unwanted luminance artifacts into the retinal image.
Photon localization In parametric downconversion
Authors: Rarity J. G. , Tapster P. R.
Published: February 2023

Quantum mechanical models of beam splitters1 predict interesting fourth-order interference effects when nonclassical light is used. If indistinguishable one-photon states are simultaneously input into each port of a 50/50 beam splitter, the theory predicts that each output will contain either two photons or none. A naive (particle) theory would predict a mixture of two’s and one’s. The required |1,1〉 photon state can be selected in nondegenerate parametric downconversion experiments by photon-counting coincidence detection. The disappearance of this coincidence after a beam splitter has recently been studied,1-2 and the range of path length differences over which the effect can be seen is related by Fourier transform to the photon bandwidth. In our work the bandwidth is not limited by external filters, and we have developed a theory which relates the measured photon length to the geometry of the apparatus and the detailed phase matching conditions at the parametric crystal. This theory of phase matching viewed through a beam splitter produces some unexpected results when the beam splitter is tilted and when large aperture detectors are considered.
Squeezed vacuum enhanced interferometry at the dark fringe
Authors: Granger P. , Slusher R. E. , Laporta A.
Published: February 2023

An experimental study of enhancement of interferometric sensitivity using squeezed vacuum fluctuations is described. By operating an interferometer at the dark fringe, large laser powers can be used for high sensitivity. It is possible to enhance the interferometric sensitivity beyond the shot-noise limit in the dark fringe arrangement by using an electrooptic modulator in the interferometer to vary the phase periodically away from the dark fringe. A detector at the dark output port can then operate at the shot-noise limit and detect phase imbalance at the sensitivity determined by power level at the bright output port.1 This shot-noise limit can be reduced further by illuminating the dark input port with squeezed vacuum, as demonstrated recently in balanced output port experiments.2,3 However, there are interesting limits to the sensitivity improvement expected in the dark fringe case.1 The experimental arrangement includes a polarization interferometer illuminated with 100 mW of 1.064-μm wavelength light from a Nd:YAG cw laser. Squeezed vacuum is generated by a KTP optical parametric amplifier. Experimental progress is reported at sensitivities in the nanoradian polarization rotation range.
Multipass amplifier for femtosecond optical pulses
Authors: Fork Richard L. , Fragnito H. L. , Becker P. C. , Hirlimann C. H.
Published: February 2023

We describe a multipass optical amplifier based on a double confocal geometry1 which we have used to amplify femtosecond optical pulses to energies of 90 nJ using only 0.7 W of pump power from a Metalaser copper vapor laser operated at 10 kHz. We use four mirrors of 20-cm radius arranged so that an incident train of pulses passes six times through a gain jet containing a mixture of rhodamine 640 and sulforhodamine 640 in ethylene glycol. The amplified pulses, which have durations of ~50 fs, are sufficiently intense to generate white light continuum pulses in an optical fiber with a 4-μm core.
Gain depletion effects in a flashlamp-pumped Nd:YAG regenerative amplifier
Authors: Schroeder W. Andreas , Norwood D. P. , Dawson Martin D. , Smirl Arthur L.
Published: February 2023

We recently reported the generation of 100-ps, 1.06-μm pulses with ~60-mJ energy from a simple 10-Hz regenerative Nd:YAG amplifier configured as a self-filtering unstable resonator.1 This permitted synchronous amplification of picosecond and subpicosecond pulses from a cw mode-locked dye laser to energies of ~1 mJ. The noncollinear longitudinal pumping geometry of the dye amplifier used allows operation over a wide wavelength range but results in a spatial beam quality directly dependent on that of the pump radiation from the regenerative amplifier.
Generation of white-light continuum using kilohertz-rate amplified tunable femtosecond laser pulses around 800 nm
Authors: Olbright G. R. , Hadley G. R. , Owyoung A.
Published: February 2023

We describe a system for the generation of amplified continuously tunable near-IR femtosecond optical pulses and the associated white-light continuum that is ideally suited for sensitive femtosecond spectroscopic measurements. The high power tunable sub-100-fs duration Fourier transform-limited pulses are generated using copper vapor laser excited dye amplifiers and fiber/grating and fiber prism optical pulse compression techniques applied to the output of a mode-locked dye laser synchronously pumped by the frequency- doubled output of a mode-locked Nd:YAG laser.
X-ray emission from subpicosecond laser-produced plasmas
Authors: Murnane M. M. , Kapteyn H. C. , Falcone R. W.
Published: February 2023

