bluuebunny/crossref_metadata_2025 huggingface dataset:
Presurgical Prediction of Postsurgical Visual Function in Cataract Patients: Multivariate Statistical Analyses of Test Battery Measurements
Authors: Davis Elizabeth Thorpe , Sherman Jerome , Bass Sherry , Schnider Cristina M.
Published: February 2023

Cataract patients, especially those with dense cataracts, present a challenge in terms of evaluating their potential visual function because the fundus cannot be clearly visualized and thus many standard clinical techniques fail to provide sufficient, accurate information. Yet, cataracts are the most prevalent cause of visual loss. Moreover, while the incidence of cataracts increases as a function of age, so does the incidence of certain macular and optic nerve/pathway diseases (e.g., age-related macular degeneration (ARMD) and ischemic optic neuropathy). Innovative supplementary tests can prove useful both in predicting post-surgical visual acuity and in differentiating cataract patients who have concurrent macular or optic nerve/pathway dysfunctions from those who do not.
Scheimpflug Slit-Lamp Photographic Characterization of the Aging of the Human Crystalline Lens and the Development of Presbyopia
Authors: Koretz Jane F. , Kaufman Paul L.
Published: February 2023

The slit-lamp biomicroscope is essential in the clinical evaluation of the human ocular anterior segment. A narrow slit of intense white light is shone into the globe, illuminating a thin optical section of the anterior segment, and the illuminated section is examined at an angle through a icroscope. While qualitatively useful, the resultant image is quantitatively severely distorted by the angle of observation, which is a variable projection of the true spacings, and by the passage of the scattered light through the cornea, a strong and sharply curved refractor.
Funding Opportunities for Non-Invasive Assessment of Visual Function
Authors: Atwell Constance W.
Published: February 2023

Participants may discuss priority topics within each of the NEI program areas for which non-invasive assessment techniques are needed. Information will also be available on current funding rates and budgetary considerations.
Early detection of anticonvulsant drug toxicity by colour vision tests
Authors: Bayer A. , Zrenner E. , Thiel H.-J. , Ried S. , Schmidt D.
Published: February 2023

Phenytoin and Carbamazepine, especially in combination or after repeated exposure to toxic blood concentrations, can produce neurological and mental syndroms. Possible mechanisms of impaired neurological and mental function include neuronal damage, or disturbance of folic acid, monoamine or hormonal metabolism. Phenytoin and Carbamazepine may also impair the ocular system. The most common symptoms are diplopia, nystagmus and blurred vision. Cerebellar or vestibulo-ocular dysfunction is suspected as mechanism of these ocular adverse effects.
Isolation of Photopic ERGs Using Dim, Red/Green Counterphase Stimuli
Authors: Loew Ellis R. , Frumkes Thomas E.
Published: February 2023

Vertebrate vision is mediated by two different types of photoreceptors. Although the range for optimal responsivity of rods and cones differs considerably, both respond over a retinal illuminance range of approximately 1–1000 trolands (T), the visual environment typically provided by modern civilization. Over this range, subjective experience as well as psychophysically measured visual capacity of normal humans relates almost exclusively to cones (e.g. Hecht, 1938). But rods greatly outnumber cones. As a consequence, the corneal electroretinogram (ERG), a field potential reflecting the sum of all transretinal components of stimulus-induced currents, is dominated by the much more numerous rods and other retinal cells involved in the scotopic pathway (Rodieck, 1973; Armington, 1974). This is particularly true of clinical ERGs which are typically elicited by brief duration, high intensity, ganzfeld stimuli and recorded by amplifiers with bandpass set between about 1–1000 Hz. Unless flash intensity is great and/or flashes are presented against a prevailing background level which saturates rods, such ERGs overwhelmingly reflect rod activity. Even with rod–saturating retinal illuminances exceeding 1000 scotopic trolands (Ts), the small amplitude of the cone response makes computer averaging essential. However, the responses so obtained have little obvious relationship to the visual capacity measured by "less objective" psychophysical procedures, since they are usually obtained with uncomfortably bright stimuli rarely encountered in everyday life.
Understanding the Swinging Flashlight Test of Pupil Function
Authors: Cornsweet Tom N.
Published: February 2023

A large proportion of pathologies that affect the retina and visual pathways reduce a patient's sensitivity to light in one eye relative to the other. The swinging flashlight test, first described by Levatin (Arch. Ophthal. 62:768,1959) is a clinically useful way to detect such imbalances. The examiner shines a flashlight into one eye for a few seconds, then shifts abruptly to the other for a few seconds, and continues swinging back and forth while watching whichever eye is being illuminated. As reported by Levatin, when this test is performed on a normal visual system the pupils show little or no reaction because signals from each retina drive both pupils and shifting the same light from one retina to the other, then, should cause no change in the drive to either pupil. However, if the test is performed on a patient whose left retina, for example, is less sensitive than the right, then both pupils will constrict each time the right eye is illuminated and both will dilate each time the light shifts to the left eye. Such a result is called a Relative Afferent Pupillary Defect (RAPD). (It is relative because it will only appear if the sensitivities of the two eyes differ; it is afferent because, at least when considering a simplified model of the anatomy, it must result from an imbalance somewhere before the signals from the two eyes converge to drive both pupils.)
Glare Testing: Methodological Considerations
Authors: van den Berg T. J. T. P.
Published: February 2023

