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DISPERSION-RELATION AT POINT-L IN THE PHOTONIC BAND-STRUCTURE OF THE FACE-CENTERED-CUBIC LATTICE WITH ACTIVE OR CONDUCTIVE DIELECTRIC MEDIA

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 1995年第4期12卷 583-591页

作者： SUZUKI, T YU, PKL Department of Electrical and Computer Engineering University of California San Diego La Jolla California 92093-0407 USA

In this paper we develop a computational method for photonic band structures with active and conductive media by transforming Maxwell's equations into high-order nonlinear polynomial eigensystems based on the plane-wave expansion method with complex k vectors. Furthermore, by assuming an infinitely fast response of the material, we reduce the high-order polynomial eigensystems to lower-order (ordinary or quadratic) eigenproblems. Numerical computations were performed at point L for the fcc lattice structure with active nonconducting and nonactive conducting dielectric media by solution of the ordinary or linearized eigensystems. For both cases physical solutions with complex k vectors for Maxwell's equations were found between the two propagating modes;however, solutions were in the unphysical region of the tunneling dispersion relation for the passive media.

关键词： Complex dielectric constant computation methods Distributed feedback lasers Photonic bandgap structure Photonic crystals Spontaneous emission

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FOCUSING OF TWO-DIMENSIONAL WAVES

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA 1981年第1期71卷 15-31页

作者： STAMNES, JJ Central Institute for Industrial Research Forskningsveien 1 Blindern Oslo 3 Norway

Two different methods are presented for efficient computation of two-dimensional wave fields in focal regions. Both methods are valid for arbitrarily large relative apertures. One method is based on the impulse-response integral and the other on the angular-spectrum representation. The latter method is used to analyze the discrepancy between applying the Kirchhoff or the Debye assumption to obtain an approximation for the field in the aperture. Two cases of idealized incident waves are analyzed in detail. First, we treat the case of a perfect incident wave, i.e., a wave that, in the limit of an infinitely large aperture, would produce a δ -function field distribution on the focal line if account were taken of evanescent waves. Second, the incident wave is taken to be the field radiated by a point source and subsequently focused by a lens that delays the phase of the incoming wave in a perfect manner without influencing its amplitude. The latter wave has the same phase distribution over the aperture as the perfect wave, but a different amplitude distribution.

关键词： computation methods Discrete Fourier transforms Evanescent waves First order optics Fourier transforms Spatial frequency

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Light field displays with computational vision correction for astigmatism and high-order aberrations with real-time implementation

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OPTICS EXPRESS 2023年第4期31卷 6262-6280页

作者： Qiu, Yuqing Zhao, Zhiqing Yang, Jinglan Cheng, Yunfan Liu, Yi Yang, Bo-ru Qin, Zong Sun Yat sen Univ Sch Elect & Informat Technol Guangdong Prov Key Lab Display Mat & Technol State Key Lab Optoelect Mat & Technol 132 East Waihuan Rd Guangzhou 510006 Peoples R China

Vision-correcting near-eye displays are necessary concerning the large population with refractive errors. However, varifocal optics cannot effectively address astigmatism (AST) and high-order aberration (HOAs);freeform optics has little prescription flexibility. Thus, a computational solution is desired to correct AST and HOA with high prescription flexibility and no increase in volume and hardware complexity. In addition, the computational complexity should support real-time rendering. We propose that the light field display can achieve such computational vision correction by manipulating sampling rays so that rays forming a voxel are re-focused on the retina. The ray manipulation merely requires updating the elemental image array (EIA), being a fully computational solution. The correction is first calculated based on an eye's wavefront map and then refined by a simulator performing iterative optimization with a schematic eye model. Using examples of HOA and AST, we demonstrate that corrected EIAs make sampling rays distributed within +/- 1 arcmin on the retina. Correspondingly, the synthesized image is recovered to nearly as clear as normal vision. We also propose a new voxel-based EIA generation method considering the computational complexity. All voxel positions and the mapping between voxels and their homogeneous pixels are acquired in advance and stored as a lookup table, bringing about an ultra-fast rendering speed of 10 ms per frame with no cost in computing hardware and rendering accuracy. Finally, experimental verification is carried out by introducing the HOA and AST with customized lenses in front of a camera. As a result, significantly recovered images are reported.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： computation methods Gradient index lenses Light fields Real time implementation Refractive anomalies Vision correction

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Characterization of natural frequencies from nanoscale tissue oscillations using dynamic optical coherence elastography

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BIOMEDICAL OPTICS EXPRESS 2020年第6期11卷 3301-3318页