We have used a high-power subpicosecond laser to produce a high-temperature high-density plasma. Under subpicosecond illumination, absorption of the laser light and plasma x-ray emission can occur at densities higher than critical. This can lead to the production of x-ray pulses with rapid rise and fall times.1,2
Colliding pulse mode-locked lasers: intracavity evolution of pulse chirp and intensity
Authors: Schehrer Kevin L. , Fry Edward S.
Published: February 2023

To obtain minimal pulse widths in colliding pulse mode-locked (CPM) lasers it is essential that the intracavity elements, both active and passive, be chosen to control pulse chirp and the time dependence of the gain and absorption. To date, the analyses of CPM lasers have dealt largely with the steady-state output and in a few cases the evolution of that output. In contrast we consider the details of the intracavity pulse evolution.
Coherence effects in a synchronously pumped mode-locked dye laser with a saturable absorber
Authors: Macfarlane Duncan L. , Casperson Lee W.
Published: February 2023

We present a semiclassical model for a synchronously pumped mode-locked dye laser with a saturable absorber included in the cavity. This combination, called a hybridly mode-locked system, has the advantage of producing stable picosecond and subpicosecond pulses for long periods of operation. The particular system of interest is the practically realized rhodamine 6G laser with either DODCI or DQOCI as the saturable absorber. Our model may be solved numerically, and our computed results are presented in terms of the pulse autocorrelations, which are the parameters usually obtained in our experiments and in similar studies elsewhere. In addition to accounting for the finite coherence times of both dyes, our model also includes molecular orientation effects which reduce the efficiencies of the interactions. A key parameter of our model is the length mismatch between the dye laser and pump laser. The effect of this length detuning on the output pulse character is discussed. The pulse shaping and shortening caused by the saturable absorber are also emphasized.
Diffractive optical elements: design principles and applications
Authors: Morris G. Michael
Published: February 2023

Diffractive optical elements are finding new and interesting uses in both commercial and military markets, such as holographic scanners, head-up displays, holographic components for optical-disk readout, aberration correction for optical systems, and diffractive elements for monochromatic and broadband imaging systems. In this tutorial the fundamental properties of diffractive optical elements that must be considered in an optical design are emphasized. Methods to incorporate diffractive optical elements into computer-lens-design programs, fabrication techniques, and illustrative applications are also discussed.
All-fiber communication systems based on fiber-optic devices
Authors: El-Sherif Mahmoud A.
Published: February 2023

Because of the importance of integrated optics in the communication industry, a great deal of effort has been expended to reduce insertion losses associated with the coupling of light between external components and fiber links to the lowest possible level. To eliminate these losses, it has been customary to examine the possible uses of fibers as optical components as well as fiber links.
Study on image superresolution by using a source encoding technique
Authors: Zhuang S. L. , Guo B. J.
Published: February 2023

This paper investigates superresolution in a partially coherent system and develops a source encoding technique for achieving superresolution images.
Resonant operation of a quartz acoustooptlcal tunable filter
Authors: Brandt Gerald B.
Published: February 2023

Single crystal quartz is one of the few usable materials for building acoustooptical tunable filters (AOTFs) which operate at wavelengths shorter than 300 nm. Unfortunately, in quartz the acoustooptic interaction coefficient is low. High power (of the order of tens of watts) is required for reasonable amounts of diffraction. If the AOTF is built so that the face opposite the acoustic transducer is parallel to the transducer, when the AOTF is operated with continuous rf excitation, the cell becomes a resonator for the acoustic energy. At resonance the power required for a given diffraction efficiency is reduced by a factor which can be as much as 20. I discuss the implications of resonance on AOTF operation and show data from quartz filters operating from 220 to 400 nm with <1 W of drive power required.
Sizable Fresnel holograms generated by computer
Authors: Leseberg Detlef
Published: February 2023

Computer-generated holograms offer the flexibility of storing and displaying images from data which represent 3-D objects. Calculation of the complex amplitude, however, requires long computing times and large storage capacities. These can be reduced by concepts which take the boundary conditions of the reconstruction process into account. A modification of the Fresnel transformation is suggested. The 3-D object is specified digitally in several planes in depth. The middle of the object is placed in the Fourier plane of the hologram. Each plane is Fresnel transformed, and the variation of the quadratic phase term in the vertical direction is suppressed. This modification has two consequences: (1) A slight astigmatism is introduced which vanishes in the Fourier plane, i.e., in the middle of the image. For a human observer, this effect can be kept below the limit of resolution for moderate image extensions. (2) The calculated hologram portion is a narrow stripe in the horizontal direction, which is repeated vertically to achieve a rectangular format. The computing time is reduced by some orders of magnitude compared to Fresnel holograms. Optical reconstructions and demonstrations show the feasibility of this process.
Isotope shifts and hyperfine splittings for neural platinum
Authors: Engleman Rolf
Published: February 2023

