bluuebunny/crossref_metadata_2025 huggingface dataset:
An Efficient Beamformer for Interference Suppression Using Rectangular Antenna Arrays
Authors:   Hanoi University of Industry, Hanoi, Vietnam, Kha H. M. , Luyen T. V. , Cuong N. V.
Published: February 2023

Over the past ten years, the development of fifth-generation cellular network technology opens the door to the deployment of huge sensors inside the Internet of Things (IoT), challenging the technologies of communications. IoT establishes wireless communication between numerous physical things to connect them over the Internet, as a result, these things may seriously pollute the environment for electromagnetic propagation. This paper proposes an efficient beamformer based on binary bat algorithm for interference suppression in wireless technology applications. The proposed beamformer utilizes the technique of controlling only the phase of excitation weights in uniform rectangular arrays. This beamformer can produce optimal patterns with minimal distortions in sidelobe regions while maintaining the main lobe and placing nulls in the direction of interfering signals. To demonstrate this ability, the proposed beamformer is evaluated through several scenarios and compared to a beamformer based on Binary Particle Swarm Optimization (BPSO). The results show that the proposed beamformer maintains the main lobe toward the desired user direction while imposing nulls in unwanted user directions (interferences) and that it surpassed BPSO-based beamformers in terms of convergence speed and interference suppression ability.
Comparative study of the attributive effects of fresh and canned Naftussya water
Authors: Popovych Andriy , Fil Vitaliy , Ruzhylo Sofiya , Zakalyak Nataliya , Żukow Xawery , Popovych Dariya
Published: February 2023

Background. There are several patented methods of preservation of medicinal waters of the Naftussya type. The authors of the patents as evidence of the correctness of the methods cite the facts of preservation of the ability of canned water to enhance motility rat’s v. portae in vitro and/or increase diuresis. However, such tests are not attributive. The most characteristic manifestation of the biological activity of Naftussya water is the stimulation of phagocytosis. Another "Method of preservation of hydrogen sulfide mineral waters" was recently patented. Based on the above, we will use attributive tests for its verification. Materials and Methods. The object of clinical-physiological observation were residents of the city of Truskavets’ (21 men aged 24-67 years and 8 women 33-76 years) with chronic pyelonephritis in remission. The subject of the study were the phagocytic function of neutrophils, excretory function of kidneys as well as leukocyturia and bacteriuria levels and components of microbiota of feces. Results. Weekly use of fresh Naftussya water causes an increase in the reduced content of probiotics in the microbiota and a decrease in the increased content of conditionally pathogenic microflora, which is accompanied by an increase in reduced bactericidal capacity of neutrophils against both E. coli and Staph. aureus, normal diuresis, phosphaturia, magnesiumuria, ureauria while reduction of bacteriuria and leveling of leukocyturia as well as decrease in concentration of uric acid in urine and creatinine and cholesterol in plasma. The beneficial effect on the listed parameters of canned Naftussya water is less pronounced, but the differences are statistically insignificant. Conclusion. The obtained results confirm the effectiveness of the Dovzhenko© method for Naftusya water conservation and provide grounds for continuing research into the effects of canned Naftusya water on the body of urological patients.
Iron Could Bring Better Batteries
Authors: Pitcher Graham
Published: February 2023

IRON AND OXYGEN HOLD THE PROSPECT OF HIGH CAPACITY LITHIUM BATTERIES.
Accelerating Development
Authors: Tyler Neil
Published: February 2023

WITH CPU ARCHITECTURES FAILING TO SCALE, THERE IS A RESURGENCE OF INTEREST IN FPGAS HELPED BY NEW SERVICES VIA THE CLOUD.
Powering Up Design Efforts
Authors: Grylls Bethan
Published: February 2023

ROHM’S POWER LAB LOOKS TO HELP CUSTOMERS USE ITS PRODUCTS IN THE BEST WAY.
Mapping The Innovation Infrastructure
Authors: Tyler Neil
Published: February 2023

UKRI is to map the UK’s research and innovation infrastructure, looking to identify what will be needed for the UK to stay competitive in the next 10 to 15 years.
People Power
Authors: Beck Chris
Published: February 2023

A focus on lean manufacturing and employee engagement has seen Oxford manufacturer Crowcon increase output and reduce costs
Around the Regions: The South East
Authors: Davison Jim
Published: February 2023

The South East has some of the most diverse manufacturing companies in the country, ranging from world-class wine makers to state-of-the-art aerospace firms. However, a lack of skills threatens to set them back, say EEF in our latest regional report
Prior Engagement
Authors: Beck Chris
Published: February 2023

Can technology assist in creating an engaged workforce, or will the rise of Industry 4.0 lead to a disconnected and segregated shopfloor? MM hosted a roundtable of leading industry names to answer these questions, and many more
No Limit Women
Authors: Bernstein Adam
Published: February 2023

Society has been slow to grant women the equal status that they ought to have; and the process has some way to go still, especially when it comes to the world of work
Letter to the Editor
Authors: Wilkins Jonathan
Published: February 2023

Continued training in digital technology is vital to combat the skills gap
Technology: The Answer to Your Worries
Authors: Bailey Martin
Published: February 2023

Manufacturers are facing an automation-related headache in 2019, unless they properly harness the technology that already sits on their shopfloor and get it working to their advantage
Around the Regions: The East of England
Authors: Horobin Charlotte
Published: February 2023

The vast East of England region is home to some of the UK’s most forward-thinking manufacturers, and is a hotbed for the nation’s research and development expertise
Implant survival of total elbow arthroplasty: analysis of 514 cases from the Dutch Arthroplasty Registry
Authors: Macken Arno A. , Prkić Ante , van Oost Iris , Spekenbrink-Spooren Anneke , The Bertram , Eygendaal Denise
Published: February 2023

Aims

The aim of this study is to report the implant survival and factors associated with revision of total elbow arthroplasty (TEA) using data from the Dutch national registry.

