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Tuning the resonance of polarization-degenerate cladding mode LP1,j in excessively tilted long period fiber grating for highly sensitive refractive index sensing

Zhihong Li, Jie Shen, Qiuping Ji, Yaoju Zhang, Xiukai Ruan, Yuxing Dai, and Zhennao Cai

Doc ID: 313853 Received 22 Nov 2017; Accepted 11 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: This work presents a sensitive refractive index sensor based on the dual resonance of excessively tiltedlong period fiber grating (Ex-TLPFG). The Ex-TLPFG is tuned to couple the guided core mode with onlypolarization-degenerate cladding mode LP1,l which consists of TE/TM0,l and HE2,l vector modes. It isfound that the p-polarized LPp1,l mode exhibits a higher sensitivity than that of s-polarized LPs1,l mode. Anoptimized sensitivity as high as 12182.9 nm/RIU is achieved for p-polarized LPp1,2 mode at low refractiveindex region by tuning initial resonance condition. The sensing performance is also evaluated throughthe power measurement method for a single resonance band. It is demonstrated that the improved sensitivityin this work for diameter-reduced Ex-TLPFG is much higher than that for the conventional LPFGbased devices, which makes this sensing platform very attractive for a variety of index sensing applications.

A Kalman filter approach for uncertainty quantification in time-resolved laser-induced incandescence

Paul Hadwin, Timothy Sipkens, Kevin Thomson, Fengshan Liu, and Kyle Daun

Doc ID: 309168 Received 16 Oct 2017; Accepted 10 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: Time-resolved laser-induced incandescence (TiRe-LII) data can be used to infer spatially- and temporallyresolvedvolume fractions and primary particle size distributions of soot-laden aerosols, but these estimatesare corrupted by measurement noise as well as uncertainties in the spectroscopic and heat transfersubmodels used to interpret the data. Estimates of the temperature, concentration, and size distributionof soot primary particles within a sample aerosol are typically made by nonlinear regression of modeledspectral incandescence decay, or effective temperature decay, to experimental data. In this work, we employnon-stationary Bayesian estimation techniques to infer aerosol properties from simulated and experimentalLII signals, specifically: the extended Kalman filter and Schmidt-Kalman filter. These techniquesexploit the time-varying nature of both the measurements and the models, and reveal how uncertaintyin the estimates computed from TiRe-LII data evolves over time. Both techniques perform better whencompared with standard deterministic estimates, however we demonstrate that the Schmidt-Kalman filterproduces more realistic uncertainty estimates.

Achieving a high mode count in the exactelectromagnetic simulation of diffractive opticalelements

Andre Junker and Karl-Heinz Brenner

Doc ID: 313631 Received 15 Nov 2017; Accepted 09 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: The application of rigorous optical simulation algorithms, both in the modal as well as in the time domain,is known to be limited to the nanooptical scale due to severe computing time and memory constraints.This is true even for today’s high performance computers. To address this problem, we develop the FastRigorous Iterative Method (FRIM), an algorithm based on an iterative approach, which, under certainconditions, allows solving also large size problems approximation free. We achieve this in the case ofa modal representation by avoiding the computationally complex eigenmode decomposition. Thereby,the numerical cost is reduced from O􀀀N3to O (NlogN), enabling a simulation of structures like certaindiffractive optical elements with a significantly higher mode count than presently possible. Apart fromspeed, another major advantage of the iterative FRIM over standard modal methods is the possibility totrade runtime against accuracy.

Averaging colors of multicolor mosaics

Eiji Kimura

Doc ID: 309463 Received 23 Oct 2017; Accepted 09 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: The present study investigated how color information was summarized in multicolor mosaics. The mosaics werecomposed of small elements of 17 colors that roughly belonged to a single color category. We manipulated thedegree of color variation around the mean by varying the proportion of different color elements. Observersmatched the mean color of the multicolor mosaic by adjusting the color of a spatially-uniform matching stimulus.Results showed that when the color variation was large, the matched color deviated from the colorimetric meantoward the most-saturated color, although hue of the matched color was almost the same as that of the colorimetricmean. These findings together suggested differential processing of hue and saturation. The deviation of thematched color decreased, but did not disappear, when the color variation was reduced. The analysis of color metricunderlying color averaging revealed differential color scaling in nearly orthogonal blue-orange and green-purpledirections, implying that the visual system does not solely rely on linear cone-opponent codes when summarizingcolor signals. The deviation itself was consistently found regardless of different color metrics tested. Therobustness of the deviation indicated an inherent bias of mean color judgments favoring highly saturated colors.