The hyperfine structure of neutral platinum lines, from hollow cathode spectra taken with the Fourier transform spectrometer at the National Solar Observatory (Kitt Peak), has been analyzed into magnetic hyperfine splitting coefficients and isotope shifts. Although the instrumental resolution was sufficient to resolve an isolated Doppler-broadened component, many of the hyperfine structures are only partially resolved due to overlapping of the components. A least-squares technique was used to fit the observed line contours to a six-parameter model of the platinum hyperfine structure. Those parameters include the Doppler width, isotope shift, and upper and lower level hyperfine splitting coefficients. Accurate isotope shifts and hyperfine splitting coefficients for many of the known levels of neutral platinum were determined from the analysis of over 100 transitions.
Empirical thermal design of Fabry-Perot interferometer mechanical supports
Authors: Goad Joseph H. , Romanczyk Kazmere C. , Engle Charles D.
Published: February 2023

Fabry-Perot interferometers have been used in many applications for wavelength and spectral measurements. Our objective is to develop and construct a wavemeter to provide laser wavelength centroid measurements of tunable solidstate lasers. Because of the high resolution and prior use in many applications, the classical Fabry-Perot-based wavemeter was chosen. With interferometers, one of the most difficult problems is to maintain thermal stability over ambient temperature excursions. For the wavemeter, a two-stage thermal control has been evaluated. The interferometer is mounted in a thermal-vacuum chamber with fine temperature control. This interferometer system is then enclosed with a second housing with course thermal control. In both cases, the temperature control is above ambient to provide simpler regulation. With the thermal control provided, the other variable is how to mount the Fabry-Perot interferometer to minimize thermally induced mechanical mounting stresses. Several support fixtures were evaluated using a Zeeman stabilized single frequency He-Ne laser as the source and a photodiode array as the detector. The laser is considered a perfect source with any end-to-end interferometer output variations caused by thermal-mechanical mounting stresses. A wide range of end-to-end measurements on a three-finger flexture support provides data to within the stabilization specification of the He-Ne laser.
Novel wavelength-division multiplexing and demultiplexing design employing efficient voume holographic gratings
Authors: Ng Joel , Harvey Phillip , Moslehi Behzad , Jannson Tomasz
Published: February 2023

Theoretical and experimental studies of a novel wavelength-division multiplexing (WDM) design employing a single fiber array, on-axial transmission focusing and collimating optics, and a Littrow reflective volume holographic grating are presented. This WDM configuration has the potential to achieve less than −1-dB insertion loss and −35-dB crosstalk for up to six channels and less than −2dB insertion loss and a − 20-dB crosstalk for up to twelve channels. A four-channel prototype in a compact geometry has been constructed utilizing a volume holographic grating with >85% efficiency and laser diodes with 3-nm nominal linewidth. Experimental results are presented. This first-of-the kind WDM is expected to have an insertion loss of less than −2 dB and crosstalk of less than −30 dB. Using multiple exposure techniques, several independent gratings can be superimposed on the same volume hologram. Utilizing this multiple exposure hologram and multiple fiber arrays, and only one single surface aspheric lens, the proposed configuration can readily be expanded to accommodate multiple wavelength windows with many channels in each window.
Filter effects in synchronously pumped mode-locked dye lasers
Authors: Zandi Bahram , Casperson Lee W.
Published: February 2023

In this study we included an improved description of the bandwidth limiting tuning elements into a semiclassical model for a synchronously pumped mode-locked dye laser system. This model is an improvement over the traditional rate equation approach since it has detailed representations of the energy levels, rotational distribution, polarization, and coherence effects. For the theory, the new set of equations is solved numerically using the best available values for the various parameters. The solutions produce autocorrelations of the output pulses for a range of length detuning and filters. For the experiments, an acoustooptically mode-locked Ar-ion laser has been used to pump synchronously a rhodamine 6G dye laser. We have used two- and three-plate birefringent filters and a tuning wedge for our bandwidth limiting tuning elements. The transmission and bandwidth of these filters have been carefully measured and incorporated in our theory. The autocorrelation of the pulses has been measured as a function of the length detuning. There is close agreement between experimental pulse shapes and theoretical solutions. Through a sensitivity analysis, it is shown how this model can be used to select values for the transmission and bandwidth of the filter to obtain optimum pulse characteristics.
Lateral interaction component and local luminance nonlinearities of the human pattern ERG
Authors: Sutter Erich E. , Vaegan X.
Published: February 2023