Methods

All TEAs recorded in the Dutch national registry between 2014 and 2020 were included. The Kaplan-Meier method was used for survival analysis, and a logistic regression model was used to assess the factors associated with revision.

Results

A total of 514 TEAs were included, of which 35 were revised. The five-year implant survival was 91%. Male sex, a higher BMI, and previous surgery to the same elbow showed a statistically significant association with revision (p < 0.036). Of the 35 revised implants, ten (29%) underwent a second revision.

Conclusion

This study reports a five-year implant survival of TEA of 91%. Patient factors associated with revision are defined and can be used to optimize informed consent and shared decision-making. There was a high rate of secondary revisions.

Cite this article: Bone Jt Open 2023;4(2):110–119.
Una busca llena de esperanzas... La variación uno y una en el español argentino
Authors: Martínez Angelita , Zanfardini Lucía
Published: February 2023

En este trabajo presentamos una inmersión en el análisis de dos formas de autorreferencia desfocalizada que alternan en el discurso emitido por mujeres: uno y una. Desde nuestra perspectiva, la alternancia no es azarosa ni responde meramente al señalamiento del género del hablante, como tradicionalmente se ha descrito, en tanto ambas formas se encuentran en variación intrahablante en el discurso femenino. En consecuencia, buscamos descubrir cuáles son los factores que influyen en la selección. En esa búsqueda, el análisis de nuestro corpus literario, desde una metodología cualitativa y cuantitativa, nos permite aseverar que los temas relacionados con la experiencia femenina favorecen la ocurrencia de la forma una, en los contextos en los que se reproduce el estereotipo.
Multi-OLT PON-based open access network for multi-service performance tuning via the Event-Horizon algorithm
Authors: Rawshan Fahmida , Hossen Monir , Islam Md. Rafiqul , Park Youngil
Published: February 2023

A multi-optical line terminal (multi-OLT) passive optical network (PON) is gaining attention for its multi-access, wide coverage, and integration capabilities. It outperforms conventional single OLT PON, reducing operational complexities, packet delay, and loss. A novel multi-OLT PON-based open-access network (OAN) architecture is proposed that integrates various service providers (SPs) as well as different access networks. Optical network unit structure is also designed to support differential access. The challenging issue here is to incorporate heterogeneous SPs and provoke downstream service with their application diversity. This paper presents what we believe is a novel algorithm named Event-Horizon (EH) to afford heterogeneous downstream services from different SPs for IEEE PONs [Ethernet PON (EPON) and 10 gigabit EPON (10G EPON)]. It incites SP competitiveness and ensures a user experience of seamless migration from service to service. Downstream resource allocation is an atypical issue in the PON area. There are reported numerous online schemes with prediction for the upstream side. Since network data is highly bursty and unpredictable, the EH algorithm uses the machine-learning-based bootstrapping method as its prediction tool. The algorithm improves downstream performance by four distinctive features. First, bandwidth is guaranteed among shared SPs according to service level agreements. Second, bandwidth is allocated for reported data; then excess bandwidth is reallocated as predicted (by bootstrapping) differed data. Third, a donor SP preserves margin before excess bandwidth release, which is a nonlinear process featuring network dynamics. Fourth, the margin satisfaction factor is formulated for tuning multi-service user satisfaction according to quality of service. The simulation is performed by a model OAN showing an emergency medical wireless sensor network (WSN) as the master shareholder OLT and a fiber to the home (FTTH) as a subsidiary one. Performance tuning on the margin reservation of 1% for the WSN case study shows 99.4% network efficiency with maximum jitter of 50 µs up to the full load owing 97.26% throughput. Network delay justifies CISCO and ITU-T requirements for real-time IP traffic. FTTH experiences the packet loss of 0.68% using the EH algorithm at the full load, maintaining WSN emergency service packet loss<0.003%.
Asymmetric transmission and entanglement in a double-cavity magnomechanical system
Authors: Yang Zhi-Bo , Ming Ying , Yang Rong-Can , Liu Hong-Yu
Published: February 2023

Quantum entanglement is a key element for quantum information that can be generated in a double-cavity magnomechanical system that consists of two microwave cavities, a magnon mode, and a vibrational mode. The magnon mode, which describes a collective excitation of spins, is excited by a strong microwave field. In this system, cavity photons and magnons are coupled via magnetic dipole interaction. The magnons and phonons interact via magnetostrictive interaction, while the two microwave cavities can be connected by a superconducting transmission line. By changing the external driving fields on the two cavities to break the symmetry of spatial inversion, we propose a scheme for asymmetric transmission and entanglement. With the use of current experimental parameters for numerical simulation, we believe our results may reveal a new strategy to build quantum resources for noise-tolerant quantum processors and realize chiral networks.
Spiral waveguide Bragg grating modulator on thin-film Z-cut lithium niobate
Authors: Ghoname Amr O. , Hassanien Ahmed E. , Chow Edmond , Goddard Lynford L. , Gong Songbin
Published: February 2023

