bluuebunny/crossref_metadata_2025 huggingface dataset:
A k.p theory of many-layer semiconductor heterostructures
Authors: Biermann Mark L. , Stroud C. R.
Published: February 2023

Improvements in growth technologies for producing semiconductor heterostructures have allowed for the manufacture of complex semiconductor superlattices, quantum well and similar devices for high precision. These structures are of great interest for their optical and optoelectronic properties. A theoretical formalism, based on that of Smith and Mailhiot [D. L. Smith and C. Mailhiot, Phys. Rev. B 33,8345-8372, (1986)], has been implemented that allows for the characterization of semiconductor heterostructures consisting of many different III-V and II-VI materials layers with a wide range of layer widths. The method implements a zone center pseudopotential calculation to produce basis states for a k.p theory. In particular, the formalism has been applied to coupled quantum wells, asymmetric quantum wells, and quantum wells with various interface profiles. Results to be presented include energy subbands, subband wavefunctions, momentum matrix elements, and optical transition probabilities for the above structures produced in GaAs-AlGaAs heterostructures. The formalism is also applicable in cases with applied electric fields, lattice mismatched induced strain, and the resultant internal piezoelectrically induced electric fields for some growth directions.
Electrooptical switching and bistability in coupled quantum wells
Authors: Khurgin Jacob B.
Published: February 2023

Modulation-doped system of asymmetric coupled quantum wells is shown theoretically to possess a large optical nonlinearity due to the charge transfer associated with intersubband transition. The range of parameters leading to optical bistability has been determined. A novel triple quantum well system is suggested, allowing a few orders of magnitude reduction in switching power density, to ~50 W/cm2, while having a response time of <100 ps. Optically assisted transfer of up to 90% of all carriers between wells can become an operating principle of novel hybrid optoelectronic devices, incorporating the triple quantum well system into the channel of modulation-doped field-effect transistor with potential applications as fast optoelectronic switches and detectors in the 10-µm range.
Dynamic optical interconnection branch device using the optically controlled nonuniform electric field distribution in CdTe
Authors: Ziari Mehrdad , Steier William H.
Published: February 2023

We have observed that near bandgap illumination (λ ~ 0.8-0.95 µm) of a CdTe:In crystal under an applied voltage alters the uniform electric field distribution and resuits in a high electric field region near the negative electrode. Although a similar effect has been reported for BSO, GaAs, and other photorefractive crystals, the behavior in CdTe differs in several aspects. We have measured the time evolution, voltage, and the intensity dependence of the magnitude and the width of the high field region. This effect is used in a transverse electrooptic modulator where a near IR (0.8-0.95-µm) beam from a GaAs laser or an incoherent source, shone through a transparent ITO electrode, modifies the electric fields, and hence the birefringence below the electrode. The polarization state of a longer wavelength signal beam is altered and accordingly routed by a polarizing prism. We have observed a very high sensitivity to the control beam (Icontrol ~ 10 µW/cm2) and have been able to demonstrate low loss (–0.5 dB corrected by the reflection losses), high contrast (>10:1), and routing of a signal beam (λ~ 1.5 µm). We have measured a latch-type switching time of 40 µs at higher intensities with a long dark decay time. Factors concerning the integration of this device into an array are being examined and are reported on.
Observation of the photorefractive effect in semiconductors on a 5-ps time scale
Authors: Smirl Arthur L. , Schroeder W. Andreas , Dawson Martin D. , Norwood David P. , Valley George C.
Published: February 2023

Recently, we reported extensive measurements of the energy transfer in picosecond two-beam coupling experiments in semi-insulating GaAs:EL2.1 In that case, a Nd:YAG laser with a pulse duration of 30 ps was used to generate a grating with a period of 1.7 µm in the semiconductor. The experiment was conducted in a regime where the laser pulse duration is an order of magnitude larger than the time required for the electrons to diffuse one grating period. In these conditions a linear dependence of the photorefractive gain with incident fluence was noted until a saturation fluence of ~1 mJ/cm2 was exceeded. Similar results have also been obtained for the doped semiconductors CdTe:V and InP:Fe.
LIF studies of the products of laser vaporized metals and semiconductors in supersonic expansions
Authors: Bondybey V. E.
Published: February 2023

Several metals of groups IA-IVA were vaporized and the products studied by LIF. Various dimer species are observed, and their spectroscopy is summarized. Several electronic transitions due to Al2 are observed and analyzed in the products of vaporization of aluminum. Analysis of our results clarifies the electronic structure of the dimer and indicates clearly that its ground electronic state is contrary to previous experimental results and in agreement with several recent ab initio theoretical studies of a 3Π
u
symmetry. Vibrational and rotational constants for several excited states are also reported and their assignments discussed. Addition of reactive gases to the flow of the carrier gas permits the observation of fluorescence spectra from metal oxides, hydrides, carbides, or nitrides. Vaporization of alloys provides a versatile method for producing heteronuclear metal clusters. Several heteronuclear molecules, including the diatomic AlCu, as well as several reaction products, were studied.
Light depolarization due to surface elastooptic effects
Authors: Graver William R.
Published: February 2023

