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Carlos Sánchez Muñoz, Franco Nori, Simone De Liberato
Recent technological developments have made it increasingly easy to access the non-perturbative regimes of cavity quantum electrodynamics known as ultrastrong or deep strong coupling, where the light-matter coupling becomes comparable to the bare modal frequencies. In this work, we address the adequacy of the broadly used single-mode cavity approximation to describe such regimes. We demonstrate that, in the non-perturbative light-matter coupling regimes, the single-mode models become unphysical, allowing for superluminal signalling...
May 15, 2018: Nature Communications
S A Carvalho, M L Martins
Microorganisms and plants very commonly release toxic secondary chemical compounds (allelochemicals) that inhibit or kill sensitive strains or individuals from their own or other species. In this work we study a model that describes two species interacting through allelopathic suppression and competing for resources. Employing linear stability analysis, the conditions for coexistence or extinction of species in spatially homogeneous systems were determined. We found that the borders between the regimes of bistability, coexistence, and the extinction of the weaker by the stronger competitor, are altered by allelopathic interactions...
April 2018: Physical Review. E
Lei Wang, Sergey S Kruk, Kirill L Koshelev, Ivan I Kravchenko, Barry Luther-Davies, Yuri S Kivshar
Metasurfaces, two-dimensional lattices of nanoscale resonators, offer unique opportunities for functional flat optics and allow to control transmission, reflection, and polarization of a wavefront of light. Recently, all-dielectric metasurfaces reached remarkable efficiencies, often matching or outperforming conventional optical elements. Exploitation of nonlinear optical response of metasurfaces offers a paradigm shift in nonlinear optics, and dielectric nonlinear metasurfaces are expected to enrich subwavelength photonics by enhancing substantially nonlinear response of natural materials combined with efficient control of the phase of nonlinear waves...
May 11, 2018: Nano Letters
Barbara Bellmann, Tina Lin, Peter Ruppersberg, Marit Zettwitz, Selma Guttmann, Verena Tscholl, Patrick Nagel, Mattias Roser, Ulf Landmesser, Andreas Rillig
BACKGROUND: The optimal ablation approach for the treatment of persistent atrial fibrillation (AF) is still under debate; however, the identification and elimination of AF sources is thought to play a key role. Currently available technologies for the identification of AF sources are not able to differentiate between active rotors or focal impulse (FI) and passive circular turbulences as generated by the interaction of a wave front with a functional obstacle such as fibrotic tissue. OBJECTIVES: This study introduces electrographic flow (EGF) mapping as a novel technology for the identification and characterization of AF sources in humans...
May 9, 2018: Clinical Research in Cardiology: Official Journal of the German Cardiac Society
Haisong Wei, Haixiang Hu, Feng Yan, Xindong Chen, Qiang Cheng, Donglin Xue, Xuejun Zhang
To test large-aperture space optical systems in a simple and highly efficient manner, the scanning Hartmann test (SHT) has been used to measure the sub-aperture wavefront slopes of optical systems by scanning with a collimated beam followed by retrieval of the overall wavefront form. However, the use of such a method contains a crucial flaw in that pointing errors of the translation stage can severely affect the test accuracy. Therefore, a multi-beam stitching method is proposed to correct pointing errors by stitching together data obtained by successive sub-aperture acquisition...
May 8, 2018: Scientific Reports
Xiaohu Zhang, Xiong Li, Jinjin Jin, Mingbo Pu, Xiaoliang Ma, Jun Luo, Yinghui Guo, Changtao Wang, Xiangang Luo
Composed of ultrathin metal or dielectric nanostructures, metasurfaces can manipulate the phase, amplitude and polarization of electromagnetic waves at a subwavelength scale, which is promising for flat optical devices. In general, metasurfaces composed of space-variant anisotropic units are sensitive to the incident polarization due to the inherent polarization dependent geometric phase. Here, we implement polarization-independent broadband metasurface holograms constructed by polarization-dependent anisotropic elliptical nanoholes by elaborate design of complex amplitude holograms...