Semantic word impressions expressed by hue

Keizo Shinomori and Honami Komatsu

Doc ID: 312641 Received 02 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We investigated the possibility of whether impressions of semantic words showing complex concepts could bestably expressed by hues. Using a paired comparison method, we asked ten subjects to select from a pair of huesthe one that more suitably matched a word impression. We employed nine Japanese semantic words and usedtwelve hues from vivid tone in the Practical Color Co-ordinate System. As examples of the results, for the word"Vigorous" the most frequently selected color was yellow and the least selected was blue to purple; for "Tranquil"the most selected was yellow to green and the least selected was red. Principal component analysis of the selectiondata indicated that the cumulative contribution rate of the first two components was 94.6%, and in the twodimensionalspace of the components, all hues were distributed as hue-circle shape. In addition, comparison withadditional data of color impressions measured by a semantic differential method suggested that most semanticword impressions can be stably expressed by hue, but the impression of some words, such as “Magnificent” cannot.These results suggest that semantic word impression can be expressed reasonably well by color, and that hues aretreated as impressions from the hue circle, not from color categories.

Photonic Crystals: Role of Architecture and Disorder on Spectral Properties

Rupesh Verma, Romil Audkhasi, Krishna Thyagarajan, and Varsha Banerjee

Doc ID: 306939 Received 11 Sep 2017; Accepted 03 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: Many of the present day optical devices use photonic crystals. These are multilayers of dielectric media which control the reflection and transmission of light falling on them. In this paper, we study the optical properties of periodic, fractal and aperiodic photonic crystals and compare them on the basis of their attributes. Our calculations of the band reflectivity and degree of robustness reveal novel features, e.g., fractal photonic crystals are found to reflect maximum amount of incident light. On the other hand, aperiodic photonic crystals have the largest immunity to disorder. We believe that such properties will be useful in a variety of applications in the field of optical communication.

The development of color vision discrimination during childhood: differences between blue-yellow, red-green and achromatic thresholds

Barbara Ling and Stephen Dain

Doc ID: 312529 Received 02 Nov 2017; Accepted 02 Jan 2018; Posted 03 Jan 2018  View: PDF

Abstract: Non-visual demands of tests affect vision test results in children. 150 children (79 female and 71 male, 5.3–12.7 years) were examined. Isoluminant blue, yellow, red, green and black & white thresholds were established with a four-alternative-forced-choice and pseudo 10-bit system with adaptive staircase and gaming elements. Where Threshold = b0+b1*age-1, b1 for RG = 6.26±1.90 (95% confidence limits), Achr = 3.96±1.07 and BY = 12.48±2.76 were significantly different. The non-color demands of the test are the same for RG, BY and Achr, so the later development of BY discrimination, especially, is not an artefact of the test.

Synchronization-based Clustering Algorithm forReconstruction of Multiple Reconstructed Targets inFluorescence Molecular Tomography

Zitong Wu, Xiaodong Wang, Jingjing Yu, Huangjian Yi, and Xiaowei He

Doc ID: 302083 Received 13 Jul 2017; Accepted 01 Jan 2018; Posted 03 Jan 2018  View: PDF

Abstract: Fluorescence molecular tomography (FMT) is an important in vivo molecular imaging technique and has beenwidely studied in preclinical research. Many methods perform well in reconstruction of single fluorescent targetbut may fail in reconstructing multiple targets because of the severe ill-poseness of FMT inverse problem. In thispaper original synchronization-inspired clustering algorithm (OSC) is introduced into FMT for resolving multipletargets from reconstruction result. Based on OSC, a synchronization-based clustering algorithm for FMT (SC-FMT)is developed to further improve location accuracy. Both algorithms utilize minimum spanning tree to automaticallyidentify the number of the reconstructed targets without prior information and human intervention. A serial ofnumerical simulation results demonstrate that SC-FMT and OSC can resolve multiple targets robustly andautomatically, which also show the potential of the proposed postprocessing algorithms in FMT reconstruction.