We are only beginning to understand the phenomenon of glare, especially in pathology. How do we cope with the demand for glare testing?
Retinal Circulation Time Changes in Diabetic Rats Using Video Fluorescein Angiography
Authors: Bursell S.-E. , Clermont A.C. , Shiba T. , King. G.L.
Published: February 2023

The non-invasive measurement of retinal blood flow changes can provide a unique method for monitoring vascular changes in diabetes and concomitant in vivo investigations into the biologic effects of various metabolic and vasoactive agents. A Video Fluorescein Angiography (VFA) system has been developed (1) and used to provide real time recordings of retinal fluorescein angiograms from a rat animal model. A low light level sensitive video camera was interfaced to a standard Nikon NFC-50 fundus camera fitted with a small pupil adaptor to facilitate better imaging of the retina through the smaller rat pupil. A silicon intensified target (Dage-MTI SIT-66) camera was used featuring low light level sensitivity and high resolution (700 video lines at 0.001 foot-candles). The gain of the image intensifier was controlled manually and for these experiments was set at 3 KV. At this gain setting and level of fundus camera illumination (1/3 of total useable intensity), the video signal did not saturate at arterial sites during VFA recording. The video images were recorded onto a high resolution monochrome optical disc recorder which facilitated a frame by frame digitization of the images.
New Microscope Based LDV Camera
Authors: Shonat Ross D. , Riva Charles E. , Petrig Benno L.
Published: February 2023

Retinal laser-Doppler velocimetry (LDV) is a powerful non-invasive technique for measuring retinal and optic nerve blood flow1. To date, the laser delivery and detection systems necessary for LDV in the eye have been incorporated in a slit-lamp microscope2,3 and fundus camera4. These instruments are optimized for a seated subject with eyes facing forward, but are not well suited to other configurations. To provide for LDV under more general circumstances (such as during a surgical procedure on an operating table), a LDV system has been incorporated in an operating microscope (model OPMI-1, Zeiss). This instrument and its applications are described below.
dmin in patients with retinitis pigmentosa and simulated photoreceptor dropout
Authors: Turano Kathleen
Published: February 2023

Retinitis pigmentosa (RP) is a pigmentary retinal degenerative disease. Although the disease process has been studied extensively, little is known about the effects of the disease on visual perception. What we do know about the perceptual effects derives from patients’ subjective comments and the results of a limited number of psychophysical studies. The experimental results suggest that some RP patients experience spatial distortions (Temme, 1985; Turano, 1990).
Immediate and Significant Changes in Sws Sensitivity Accompany Variations in Blood Glucose in Diabetic Observers
Authors: Schneck Marilyn E. , Volbrecht Vicki J. , Adams Anthony J.
Published: February 2023

Our laboratory, as well as others (eg: Adams et al, 1982; Zisman and Adams, 1982; Greenstein et al, 1989) have reported that the short-wavelength sensitive (SWS) pathway is selectively compromised in diabetes. It is well known that the loss of short-wavelength system sensitivity, as well as the development of tritan (blue-yellow) defects are among the earliest visual changes in diabetes, often occurring in patients for whom clinical examination reveals no evidence of retinopathy. On the other hand, the degree of SWS sensitivity loss increases with the severity of retinopathy and is increased in the presence of macular edema (Adams et al, 1987; Greenstein et al, 1990). The changes in visual function are therefore assumed to be an indirect consequence of diabetes, resulting from the vascular damage and resulting retinal hypoxia caused by diabetes, rather than a direct action of metabolites on tissue function in an "acute" sense.
S-cone discrimination and the 100-hue test
Authors: Yeh Tsaiyao , Pokorny Joel , Smith Vivianne C.
Published: February 2023

Last year, we presented a analysis which provided a framework for reconciling S-cone detection and discrimination data [1]. A theoretical template which used Boynton & Kambe's [2] definition of S-cone trolands was used to derive a model template relating S-cone detection to S-cone backgrounds. In the past year, we have examined detection and discrimination data collected under various adaptation conditions. These data demonstrate that short and long wavelength backgrounds affect the theoretical template differently. The purpose of this paper is to present these experimental data and extend the analysis. Data collected under diverse conditions all point to the TVR function for the S-cones having more than one gain control mechanism. First we will describe the data set and then the modeling.
Optical Methods for the Measurement of Anterior Chamber Depth
Authors: Howland H.C. , Lempert P. , Peck L. , Bock G. , Widdersheim K. , Giuffre L. , Gupta R. , Li T. , Schafer S.
Published: February 2023

The depth of the anterior chamber of the eye has important implications both for the vegatative physiology of the eye and for its optics. Additionally, measurements of angle of gaze may depend upon the location of the image of the pupil, which depends upon the actual anterior chamber depth. We have used this fact to determine anterior chamber depth from a knowledge of the location of the pupillary image and the power of the cornea in the horizontal meridian.
Straylight Meter
Authors: van den Berg T.J.T.P. , IJspeert J.K.
Published: February 2023