Next-generation photonic integrated circuits require compact electro-optic modulators (EOMs) that achieve high performance and efficient use of the on-chip area simultaneously. We demonstrate a compact EOM based on a spiral-shaped waveguide Bragg grating on thin-film lithium niobate. The modulator utilizes the grating’s optical filter characteristics along with electro-optic tuning of the central Bragg wavelength to achieve simple and efficient intensity modulation. The spiral Bragg gratings were realized on Z-cut lithium niobate and modulated using top and bottom electrodes. The integrated design wrapped a 2.2 mm long grating into a 120×120µm2 area. The modulator bandgap, with an extinction ratio of over 35 dB at 1550 nm, could be efficiently tuned with a sensitivity of 8.36 pm/V and a 3 dB operating bandwidth of 25 GHz.
Broadband cavity architecture for ultra-thin type-II superlattice mid-infrared detectors
Authors: Das Sona , Dutta Jhuma , Das Gupta Sudipto , Jayaswal Gaurav , Hooda Manish Kumar
Published: February 2023

A broadband cavity architecture for ultra-thin type-II superlattice (T2SL) mid-infrared detectors is designed by exploiting coordinated coupling of the surface plasmon polariton mode and cavity mode in an Au-antenna/detector/highly doped semiconductor ground-plane configuration. By optimizing the doping concentration of the doped semiconductor ground-plane and the size of the antenna, the desired extent of coupling between the modes can be achieved, resulting in enhanced absorption over a broad infrared wavelength band. The absorption in the T2SL active layer in the proposed cavity architecture can be enhanced by nearly 10 times compared with that in the reference structure (without ground-plane and antenna). The cavity architecture is also studied by investigating angular and polarization dependence. This cavity architecture offers potential benefits to type-II superlattice detector performance with minimal growth cost.
Dual narrow surface lattice resonances in Si/SiO2 nanopillar dimer arrays
Authors: Huang Xiaodan , Shao Guojian
Published: February 2023

Si/SiO2 nanopillar dimer arrays are proposed to form two narrow surface lattice resonances (SLRs). One (named SLR1) mainly comes from the coupling between single Si/SiO2 nanopillar dimers’ electric dipole resonance and arrays’ diffraction waves. Another (named SLR2) mainly comes from the coupling between single Si/SiO2 nanopillar dimers’ magnetic dipole resonance and arrays’ diffraction waves. In the array, Si nanopillar dimers are on SiO2 nanopillar dimers, and SiO2 nanopillar dimers are on a quartz substrate. The simulated results reveal that the two SLRs’ linewidths can be as small as 2.6 nm. However, for the Si/SiO2 nanopillar array without dimers, only one SLR can be formed. Compared to the SLR of the Si/SiO2 nanopillar array, the SLRs’ intensity of the Si/SiO2 nanopillar dimer array is stronger and the SLRs’ linewidth of the Si/SiO2 nanopillar dimer array is smaller. The Si/SiO2 nanopillar dimers’ height and diameter, the gap of dimers, and the arrays’ period are all important to regulate the two SLRs. This work is important to the design of micro–nano photonic devices based on multiple SLRs.
Two-dimensional m-ary extension of the Hopfield neural network model
Authors: Bijjani Richard , Das P. K.
Published: February 2023

Hopfield presented a simple model to describe the storage of 1-D binary signals in a neural network. In this model, signals are stored in the interconnections between the processing elements and not in the elements themselves. The model is capable of retrieving a stored signal even if presented with very distorted versions. The retrieval operation requires a series of matrix-vector multiplications followed by simple threshold operations. An extension of this model which enables the network to process 2-D m-ary signals is proposed. The amount of calculation required remains largely unchanged.
Effect of varying asymmetry on a dye ring laser
Authors: Gage E. C. , Mandel Leonard
Published: February 2023

The effects o, controlled variation of losses of the clockwise and counterclockwise propagating modes in a two-mode dye ring laser are investigated experimentally. A current-controlled variable Faraday rotator with crystal quartz compensator is introduced into the dye laser cavity, and the probability distributions P1(I1) and P2(I2) of the two mode intensities I1,I2 are measured photoelectrically with the help of a fast Transiac digitizer as the loss asymmetry is varied. Both P1(I1) and P2(I2) typically have two peaks at zero and nonzero intensities, corresponding to the off and on states for that mode. From the measurements the average light intensities 〈I1〉 and 〈I2〉 and the relative on-off probabilities can be extracted and compared with theory.
Comparison of various shortwave-pass filter designs
Authors: Carniglia Charles K.
Published: February 2023