May 8, 2018: Nanoscale
Yifei Wu, Larry N Thibos, T Rowan Candy
PURPOSE: Eccentric photorefraction and Purkinje image tracking are used to estimate refractive state and eye position simultaneously. Beyond vision screening, they provide insight into typical and atypical visual development. Systematic analysis of the effect of refractive error and spectacles on photorefraction data is needed to gauge the accuracy and precision of the technique. METHODS: Simulation of two-dimensional, double-pass eccentric photorefraction was performed (Zemax)...
May 7, 2018: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
René Rahn, Stefan Budach, Pascal Costanza, Marcel Ehrhardt, Jonny Hancox, Knut Reinert
Motivation: Pairwise sequence alignment is undoubtedly a central tool in many bioinformatics analyses. In this paper, we present a generically accelerated module for pairwise sequence alignments applicable for a broad range of applications. In our module, we unified the standard dynamic programming kernel used for pairwise sequence alignments and extended it with a generalized inter-sequence vectorization layout, such that many alignments can be computed simultaneously by exploiting SIMD (Single Instruction Multiple Data) instructions of modern processors...
May 3, 2018: Bioinformatics
Lin Zhang, Wenchen Zhou, Neil J Naples, Allen Y Yi
A novel fabrication method by combining high-speed single-point diamond milling and precision compression molding processes for fabrication of discontinuous freeform microlens arrays was proposed. Compared with slow tool servo diamond broaching, high-speed single-point diamond milling was selected for its flexibility in the fabrication of true 3D optical surfaces with discontinuous features. The advantage of single-point diamond milling is that the surface features can be constructed sequentially by spacing the axes of a virtual spindle at arbitrary positions based on the combination of rotational and translational motions of both the high-speed spindle and linear slides...
May 1, 2018: Applied Optics
Haoyuan Du, Rigui Yi, Liquan Dong, Ming Liu, Wei Jia, Yuejin Zhao, Xiaohua Liu, Mei Hui, Lingqin Kong, Xi Chen
We present a method that combines an asymmetrical phase mask (PM) and its rotated PM to potentially improve the signal-to-noise ratio in wavefront coding systems. The property of the rotated PM is analyzed. A complementary promotional synthetic optical transfer function is generated as the deconvolution filter for image recovery. The image artifacts are suppressed through processing in the frequency domain. Simulation results provide a quantitative analysis that is based on a cubic PM. Experimental results show that our method can improve image quality over a wide range of defocus...
May 1, 2018: Applied Optics
Gareth D Hastings, Jason D Marsack, Larry N Thibos, Raymond A Applegate
The visual image quality metric the visual Strehl ratio (VSX) combines a comprehensive description of the optics of an eye (wavefront error) with an estimate of the photopic neural processing of the visual system, and has been shown to be predictive of subjective best focus and well correlated with change in visual performance. Best-corrected visual image quality was determined for 146 eyes, and the quantitative relation of VSX, age, and pupil size is presented, including 95% confidence interval norms for age groups between 20 and 80 years and pupil diameters from 3 to 7 mm...
May 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Erik Clark, Andrew D Peel
Long-germ insects, such as the fruit fly Drosophila melanogaster , pattern their segments simultaneously, whereas short-germ insects, such as the beetle Tribolium castaneum , pattern their segments sequentially, from anterior to posterior. While the two modes of segmentation at first appear quite distinct, much of this difference might simply reflect developmental heterochrony. We now show here that, in both Drosophila and Tribolium , segment patterning occurs within a common framework of sequential Caudal, Dichaete, and Odd-paired expression...
May 3, 2018: Development
Jing Wang, Yanlin Ren, Kun Liang, Zhengxuan Jiang, Liming Tao
BACKGROUND: Femtosecond laser-assisted in situ keratomileusis (FS-LASIK) has gained widespread popularity as a safe, effective and predictable treatment for correcting myopia and myopic astigmatism.However, complications such as biomechanical changes, structural weakness, dry eye and induction of high-order aberrations (HOAs) have been associated with FS laser excision. The induction of HOAs has been reported to reduce quality of vision, leading to increased glare, halos, starburst and deterioration of contrast function corneal HOAs play a significant role in whole-eye aberration...