It is widely realised that disturbance in the function of the eye is often inadequately assessed with visual acuity only. Contrast sensitivity and glare sensitivity have been proposed for more complete assessment. But in the absence of a golden standard for visual function it has been impossible to judge the adequacy of these, or any, visual function tests. For practical application it is unclear how results can be extrapolated to actual conditions of the visual environment, other than precisely the test condition.
Motion-Defined Letter Reading Test
Authors: Regan D. , Hong X.H.
Published: February 2023

We have compared detection and spatial discrimination for motion-defined (MD) and contrast-defined (CD) form in normally-sighted subjects using a hardware stimulus generator of our own design and fabrication.1 The device displays approximately 1000 dots on a Tektronix 608 display with 100 frames/sec. The dot display is superimposed on a uniform patch of light so that dot contrast can be controlled. A new dot pattern can be generated every frame from a very large menu of patterns. The dot pattern contains a rectangular area whose aspect ratio, orientation, size and location can be controlled on a frame-by-frame basis. The speed and direction of motion of dots inside and outside the rectangle can be controlled independently. When all dots are stationary, the rectangle is perfectly camouflaged. When the velocity of dots inside the rectangle is sufficiently different from the velocity of dots outside the rectangle, the camouflaged rectangle is clearly visible to normally-sighted subjects. In this situation, the rectangle is rendered visible by relative motion. If we switch off all dots outside the rectangle, the rectangle is rendered visible by luminance contrast.
Psychophysical Evidence for Anomalous Visual Processing in Dyslexic Children
Authors: Evans Bruce J.W. , Drasdo N. , Richards I.L.
Published: February 2023

Many factors have been associated with dyslexia, including visual anomalies (Evans and Drasdo, 1990) and subtle cortical pathology (Sherman et al., 1989). Recent research has suggested that up to 70% of reading disabled children may have a deficit of the transient visual system (Lovegrove et al., 1986). The transient/sustained distinction is likely to be an oversimplification (Kaplan et al., 1991); it has, however, withstood investigation reasonably well and its usefulness as an organising tool in dyslexia research seems to warrant further investigation at the present time.
Effect of Diffuse Luminance Flicker on Retinal Macular Blood Flow: An Investigation Using the Blue Field Simulation Technique
Authors: Scheiner A.J. , Kazahaya K. , Riva C.E. , Petrig B.L.
Published: February 2023

The motivation for this work has been the observation by the majority of subjects who were asked to observe the motion of their own leukocytes (WBCs) in retinal macular capillaries by means of the blue field entoptic phenomenon that these WBCs move more swiftly or in greater number for a few seconds after the diffuse blue light illumination had been flickered for a short period of time. This finding is important because it suggests a possible coupling between local retinal activity induced by flicker and local blood flow. Consequently, we have attempted to quantitate this effect using the blue field simulation technique (BFST). In this paper, we report on the following aspects: (i) the effect of the duration of the diffuse luminance flicker on the motion of the WBCs; (ii) the motion of WBCs after cessation of the flicker stimulus; and (iii) the effect of the frequency of the flicker stimulus on the WBCs motion.
A Model for the Blood Flow-Vessel Diameter Relation in the Retina
Authors: Milbocker Michael T. , Feke Gilbert T.
Published: February 2023

Volumetric blood flow rate in the human retina is an important measure of its health. Total blood flow is measured by measuring the flow through the major arteries or veins of the retina. The technique involves measuring the spatial and time averaged blood speed V in individual vessels using LDV1 or a fluorescein angiography procedure such as microencapsulated liposomes2. A measure of the red blood cell column RBCC radius combined with V yields the volumetric blood flow rate. It is natural to determine blood flow rate as a function of vessel radius. Riva et al.3 report a functional dependence of the blood flow rate F on RBCC radius R as (1) where m ≈ 3. Feke et al.1 report m ≈ 4. The majority of studies in the eye and elsewhere in the body, both in humans and in animals, report 3 ≤ m ≤ 4. In this paper a simple model is given which explains the disparity in values of m obtained by different groups.
Optic Nerve Head Blood Flow in the Rhesus Monkey Measured by Laser Doppler Flowmetry
Authors: Petrig B.L. , Riva C.E. , Hayreh S.S.
Published: February 2023

The measurement of optic nerve head (ONH) blood flow could have substantial clinical value, because of frequent occurrence of a variety of ischemic disorders of the ONH.
Statistical Issues Regarding Analyses of Disease-Related Functional Abnormalities
Authors: Eisner Alvin
Published: February 2023

There are many reasons for studying the ways in which visual function changes with disease. One very general reason is to help understand how the visual system works. More specifically, by testing diseased eyes it may be possible to evaluate the generality of conclusions derived from studies of healthy eyes. This type of evaluation may help reveal implicit assumptions that underlie studies of normally functioning visual systems, which typically are investigated using small-sample designs.
Intensity Dependence of cGMP Models Applied to A-Wave Leading Edge
Authors: Breton M.E. , Pugh E.N. , Schueller A.W.
Published: February 2023

Two quantitative models of the cGMP phototransduction cascade have been proposed based on studies of the photocurrent response in isolated amphibian rods (Cobbs and Pugh, 1987; Lamb and Pugh, 1991). These models, when fitted to photocurrent data, provide estimates of rate parameters of the cGMP cascade. Application of such quantitative models to a-wave data of the ERG can, in principle, provide information equivalent to that obtained from isolated rods at the biochemical level on photoreceptor function in vivo. Information at this biochemical level has not been obtained previously from corneal ERG recordings and has the potential to provide a basis for new, more fundamental, understanding of retinal disease processes affecting both photoreceptor and inner retinal elements.
Measuring Foveal Cone Photopigment Optical Density Rapidly
Authors: Elsner Ann E. , Burns Stephen A. , Weiter John J.
Published: February 2023