The simplest shortwave-pass filter design consists of repetitions of the basic period of the form L/2 H L/2, where L and H refer to quarterwaves of low- and high-index materials at a particular wavelength. Such a filter has a passband limited by the first- and third-order rejection bands. The width of the passband can be extended to shorter wavelengths by further subdividing the basic period using materials of intermediate indices. One such class of design, due to Baumeister,1 involves intermediate layers of equal optical thickness, except that the layer of lowest index has twice the optical thickness of the other layers. An alternate design with all layers having equal optical thickness requires that the log of the indices of the layers follows a sinusoidal profile between the lowest and highest indices. To provide the best performance over the transmission band, the Herpin-equivalent index of the coating should be close to the index required for an antireflection coating. Various designs are compared for nondispersive indices ranging from 1.38 to 2.25 on a 1.52 index substrate.
Spectral characterization of butterfly L-receptors using extended Dartnall/MacNichol template functions
Authors: Bernard Gary D.
Published: February 2023

Butterfly visual pigments have absorbance spectra that are very similar to spectra of vertebrate cone pigments. Template polynomials of absorbance as a function of the normalized frequency ratio were created for both rod and cone visual pigments. The spectral range of validity for these polynomials was extended beyond that of published nomograms by incorporating modern electrophysiological data. High-quality measurements of both the absorbance spectrum of visual pigment and the spectral sensitivity function of the very same receptor cells were obtained from the eyes of intact butterflies using optical methods. Partial bleaches measured with retinal densitometry were least-squares fit very well by the cone polynomial. Spectral sensitivity functions measured optophysiologically were least-squares fit very well to theoretical absorptance spectra that were computed using the cone polynomial. Fits based on the rod polynomial were very poor on the long-wavelength limb of the functions.
Spatial summation of noncontiguous stimuli
Authors: Cannon Mark W. , Fullenkamp Steven C.
Published: February 2023

The Quick summation rule describing probability summation has proved a useful algorithm for predicting threshold changes obtained when the spatial extent of a stimulus is changed and has been successfully used in several models of threshold vision. In particular, for sine wave grating stimuli, the Quick summation rule predicts that thresholds should decrease as a power function of the number of cycles in the grating with an exponent of about −0.3 if the sensitivities of the mechanisms activated by the sine wave are approximately equal.
Contrast sensitivity In Alzheimer's disease
Authors: Cronin-Golomb Alice , Corkin Suzanne , Growdon John H.
Published: February 2023

Studies on contrast sensitivity function (CSF) in Alzheimer’s disease (AD) have produced conflicting results, with some investigators suggesting that CSF is impaired generally1 and others reporting that CSF is normal in AD.2 An explanation for the discrepancy in results may involve the range of dementia severity represented by the subject groups in the two studies: Many moderately to severely demented subjects with AD are unable to perform particular CSF tests due to memory, attentional, or other deficits unrelated to visual skills. We have administered to a group of ten patients with AD, of a wide range of dementia severity, a CSF test with low task demands. Sinusoidal gratings of six spatial frequencies (1.5, 3, 6, 12, and 18 cycles/deg) and eight levels of contrast were displayed on photographic plates; subjects indicated the orientation of the gratings (vertical, left oblique, or right oblique). Patients who had been unable to perform tests of CSF involving monitor display of static vertical gratings performed ably with the photographic plates. The results indicate that CSF is depressed at each frequency tested for patients with AD relative to healthy age-matched subjects. This deficit appears to be unrelated to the severity of dementia.
Squeezing and subnatural linewidth in the Mollow spectrum
Authors: Carmichael H. J. , Rice P. R.
Published: February 2023

In his original work on the spectrum of resonance fluorescence, Mollow noted that, at weak excitation, one of the three Lorentzian components comprising the incoherent spectrum has negative weight.1 He commented that, as a consequence, for |ω − ω
0
| → ∞ the spectrum falls to zero as (ω − ω0)−4 rather than (ω − ω0)−2. In fact, the incoherent spectrum for weak excitation is a Lorentzian squared rather than a Lorentzian. The half-width is

(

2

−
1
)

1
/
2

(
γ
/
2
)
≈
0.64
(
γ
/
2
)

, showing significant narrowing over the natural width γ/2. Although this result has been rederived a number of times, nothing appears to have been said about its physical significance. Recently it has been recognized that the fluorescence from a two-level atom exhibits squeezing.2 For weak excitation, photon antibunching in resonance fluorescence results from the self-homodyning of incoherent fluorescence from squeezed polarization fluctuations with coherent Rayleigh scattering. We show that the noted subnatural linewidth is also a manifestation of squeezing. A relationship exists between the incoherent optical spectrum and the spectrum of squeezing. The optical spectrum is formed from the sum of squeezing spectra for field quadratures in phase and out of phase with the Rayleigh scattering. The reduced linewidth results because inphase fluctuations are squeezed and contribute to the incoherent spectrum with negative weight.
Quantum nondemolition measurements in the nondegenerate optical parametric oscillator
Authors: Pereira S. F. , Kimble H. J. , Alsing P. , Walls D. F.
Published: February 2023

We consider a scheme for quantum nondemoliton (QND) measurements involving a cavity containing a Faraday rotator and a nonlinear crystal for (frequency degenerate) parametric downconversion into orthogonal polarizations. For the case of nondepletion of the pump field we analyze the coupled equations for the quadrature amplitudes of the fields using both semiclassical and quantum mechanical approaches. We show that when the magnitudes of the coupling coefficients κ of the crystal and σ of the Faraday rotator are appropriately chosen, the Hamiltonian of the system is of an ideal QND form for the intracavity field in the absence of dissipation. With the inclusion of cavity damping in the form of a single mirror of finite transmissivity, we demonstrate that information in the quadrature amplitude X1 of one polarization of the incident field can be measured (in a QND sense) by monitoring the quadrature amplitude Y2 of the orthogonal polarization.
Nondegenerate two-photon phase conjugation
Authors: Capron Barbara A. , Sargent Murray
Published: February 2023