The acoustically driven elastooptic effect at the boundary of a surface corrugation is observed by means of the scattered optical field. A physical model of the elastooptic interaction is developed for different materials and several optical and acoustical frequency combinations. An optical analog matrix is used to evaluate the elastooptic coupling effect on the depolarized scattered optical field in coplanar and noncoplanar acoustooptic conditions. In this analysis, the acoustic-to-optical wave-number ratio was compared to the elastooptic scattered field amplitude and polarization state. The significance of the elastooptic contribution as a function of wave-number ratio is shown to be greater for ratios that approach unity in coplanar conditions. However, the depolarization of the noncoplanar scattered field indicates a complementary effect occurring between polarization state coupling is also significant.
Two-wave mixing in Fe doped KNSBN
Authors: Sun Y. , Moharam M. G. , Lin J. T. , Xu Yuhuan
Published: February 2023

Photorefractive materials such as LiNbOa3, BaTiOa3, KNbO3, Sr1-
x
Ba
x
Nb2O6 (SBN), Ba2-
x
Sr
x
K1-
y
Na
y
Nb5O15 (KNSBN), and Bi12SiO20 (BSO) are attractive candidates for optical data processing applications. The real time holographic gratings formed by the photorefractive effect produce energy coupling between the two writing beams (two-wave mixing). This energy transfer from one optical to another has potential applications in image amplification and correlation convolution operations. In this work, investigation of two-wave mixing (beam coupling) has been performed for the first time in Fe-doped (K
x
Na1-
x
)0.4(Sr
y
Ba1-
y
)0.8Nb2O6 (KNSBN) crystals. These crystals have photorefractive sensitivity and time response comparable with those of BaTiO3, KNbO3, and SBN. Large size crystals of relatively good optical quality have been grow. The composition of the crystal used is (K0.5Na0.5)0.4 (Sr0.61Ba0.39)0.8Nb2O6 with 0.05-wt. % Fe doping. The crystal dimension is 10 × 6.7 × 3.5 mm with the c-axis normal to the 10 × 3.5-mm face. Beam coupling and object beam amplification have been investigated as a function of light intensity, light wavelength, object beam to reference beam ratio, and the ange between the two beams. Beam coupling at 488-nm wavelength is observed to be stronger than that at 514.5 nm. The object beam gain is observed to be less dependent on the total beams' intensity and on the ratio between the object and reference beams.
Photorefractive properties of KNbO3
Authors: Reeves Roger J. , Jani Mahendra , Powell Richard C. , Chase L. L. , Mizell Greg J.
Published: February 2023

Measurements were made of the time evolution of the photorefractive signals and of the two-beam coupling gain of doped and undoped KNbO3 for both picosecond pulse and continuous excitation. The major features of the time response are a very fast spike and a slower signal that builds up in milliseconds. The characteristics of each of these components depend on doping, laser power, and sample orientation. The slow signal has the characteristics of the photorefractive response seen in KNbO3 for continuous excitation. One possible origin of the fast signal is scattering from the lattice mode associated with the oscillation of the Nb ions between equivalent sites in the unit cell; a model based on this proposition is discussed. No gain was observed for picosecond pulse excitation. For continuous excitation, the two-beam coupling gain was greater in the undoped sample than in the Ta-doped sample. By analyzing the measured gain vs crossing angle of the laser beams the trap concentrations and effective electrooptic coefficients were determined.
Simultaneous parallel operation of an array of symmetric self-electrooptic effect devices
Authors: Mccormick F. B. , Lentine A. L. , Morrison R. L. , Walker S. L. , Chirovsky L. M. F. , D'asaro L. A.
Published: February 2023

One of the proposed advantages of free-space optics for digital optical computing or for electrooptic interconnections is the potential for large numbers of input/output connections (pin-outs). In this experiment, we demonstrate the parallel operation of a 2-D array of 209 (an 11 X 19 array) symmetric self-electrooptic effect devices (S-SEEDs).1
Nonconventional materials in optical thin films
Authors: Allen Thomas H.
Published: February 2023

Ion beam sputtering was used to deposit a series of silicon nitride films. These films, ranging in chemical composition from silicon to stoichiometric silicon nitride, were deposited with various deposition parameters. The variations in optical constants and stresses with chemical composition were investigated using Rutherford backscatter spectroscopy to determine both the chemical composition and density. Aluminum and boron nitride films were also deposited with ion beam sputtering. The properties of these materials are discussed. An alternate deposition process, plasma plating, was used to investigate the effects of hydrogen on the optical and mechanical properties of silicon nitride, silicon, and germanium films. The optical constants, stresses, and bandgap energies were measured and compared with those of nonhydrogenated films. It was found that the incorporation of hydrogen in these materials resulted in a decrease in refractive index and an increase in bandgap energy. The role of hydrogen in altering film properties and how it is incorporated into the atomic structure of these materials are discussed.
Cue interaction in object recognition
Authors: Bulthoff Heinrich H. , Edelman Shimon , Weinshall Daphna
Published: February 2023