Stroboscopic effect: contrast threshold function anddependence on illumination level

Malgorzata Perz, Dragan Sekulovski, Ingrid vogels, and Ingrid Heynderickx

Doc ID: 308423 Received 06 Oct 2017; Accepted 28 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: The Stroboscopic effect Visibility Measure (SVM) is a method used to quantify the stroboscopic effect visibilityin general illumination applications. SVM has been defined previously based on a limited numberof frequencies and participants. To validate and extend SVM, five perception experiments are presented,measuring the visibility threshold of light waveforms modulated at several frequencies, conducted intwo different labs. A power function is fitted through the aggregated results to develop a stroboscopiceffect contrast threshold function for a “standard observer”, which can be used to normalize SVM. An additionalexperiment shows the dependency on illumination level, extending the validity of SVM to otherapplications.

Paradoxical pupil constriction to isolated M-cone increments

Ian Murray, Jan Kremers, Declan McKeefry, and Neil Parry

Doc ID: 312400 Received 03 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: M-cone onsets appear dimmer and elicit ERGs resembling the light offset response. We sought a corresponding anomalous pupillary light reflex (PLR) using a 4-primary ganzfeld as stimulator and pupillometer. Increments and decrements of white light were compared with M- and L-cone onsets and offsets. Luminance bias (LB) could be added to or subtracted from the cone-isolating stimuli. There was a normal PLR to L-cone increments but the pupil constricted to M-cone decrements. Changing LB produced a neutral point where on and off responses were balanced. The results reflect ERG and psychophysical studies. It may be linked to the antagonistic nature of the M-cone input to cone opponent mechanisms.

Human S-cone ERGs obtained by Silent Substitution Stimulation

John Maguire, Neil Parry, Jan Kremers, Ian Murray, and Declan McKeefry

Doc ID: 312491 Received 02 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We used triple silent substitution stimuli to characterize human S-cone ERGs in normal trichromats. S-cone ERGs were found to have different morphological features and temporal frequency response characteristics compared to ERGs derived from L-cone, M-cone and rod photoreceptors in normal participants. Furthermore, in two cases of retinal pathology, Blue Cone Monochromatism (BCM) and Enhanced S-cone Syndrome (ESCS), S-cone ERGs elicited by our stimuli were preserved and enhanced, respectively. The results from both normal and pathological retinae demonstrate that triple silent substitution stimuli can be used to generate ERGs that selectively that provide an assay of human S-cone function.

Age-related changes in ON and OFF responses toluminance increments and decrements

Keizo Shinomori, Athanasios Panorgias, and John Werner

Doc ID: 312637 Received 02 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: Impulse response functions for an incremental luminous pulse (ON flash) or a decremental luminous pulse (OFFflash) were derived for twelve young (19-24 years old) and ten old (65-84 years old) observers. Thresholds weremeasured for two pulses separated by stimulus-onset-asynchronies from 13.3 to 186.7 ms. The pulses had a spatialGaussian shape and were presented as increments or decrements on a 15 cd/m2 equal-energy white background,having the same chromaticity as the pulse. A spatial 4-alternative forced-choice method was combined with astaircase procedure. Retinal illuminance was equated individually by heterochromatic flicker photometry andusing a 2.3 mm exit pupil in a Maxwellian-view optical system to reduce the effects of age-related changes andindividual variations in lens density and pupil size. Luminance ON- and OFF-impulse response functions calculatedfrom the threshold data revealed significant age-related changes in the response amplitude of both first excitatoryand first inhibitory phases. However, there were no significant changes in the time to the first peak or the secondpeak. These age-related changes in luminance varying ON- and OFF-IRFs, reflecting putative properties of themagnocellular pathway, are discussed in relation to motion detection and the balance of ON and OFF pathwaysacross the life span.