The electroretinogram in response to pattern reversal stimuli (PERG) consists of two distinct components: contribution from the nonlinearities of the local luminance response and effect of lateral interactions in the retina. By subtracting the local luminance nonlinearities from the PERG we extracted the lateral interaction component for checkerboard pattern stimuli of different check sizes. This response component is of special interest as it originates from neural interactions in the retina and cannot be accounted for by nonlinearities of any single active element. This decomposition of the pattern reversal response leads to two components of a strikingly simple structure. Both components have the characteristics of adaptive mechanisms. Both seem to be of second order, as the fourth-order kernels are negligible in size. The second-order luminance kernel has a structure consistent with a luminance gain control mechanism and a time course, which is in general agreement with known psychophysical and microelectrophysiological data. The lateral interaction component has a similar structure and could be interpreted as contrast gain control. It distinguishes itself by its slightly longer latency and a faster adaptation rate.
Critical flicker frequency of equiluminous red-green alternation across the human visual field
Authors: Raninen Antti , Rovamo Jyrki
Published: February 2023

Luminous critical flicker frequency (OFF) becomes independent of visual field location1 when (1) the stimulus is enlarged with increasing eccentricity in inverse proportion to the sampling density of ganglion-cell receptive fields across the human retina (M-scaling) and (2) stimulus luminance is reduced toward the retinal periphery in inverse proportion to photopic Ricco’s area (F-scaling). Using two low-frequency oscillators and a panel consisting of 256 red and 256 green light-emitting diodes we generated sinusoidal chromatic flicker. The diodes flickered in counterphase. The panel was covered with a white diffusion screen. Its average luminance was 60 cd m−2, and CIE 1931 chromaticity coordinates (x, y) were (0.68, 0.32). Luminance modulations in red and green light were both 20%. Chromaticity coordinates varied between (0.61, 0.39) and (0.72, 0.28). CFF of equiluminous red-green alternation was measured in the temporal visual field. When stimulus size and luminance were constant, CFF first increased and then decreased with increasing eccentricity. However, CFF increased monotonically with eccentricity when the stimulus size was M-scaled but decreased monotonically when the stimulus luminance was F-scaled. In addition, CFF became independent of visual field location when stimulus size and luminance were MF-scaled.
Field size and procedural effects on interference fringe visual acuity measurements
Authors: Geller Andrew M. , Shentu Lian , Sieving Paul A.
Published: February 2023

Several researchers have measured threshold visual acuity at different retinal eccentricities using different methodologies and field sizes and have produced strikingly different results. To address these differences, we measured interference fringe (grating) acuity in the foveal and parafoveal retina using laser interferometry, employing both two-alternative forced-choice discrimination of grating orientation and method of limits (grating appearance) methodologies. Our forced-choice results at 2-deg retinal eccentricity yield orientation discrimination thresholds which are approximately 2 cycles/deg less for 0.6-deg vs 2-deg test fields. However, no difference was found between results with 0.6- and 2-deg test fields at 4-deg eccentricity. This pattern of results holds for two observers tested. While the results vary with field size, estimates of orientation discrimination threshold produced under forced-choice conditions well approximate the theoretical Nyquist limit.
Efficient expanded-beam multimode fiber-optic coupler based on nonimaging optics
Authors: Ng Joel , Kasimoff Ivan , Moslehi Behzad , Jannson Tomasz
Published: February 2023

Expanded beam fiber-optic couplers offer great convenience for fiber cable connection, which is very desirable for local area network and other short-haul applications. But because most short-haul fibers are usually multimode, the large core causes significant aberration losses in conventional designs such as aspherics and GRIN lenses. Based on Liouville's theorem applied to nonimaging optics, we have developed a class of high efficiency expanded beam multimode fiber-optic coupler.
Multiplex Intensity correlator with Fourier transform holographic filters
Authors: Mu Guo-Guang , Wang Zhao-Qi , Zhang Zhen-Long
Published: February 2023

The importance of a multiplex correlator is stressed in its use in target recognition with a change in scale and rotation for a large number of patterns of various sizes, and orientations of the target should be stored in the filter.
Holographic rapid machined-surface inspector
Authors: Epling B. , Olson D. W. , Trunnell Mark
Published: February 2023