We are investigating techniques to quickly and noninvasively measure foveal cone photopigment optical density. Since the foveal cones provide the best visual acuity and color vision, it is important to assess their health in many retinal diseases. In some cases, such as patients with retinal detachments, there is the possibility of recovery of visual function following reattachment, and the prognosis for a given patient can be unclear. In these and other diseases, visual acuity or fixation can be too poor to use other techniques, such as color matching or increment threshold for small targets. Thus, a rapid, clinically useful technique could help in the understanding of mechanisms of recovery and help with prognosis for a given patient. Thus, we present our current retinal densitometry technique, data for 7 normal (male) observers, and data for 4 patients with retinal tears and detachments. We discuss the potential benefits and weaknesses, and future developments, of this technique.
Fluorophotometer for Noninvasive Measurement of RPE Lipofuscin
Authors: Delori François C.
Published: February 2023

Lipofuscin is a fluorescent pigment that accumulates throughout life preferentially in the macular RPE. At old age, lipofuscin is the major constituent of the cell as it occupies most of the free cytoplasmic [1]. It has been hypothesized that cell congestion by lipofuscin affects the normal metabolic activity of the RPE [1-3], and that this process plays a role in the pathogenesis of age-related macular degeneration (AMD). Massively engorged RPE cells are found adjacent to areas where the RPE is absent secondary to atrophy in AMD [3]. Although the evidence for lipofuscin involvement in AMD is circumstantial, the possibility of quantifying lipofuscin concentration in old subjects and in patients with AMD offers the potential of a meaningful clinical evaluation of the role of lipofuscin in the development of degenerative diseases such as AMD.
Visual Stimulator Monitored by Microcontroller
Authors: Van Toi Vo , Burckhardt C.W.
Published: February 2023

The temporal modulation transfer function (De Lange curve), using a sinusoidally modulated stimulus, is an important investigative method in physiological as well as clinical studies (e.g., ref 1) of the human visual system. Both mechanical and electrical techniques have been used to modulate the light sinusoidally. A common mechanical technique is to use a steady light source and cross polarizer system to modulate the light beam (e.g., ref 1). By contrast, in electrical techniques the power supplying the light source is modulated. Commonly, the light source used is an LED because of its large frequency response and its short time constant. However, its luminance vs. supplied voltage is nonlinear. In order to overcome this nonlinearity different techniques have been used. Analog techniques use, for example, a feedback controller to correct the nonlinearity. This technique requires special sensors, is elaborate, and is unsatisfactory for a large range of modulation depths. Pulse width modulation (PWM) techniques supply the LED with pulses whose amplitude and frequency are constant and whose width is variable depending on the desired modulation depth of the stimulus (e.g., ref 2). This technique requires elaborate analog electrical circuits. It is not always satisfactory for very small modulation depths because the pulse widths may be smaller than the time constant of the LED, preventing it from following the supplied signal. In addition, varying the pulse width can produce fluctuations in the junction temperature of the LED causing variations in the LED’s luminance. One way to overcome this drawback is to use a pulse density modulation technique (PDM). With PDM the amplitude and pulse width are kept constant and the pulse density is varied with respect to the desired modulation depth of the signal (e.g., ref 3). However, this technique still requires elaborate analog circuits.
The Assessment of Residual Vision in Patients with Maculopathies.
Authors: Mackeben Manfred , Colenbrander August
Published: February 2023

There is evidence that some patients with damaged macular vision can improve their visual performance by learning to utilize intact parts of the retina for "eccentric viewing" (Holcomb and Goodrich (1976), Goodrich and Mehr (1986), Carman-Merifield (1990), McMahon, Hansen, Stelmack, Oliver and Viana (1992)). The chance for such improvement varies greatly with the task, e.g. reading, and with the position of the utilized retinal spot relative to the fovea. In order to optimally guide the patient's learning of eccentric viewing, it is necessary to assess residual vision topographically and in a way releveant to practical viewing tasks. We have developed a computerized test that focusses on finding the best "candidate spot(s)" for eccentric viewing, rather than on mapping scotomata. The test is non-invasive, easy to administer and yields results within minutes.
ERG Flicker Sensitivity as a Function of Retinal Eccentricity and Adaptation Level.
Authors: Seiple William , Holopigian Karen , Lorenzo Monica
Published: February 2023

Both temporal modulation sensitivity and flicker fusion frequency (CFF) increase with increasing eccentricity. Based upon correlations between temporal sensitivity and cone outer segment diameter, it has been proposed that these temporal frequency changes may be due to differences in receptor morphology.1,2 Alternatively, CFF can be made independent of retinal eccentricity by M-scaling (scaling for the number of ganglion cells) and F-scaling (scaling for the luminous flux per ganglion cell). These findings suggested that changes in sensitivity may be correlated with post-receptoral factors such as the number of ganglion cells stimulated, their average receptive field size, and cortical magnification.3,4,5
Relations Between Three Measures of Ocular Forward Light Scatter and Two Measures of Backward Light Scatter.
Authors: Yager Dean , Liu Chih Ling , Kapoor Neera , Yuan Rumei
Published: February 2023