Security analysis of double-image encryptiontechnique based on an asymmetric algorithm

YI XIONG, Aohan He, and Chenggen Quan

Doc ID: 310073 Received 27 Oct 2017; Accepted 26 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: In this paper, we evaluate the security of a double-image encryption technique based on an asymmetric algorithm.Compared with traditional cryptosystems based on phase-truncated Fourier transform (PTFT), the technique isable to improve the security of the encryption by combining a joint transform correlator (JTC); consequently, theencryption scheme is immune to some common attacks. We propose a special attack based on a phase retrievalalgorithm with median filtering and normalization operation to break the cryptosystem. Low key sensitivity of aposition parameter set has been found and an additional constraint is utilized to improve the attack to simplify theprocess and further decrease the computational time. Numerical simulation results show that the cryptosystem isvulnerable to the proposed special attack.

Optimized diffusion approximation

Vadim Markel, Ugo Tricoli, Callum Macdonald, and Anabela Da Silva

Doc ID: 308082 Received 27 Sep 2017; Accepted 22 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: We show that the diffusion approximation to the radiative transport equation, which is commonly used inbiomedical optics to describe propagation of light in tissues, contains a previously unexplored adjustableparameter. This parameter is related to the rate of exponential decay of the reduced intensity. In the conventionaltheories, there are two distinct choices for this parameter. However, neither of these choicesare optimal. When the optimal value for the parameter is used, the resulting DA becomes much moreaccurate near the medium boundaries, e.g., at the depth of up to a few `, where ` is the transport meanfree path (typically, about 1mm in tissues). We refer to the new adjustable parameter as to the reduced extinctioncoefficient. The proposed technique can reduce the relative error of the predicted diffuse densityof the optical energy from about 30% to less than 1%. The optimized diffusion approximation can still beinaccurate very close to an interface or in some other physical situations. Still the proposed developmentextends the applicability range of the diffusion approximation significantly. This result can be useful,for instance, in tomographic imaging of relatively shallow (up to a few ` deep) layers of tissues in thereflection geometry.

Age and gender effects on perceptual colour scaling using triadic comparisons

David Bimler and Valerie Bonnardel

Doc ID: 312624 Received 03 Nov 2017; Accepted 20 Dec 2017; Posted 20 Dec 2017  View: PDF

Abstract: We examined age and gender as possible determinants of individual differences in triadic judgments of color dissimilarity. Seventy triads were constructed from 21 equal-lightness Munsell samples, at equal hue steps, forming a rough ellipse in the CIE-LAB plane, and presented to 51 males and 53 females (half young, half elderly adults) who indicated each triad’s “odd-one-out”. Principal Components Analysis, followed by MDS, revealed gender and age differences in judgment reliability, and localised gender differences in color similarity, perhaps involving the use of ‘color-circle’ propositional knowledge. Maximum-Likelihood MDS and inspection of specific triads allowed a more detailed description of these differences.

One-stop Measurement Model for Fast and Accurate Tensor Display Characterization

philip Surman, SHIZHENG WANG, Junsong Yuan, and Yuanjin Zheng

Doc ID: 303943 Received 02 Aug 2017; Accepted 19 Dec 2017; Posted 19 Dec 2017  View: PDF

Abstract: Many light field displays are fundamentally different to other displays in that they do not have quantizedpixels, quantized angular outputs or a physical screen position; this can make definitions and characterizationproblematic. We have determined that it is more appropriate the express the spatial resolutionin terms spatial cut-off frequency rather than a physical distance as in the case of a display with actualquantized pixels; this concept is then extended to encompass angular resolution. The technique exploitsthe fact that when spatial resolution of a sinusoidal grating pattern is halved, its contrast ratio is reducedby a known proportion. An improved model, based on an earlier design concept has been developed, cannot only be used to measure spatial and angular cut-off frequencies but can also enable comprehensivecharacterization of the display. This provides fast and simple measurement with good accuracy. It doesnot use special equipment or require time-consuming subjective evaluations. The result of using themodel to characterize images in a rapid and accurate manner validates the effectiveness of this technique.