Honda et al.1 have described the use of a holographic optical element (HOE) for the rapid inspection of the shape errors of gear surfaces. In their system laser light reflected specularly from the gear and was then modified to a converging spherical wavefront by the HOE. The resulting point of light passed through a pinhole in front of an optical detector. We have completed gear-surface experiments in which the HOE receives both specular and diffuse scattered light, and the measurements are made in a continuous-rotation mode. The data suggest that the continuous-rotation mode permits specular and diffuse light to be distinguished. This in turn suggests that both average surface profile and surface texture may be monitored by one experimental configuration. Experiments are in progress on hemispherical hydraulic-pump piston heads.
One-way image transmission through a distorting medium using two holograms
Authors: Lee H. S. , Fenichel Henry
Published: February 2023

A method is demonstrated for transmitting an image through a distorting medium using two holograms. A lens projects the object beam A1 to form an image onto an image plane where the first holographic plate H1 is located. A second holographic plate H2 is placed a short distance beyond H1. The reference beam R2 for H2 is a plane wave incident normal to H2. The reference beam R1 for H1 traverses the distorting medium prior to reaching H1. After the holograms are developed, a mirror placed beyond H2 and parallel to it reflects R2 back onto H2. This in turn generates the complex conjugate of the object A1*, which is incident on H1 from behind. A1* acts as a reference beam for viewing H1 and produces a conjugate signal beam R1*. This beam is retraced through the distorter carrying with it an undistorted conjugate image of the original object. Thus R1 acts as a carrier of the information through the distorting medium.
Composite structure for two-state atoms in an optical cavity
Authors: Raizen M. G. , Brecha R. J. , Thompson R. J. , Kimble H. J.
Published: February 2023

Experimental and theoretical investigations of the radiative processes of a collection of two-state atoms contained in a high-finesse optical cavity are reported. To make contact with previous work on this subject, we consider the usual regimens in which either the cavity or the atomic damping is dominant. However, of greater interest and relevance to our experiments is the regime of strong coupling that generates splittings and new features in the normal-mode structure of the composite atom-field system. We identify possible mechanisms for producing line shapes with subnatural linewidths. Our experimental investigations are conducted with two-state sodium atoms that interact with a single mode of an ultra-high-finesse optical cavity. The incoherent spectral density of the transmitted field is detected by optical heterodyne. We obtain good qualitative agreement between theory and experiment for the general features of the composite atom-field system as manifested in the spectral density of the transmitted field. Experiments to probe the response of the system to weak modulation of the incident field are in progress.
Decay of number-state superpositions in a micromaser
Authors: Slosser John , Kennedy T. A. B. , Meystre P.
Published: February 2023

Coherent superpositions of quantum states are very sensitive to coupling to the environment. The fluctuations associated with this coupling tend to wash out quantum phases, so that in practice only quantum mixtures are observed at the macroscopic level. This problem has been the object of recent interest in connection with measurement theory (Schrodinger cat). Theoretical predictions indicate that the decay of quantum coherences in the so-called pointer basis is amplified by a factor proportional to a measure of the distance in Hilbert space between the states. Micromasers offer a possible experimental tool to investigate the decay of such coherences. Theoretical studies of a lossless version of the micromaster have shown the existence of trapping states

|

n
q

〉

of the cavity mode. These number states are such that atoms injected in the upper state into the cavity experience a 2qπ interaction with the field. Cavity states of the form

|
ψ
〉

=

Σ
q

C
q

|

n
q

〉

are easily shown to be dynamic steady states of the system. Number states are not a pointer basis for the micromaser, and our theoretical results will evidence the qualitative difference in the nature of coherence decay between this and previously studied cases. Because the decay times of micromaser cavities are typically of the order of hundreds of milliseconds, our results should be amenable to experimental verification.
Quantum revivals in micromasers
Authors: Wright E. M. , Meystre P.
Published: February 2023

A distinctive signature of the granulated nature of the electromagnetic field is the revivals known to occur in the dynamics of a two-level atom interacting with a single-field mode (Jaynes-Cummings model). The development of high-Q single-mode cavities combined with progress in Rydberg atom spectroscopy has led to a possibility of verifying these predictions. Revival experiments using micromasers have been performed by Walther et al. Here the cavity mode is first allowed to reach a steady state, and then probe atoms are injected into the resonator. By measuring their state as they exit the cavity, one can infer the state of the field. We show that the micromaser experiences Jaynes-Cummingslike revivals when the pump parameter θ is varied. However, in contrast to the conventional Jaynes-Cummings situation, which considers initially coherent fields, the micromaser photon statistics are usually not Poissonian and depend sensitively on θ. The micromaser revivals cannot be explained by a semiclassical theory or linearized quantum fluctuations about the semiclassical solution. Rather, an exact quantum treatment, considering fully the granularity of the cavity mode, is required.
Programmable optoelectronic multiprocessors
Authors: Kiamilev F. , Ersen A. , Esener S. , Fainman Y. , Lee S. H.
Published: February 2023