Measures of light scattered back from the lens may be useful if they are able to predict disability glare effects, and serve as reliable indices of forward scatter. We measured forward and back scatter by several methods to examine this issue.
Eye-Head Coordination During Visual Search With Telescopic Spectacles
Authors: Li James , Demer Joseph L.
Published: February 2023

Telescopic spectacles are telescopes mounted in spectacle frames for use as aids for the visually impaired. Although their magnifications ranging typically from 2-8× offer substantial potential visual advantage, these devices are also subject to two significant limitations: first, their field of vision is limited, and second, they magnify the visual effects of head movements. The field limitation creates problems with orientation in the environment, and requires visual search to locate the target of interest for detailed scrutiny. The visual-vestibulo-ocular reflex (VVOR) normally produces eye movements equal in velocity but opposite in direction to head movements in order to stabilize images of fixed objects on the retina. Normal VVOR gain, eye velocity divided by head velocity, is thus ordinarily equal to 1.0. When telescopic spectacles are worn, however, the visual effects of head movements are magnified, so that a VVOR gain equal to telescope magnification is ideally required. For high velocity head movements, the VVOR is overwhelmed and actual gain is less than ideal, permitting instability of images on the retina,1 and consequent reduction in dynamic visual acuity, the acuity during motion.2 However, due to the limited visual field extent, rapid searching head movements would be desirable to minimize search time. What search strategy represents an optimal balance between these two effects? We studied visual search strategies for several types of targets.
Macular Pigment Density measured by Reflectometry and Fluorophotometry
Authors: Delori Frangois C. , Staurenghi Giovanni , Goger Douglas G. , Weiter John J.
Published: February 2023

Lipofuscin fluorescence measurements (Delori, 1992) in the fovea of normal subjects and of patients with age-related macular degeneration are affected by macular pigment (MP) absorption. Measurements of MP density are needed to correct the fluorescence data, but also to study the role of this pigment in aging and disease. MP densities have been measured by reflectometry and psychophysics (see Pease et al, 1987 for a literature survey): reflectometry appears to underestimate the MP density (0.1-0.2 D.U, single pass) compared to psychophysical estimates (0.4-0.8 D.U.). In this report we introduce a novel method for MP density determination, based on fundus fluorophotometry, and compare the results of this technique with those obtained by reflectometry.
There is Hope in Honest Error
Authors: Hill Adrian R
Published: February 2023

If we are to believe the great medical teacher William Osler that medicine is a science of uncertainty and an art of probability [1], then errors in judgement are inevitable and it is incumbent on those involved in clinical research, teaching and practice to seek ways of handling them. All too often, the behaviour of clinicians tends to suggest that they are neither aware of the implications of the inherent errors in their measurements or observations, nor are they always honest with themselves in the confidence expressed in their decisions [2]. Decision analysis provides a framework for handling uncertainties but its effective use in the clinical sciences requires not only a knowledge of the nature and function of clinical tests but also of the sources of potential error.
Discrete Dynamics of Spatio-Temporal Structures
Authors: Kapral Raymond
Published: February 2023

A heirarchy of discrete models for the description of spatio-temporal structures will be presented and applied to the study of specific physical systems. These models include classical cellular automata, coupled map lattices and lattice gas cellular automata.
Multistable Operation Effect on the Low Frequency Noises in the Delayed Feedback Injection Laser.
Authors: Kon M.A. , Rabinovich E.M.
Published: February 2023

The semiconductor laser with optical feedback is very attractive today as the object of research both from the practical and theoretical view - points. The bistable and multistable laser operation is veil known to be equally feasible in such a system [1,2]. As was pointed out in the ref.[3] at the certain feedback level the noise sygnal increase takes place, assotiated with the bistable laser operation influence and with the system switching from one stationary state to another. However, the main properties of the noise sygnal as well as the causes of the system switching mentioned above have not been analysed so far.
Antiphase States in a Multimode Laser
Authors: Wiesenfeld K. , Bracikowski C. , James G. , Roy R.
Published: February 2023

We have predicted and experimentally observed "antiphase" dynamical states in a laser with intracavity second harmonic generation. Analogous dynamical states have been predicted to exist in superconducting circuits.
Picosecond Pulsations of Electron Temperature and Gain in Semiconductor Injection Lasers
Authors: Rivlin L. A.
Published: February 2023

The electrons in a laser react to a laser’s own pulse by fast heating-cooling or cooling-heating pulses that play a significant role in subpicosecond laser dynamics.
Nonlinearities in the Characteristic Curve for Single-Mode InGaAsP Lasers with Weak Optical Feedback
Authors: Milani M. , Brivio F. , Calcaterra F. , Chiaretti G.
Published: February 2023

In a microscopic approach to single-mode semiconductor laser dynamics, the nonlinear dependence of interband carrier lifetime on optical field intensity accounts for some nonlinearities in the characteristic curve appearing in the weak feedback regime.