We describe an experimental framework for a quantitative study of object recognition. Devising stimuli for 3-D object recognition that are both easily controlled in their complexity and sufficiently realistic is rather difficult. In this study we use a computer graphics system (Symbolics 3600) that permits us to overcome this difficulty. Stimulus complexity is controlled by using wirelike objects created by a random walk in 3-D and governed by a single parameter which reflects the complexity of the resulting structure. Our system allows us to investigate different theoretical approaches to object representation for recognition. We compare representations based on 3-D models, sets of 2½D canonical views, and a small number of distinctive 2-D features. Partial results of our study indicate that subjects tend to rely in their response, whenever possible, on local, 2-D features of the objects. Moreover, the choice of such features varies among subjects, as it appears from both reaction time and subjective judgment experiments.
Two stage model for segregation of moving objects
Authors: Ogata Masami , Sato Takao
Published: February 2023

We propose a method of segregating moving objects which combines spatiotemporal filtering and feature matching. The matching scheme is preferred in many computer vision studies of shape from motion, since it produces accurate motion estimates and thus leads to sharp segregation. However, it has an inherent problem called false matching. To get around this problem, we combined the matching scheme with the spatiotemporal filtering scheme frequently used to model biological motion detectors. In our two-stage model, image sequences are first processed by spatiotemporal filters to obtain estimates of local motion. Several velocity candidates are detected in this filtering stage, and these are fed into the second matching stage to reduce the load of the matching process by limiting the range of correspondences. In the matching stage, local velocities are obtained for several kinds of feature. These features vote for velocity estimates, and the velocity with the highest score is assigned to each pixel as the best estimate. Moving objects are identified as sets of pixels with the same velocity. We used this two stage model in natural image sequences and obtained good results.
Toward a fundamental dynamic image preprocessor
Authors: Johnson John L.
Published: February 2023

An image is a perceived, or measured, representation of the actual scene and depends on coordinate transformations. A set of proper coordinate transformations which provides a complete 4-D linear superposition of every coordinate component can be decomposed into scale, rotation, translation, and velocity transformations. For the case of small continuous incremental changes, a general transformation equation is derived. It is a basic transformation which applies to many physical situations. The transformation is applied to dynamic imagery from a single missile-mounted camera, to static imagery from stereo cameras, and to a rotating surveillance camera. It is shown that mappings are generated which display the range to every scene point, the rotation and velocity at every point, and maps of the centers of rotation. Camera motion yields global maps of these parameters while intrinsic scene variations yield local maps. The issue of extraction of these parameter maps is addressed. It leads to the statement of a requirement for a new adaptive training algorithm. If such an algorithm can be developed, neural network architectures could be applied to implement a preprocessor for image feature extraction, where the features are range, rotation, velocity, and translation of scene element.
χ3 enhancement by carrier multiplication in semiconductor junctions
Authors: Brown T. G. , Horbatuck S. M.
Published: February 2023

Two important mechanisms for the nonlinear refractive index in bulk semiconductors are: (1) free carrier plasma interactions and (2) bandfilling and the associated Burstein-Moss shift. Both effects require the creation of excess free carriers by photons having energies slightly less than the bandgap of the semiconductor. This produces a fundamental limit to the strength of the nonlinear optical interaction, since high absorption (required for a high density of free carriers) significantly limits the interaction length over which switching or other functions may be accomplished. One way to exceed this fundamental limit in bulk semiconductors is by carrier multiplication. It is well known that suitable avalanche photodiode structures can enhance the free carrier population by a factor equal to the mean avalanche multiplication. This results in a direct enhancement of the nonlinear refractive index in both direct and indirect semiconductor junctions. The performance of such junctions in quantum-limited optical switching is examined. We show that enhancements in the nonlinear refractive index ranging from 102 to 109 are possible, depending on the choice of materials and operating conditions.
Organic and polymeric electrooptic waveguide devices
Authors: Lytel R. , Lipscomb G. F. , Thackara J. I. , Thicknor A. J.
Published: February 2023

We review the organic integrated optics field covering the synthesis of glassy polymer materials, fabrication of devices, and recent results achieved at Lockheed and by other groups. We survey current materials produced by academic and industrial efforts, some of the material properties and structures, as well as a summary of the current status of the research under way in the U.S. and abroad.
Fabrication of polymer based electrooptic devices
Authors: Holland W. R. , Wolk G. L. , Gordon H. M.
Published: February 2023

The potential to produce low cost, high efficiency electrooptic switching and modulating devices from organic materials has been a subject of intensive research for some time. The recent development of optically nonlinear polymeric materials with electrooptic coefficient equaling or exceeding those of inorganic crystals has produced renewed interest in the fabrication of demonstration devices. Such devices must show not only the advantages of the electrooptic material over traditional materials, but also the advantages obtained from the fabrication of such devices with spin-on, low cost, easily processed polymer materials.
Mechanism, dynamics, and temperature dependence of infrared optical nonlinearities in nematic liquid crystals
Authors: Khoo I. C. , Mansfield R. , Zhou P. , Michael R. R.
Published: February 2023