Our semiclassical theory of two-photon multiwave mixing1 is a generalization of the degenerate four-wave mixing case2 to treat nondegenerate pump/signal/conjugate frequencies. We apply that theory to four-wave mixing in two-photon media. We present explicit formulas for the nondegenerate signal/conjugate absorption and coupling coefficients for cases for which the two-photon Stark shifts are sufficiently small compared to the homogeneous linewidths. More general cases require that the spatial hole burning averages be performed numerically. We find intricate dependencies of the transmission and reflection spectra on the pump intensity and on dynamic Stark shifts. In particular, the reflection coefficients do not necessarily bleach to zero as the pump intensity is increased indefinitely, and interferences occur between pure index and mixed absorption/index contributions
Synthesis of Sp(4,R) first-order systems using thin cylindrical lenses
Authors: Simon R. , Sudarshan E. C. G. , Mukunda N.
Published: February 2023

Group theoretical methods have become a powerful set of tools in the analysis of first-order optical systems. We earlier showed that every axially symmetric SL(2,R) first-order system, including the inverse free propagation process, can be synthesized with at most three thin spherical lenses.1 It is shown that every system in the larger family of first-order systems corresponding to the group Sp(4,R) can be synthesized using thin cylindrical lenses separated by free propagation sections. Synthesis of a system for scale transformation and image rotation2 is worked out in detail.
Design technique for guided-wave gratings
Authors: Li Lifeng , Burke James , Stegeman George , Seaton Colin T.
Published: February 2023

We present a design technique for accurately predicting coupling efficiency in guided-wave applications of gratings. We approach the problem by separating the planar waveguide and diffraction grating. The wave guiding is treated by ray optics techniques, and grating diffraction is treated by rigorous diffraction grating theory or direct measurement. In this way, we get more feeling for the working of the grating as a diffraction element and how it interacts with the waveguide structure. When the grating groove depth is small our results agree with the phenomenological expressions given by Zory1 and the result of coupled-mode theory by Yariv.2 It is shown that the phase difference between reflected plane waves with and without the presence of the grating is important for determining the reflection coefficient of a distributed feedback reflector.
Segmentation method for natural color images
Authors: Tominaga Shoji
Published: February 2023

Image segmentation for partitioning an image into a set of meaningful regions is a key step in color image analysis. One basic technique is a histogram thresholding method using 3-D color features of RGB signals. However, the performance of segmentation depends not only on its algorithm but also on the color features. We have developed a useful segmentation method by means of the three perceptual attributes of hue, lightness, and saturation. The algorithm is based on a recursive thresholding of the histograms. The Munsell color system is used as the perceptually uniform color space. We use direct mapping to assign observed RGB signals to Munsell attributes for each pixel quickly. We give a criterion for finding the most significant peak from all the histogram peaks. A set of subregions with uniform color is extracted, and the operation is repeated on the remaining data to generate a sequence of uniform color regions in an image. Some additional algorithms are also described.
Piggins illusion: effects of grating orientation and spatial frequency
Authors: Odom J. Vernon , Wang Yun-Jui , Chao G.-M. , Li Feng
Published: February 2023

Piggins1 reported that dichoptically presented gratings induce an illusion of multiple levels of depth. Tyler2 attributed this perception to operation of fusional displacement and the vertical horopter. Three experiments were performed to quantify the Piggins illusion as a function of grating orientation and spatial frequency. In each experiment the grating presented to one eye was varied in orientation relative to the orientation of the grating for the other eye. Subjects were asked to indicate the number of distinct edges they saw and if they sensed rivalry, depth, or fusion. Spatial frequency of the gratings varied from 1.7 to 5.5 cycles/deg in 4 steps. The stereo illusion can be accounted for on the basis of the disparities generated by the differences in orientation.
Pulsed squeezed light
Authors: Slusher Richard E. , Yurke B. , Grangier P. , La Porta A. , Potasek M. J.
Published: February 2023

The degree of squeezing generated by parametric downconversion or four-wave mixing can be limited by the ratio of the nonlinear coupling to the linear losses in many practical systems. This ratio can be enhanced by increasing the pump power used for the nonlinear coupling in many solid nonlinear systems where the linear losses are not directly related to the nonlinear squeezing process. Pulsed pump sources are attractive for optimizing the nonlinear coupling-to-loss ratio. We have shown1 that homodyne detection can be used to detect the pulsed squeezing generated by a mode-locked pulse train from the pump laser. A portion of the pump beam is used as the local oscillator which stroboscopically samples portions of the squeezed light pulse train. The amount of squeezing which can be measured as a function of the relative durations of the pump and local oscillator pulses is shown. Progress of recent experiments using both four-wave mixing and parametric downconversion is described.
Photonic band structure: the band theory of light in 3-D dielectric structures
Authors: Yablonovitch Eli
Published: February 2023