The comparison with actual optical communication systems is discussed.
Dynamics of a Laser Diode with Optical Feedback
Authors: Etrich C. , Mandel Paul
Published: February 2023

We study a laser diode (cavity length Ld, facet reflectivities Rd) with a feedback provided by an empty external Fabry-Perot resonator (length Lr, mirror reflectivities Rr) at a distance L0 from the laser diode. The characteristic lengths Ld, Lr and L0 are associated with the roundtrip times τd, τr and τ0, respectively. The external resonator is slightly tilted offaxis to avoid direct back-reflection and introduces an infinite number of delay terms into the evolution equation for the electric field.
Bistability and Dwell-Time Instabilities in Diode Lasers
Authors: Postan A. , Bowden C. M.
Published: February 2023

Bistability in a diode laser amplifier performance, and bistability, instability and mode hopping in a diode laser oscillator performance are investigated. In the amplifier case the steady state solutions are characterized by an S curve while in the oscillator case, a different behavior is predicted. The Fokker-Planck equations are derived and solved in both cases. First passage times are evaluated.
Dynamic Behavior of Directly Modulated Single-Quantum-Well Semiconductor Lasers
Authors: Müller R.
Published: February 2023

This paper deals theoretically with light emission from GRIN-SCH single-quantum-well diode lasers where the optical transitions between the first subbands (n=1) as well as between the second ones (n=2) are taken into account, see Fig.1. The mathematical model consists of three rate equations describing the time evolution of the carrier concentration N and the photon densities P1, P2 at the frequencies γ1 = E1/h and γ2 = E2/h, Moreover, nonlinear gain suppression depending on P1 and P2 and noise terms are considered too. In addition, algebraic equations are used giving the gain at the two frequencies of interest in dependence on the time-varying electron and heavy-hole concentration via the Fermi-Dirac distribution functions. Since the nonlinear gain flattening effect /1/ is larger for γ1 than for γ2 the gain at γ2 will succeed that at γ1 for sufficiently large values of N. Hence it depends on the threshold value of N (or on the laser losses respectively) if stationary laser action is reached at frequency γ1 or γ2. Fig. 2 shows the static maximum modal gain g1mod (first subband transition, solid curves) and g2mod (second subband transition, broken curves) versus N for various well widths Lz (10, 15, and 20 nm). Some loss levels are indicated by broken horizontal lines (a,…,d) crossing both the gain curves for each well width. For a constant injection current these crossing points relate to stationary stable or unstable solutions. For example, the points marked C1 and D2 belong to stable stationary solutions for P1 (loss level c) and P2 (level d) at Lz = 20 nm, respectively, while C2 and D1 relate to unstable solutions for P2 and P1. Relaxation oscillations to stable stationary states and the behavior of the light output in case of sinusoidal modulation of the applied current have been investigated by numerical calculations.
Dynamics of Nonlinearly Coupled Modelocked Laser Arrays
Authors: Wu Song , Smith Sandra L. , Fork Richard L.
Published: February 2023

We have used experiments and calculations to explore the dynamics of two nonlinearly coupled modelocked lasers. A special feature of this study is the presence of two distinct adjustable nonlinear mechanisms, where one mechanism causes an attraction of the pulses in the two separate lasers and the other causes a repulsion of the pulses. We find that adjustment of the relative importance of these attractive and repulsive mechanisms, as well as of the relative cavity length, provides a rich variety of dynamical behavior that is not available in alternative laser systems.
Diversity of Chaos in Multimode Solid-State Lasers
Authors: Viktorov E.A. , Mak A.A. , Orlov O.A. , Ustyugov V.I. , Vitrishchak I. B.
Published: February 2023

Multimode solid-state lasers display deterministic chaos in individual mode intensities (total intensity nearly constant) at free-running generation, and in total output power at intracavity second harmonic generation (ISHG). ("green problem")1. The goal of our investigation is comprehensive study for both these cases of lasing.
Interaction of Relaxation Oscillations and Instability in a Bidirectional Nd:YAG Laser with a Nonreciprocal Ring Cavity
Authors: Khandokhin P. A. , Khanin Ya. I.
Published: February 2023

It is shown that the phase nonreciprocity influences the stability of the traveling wave regime due to changing the interaction between different types of relaxation oscillation. The laser sensitivity to the sign of phase nonreciprocity appears with detuning.
Thin Layer Lasers
Authors: Oraevsky A. N.
Published: February 2023

A theory of a thin layer laser is presented, i.e., a laser whose active medium length along the wave propagation is less than the wavelength. It is shown that such a laser exhibits a number of peculiarities compared with an ordinary laser.
Nonlinear Dynamics of the broadband Dye Ring Laser with Regulated Cavity Dispersion
Authors: Vinogradov S. E. , Kachanov A. A. , Kovalenko S. A. , Sviridenkov E. A. , Ivanov V. V.
Published: February 2023

Summary not available.
Spatial Correlation Dimension and Critical Phenomena in Complex Ginzburg-Lardan Mode
Authors: Rabinovich M.
Published: February 2023

Summary not available at press time.
On the Deterministic Dynamics of Stimulated Scattering Phenomenon
Authors: Harrison R.G. , Lu Weiping , Johnstone A. , Lim D.S. , Uppal J.S.
Published: February 2023