We present a detailed theory for and experimental studies of the mechanisms, the dynamics, and the temperature dependences of optical nonlinearities of nematic liquid crystals in the infrared regime. Material characterizations have been conducted on a collection of nematic liquid crystals having various nematic → isotropic transition temperature and absorption characteristics in the 2-12-μm spectral area. Optical wave mixing experiments are performed to evaluate the relative contributions of orientational and thermal nonlinearities using CO and CO2 lasers.
Pseudolinear phase retrieval
Authors: Frieden B. Roy
Published: February 2023

A new algorithm is given for inverting an autocorrelation function R = R1,…,Rn for its inputs a. The autocorrelation of a function a may be regarded as the cross correlation between two functions b and a, where b = a. This is made the basis for a cyclic algorithm. In the cross-correlation operation b ⊗ a, make b a numerical guess at a, and leave a as a set of unknowns. The resulting n equations R = b ⊗ a are linear in a and are in echelon form, allowing immediate solution (without recourse to a matrix inversion scheme). If output a obeys a = b, then a is the final solution, and the algorithm is stopped. Otherwise, continue by now making a the new guess solution b. This algorithm is cycled until a bistable solution state is reached: An input guess b gives an output a; then a used as input again gives b, etc. If the geometric mean

a
b

between these bistable solutions is taken, the result is very close to solving the problem. At this point, each new guess solution b is formed as the geometric mean between the previous input-output pair. Convergence is then attained at an exponential rate. Application to 1-D and 2-D problems is discussed.
Using nonsoliton inputs for soliton-based fiber communications
Authors: Hong B. J. , Yang C. C.
Published: February 2023

Since Mollenauer and Smith experimentally evidenced the stable propagation of solitons in fibers over 6000 km, soliton-based communications become even more attractive. Although solitons, produced by a soliton laser, are used as inputs in the aforementioned experiment, nonsoliton pulses can actually be used as input signal carriers in soliton-based communications. It has been shown that, if the input energy is high enough, during the evolution of a nonsoliton pulse, a solitonlike central part is formed and the remaining energy is separated from the central part to form dispersive tails. We report the research results of some problems in using nonsoliton inputs for soliton-based communications. First, it is discovered that besides the slow oscillations of soliton shape during evolution, fast oscillations are produced when the generated dispersive tails of the neighboring bits extend into the soliton part. Second, we found that the bit-bit interaction becomes stronger due to the existence of dispersive tails. For example, the evolving solitons in two consecutive bits will merge earlier than two ideal solitons. This implies a more restrictive limitation on bit rate when nonsoliton pulses are used as inputs. The third problem is related to the cross-phase modulation between two channels. It is discovered that pulses become asymmetric in cross-phase modulation due to the afore-mentioned fast oscillations.
State-space representation for multifrequency acoustooptic interactions
Authors: Xu Jieping , Rhodes William T.
Published: February 2023

The theory of acoustooptic (AO) interactions can be established from a wave (diffraction) viewpoint or a particle (photon-photon scattering) viewpoint. Recently the theory of Feynman diagrams was used with some success to further develop a scattering-based theory of acoustooptic interactions. We have augmented that approach with a state-space representation of the possible scattering interactions. This state-space representation greatly simplifies the combinatoric problems that must be solved to determine scattering amplitudes (diffraction efficiencies) in various acoustooptic diffraction regimes. We have used it to extend the Feynman diagram theory of AO interactions to include the case where an arbitrary number of acoustic frequencies are present in the AO device. No other method, wave- or particle-based, has been successful in this regard. The basic approach is outlined and results are presented for multiple-frequency diffraction in four different regimes: Raman-Nath, isotropic or nondegenerate birefringent Bragg, axial birefringent Bragg, and rediffractable birefringent Bragg.
Hybrid optical-electronic nonlinear optical device using acoustooptic deflectors with nonlinear electronic feedback
Authors: Vlannes Nickolas P. , Decusatis Casimer , Das Pankaj K.
Published: February 2023

Nonlinear optical devices based on the intrinsic nonlinearities of a material are limited to relatively high optical intensities. Hybrid nonlinear devices using optical modulators and nonlinear electronic feedback are proposed. These devices exploit the advantages of both optical and electronic processing to generate large nonlinear properties such as bistability, programmable hysteresis responses, and control of light with light. Bulk and integrated devices can be formulated. A hybrid optical-electronic nonlinear optical device has been developed from an acoustooptic deflector with nonlinear electronic feedback controlling the acoustooptic deflector. Light from the deflector is detected and used to control a nonlinear electronic switching element. If the voltage applied to the acoustooptic device remains constant, the first-order diffracted light intensity increases linearly with increasing incident light intensity. Thus, as the input light intensity is increased, the diffracted output increases linearly as long as the detected light intensity remains below the threshold value of the electronic device. When the diffracted light signal increases above the threshold, the switch engages an electronic feedback loop which applies a variable voltage control to the acoustooptic deflector. This feedback produces nonlinearity in the optical input-output characteristic which can be adjusted electronically. By controlling the threshold intensity, hysteresis effects can be generated. An implementation of this device, including experimentally obtained bistability and hysteresis, is presented.
Growth and Characterization of Photorefractive KTa1−xNbxO3:Cu,V
Authors: Leyva Victor , Agranat Aharon , Yariv Amnon
Published: February 2023