By analogy to electron waves in a crystal, light waves in a 3-D periodic dielectric structure should be described by band theory. Recently, the idea of the photonic band structure1 has been introduced, meaning that the concepts of reciprocal space, Brillouin zones, dispersion relations, Bloch wave functions, Van Hove singularities, etc. can now be applied to optical waves. If the depth of index of refraction modulation is sufficient, a photonic band gap can exist. This is an energy band in which optical modes, spontaneous emission, and zero point fluctuations are all absent. Therefore, inhibited spontaneous emission can now begin to play a role in semiconductors and solid-state electronics.
New approach to femtosecond spectroscopy in the near infrared
Authors: Knox Wayne H.
Published: February 2023

Generation of optical pulses of <100-fs duration and a subsequent amplification at kilohertz repetition rate has been shown to be a powerful technique for nonlinear optical investigations requiring simultaneously high excitation intensities (>1013W/cm2) and sensitive detection (transmission changes of <10−4). It is interesting to extend these techniques to the near-IR region (800-1100 nm). Recently, pulses of <100-fs duration have been produced in the near-IR region at 8601 and 805 nm.2 In the latter case, amplification of 805-nm pulses to microjoule energies has been demonstrated at 6-kHz repetition rate2 using a copper-vapor laser-pumped amplifier, which is similar to that which has been developed for the 625-nm CPM laser wavelength range.2 Continuum generation in ethylene glycol results in broadband white light which is now very intense in the 820-1100-nm region.
Hierarchical, computationally efficient motion estimation algorithm
Authors: Bergen James R. , Adelson Edward H.
Published: February 2023

Deriving optical flow information from image sequences is an important early step in image understanding. This information is also very useful directly in a number of image processing tasks. We have developed a low-level intensity based algorithm for computing optical flow. This computation proceeds in a coarse-to-fine manner within an image pyramid representation.
Infrared absorption of small molecular clusters in molecular beams
Authors: Muenter J. S.
Published: February 2023

Small molecular clusters are formed in pulsed molecular beams of rare gas atoms seeded with a few percent of the molecule of interest. The molecular beam is interrogated by a beam from either a color center or diode IR laser. The laser beam undergoes multiple reflections and intersects the molecular beam typically 25 times before being detected with an InSb photodiode. The combination of short duration molecular beam pulses and boxcar integration of the photodiode current avoids low-frequency laser noise and permits absorptions as small as 10 μm to be detected. Color center laser radiation at 3 μm is used to excite C-H stretching vibrations in complexes containing acetylene, including argon-acetylene, acetylene dimer, and acetylene trimer. The observed vibration-rotation spectra provide geometries for the clusters as well as changes in vibrational frequencies on complex formation. It is notable that the structure of acetylene trimer is that of a planar triangle. Five-micron diode laser radiation is used to study the carbonyl stretching vibrations in clusters containing carbonyl sulfide.
Frequency shifts of spectral lines produced by scattering on spatially random media
Authors: Wolf Emil , Gori Franco
Published: February 2023

It was predicted theoretically not long ago that correlation between source fluctuations, in general, produces changes in the spectrum of the emitted light.1,2 For radiation from planar secondary sources this prediction was subsequently verified by experiment.3 It has also been shown that the changes may be such as to produce red shifts or blue shifts of spectral lines.4
Total transmittance measurements of anomalous blue VO2
Authors: Case F. C.
Published: February 2023

Thin-film vanadium dioxide undergoes a thermally induced phase transition over a small temperature interval near 67°C. The standard material exhibits a large change in its IR transmission on switching but no significant deviation from a room-temperature bronze color. However, an anomalous form of VO2 was recently deposited1 which shows a striking blue to red color change through the transition. The surface morphology of these films is radically different from the standard material, consisting of large grains 1-2 µm in diameter and separated by wide-grain boundaries. Considering the unusual microstructure of the films, it was expected that the scattered component of transmission would be large. The magnitude of scattered and directional components of the total transmittance at 24 and 100°C has been investigated in the 800-350-nm spectral range using an integrating sphere assembly and spectrophotometer. Results of these measurements are discussed, and the optical constants at visible wavelengths of the anomalous VO2 are compared with those of the standard material.
Optical binary adder using liquid crystal televisions
Authors: Jin Yong , Yu Francis T. S.
Published: February 2023

Recently, Lohmann and Weigelt1 have proposed an optical half-adder for binary addition. We reported a technique to perform XOR operation using programmable liquid crystal televisions (LCTVs).2 Since XOR operation is the key operation in a binary adder, we report an optical half-adder constructed with an LCTV. The binary number can be easily written into the LCTV with respect to the polarization of the LCTV. The output would be the half-sum of two binary numbers. This programmable half-adder can be easily extended for performing large arrays of numbers. We stress that this proposed half-adder can also be used as a full adder, if an optical read-only-memory (OROM) is implemented. The OROM is used for the carry transmission and overflow error detection. We have also illustrated that a 2-bit full adder can actually be built with the OROM concept.
Effects of vertex phase and velocity on the perceived deformation of rigidly rotating polygons of eight vertices
Authors: Sparrow John E. , Stine W. Wren
Published: February 2023