The programmable optoelectronic multiprocessors (POEMs) machine has a highly parallel architecture based on wafer scale integration of optoelectronic processing elements (PEs) and reconfigurable free-space optical interconnects. The POEMs machine is realized with an integrated silicon/electrooptic modulator technology (e.g., Si/PLZT) to implement the PE arrays and 3-D holographic storage medium such as photorefractive crystals to support the programmable interconnects. The architecture of POEMs can support any variation of the parameters commonly used to classify parallel architectures: granularity (fine, coarse, or large grain), synchrony (SIMD or MIMD), and topology (local or global). Here we describe a fine-grain POEMs machine containing a very large number (100,000 or more) of simple 1-bit silicon PEs. An optoelectronic controller is used to broadcast optically an instruction stream to the PEs for SIMD processing. Unlike conventional parallel systems, there is no fixed Interconnection topology among the processors. Instead the programmable optical interconnects are determined by the optoelectronic controller. The programmer implements a topology that best matches his algorithm. Experimentally, we have designed a scalable prototype of such POEM machines with eight PEs. Each PE has the capability of performing logic, data movement, conditional execution, memory, and I/O operations. Among a wide variety of algorithms to which it was designed to apply parallelism, the fine-grain POEMs machine is especially effective for the rapid execution of symbolic information processing tasks and graph algorithms because of the programmability of optical interconnects and the large number of simple PEs. In particular, it is expected to offer extremely high performance in the rapid execution of semantic networks, production systems, management of large knowledge bases, parallel databases, transportation and communication optimization problems, computer-aided design, VLSI circuit simulation, and game playing. Some sample algorithms are presented and their performance compared with that of the conventional systems.
Signal, noise, and background theory for white-light correlation filters
Authors: Wang Shen-Ge , George Nicholas
Published: February 2023

A theoretical study is presented comparing the performance of several correlation filters including the Fourier-based matched filter, the Hartley transform system, and the sine-filter-cosine configuration.1 In principle all these can be realized in systems using incoherent illumination, but the latter two possess the distinct advantage that the filter transmittance is a real number. Both a sine filter and a binarized sine filter are studied for the sine-cosine cascade correlator, and the latter is clearly shown to be superior. The evaluation is based on calculations of the ratio of peak output signal-to-noise as is customary. Additionally it is important to consider the ambient background signal in regions near the correlation peak and the spatial variation in this local background. We show that all four systems provide matched filter performance. However, the sine transform filter and its binary version are superior, since for these the mean value of the local background is zero. Computer simulations are provided, illustrating the two important applications of sorting pictorial scenes and words.
Nonlinear matched filtering and beyond
Authors: Ersoy O. K.
Published: February 2023

Nonlinear matched filtering involves incorporating nonlinear operations on the transfer function of the matched filter as well as the spectrum of the signal.1 Recent developments in optical computing hold the promise of achieving such operations routinely. Considerably better accuracy and very high resolution such as in the detection of similar, closeby signals, and their exact locations are possible with nonlinear matched filtering.
Source sampling for incoherent imaging and spatial filtering
Authors: Van Der Gracht Joseph , Rhodes William T.
Published: February 2023

Incoherent imaging and spatial filtering systems may employ illumination sources that are effectively discrete spatially. We show that such sources can be used while still preserving the linear-in-intensity imaging characteristics of the system. The source is modeled as a sampled continuous distribution, the Fourier optics methods are used to obtain a sampling condition that specifies the minimum allowable spacing between source points. This minimum spacing depends on the reciprocal of the smaller of the width of the object and width of the imaging system coherent point spread function. Relatively coarse sampling in the source plane is allowed in many cases of practical interest. We provide additional physical insight by examining the distributions (wave amplitude distributions and transmittance function) in the pupil plane of the system. Although linear-in-intensity imaging is maintained through observance of the source sampling condition, image-plane noise may increase because of the removal of redundancy.
Generation and propagation of bright solitonlike pulses in the normal dispersion regime
Authors: Trillo S. , Wabnitz S. , Wright E. M. , Stegeman G. I.
Published: February 2023