KTa1−
x
Nb
x
O3:Cu,V (KTN) has shown promise as a photorefractive material. Past attempts at growing optical quality KTN have proved difficult. By careful choice of dopants and growth conditions we have successfully grown optical quality KTN:Cu,V using the top seeded solution growth method. A complete characterization of the photorefractive properties of KTN:Cu,V in the paraelectric phase is presented. The photorefractive properties have been found to strongly depend on bias field and temperature. Chemical reduction treatments and absorption measurements have been used to control and study the photorefractive properties.
Optical properties of vanadium oxide films
Authors: Chain Elizabeth E.
Published: February 2023

Several oxides of vanadium undergo a transition from a semiconductor or insulating state to a metal phase at a critical temperature. VO2 undergoes this transition near 68°C, while V2O5 undergoes a similar phase transition near 257°C, and V2O3 undergoes a similar transition near 150 K. During the transition a change in oxide crystal structure is accompanied by large changes in electrical and optical behavior. Thin films of vanadium oxides are capable of reversibly switching from the semiconductor to the metallic state at high speeds with high spatial resolution. Therefore, these oxides have potential use, particularly in thin film form, for a wide variety of applications involving thermally activated electronic or optical switching devices. Such films are of considerable technical interest because of applications in chemical sensors, energy-conserving coatings, transparent conductors, and switching materials. The numerous potential electronic, optic, and optoelectronic device applications which have been suggested have stimulated work on the preparation of thin films by a variety of techniques, including chemical vapor deposition, solgel, evaporation, and sputter deposition.
Principle of a new design for an apochromatic microobjective with flat image field
Authors: Zheng Le Nian
Published: February 2023

A series of new apochromatic microobjectives with a flat image field have been developed having magnifications and N.A.s of 5× to 100× and 0.15-1.3 (oil immersion), respectively.
A Frostpreventing Insulator
Authors: Ribbing Carl G.
Published: February 2023

Existing techniques to prevent condensation upon outdoor surfaces is based upon metallic like coatings. An easily polarizable gas of conduction electrons results in high bulk reflectance in the near infrared and infrared regions i. e. low thermal emittance. In particular condensation prevention has been combined with high visible transmittance by coating glass with doped tinoxide for the reduction of frost formation on car windows.
Surface-Polariton Polarizer for a Planar Optical Waveguide
Authors: Sletten Mark A.
Published: February 2023

A planar, thick slab or thin film, metal waveguide is situated parallel to a planar dielectric film waveguide. As a consequence of the wave interaction between the surface polariton supported by the metal waveguide and the transverse magnetic guided mode of the dielectric waveguide, the latter can be either completely extinguished or its power substantially reduced in a small interaction length. The insertion loss in the same interaction length for the transverse electric guided mode of the dielectric film waveguide is negligibly small. A metal cladding therefore serves as a polarizer for a planar dielectric film waveguide. The theory of this surface polariton polarizer for a planar dielectric film optical waveguide is developed and representative numerical results are presented.
High-sensitivity Frequency Modulation Spectroscopy With A GaAlAs Diode Laser
Authors: Wang Liang-guo , Tate Duncan , Riris Haris , Gallagher Thomas F.
Published: February 2023

A near quantum limited, high-sensitivity spectroscopic measurement has been conducted with a GaAlAs diode laser using frequency modulation spectroscopy. We have demonstrated an absorption sensitivity of 3×10−7 in a 0.84 Hz bandwidth from a water vapor absorption line.
Perception of moving isoluminant gratings
Authors: Lindsey Delwin T. , Teller Davida Y.
Published: February 2023

In a previous study (ARVO, 1989), we found that contrast thresholds for discriminating upward- from downward-moving isoluminant gratings (motion discrimination) are 4 to 16 times the thresholds measured for grating detection. We also found that minimum and maximum thresholds for motion discrimination fell on azimuths intermediate between those which define the isoluminant plane in Krauskopf-Lennie space. These results were obtained using 1.3-c/d, 13.75-Hz gratings produced by modulation of chromaticity around an 18-cd/m2 white point and presented in a 2.3 × 2.3° field located 0.75° from fixation. We now report that, in the same conditions, the contrast required for discrimination of the orientation (horizontal vs vertical) of moving isoluminant gratings is at or near that required for grating detection. Furthermore, preliminary measurements at an azimuth for which motion discrimination is poorest indicate that the discrimination of a moving from a stationary grating occurs at a contrast well above that required for grating detection, but below that required for motion discrimination. Thus, the failures of up-vs-down motion discrimination at contrasts well above those required for grating detection are related specifically to the processing of motion information in isoluminant gratings and cannot be attributed to failures of the visual system to encode an adequate representation of the spatial structure of the stimuli.
Vacuum ultraviolet laser spectroscopy of jet cooled halogens
Authors: Lipson R. H.
Published: February 2023