On the depolarization in granular thin films: A Mueller-Matrix approach.

Bruno Gompf, Maximilian Gill, Martin Dressel, and Audrey Berrier

Doc ID: 303584 Received 27 Jul 2017; Accepted 18 Dec 2017; Posted 19 Dec 2017  View: PDF

Abstract: We describe a general method to disclose the information hidden in Mueller-matrices experimentally obtained from depolarizing samples. Although spectroscopic Mueller-matrix ellipsometry allows for a model-free characterization of inhomogeneous samples, i.e., independently from any assumption on the sample structure, the interpretation of the obtained results is often challenging. The proposed method combines three different decomposition techniques applied to the measured Mueller-matrices in transmission and reflection of granular thin films with different thicknesses and densities. We demonstrate that the comparative analysis of the respective differential-, product, and sum-decomposition of the Mueller-matrices, together with correlation effects and the visualization as Poincaré sphere, reveals the particular underlying physical processes of depolarization. As an example, we apply this method on granular BaS04 thin films. This method is general and can be applied to a wide variety of intrinsically inhomogeneous materials with applications in physics, industry, biology or medicine.

Cone and melanopsin contributions to human brightness estimation

Andrew Zele, Prakash Adhikari, Beatrix Feigl, and Dingcai Cao

Doc ID: 309510 Received 18 Oct 2017; Accepted 17 Dec 2017; Posted 19 Dec 2017  View: PDF

Abstract: We determined the contributions of cone and melanopsin luminance signaling to human brightness perception. The absolute brightness of four narrow-band primary lights presented in a full-field Ganzfeld were estimated in two conditions, either cone luminance equated (186.7 – 1,867.0 cd.m-2) or melanopsin luminance equated (31.6 – 316.3 melanopsin cd.m-2). We show that brightness estimations for each primary light follow an approximately linear increase with increasing cone- or melanopsin luminance (in log units), but are not equivalent for primary lights equated with either cone- or melanopsin luminance. Instead, brightness estimations result from a combined interaction between cone and melanopsin signaling. Analytical modeling with wavelength dependent coefficients signify that melanopsin luminance positively correlates with brightness magnitudes and the cone luminance has two contribution components, one that is additive to melanopsin luminance and a second that is negative, implicating an adaptation process. These results provide a new framework for evaluating the physiological basis of brightness perception and have direct practical applications for the development of energy efficient light sources.

Amplitude and phase retrieval with simultaneousdiversity estimation using expectation-maximization

Joyce Fang and Dmitry Savransky

Doc ID: 300865 Received 07 Aug 2017; Accepted 17 Dec 2017; Posted 19 Dec 2017  View: PDF

Abstract: Iterative amplitude and phase retrieval algorithms have been proven to accurately reconstruct arbitrarywavefronts from multiple intensity measurements when system parameters are known exactly, given theability to induce phase diversity between images. Such sets of intensity images with phase diversity canbe generated by moving a lens in the optical system, but any position error on the lens will degeneratethe reconstruction result. We demonstrate the use of an expectation-maximization algorithm with Kalmansmoothing for recovering both the complex field and the lens position from a stack of intensity images.Our method successfully reduces the mean-squared-error of the estimated wavefront in comparison toan approach without position error estimation. We present and discuss the results of using a Kalmansmoother and nonlinear least-square optimization for the estimation of the moving lens position.