In certain conditions, the isometric projection of a rigidly rotating eight-vertex polygon appears to deform.1 Sparrow and Stine2 suggested that the difference in rotational phase between vertices controls the degree to which a change of shape is perceived during rotation. The degree to which the rotating polygon appeared to deform was measured by asking subjects to adjust the retinal disparity required to just cancel deformation. Given that a rigidly rotating polygon appears rigid when viewed directly (as opposed to viewing an isometric projection of the polygon), our disparity threshold represents the depth information required to resolve ambiguities in the perceived shape of the figure.
Evaluation of CRT display scales with threshold data
Authors: Schuchard Ronald A.
Published: February 2023

Some medical imaging modalities, such as position emission tomography, magnetic resonance imaging, and computed tomography, are exploring the use of monochrome and color CRT displays instead of traditional film displays. To investigate the advantages of different displays the display scales need to be evaluated and compared. I have developed a protocol to evaluate CRT display scales and used it to compare a pseudocolor scale, the heated object scale, and an achromatic scale. The heated object scale was selected because it appears as a natural color scale which can be effectively implemented on a CRT. Chromatic and luminance threshold data were obtained along the heated object scale. The stimuli were presented on a high-resolution graphics monitor using a spatial two-alternative forced-choice staircase procedure. The effects of reference chromaticity, stimulus size, mean luminance, blur, background field chromaticity, noise (uniform or magnetic resonance imaging), and observer differences were investigated. Results were transformed to the cube root of luminance and u′, v′ coordinates1 and analyzed with statistical techniques.
Optical and optoelectronic broadband switching architectures
Authors: Su S. F. , Jou L.
Published: February 2023

With the increasing deployment of optical fibers in transmission systems and the demand for high-bandwidth services, such as video and high definition TV, broadband switching is desirable in telecommunications. We describe a variety of optoelectronic and optical broadband switching architectures. These include crossbar, power-divided, optical coupled, and holographic switching architectures. Optoelectronic switching employs a hybrid optical/electronic principle to perform the switching function. Optical switching does not require optical to electrical conversion. Performances of these switching architectures are evaluated based on throughput, reconfiguration rate, switch size, and switching speed. The advantages and disadvantages of these switching architectures as applied to onboard satellite and terrestrial broadband switching are identified.
Nonlinear refractive index of CS2 at 10 μm
Authors: Beaudoin Y. , Taylor J. , Golub I. , Chin S. L.
Published: February 2023

The reported values of the nonlinear refractive index n(l) of CS2 near 10 μm differ by 3 orders of magnitude, and the mechanisms responsible for the nonlinearity are not understood.1 We measure n(l) for CS2 directly by observing the deflection of a CO2 laser beam which traverses a prismatic cell filled with CS2 as a function of intensity up to 10 MW/cm2 at different frequencies. At 10.6 μm ∂n/∂l is positive, while at 9.5 μm ∂n/∂l is negative. Based on our results and the known CS2 absorption and linear dispersion curves, we conclude that three mechanisms contribute to the nonlinearity: (1) the molecular reorientation Kerr effect resulting in frequency-independent relatively small positive n2 values1; (2) thermal effects with negative n2 responsible for self-defocusing; (3) near two-photon resonance with vibronic states2 at 6.7 and 4.7 μm. The sign of the third contribution to n(l) depends on which side of the corresponding resonance the 2v
L
frequency is situated, while its magnitude is proportional to the laser intensity squared.
Fluorescence spectra from cancerous and normal human breast and lung tissues
Authors: Alfano Robert F. , Tang G. C. , Pradhan Asima , Choy D. J. , Opher E.
Published: February 2023

Laser spectroscopy provides a unique and sensitive approach to reveal changes in the physical and chemical properties that occur in healthy and abnormal cells in tissues. There are well-known intrinsic fluorophors, flavins, and porphyrins bound to proteins within cells that fluoresce in the visible spectral region. These native fluorophors display well-defined spectral features that characterize the local environment and state of the cells. Recently, Alfano and co-workers1,2 established that the fluorescence spectroscopy and relaxation times from malignant and normal rat tissues were different. The differences were attributed to the transformation of the local environment surrounding the fluorophors assigned to be flavins and porphyrins in the normal and cancerous rat tissues. We extended our past fluorescence work1-3 to human breast and lung tissues. We show that there exist differences in the spectral profiles measured for normal and malignant tissues. The assignments of the fluorescence peaks at ~520 and 600 nm are consistent with our past assignments in rat kidney tissues.1-3 The fluorescence profile for the cancer tissues exhibit smoother spectral profiles than the normal tissues. The 600-nm peaks in the cancer tissue are reduced compared to normal tissues.
Improvement In the conjugate gradient method for the numerical solution of scattering from a frequency selective surface
Authors: Schimert Thomas , Cwik Tom
Published: February 2023

Periodic frequency selective surfaces (FSSs) have been exploited extensively as filters, polarizers, and antennas over much of the electromagnetic spectrum from the far-infrared to microwave regions. Advances in microlithography now make it possible to fabricate these structures for use in the mid-infrared.1
Optics of the eyes of invertebrates
Authors: Land Michael
Published: February 2023

No summary of this tutorial or biographical information was available at press time.
Nonlinear absorption in liquid phase epitaxially grown InGaAsP
Authors: Jokerst Nan Marie , Garmire Elsa M.
Published: February 2023