VUV spectra involving ion-pair states for many of the halogens have been known since the beginning of quantum mechanics. To date, the use of synchrotron radiation has offered the most flexible method to record these spectra. However, since vertical transitions from the ground state probe very high ion-pair state vibrational levels, room temperature spectra tend to be severely congested from extensive rotational structure, hot bands, and naturally occurring isotopomers. We have demonstrated, for Br2 and ICl, that combining four-wave mixing to generate tunable, coherent, and monochromatic VUV radiation, with supersonic jet cooling, allows ion-pair vibrational structures to be readily resolved. New results on the lowest ion-pair states of IBr (EO+) and I2

(

DO

u
+

)

are presented which include the first unambiguous vibrational analyses of their VUV spectra. Unlike I2, IBr spectra exhibit perturbations which manifest themselves in large and erratic intensity variations in fluorescence excitation.
New approaches to computer-generated holography
Authors: Ersoy O. K. , Bubb C. , Brede J.
Published: February 2023

Computer-generated holograms have limitations such as in quality of coding, space-bandwidth product, and plotting technologies. In representation of 3-D information, the problem of how to represent 3-D scenes so that they can be viewed with satisfaction presents an important challenge.
Coherent sum and frequency difference generation in microparticle composites
Authors: Shen T. P. , Rogovin Dan
Published: February 2023

We examine coherent sum and difference frequency generation in two-component media composed of dilute suspensions of metallic or n-type semiconductor microspheres embedded in a passive dielectric host. If one or both of the incident laser beam frequencies is near the surface dipole resonance, the Frohlich mode is excited and the medium exhibits an enhanced response. Enhancement of the sum or difference frequency wave is also possible if this frequency coincides with the surface quadrupole resonance of the microsphere. It is shown that a coherent second-order response is possible only if the symmetry of the system is reduced, which requires two laser beams in a noncollinear configuration. Detailed calculations are presented for the macroscopic response of the individual particles as well as the macroscopic electrodynamics of the composite as a whole. Results for the perturbed electron density and drift velocity as well as the laser-induced microparticle quadrupole moment are displayed. Expressions for the intensity, polarization, and angular dependence of the coherent sum and difference frequency radiation are given.
Spectral changes induced by source correlations
Authors: Wolf Emil
Published: February 2023

It is generally taken for granted that the spectrum of light does not change on propagation. This belief is implicit in all spectroscopy. In the last few years it was discovered that while such spectral invariance holds for radiation from commonly used sources it does not hold, in general, because the spectrum of emitted radiation depends not only on the source spectrum but also on the coherence properties of the source. It was found that in some cases the induced changes may be appreciable, possibly resulting in frequency shifts of spectral lines. It has also been demonstrated that similar spectral changes may be produced by scattering on media whose dielectric susceptibility is appropriately correlated.
Finite beam analysis of nonlinear surface wave excitation
Authors: Li Guifang , Seshadri S. R.
Published: February 2023

Nonlinear surface and guided waves are potential candidates for information carriers in integrated all-optic signal processors. The instability of these waves determines whether they are available for application. The understanding of the mechanisms of distributive excitation of these waves is a prerequisite for using them. For nonlinear waves which degenerate into linear waves in the limit of small amplitudes, instability is deducible using Whitham's method, if the explicit power-dependent dispersion relation can be established. We present a perturbation method which is capable of analyzing the instability even if the powerdependent dispersion relation cannot be found or the waves have no linear analogy. We applied this method to the nonlinear surface wave supported by an interface between a nonlinear metal and vacuum, where power-dependent dispersion relation cannot be found, and subsequently developed a formalism governing the distributive grating and prism excitations of this wave. The self-modulation of this wave is found to be comparable with that of waves supported by Kerr type media.
Joint transform correlation using optically addressed chiral smectic liquid crystal spatial light modulators
Authors: Jared David A. , Johnson Kristina M. , Moddel Garret
Published: February 2023

Experimental results of joint transform correlators that utilize a high speed, binary or analog, optically addressed spatial light modulator (OASLM) in the Fourier plane are presented. The OASLMs consist of an amorphous silicon photosensor and a smectic A* or C* ferroelectric liquid crystal modulator. The OASLMs were used to compute the power spectra of the interfering Fourier transforms of the input and reference images. The devices are fabricated by depositing an a-Si:H photodiode in the PIN configuration on an indium-tin-oxide coated sheet of soda lime glass. A chiral smectic ferroelectric liquid is sandwiched between the a-Si:H thin film and another indium-tin-oxide coated sheet of glass. This produces a switchable halfwave plate at the read beam wavelength. For the smectic A* OASLM, heating elements are used to raise the temperature of the ferroelectric liquid crystal above the smectic C*—A* phase transition. The active area of the devices is a 1.27-cm diam circle. The devices exhibit response times of 10-155 µs with a resolution of 40 line pairs/mm.
Appearance of sinusoidal gratings and increment threshold data
Authors: Zaidi Qasim , Shapiro Arthur , Yoshimi Billibon
Published: February 2023