Optical solitons are potentially useful both in future optical communication systems and in optical computing logic gates. As is well known, anomalous dispersion is a necessary condition for the generation and propagation of a bright soliton. We present analytical and numerical results predicting the propagation of bright solitary waves even in the normal dispersion regime. First, we show that when two pulses interact through linear coupling, as in the case of two orthogonal polarization modes in a birefringent fiber, modulational polarization instabilities1 may induce the generation of a train of ultrashort pulses in the visible. We compare the characteristics of these pulses with those obtainable in the anomalous dispersion regime. Another mechanism for the propagation of a bright solitary pulse in the normal dispersion regime is the interaction via cross-phase modulation2 with a fundamental dark soliton, which in turn is allowed to propagate in the anomalous dispersion regime. We discuss the stability of this analytical solution to the coupled nonlinear Schrodinger equations by means of beam propagation simulations. (12 min)
Measurement of coherence time by fourth-order Interference
Authors: Ou Z. Y. , Gage E. C. , Magill B. E. , Mandel Leonard
Published: February 2023

By using an intensity correlation, or photon coincidence, technique and a Mach-Zehnder interferometer with artificially applied phase fluctuations in one arm, we measured the coherence time of a thermal light beam. The light was derived from the filtered fluorescence of a rhodamine 6G dye solution. The two-photon coincidence rate was measured as a function of path difference and was found to dip 50% when the two arms of the interferometer are balanced. The coherence time of ~100 fs is determined from the measured width of the dip and is consistent with the passband of the filters. The method does not require the stability needed in second-order interference measurements, and its time resolution can be much shorter than that of the photodetectors. The theory of this type of fourth-order interference technique is discussed.
Further analysis of the interference patterns in cross-grating Interferometers
Authors: Cheng Yih-Shyang
Published: February 2023

The fringe characteristics in cross-grating interferometers, illuminated by a source at finite distance, are analyzed. From the measurements of the fringe visibilities and the fringe shifts on discrete planes, the spatial irradiance distribution of the illuminating source, which is separable in two orthogonal directions, can be synthesized. To recover a general 2-D source structure, a line-grating interferometer and the technique of computed tomography should be used. When the line structures of the two cross gratings are not parallel, the fringe pattern has lower contrast, which suggests that four-line gratings should be used to replace the second cross grating to have high contrast fringes. The possibility of forming cross-gratinglike patterns using either the combination of one cross grating and two line gratings or the combination of two line-grating interferometers is discussed. Finally, moire interferometry using a cross-grating interferometer (a line-grating interferometer when only two beams of light are used) is analyzed. Experimental results are given.
Achromatic imaging through an inhomogeneity grating interferometer
Authors: Chen Hsuan , Shentu Lian
Published: February 2023

The use of a symmetric two-grating interferometer as an effective achromatic device for imaging through a phase distorting medium was explored previously.1 The theory was developed for image restoration through solving a set of nonlinear simultaneous equations obtained by the discrete samplings of intensity and phase at designated sites within the interference field. We have reduced the theory to practice for a specific astronomical problem: the imaging of a double star through turbulence.
New developments in Mirau interferometry
Authors: Biegen James F.
Published: February 2023

A Mirau-type interferometer has been developed for microscope objectives with an unobscuring reference surface. Using polarization optics and a specially designed coating, the central obscuration inherent in the Mirau interferometer has been eliminated. The absence of a central obscuration improves the mid-range spatial frequency, response of the objective lens transfer function, thereby improving image contrast. The unobscuring reference surface extends the Mirau interferometer technique to low magnification objective lenses. (i.e., 1–5×). The Mirau interferometer technique used at low magnification allows increased working distances, compared with the Michelson- type interferometer technique for microscopic objectives. The Mirau interferometer technique can be extended to high-power high-N.A. (i.e., 100×/N.A. = 1.4) oil immersion objectives so that the highest possible lateral resolution is achievable.
Multiphoton ionization of atoms in strong fields
Authors: Crance Michele
Published: February 2023

The effect of a strong light field is essentially to shift the atomic levels and to broaden the resonances. Moreover, the quiver energy of an ejected electron increases and may become much larger than the photon energy. The observed behavior of the ion yield and the electron energy spectrum is sometimes paradoxial. We discuss the example of hydrogen at 0.53 [cf9]m[cf341]m and show how the quantum mechanical prediction agrees with phenomenological interpretations.
Two- and three-photon processes in atomic krypton and their use in laser guiding of electron beams
Authors: Radziemski Leon J. , Khambatta Noshir M. , Oertel John A. , Silk Robert
Published: February 2023