Lu and Harrison have recently shown [1] in a more complete treatment of stimulated scattering that the interplay of nonlinear refraction with the gain of stimulated scattering lead to rich dynamical instabilities and chaos in the scattered and pump fields; omissions of dispersive effects as in conventional treatments resulting in stable emission only. Such behaviour is shown to be prevalent over broad experimentally accessible operating conditions, in some instances from the onset of stimulated scattering.
Spatial Symmetry Breaking and Coexistence of Attractors in a Nonlinear Ring Cavity
Authors: Sauer M. , Kaiser F.
Published: February 2023

Modulational instabilities in nonlinear optical systems play an important role for pattern formation since they give rise to characteristic internal space frequencies [1]. We address the question how the pattern formation by modulational instabilities influenced by an external spatial modulation of the input. We find a sequence of temporal frequency locking when the wavelength of the modulation is increased. It also leads to a spontaneous symmetry breaking of the solutions which allows for the coexistence of various periodic attractors. This can be explained by the concept of cooperative frequency locking[2, 3].
2 Dimensional Transverse Patterns in Optical Bistability
Authors: Firth W.J. , McDonald G.S. , Scroggie A.J. , Lugiato L.A. , Lefever R.
Published: February 2023

Pioneered by Moloney and collaborators [1], transverse effects of nonlinear passive systems in a ring cavity have been the object of extensive study. Analytical investigations with diffractive coupling in one transverse dimension have demonstrated [1] that static and dynamic transverse structures occur in this system. Extension of the mean-field dispersive model developed from optical bistability to include diffraction [2] independently demonstrated qualitatively similar features, again in one transverse dimension. Investigations in two transverse dimensions have been largely confined to numerical studies by the Moloney group [1], showing for gaussian beam illumination ring structures which develop through azimuthal instability to a pattern of spots which typically execute a slow chaotic motion with a progressive loss of symmetries.
Pattern Formation Due to Nonlinear Counterpropagation in Kerr and Brillouin-active Media
Authors: Geddes J.B. , Indik R. , Moloney J.V. , Firth W.J. , McDonald G.S.
Published: February 2023

Spontaneous hexagon formation has been observed when two counterpropagating laser beams interact in sodium vapor [1] and carbon disulfide [2]. Here we report on investigations into the nature, stability and range of patterns in such systems. We model an anti-reflected slab of either a Kerr or Brillouin-active medium irradiated on each side by smooth constant input fields. These may be Gaussian beams [3] or plane-waves.
Nonlinear single wavelength polarisation switching in InP-based waveguides
Authors: Gontijo I. , Neilson D. T. , Walker A. C. , Kennedy G. T. , Sibbett W.
Published: February 2023

All-optical switches have attracted much attention due to their potential application in high speed optical communication systems. Among the many concepts that have been studied are pump/probe nonlinear etalon devices, both in InGaAs/InP1 in the wavelength range of 1.5μm and in GaAs-based structures2at 0.85μm. In general, the excite (pump) and probe wavelengths have to be different, to avoid probe absorption. The use of a single wavelength but different states of polarisation in the pump and probe beams to produce switching has been investigated in CdS.3 In this case, the device relies on the natural dichroism of a CdS crystal platelet, to absorb only light of a specific polarisation, which is chosen to be the pump. InGaAs/InP quantum wells exhibit much larger dichroism for TE/TM polarisations and we have observed large refractive index changes at wavelengths away from the bandedge.4 Reported below are experiments where a single wavelength was used, together with the large splitting between the heavy and light hole absorption bandedges in InGaAs/InP quantum well waveguides, to demonstrate a two- polarisation switch with signal gain. The waveguide, with uncoated facets, is a nonlinear Fabry-Perot etalon, whose refractive index can be changed by the absorption of the pump beam which in turn changes the cavity transmission characteristics sensed by the probe beam. This type of device could have important applications, as it uses a single wavelength and offers cascadability and compatibility of all-optical switching with optical fibre communications.
A Hybrid Mode Locked Semiconductor Laser as Tunable Source for 17 ps to 200 fs Pulses, Repetition Rates from 2 to 7 GHz and a Wavelength Range over 100 nm
Authors: Ludwig R. , Ehrhardt A.
Published: February 2023

Optical communication systems with very high transmission speed need compact and stable sources for ultra short pulses at high repetition rates. Besides, system experiments require tunability of wavelength, pulse width and repetition rate.
KrF-Laser-Induced Refractive Index Changes in Germanosilicate Fibers
Authors: Mizunami Toru , Itoh Tatsuya , Gupta Sanjay , Takagi Keiji
Published: February 2023

The formation of photorefractive Bragg gratings in fibers has recently attracted attention. To achieve high reflectivity, high-Ge fibers are usually considered to be better than telecommunication fibers. However, Limberger et al. reported that a reflectivity of 94% and an index change of 1.3×10−3 were obtained in a standard telecommunication fiber with a Ge concentration of 3%. 1 It is also noted that Archambault et al. reported type II gratings with a reflectivity of 99.8% and an index change of 6×10−3 in a high-Ge fiber.2 Therefore the relation between index change and Ge concentration is still unclear, and the mechanism of index changes is under discussion. These reported index changes are calculated values from reflectivities of gratings, and thus a directly measured value is rare. Hand et al. measured index changes at 266 nm using interferometry. 3 In this paper, we describe a measurement on refractive index changes induced by a 248-nm KrF laser. We used a telecommunication fiber and a 50wt%- GeO2 fiber. Analysis with the Frantz-Nodvik equation is performed, and absorption cross sections of the related defects (Ge-Si and Ge2+) are calculated.
Te-Tm Coupling of Spatial Solitons in Planar Waveguides With Cascaded Second-Order Nonlinearity
Authors: Boardman A D , Xie K , Sangarpaul A K , Mehta H M
Published: February 2023