Isoluminant sine wave gratings appear almost square to most observers, i.e., as bars of color separated by a fuzzy edge. A simple hypothesis can explain this phenomenon qualitatively: the observer adapts to the mean color in the grating, contrast discrimination is then most acute around the adaptation color, and discrimination falls off as a function of distance in color space from the adaptation point. An equivalent hypothesis is that a sigmoid response function with compressive nonlinearities on both sides of the mean color introduces higher harmonics of the physical sine wave into the percept. This response function has been estimated by measuring increment thresholds for brief tests and flashes at different points along lines in color space while keeping adaptation constant at the mid-white. The results can be used to predict both the apparent squaring and the change in duty cycle. Additional tests of this hypothesis can be performed by adapting to different lights and comparing the change in appearance of the grating to the change in increment threshold curves. The estimated response function along a color line can be used to correct a grating so that it appears sinusoidal.
Isolated SWS cone spatial frequency mechanisms
Authors: Humanski Richard A. , Wilson Hugh R.
Published: February 2023

Short wavelength-sensitive (SWS) cones have been demonstrated to contribute to visual tasks requiring spatial information (e.g., stereo). These findings necessarily imply that spatial frequency mechanisms (SFMs) exist, which receive SWS cone signals. We determined the number and frequency tuning of SFMs, receiving SWS cone signals, by isolating SWS cones with intense yellow adaptation and measuring threshold elevation functions for blue, spatially localized test stimuli (i.e., DOGs or D6s) masked by obliquely oriented, blue cosine gratings. The intensity of the yellow adapting field required for SWS cone isolation was determined by identifying the adapting intensity beyond which acuity for blue gratings became independent of further increases in field intensity. Spatial frequency of the cosine gratings and peak spatial frequency of the test stimuli varied from 0.25 to 2.83 cpd in 0.5 octave steps. The resulting threshold elevation functions, derived in this manner, define at least two clusters peaking at ~0.7 and 1.4 cpd.
Optical morphological transformations using gray-scale convolution kernels
Authors: Hereford James M. , Rhodes William T.
Published: February 2023

Morphological transformations like erosion and dilation can be performed optically by convolving the binary input image with a binary kernel and then passing the result through an ideal thresholder/hardlimiter. Generalizations result from using gray-scale convolution kernels. In particular, gray-scale kernels can be used to perform asymmetrical median (AM) filtering on 1-D continuous, binary signals. AM filters are similar to the median filter, except one AM filter removes only positive-going noise spikes and the other filter removes only negative-going noise spikes from binary images. The two AM filter operations are equivalent to the opening and closing operations for a broad class of 1-D signals, but they can be implemented with just one convolution operation instead of a two-step cascade of erosion and dilation operations.
Benham's Top: an information theoretic approach
Authors: Billock Vincent A.
Published: February 2023

The color opponent type I cells of primates multiplex color and luminance signals, adding center and surround responses for color and subtracting center and surround response for luminance [Ingling and Martinez, Vision Res. 23, 1495 (1983)]. Thus color is encoded by a low pass filter and luminance is encoded by a bandpass filter. The overlap of the low pass chromatic and bandpass achromatic response functions in frequency space places fundamental limits on recovery of the individual signals. This may be shown explicitly using information theory. One consequence of color and luminance multiplexing is that color may be imputed to signals that contain only luminance information. Employing an analog of signal detection theory, it can be shown that the overlap of the color and luminance temporal contrast sensitivity functions predicts the excitation purity vs temporal frequency functions found for pattern-induced flicker colors by Jarvis [Vision Res. 17, 445 (1977)]. The result suggests that stimuli that produce pattern-induced flicker colors (e.g., Benham's Top) constitute a unique probe of the spatiotemporal properties of the various ganglion cells that make up the color opponent channels.
Single frequency laser diode pumped laser at 1064 nm
Authors: Kintz Gregory J. , Baer Thomas
Published: February 2023

We report a simple technique for generating single frequency operation in an extended linear cavity. The technique requires the selection of a material with a strong absorption coefficient and a cavity mirror deposited on the surface of the solid state medium. If all the pump power is absorbed in a short distance from the mirror, all the longitudinal modes overlap spatially, thus each mode sees the same population inversion. The modification of the population inversion due to gain clamping by the first mode and the lower cross sections of other cavity modes prevents threshold. However, at some pump power, the contributions to the gain due to the spatial dephasing is large enough for other cavity modes to reach threshold. An analytical expression has been developed modeling this effect. In a nearly hemispherical laser cavity formed by a 2-mm sample of Nd:YVO4 and a 50-mm radius output coupler, pumped by a laser diode array, the threshold for laser emission is 40 mW. At 180 mW of incident pump power from a laser diode array, the single frequency output power is 35 mW.
Simulation of random Gaussian errors in interferogram fringes
Authors: Cordero-Davila A. , Cornejo-Rodriguez A. , Cardona-Nunez O.
Published: February 2023