Analysis of lateral binding force exerted on bi-sphere induced by Elliptic Gaussian beam

Bai Jing, Zhen-Sen Wu, Ge Chengxian, Zheng-Jun Li, Tan Qu, and Qingchao Shang

Doc ID: 301147 Received 28 Jun 2017; Accepted 16 Dec 2017; Posted 18 Dec 2017  View: PDF

Abstract: Based on the Generalized Lorentz Mie theory and the localized approximation of the beam shaped coefficients, we derived the expansions of incident elliptic Gaussian (EG) beam in terms of spherical vector wave functions (SVWFs). Utilizing Multiple Scattering (MS) equations and Electromagnetic Momentum (EM) theory, the lateral binding force (BF) exerted on bi-sphere induced by EG beam is calculated. Numerical effects of various parameters such as beam waist widths, beam polarization states, incident wavelengths, particle sizes and material losses are analyzed and compared with the results of circular Gaussian (CG) beam in detail. The observed dependence of the separation of optically bound particles on the incidence of EG beam is in agreement with earlier theoretical prediction. Accurate investigation of BF induced by EG beam could provide an effective test for further research on BF between more complex particles, which plays an important role in using optical manipulation on particle self-assembly.

Goos-Hänchen and Imbert-Fedorov shifts: relation with the irradiance moments of a beam

Miguel Angel Berbel, Alejandro Cunillera, and Rosario Martinez-Herrero

Doc ID: 309086 Received 12 Oct 2017; Accepted 13 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: We present closed and simple expressions of the spatial and angular Goos-Hänchen and Imbert-Fedorovshifts in terms of the second order irradiance moments of a beam. Our results are applicable to a generaltotally polarized partially coherent beam. One of the main advantages of this formalism is that it canbe applied directly from the knowledge of the cross spectral density function and the polarization statewithout using any modal beam expansion. The obtained expressions allow to understand the relationshipbetween the global spatial characteristics of the incident beam and the experimented shifts in the reflectedbeam. Cosine-Gaussian Schell-model beams with rectangular symmetry are used to exemplify results.

Advances in Edge Diffraction Algorithms

Anthony Harness, Stuart Shaklan, Webster Cash, and Philip Dumon

Doc ID: 306854 Received 13 Sep 2017; Accepted 08 Dec 2017; Posted 14 Dec 2017  View: PDF

Abstract: Starshade external occulters are a leading technology that provides the starlight suppression needed to directly image and spectroscopically characterize Earth-sized exoplanets in the habitable zone of nearby stars. A high-priority, high-risk technology area identified in need of development for a future starshade mission is the development and validation of high-fidelity optical models to predict the performance of a full-scale starshade. We present the generalization of an algorithm to formulate the Fresnel diffraction equation as a one-dimensional integral around the edge of an arbitrary binary diffraction screen. Our edge integral provides an efficient method to capturing diffraction over a large range of size scales and are computationally superior to standard two-dimensional codes. We also a present a novel method to implement wavefront errors with the edge integral. This paper provides the derivation of the algorithms and their validation with comparisons to known solutions and results from standard Fresnel propagation codes.

Forward scattering of polarized light from birefringentturbid slab media: Monte Carlo simulation

Soichi Otsuki

Doc ID: 303251 Received 02 Aug 2017; Accepted 24 Nov 2017; Posted 11 Jan 2018  View: PDF

Abstract: The reduced effective Mueller matrices of forward scattering from birefringent turbid slab media were calculatedusing a Monte Carlo simulation and were factorized in two dimension by the Lu-Chipman polar decomposition. Fora slab medium with the birefringence axis parallel to the y axis, the polarization parameters have second- orfourth-order rotational symmetry. Especially, the absolute value of linear retardance || shows a characteristicvariation; it becomes maximal at the azimuths of 0 and 180 but minimal at 90 and 270. These features exactlyagree with the measurement results. However, when the birefringence axis is inclined to the slab surfaces, thepolarization parameters become non-symmetric with respect to the x-z plane, though they are symmetric or antisymmetricwith respect to the y-z plane. Moreover, as the inclination angle becomes larger than 45, the fast-axisorientation exhibits new centers of the radial pattern whose position becomes closer to the preexisting center. Thephoton trajectory in the medium may be approximated by a double scattering model in which the photonpenetrates forward into a depth, travels along the radial direction, and propagates forward to the front surface forexiting. The non-symmetry of the polarization parameters and the appearance of the second centers of the radialpattern suggest that the radial traveling of the photon may be oblique forward and that the obliqueness anglebecomes smaller as the photon exits at the distance farther away from the center.

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