Neutral krypton atoms were excited from the ground state 4p6 1S0 to the 4p5 6p[3/2]2 state by two-photon absorption from a line-narrowed ArF excimer laser operating at 193.41 nm. A third photon, absorbed while the atom is in the excited state, ionizes it. Excited state and ion densities were theoretically computed using a standard rate equation analysis. The irradiance levels used (1–5 × 108 W/cm2) were too low for significant ground and excited state ac Stark and Rabi effects. The photon detection system was calibrated with a standard tungsten lamp. Ion signals were measured with known electrical components. The resulting ion and excited state densities, corrected for collisional losses, agreed with the theoretical analysis to within 20% on the average. These results have been used with a modified electron beam propagation code to model such propagation in a low-pressure laser-excited krypton channel. The modifications included the effects of field ionization and enhanced collisional ionization of the excited krypton atoms.
Rabi structures in a Doppler broadened gas?
Authors: Ruyten Wilhelmus R.
Published: February 2023

The problem of a two-level atom interacting with modulated or multifrequency fields has been the subject of much work in magnetic resonance experiments. More recently, experiments dealing with optical interactions have been reported.1,2 Unlike the former, these have been performed in beam experiments to eliminate the effect of Doppler broadening. Here we calculate that Rabi structures, in particular, multiphoton resonances, should be observable even in a gas cell and/or for a broadband source. However, this is true only for fluorescence and absorption at the modulation frequency or harmonics thereof. By contrast, the time-averaged fluorescence, which is the quantity usually studied, becomes structureless on integration over the Doppler profile. The result, which is not consistent with a rate equation analysis, can be qualitatively understood from the resonance behavior of the system. In particular, earlier studies on generalized Bloch-Siegert shifts are extended to harmonic components of the interaction.
Diffractive Bifocal Intraocular Lens for Post-Cataract Vision Correction
Authors: Simpson Michael J.
Published: February 2023

The imaging properties of a diffractive bifocal intraocular lens are discussed. It is demonstrated that the lens properties closely match the application requirements.
Coherent Summation of Injection Locked Single Mode Diode Lasers by Two-Beam Coupling in BaTiO3
Authors: Christian William R. , Beckwith Paul H. , McMichael Ian
Published: February 2023

The photorefractive effect in electro-optic crystals has been extensively studied for many applications. These include real-time holography, optical data storage, and phase-conjugate wavefront generation. Recently, interest has grown in the use of two-wave mixing to produce nonreciprocal energy transfer between two beams. Both theoretical and experimental evidence indicate that the energy transfer occurs without any phase crosstalk. This unique characteristic allows coherent combination of light from two (or more) injection locked lasers whose relative phases cannot be controlled. We describe and demonstrate he use of two-wave mixing in photorefractive BaTiO3 to coherently combine the outputs from two locked, single mode diode lasers operating near 830 nm. Neglecting Fresnel and absorption loses, transfer of over 70% of the power in one beam to the other has been observed using this method. In addition to the coherent summation of light from two single element laser diodes, the results of experiments on combining the output of an injection locked multi-element laser diode array with light from a single element laser diode will be presented.
Propagation of 1-ps Electrical Pulses on High-Tc Superconducting Transmission Lines Deposited on LaGaO3
Authors: Nuss Martin C. , Mankiewich P. M. , Howard R. E. , Harvey T. E. , Brandle C. D. , Straughn B. L. , Smith P. R.
Published: February 2023

Recently, essentially distortion-free electrical pulse propagation of ~100 GHz bandwidth pulses was reported on YBa2Cu3O7-δ (YBCO) superconducting transmission lines [1]. Here, we report on the launching and propagation of 1-ps electrical pulses onto a superconducting YBCO coplanar stripline. The high-Tc transmission lines are defined on LaGaO3 as a substrate. LaGaO3 allows highly oriented growth of YBCO films and has dielectric losses smaller than cubic zirconia and a low dielectric constant in the d.c. to 1 THz range [2].
Observation of the Formation of an Optical Intensity Shock and Wave Breaking in the Nonlinear Propagation of Pulses in Optical Fibers
Authors: Rothenberg Joshua E.
Published: February 2023

The first high resolution (120 fsec) measurements of the formation of an intensity (envelope) shock and the subsequent oscillations due to wave breaking1 are described. The reshaped output pulse is measured from a 250 cm single-mode optical fiber versus the power of a 1 psec input pulse. Over a wide range of input powers, the output pulse has a remarkably sharp self-steepened trailing shock with less than 200 fsec fall times. At a critical peak power of 250 W, well defined 300 fsec oscillations, due to interference of the frequencies which bridge the shock, begin to appear trailing the shock (optical wave-breaking). The development of the oscillations was accompanied by the appearance of spectral sattelites due to the nonlinear mixing of the overlapping frequency components. This measurement was accomplished by cross correlation with a 120 fs probe pulse, using an electronic selection technique to maintain the neccessary resolution over the sampled ensemble.