作者： Lan, Gongpu Larin, Kirill, V Aglyamov, Salavat Twa, Michael D. Foshan Univ Sch Phys & Optoelect Engn Foshan 528000 Guangdong Peoples R China Univ Alabama Birmingham Sch Optometry Birmingham AL 35290 USA Univ Houston Coll Optometry Houston TX 77204 USA Univ Houston Biomed Engn Houston TX 77204 USA Univ Houston Mech Engn Houston TX 77204 USA

We demonstrate the use of OCT-based elastography for soft-tissue characterization using natural frequency oscillations. Sub-micrometer to sub-manometer oscillations were induced in tissue phantoms and human cornea in vivo by perpendicular air-pulse stimulation and observed by common-path OCT imaging (sensitivity: 0.24 nm). Natural frequency and damping ratio were acquired in temporal and frequency domains using a single degree of freedom method. The dominant natural frequency was constant for different stimulation pressures (4-32 Pa) and measured distances (0.3-5.3 mm), and decreased as the sample thickness increased. The dominant natural frequencies of 0.75-2% agar phantoms were 127-774 Hz (mean coefficient of variation [CV]: 0.9%), and correlated with the square root of Young's moduli (16.5-117.8 kPa, mean CV: 5.8%). These preliminary studies show repeatable in vivo corneal natural frequency measurements (259 Hz, CV: 1.9%). This novel OCE approach can distinguish tissues and materials with different mechanical properties using the small-amplitude tissue oscillation features, and is suitable for characterizing delicate tissues in vivo such as the eye. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Imaging techniques In vivo imaging Propagation methods Tissue Wave propagation

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Enhanced field-of-view integral imaging display using multi-Kohler illumination

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OPTICS EXPRESS 2014年第26期22卷 31853-31863页

作者： Tolosa, Angel Martinez-Cuenca, Raul Navarro, Hector Saavedra, Genaro Martinez-Corral, Manuel Javidi, Bahram Pons, Amparo Technol Inst Opt Color & Imaging AIDO E-46117 Paterna Spain Univ Jaume 1 Dept Mech Engn & Construct E-12071 Castellon de La Plana Spain Univ Valencia Dept Opt E-46100 Burjassot Spain Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA

A common drawback in 3D integral imaging displays is the appearance of pseudoimages beyond the viewing angle. These pseudoimages appear when the light rays coming from each elemental image are not passing through the corresponding microlens, and a set of barriers must be used to avoid this flipping effect. We present a pure optical arrangement based on Kohler illumination to generate these barriers thus avoiding the pseudoimages. The proposed system does not use additional lenses to project the elemental images, so no optical aberrations are introduced. As an added benefit, Kohler illumination provides a higher contrast 3D display. (C) 2014 Optical Society of America

关键词： computation methods Gradient index lenses Integral photography Optical aberrations Three dimensional imaging Viewing angles

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Optimized moth-eye anti-reflective structures for As₂S₃ chalcogenide optical fibers

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OPTICS EXPRESS 2016年第10期24卷 10172-10187页

作者： Weiblen, R. J. Menyuk, C. R. Busse, L. E. Shaw, L. B. Sanghera, J. S. Aggarwal, I. D. Univ Maryland Baltimore Cty Dept Comp Sci & Elect Engn TRC 2031000 Hilltop Circle Baltimore MD 21250 USA Naval Res Lab Code 5620 Washington DC 20375 USA Sotera Def Solut Crofton MD 21114 USA

We computationally investigate moth-eye anti-reflective nanostructures imprinted on the endfaces of As2S3 chalcogenide optical fibers. With a goal of maximizing the transmission through the endfaces, we investigate the effect of changing the parameters of the structure, including the height, width, period, shape, and angle-of-incidence. Using these results, we design two different moth-eye structures that can theoretically achieve almost 99.9% average transmisison through an As2S3 surface. (C) 2016 Optical Society of America

关键词： Chalcogenide fibers computation methods Effective refractive index Fresnel reflection High power lasers Total internal reflection

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Multimodal fusion of EEG-fNIRS: a mutual information-based hybrid classification framework

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BIOMEDICAL OPTICS EXPRESS 2021年第3期12卷 1635-1650页

作者： Deligani, Roohollah Jafari Borgheai, Seyyed Bahram McLinden, John Shahriari, Yalda Univ Rhode Isl Dept Elect Comp & Biomed Engn Kingston RI 02881 USA Univ Rhode Isl Interdisciplinary Neurosci Program Kingston RI 02881 USA