For a fringe pattern interferogram with only tilt, we did a computer simulation to evaluate the wavefront aberrations, considering mainly two aspects: to assume that the positions of the fringes have random Gaussian errors, the proper selection of the order of the fitted polynomy.
Electric field measurements using helium and hydrogen Stark modified spectra
Authors: Shoemaker James R. , Gars-Cadden Alan , Ganguly Biswa
Published: February 2023

The prediction of the energy level shifts and intensity transfer in atomic hydrogen and helium spectra caused by an external electric field was one of the first applications of wave mechanics. Early measurements relied on electrical discharge sources for excited atoms; since discharge processes will not produce excited states with n > 7 in observable densities, very large (10s to 100s kV cm) electric fields were required to resolve spectral modifications. The development of high peak power lasers enabled excitation to high n (Rydberg) states, increasing field sensitivity down to millivolts/cm and allowing comparison of experiment and theory in well-defined conditions. Field modified selection rules can be used to measure the field direction as well as magnitude. Analysis of line shape simulations of Stark modified Rydberg spectra reveals pitfalls in commonly used field measurement techniques. An ambiguity in defining series termination results in a factor of 2 discrepancy in field measurements based on Inglis Teller line merging. Field-induced line broadening (unresolved manifold splitting) in triplet and singlet helium are shown to differ significantly, with triplet broadening nonlinear with field.
Infrared laser absorption studies of CF4 and CH4 rf plasmas
Authors: Wormhoudt J.
Published: February 2023

Infrared tunable diode laser absorption studies of process plasmas are being carried out in a laboratory reactor which allows a long absorption path. In this paper we report studies of CF4 and CH4 radio frequency plasmas. The molecular species whose concentrations have been measured include CF2, CF3, and C2F6 as well as CF4 in CF4 plasmas, CH3, CH2, and C2H2 as well as CH4 in methane plasmas. Observations are made for ranges of reactor parameters, including rf power, dilution by Ar or H2, total pressure, and O2 addition. Estimation of the plasma temperature from rotational line absorption intensities is also discussed. Recently, several groups have undertaken detailed chemical kinetic modeling of CF4 and CH4 discharges. The absolute concentrations presented here should be of use in assessing the predictive capabilities of the models.
Analogue of the van Cittert-Zernike theorem for statistically homogeneous wavefields
Authors: Wolf E. , Jannson J. , Jannson T.
Published: February 2023

A classic theorem due to van Cittert and Zernike establishes a one-one correspondence between the distribution of the degree of coherence of light generated by a spatially incoherent planar source and the distribution of the complex amplitude in a certain monochromatic field produced by diffraction at an aperture.1 In this paper we present a somewhat analogous theorem which expresses a one-one correspondence between the distribution of the degree of spatial coherence throughout any statistically homogeneous wavefield that propagates into a half-space and the complex amplitude distribution in an associated monochromatic wavefield that propagates into the same half-space. With the help of this theorem one can readily obtain information about the 3-D distribution of the degree of spatial coherence in certain types of statistical wavefield from well-known solutions of some wave propagation problems.
Measurement of spatial coherence of quantum well laser diodes
Authors: Anderson Betty Lise , Fuhr Peter L.
Published: February 2023

The radiation pattern of multiple quantum well phased array laser diodes is generally complicated. The spatial coherence of such a beam has been measured experimentally using a twin single-mode optical fiber arrangement for sampling the beam at arbitrary points, as well as the traditional Young's double slit method. The aperture separation distances were varied to greater than twice the beamwidth, taken to be the full width at the half-maximum intensity points. Spatial coherence measurements were obtained for emissions parallel and perpendicular to the junction plane. The spatial coherence was found to lie in the 0.2-0.4 range. The visibility also increases slightly with bias current, with zero spatial coherence for below lasing threshold operation.
Ferroelectric liquid crystal/silicon VLSI spatial light modulators
Authors: Drabik Timothy J. , Cotter Lise K. , Handschy Mark A.
Published: February 2023

We present the design and characterization of a spatial light modulator (SLM) comprising a ferroelectric liquid crystal (FLC) light modulating layer atop a silicon CMOS VLSI circuit. Our SLM consists of two electrically addressable arrays on the same integrated circuit die. The first, a 1 × 128 linear array with 20-μm center-to-center pixel spacing, used shift register addressing, while the second, a 64 × 64 square array with 60-μm pitch, used static random access memory (SRAM) addressing. In both cases, latching and buffering of the cells states with CMOS circuitry has led to the capability of writing a complete frame in less than the switching time of the FLC material used and has eliminated the need for refresh. The resulting SLM could be addressed at frame rates of up to 4.5 kHz and gave single-element intensity contrast ratios of 12:1. Our light modulator fabrication procedure is independent of the nature of the circuitry on the silicon die. Thus the entire functional repertoire of silicon technology is available for incorporation into high performance SLMs based on FLC materials.