Electronic nonlinear absorption has been observed in thin films of InGaAsP grown by liquid phase epitaxy (LPE). The nonlinear optical absorption studies utilize a thin film of InGaAsP grown by LPE, lattice matched to InP, with a band gap corresponding to 1.06 μm. Gold is vacuum deposited on this grown layer, and a Nd:YAG laser (wavelength = 1.06 μm) is then used to probe the quaternary layer using the substrate as a window. The incident beam passes through the substrate and grown layer and is then reflected by the gold layer back through the sample again. We have noted nonlinearities (in output intensity as a function of input intensity) due to electronic absorption (separated from thermal effects) with short (1-μs) laser pulses and thermal effects (time scale, 20 μs) with longer (60-μs) laser pulses.
Far-IR intensity dependence of the cyclotron resonance of a 2-D electron gas
Authors: Rodriguez G. A. , Hart R. M. , Sievers A. J. , Schlesinger Z.
Published: February 2023

A transversely excited atmospheric CO2 laser pumped far-IR laser has been used to prove the cyclotron resonance line shape of a 2-D electron gas at GaAs/AlGaAs interface for intensities up to 1 MW/cm2. Samples with densities between 0.9 and 4.5 × 1011 electrons/cm2 at 1.7 K as determined by Shubnikov-de Haas resistivity measurements have been studied. The present work focuses on extending the range of frequencies beyond that reported previously.1 The sample is mounted in the Faraday configuration inside a 10-T superconducting solenoid in an optical access cryostat. At far-IR frequencies between 8 and 120 cm−1 the cyclotron resonance line shape is obtained by measuring the transmission as a function of the magnetic field. At high intensity the cyclotron resonance line shape broadens in a way consistent with carrier heating. The onset intensity for this nonlinear behavior increases with increasing frequency.
Improvement in the theory of χ2 for zincblende crystals
Authors: Moss D. J. , Sipe John E. , Van Driel H. M.
Published: February 2023

Although the linear optical properties {χ1(ω)} of semiconductors are well understood theoretically, the nonlinear optical properties {χ2(2ω,ω,ω)} are more poorly understood, with an order of magnitude typically separating theoretical and experimental results. Because optical properties reflect both the band structure and momentum matrix elements, it is clear that nonlinear optics provides a more rigorous test of models of the optical properties of semiconductors.
Interference between resolvable wavelengths
Authors: Davis Lloyd M.
Published: February 2023

When a frequency stabilized dye laser (linewidth ~1 MHz) is passed through a 15.25-MHz Bragg cell, a Doppler-shifted beam emerges at a small angle. Lenses are used to cross this beam with the unshifted beam to form moving interference fringes at the photocathode of a streak camera. By using a large gain of the streak camera intensifier and an intensified low-background readout of the phosphor, single photons are detectable at the photocathode. This forms a novel Young’s experiment conducted with two resolvable frequency beams passing through one known pinhole each. If the photocathode could discriminate the frequency of the detected photon, and hence which beam it came from, or if either beam were blocked, zero visibility results. The experiment gives a direct measurement of the first-order cross-coherence at single-photon detection levels of two-frequency resolvable beams. By contrast, in quantum beat experiments only the photon probability intensity vs time is measured, and the beats are then attributed to a first-order cross-coherence of the quantum pathways. The question of the frequency spectrum and cross-spectral density of each detected photon is addressed with reference to a time-dependent physical spectrum of light.1
Temporal and spatial response of semiconductor power limiters
Authors: Van Stryland E. W. , Soileau M. J. , Wu Y. Y. , Mansour K. , Hagan David J.
Published: February 2023

An optical limiter is a device which has high transmittance for low inputs (energy, power, or irradiance) and low transmittance for large inputs. The devices which we have been investigating perform this task passively, exploiting the large optical nonlinearities of semiconductors. These devices have been reported previously. We have now improved these devices to obtain a combination of low limiting energy with high damage threshold.
Application of an improved coupled-mode theory to optoelectronic devices
Authors: Chuang S. L. , Do B.
Published: February 2023

An improved coupled-mode theory derived from a generalized reciprocity theorem is employed to study optical and optoelectronic devices. Using an exact analytical relation between the coupling coefficients of two general parallel waveguides and a vector formulation of the coupled-mode theory, we study the electrooptical effects for two-and three-coupled waveguide systems.1 Theoretical investigations on the validity of the coupled-mode theory have been performed. The field profiles for two coupled waveguides that are separated by a distance t and that are merged to one waveguide with a zero spacing have all been calculated. The results of the coupled-mode theory are presented and compared with those from the direct numerical solutions.
Two-dimensional detection of ultraweak bioluminescence using a single-photon image acquisition system
Authors: Scott R. Q. , Mashiko S. , Kobayashi M. , Hishinuma K. , Ichimura T. , Yoda B. , Inaba H.
Published: February 2023

Ultraweak light emission phenomena of various living organisms and tissues are now attracting a great deal of interest. However, an adequate means of obtaining information about the distribution of such ultraweak bioluminescence within a specimen is lacking. We are currently investigating an improved ultraweak photon imaging system for this purpose. Earlier low-intensity light imaging systems have relied on the vidicon. A recently developed system (PIAS, Hamamatsu Photonics) employing a position sensitive detector in conjunction with a microchannel plate produces lower noise and significantly increased resolution.