Multimodal data fusion is one of the current primary neuroimaging research directions to overcome the fundamental limitations of individual modalities by exploiting complementary information from different modalities. Electroencephalography (EEG) and functional near infrared spectroscopy (fNIRS) are especially compelling modalities due to their potentially complementary features reflecting the electro-hemodynamic characteristics of neural responses. However, the current multimodal studies lack a comprehensive systematic approach to properly merge the complementary features from their multimodal data. Identifying a systematic approach to properly fuse EEG-fNIRS data and exploit their complementary potential is crucial in improving performance. This paper proposes a framework for classifying fused EEG-fNIRS data at the feature level, relying on a mutual information-based feature selection approach with respect to the complementarity between features. The goal is to optimize the complementarity, redundancy and relevance between multimodal features with respect to the class labels as belonging to a pathological condition or healthy control. Nine amyotrophic lateral sclerosis (ALS) patients and nine controls underwent multimodal data recording during a visuo-mental task. Multiple spectral and temporal features were extracted and fed to a feature selection algorithm followed by a classifier, which selected the optimized subset of features through a cross-validation process. The results demonstrated considerably improved hybrid classification performance compared to the individual modalities and compared to conventional classification without feature selection, suggesting a potential efficacy of our proposed framework for wider neuro-clinical applications. (c) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Magnetic resonance imaging Near infrared spectroscopy Neural networks Spatial resolution Temporal resolution

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CDDA: extension and analysis of the discrete dipole approximation for chiral systems

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OPTICS EXPRESS 2021年第19期29卷 30020-30034页

作者： Rosales, S. A. Albella, P. Gonzalez, F. Gutierrez, Y. Moreno, F. Univ Cantabria Grp Opt Dept Appl Phys Fac Sci Santander 39005 Cantabria Spain CNR Inst Nanotechnol NANOTEC Via Orabona 4 I-70126 Bari Italy

Discrete dipole approximation (DDA) is a computational method broadly used to solve light scattering problems. In this work, we propose an extension of DDA that we call Chiral-DDA (CDDA), to study light-chiral matter interactions with the capability of describing the underlying physics behind. Here, CDDA is used to solve and analyze the interaction of a nanoantenna (either metallic or dielectric) with a chiral molecule located in its near field at different positions. Our method allowed to relate near field interactions with far field spectral response of the system, elucidating the role that the nanoantenna electric and magnetic polarizabilities play in the coupling with a chiral molecule. In general, this is not straightforward with other methods. We believe that CDDA has the potential to help researchers revealing some of the still unclear mechanisms responsible for the chiral signal enhancements induced by nanoantennas. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： computation methods Extinction coefficients Light scattering Mie theory Optical activity Refractive index

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Efficient high-order analysis of bowtie nanoantennas using the locally corrected Nystrom method

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OPTICS EXPRESS 2015年第24期23卷 31452-31459页

作者： Chorsi, Hamid T. Gedney, Stephen D. Univ Colorado Dept Elect Engn Denver CO 80204 USA

It is demonstrated that the Locally Corrected Nystrom (LCN) method is a versatile and numerically efficient computational method for the modeling of scattering from plasmonic bowtie nanoantennas. The LCN method is a high-order analysis method that can provide exponential convergence. It is straightforward to implement, accurate and computationally efficient. To the best of the author's knowledge, the high-order LCN is here applied for the first time to 3D nanostructures. Numerical results show the accuracy and efficiency of the LCN applied to the electromagnetic analysis of nanostructures. (C) 2015 Optical Society of America

关键词： Analytical techniques computation methods Electromagnetic scattering Optical antennas Optical fields Quantum optics

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Multi-angle lensless ptychographic imaging via adaptive correction and the Nesterov method

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APPLIED OPTICS 2023年第10期62卷 2617-2628页

作者： Wang, Jichen Zhao, Jufeng Lin, Binbin Zhang, Peiwei Cui, Guangmang Hou, Changlun Hangzhou Dianzi Univ Inst Carbon Neutral & New Energy Sch Elect & Informat Hangzhou 310018 Peoples R China Hangzhou Dianzi Univ Zhejiang Prov Key Lab Equipment Elect Hangzhou 10018 Peoples R China

Lensless systems based on ptychographic imaging can simultaneously achieve a large field of view and high reso-lution while having the advantages of small size, portability, and low cost compared to traditional lensed imaging. However, lensless imaging systems are susceptible to environmental noise and have a lower resolution of individ-ual images than lens-based imaging systems, which means that they require a longer time to obtain a good result. Therefore, in this paper, to improve the convergence rate and robustness of noise in lensless ptychographic imag-ing, we propose an adaptive correction method, in which we add an adaptive error term and noise correction term in lensless ptychographic algorithms to reach convergence faster and create a better suppression effect on both Gaussian noise and Poisson noise. The Wirtinger flow and the Nesterov algorithms are used in our method to reduce computational complexity and improve the convergence rate. We applied the method to phase reconstruc-tion for lensless imaging and demonstrated the effectiveness of the method by simulation and experiment. The method can be easily applied to other ptychographic iterative algorithms.(c) 2023 Optica Publishing Group

关键词： Adaptive imaging computation methods Optical imaging Phase retrieval Ptychography Three dimensional imaging

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