Second-order nonlinearity is traditionally associated with second-harmonic generation and was not, until recently1-7, seen as a source of intensity dependent phenomena. The rejection of second-order materials, as envelope or spatial soliton hosts, appears to have been centred upon a phase-matching argument1. This view has now changed and the back-mixing 1,2,7, or down-mixing [cascading], of the second-harmonic with the fundamental wave to create useable third-order nonlinearity in the form of an intensity-dependent refractive index is opening up exciting prospects. Featuring strongly among these are spatial soliton interactions. Such excitations depend upon the competing roles of diffraction and nonlinearity8,9 and have already received some attention10.
All-Optical Modulation via Cascading in Type II Second-Harmonic Generation
Authors: Torelli Irina , Assanto Gaetano
Published: February 2023

Second-order cascading via second-harmonic generation (SHG) and downconversion back to the fundamental frequency (FF) has been proven to be an effective approach in obtaining large phase shifts. [1-4] We discuss here a specific SHG configuration involving two spatially orthogonal components of the FF input wave, i.e. a Type II configuration, which only recently Belostotsky et al. have addressed for cascading effects. [5] Hereby, on the grounds of a numerical analysis, we demonstrate that cascading in Type II SHG can be effectively utilized for all-optical modulation and transistor action. This scheme is simple and promising in terms of practical implementations with existing crystals.
Ultrashort soliton propagation in the vicinity of a two-photon resonance
Authors: Rodrigues Augusto S. , Santagiustina Marco , Wright Ewan M.
Published: February 2023

A new formalism to describe pulse propagation in the vicinity of a two-photon resonance is applied to GaAs-doped glass waveguides. Ultrashort soliton propagation is predicted.
Soliton-based RZ Transmission over Transoceanic Distances using Periodic Dispersion Compensation
Authors: Suzuki Masatoshi
Published: February 2023

5Gbit/s transoceanic optical submarine cable systems using EDFA repeaters and NRZ signals will be in service in 1995-1996 in the Pacific and the Atlantic Ocean[1]. Research interest is now being directed toward the development of optical amplifier systems with a transmission capacity of multi-ten Gbit/s or more. To increase an aggregate system capacity, both the wavelength-division-multiplexing (WDM) transmission scheme using NRZ signals and soliton signals have been intensively studied[2]-[5]. Recently, the feasibility of 100Gbit/s transmission over 6300km by using 20-channel 5Gbit/s NRZ WDM signals[2] and 80Gbit/s transmission over 10,000km by using 8-channel 10Gbit/s soliton WDM signals[3] have been demonstrated. Soliton transmission systems are expected to carry higher bit rate (per channel) than NRZ systems[4]-[11], and thus soliton-WDM transmission with a channel bit rate of more than 10Gbit/s is quite attractive for transmission systems with ultra large capacity[4],[5].
Vertical coupler device design for reduced-power optical switching using nonlinearity mismatch
Authors: Geatches Rachel M , Dewar Susan V , Penty Richard V
Published: February 2023

The potential of nonlinear directional couplers (NLDCs) as the basis for all-optical switching devices has been studied extensively [1]. The mode of operation of an NLDC as an all-optical switch is based on the optical intensity dependence of the nonlinear refractive indices of the two waveguiding regions of the coupler, where the modal propagation contants (β) of the waveguides are matched at low powers and mismatched at high powers. When the waveguides are in close proximity, the light in the input waveguide will couple to the other waveguide in a coupling distance Lc at low powers, but at high powers the waveguides will decouple and the light will remain in the input waveguide. The power at which the light is equally split between the waveguides is defined as the critical power, Pc [2]. Proposals to reduce Pc in fibers NLDCs have included asymmetric designs, matched gain in the input waveguide to loss in the other [3], and non-identical nonlinear refractive indices in the two waveguides [4], However, for true optoelectronic integration it is desirable to design NLDCs using semiconductor materials. Our previous studies of semiconductor NLDCs for the first time have focussed on the enhancement of asymmetry and realistic geometries for matching gain to loss [5]. This has been demonstrated by the use of vertical design configurations with a quasi- planar-waveguide coupled to a rib-waveguide (see figure 1). Such designs have a high degree of geometric asymmetry, and because the waveguides are in separate planes the doping and biasing requirements needed for inducing gain in only one waveguide are experimentally realisable. Furthermore, the separation of the waveguides is only limited by the epitaxial fabrication process. This indicates that the waveguide separation in a vertical NLDC can be much smaller than that for a conventional two-rib horizontal design, thereby further enhancing the predicted characteristics of the design by minimizing Lc. In this paper, we extend these studies to the design of vertical NLDC geometries with nonlinear refractive index mismatch between the two waveguides. This is achieved by having the two waveguiding layers made of different semiconductor materials. The structures have been designed and optimized using two computational modelling techniques, the Spectral Index method and Coupled Mode Theory. In this paper we report a fesibility study of the predicted advantages of such a design and the possible reductions in Pc.