May 2018: Medicine (Baltimore)
Takato Inoue, Satoshi Matsuyama, Shogo Kawai, Hirokatsu Yumoto, Yuichi Inubushi, Taito Osaka, Ichiro Inoue, Takahisa Koyama, Kensuke Tono, Haruhiko Ohashi, Makina Yabashi, Tetsuya Ishikawa, Kazuto Yamauchi
In this study, the systematic errors of an X-ray single-grating interferometer based on the Talbot effect were investigated in detail. Non-negligible systematic errors induced by an X-ray camera were identified and a method to eliminate the systematic error was proposed. Systematic-error-free measurements of the wavefront error produced by multilayer focusing mirrors with large numerical apertures were demonstrated at the SPring-8 Angstrom Compact free electron LAser. Consequently, wavefront aberration obtained with two different cameras was found to be consistent with an accuracy better than λ/12...
April 2018: Review of Scientific Instruments
F F Qin, Z Z Liu, Z Zhang, Q Zhang, J J Xiao
Due to the abilities of manipulating the wavefront of light with well-controlled amplitude, and phase and polarization, optical metasurfaces are very suitable for optical holography, enabling applications with multiple functionalities and high data capacity. Here, we demonstrate encoding two- and three-dimensional full-color holographic images by an ultrathin metasurface hologram whose unit cells are subwavelength nanoslits with spatially varying orientations. We further show that it is possible to achieve full-color holographic multiplexing with such kind of geometric metasurfaces, realized by a synthetic spectrum holographic algorithm...
April 30, 2018: Optics Express
Nicolás Dubost, Nazim Ali Bharmal, Richard M Myers
The direct detection and imaging of exoplanets requires the use of high-contrast adaptive optics (AO). In these systems quasi-static aberrations need to be highly corrected and calibrated. In order to achieve this, a high-sensitivity wavefront sensor, the pupil-modulated point-diffraction interferometer (m-PDI), is presented. This sensor modulates and retrieves both the phase and the amplitude of an incoming electric field. The theory behind the wavefront reconstruction, the visibility of fringes, chromatic effects and noise propagation are developed...
April 30, 2018: Optics Express
Darshika Singh, Rakesh Kumar Singh
The recording and reconstruction of the Stokes parameter is of paramount importance for the description of the vectorial interference of light. Polarization holography provides a complete vectorial wavefront, however, direct recording and reconstruction of the hologram is not possible in a situation where the object is located behind the random scattering layer. The Stokes holography plays an important role in such situations and makes use of the Fourier transform relation between the Stokes parameters (SPs) at the scattering plane and the generalized Stokes parameters (GSPs) of the random field...
April 16, 2018: Optics Express
Shunsuke Igarashi, Tomoya Nakamura, Kyoji Matsushima, Masahiro Yamaguchi
In the calculation of large-scale computer-generated holograms, an approach called "tiling," which divides the hologram plane into small rectangles, is often employed due to limitations on computational memory. However, the total amount of computational complexity severely increases with the number of divisions. In this paper, we propose an efficient method for calculating tiled large-scale holograms using ray-wavefront conversion. In experiments, the effectiveness of the proposed method was verified by comparing its calculation cost with that using the previous method...
April 16, 2018: Optics Express
Raphaël Florentin, Vincent Kermene, Agnès Desfarges-Berthelemot, Alain Barthelemy
Ultrashort light pulse transport and amplification in a 1.3 m long step-index multimode fiber with gain and with weak coupling has been investigated. An adaptive shaping of the input wavefront, only based on the output intensity pattern, has led to an amplified pulse focused both in space (1/32) and in time (1/10) despite a strong modal group delay dispersion. Optimization of the input owing to the two-photon detection of the amplified signal permitted to excite the fastest and more intense principal mode of the fiber and to get an output pulse duration limited by group velocity dispersion...
April 16, 2018: Optics Express
Christopher Schindlbeck, Christian Pape, Eduard Reithmeier
Alignment of optical components is crucial for the assembly of optical systems to ensure their full functionality. In this paper we present a novel predictor-corrector framework for the sequential assembly of serial optical systems. Therein, we use a hybrid optical simulation model that comprises virtual and identified component positions. The hybrid model is constantly adapted throughout the assembly process with the help of nonlinear identification techniques and wavefront measurements. This enables prediction of the future wavefront at the detector plane and therefore allows for taking corrective measures accordingly during the assembly process if a user-defined tolerance on the wavefront error is violated...
April 16, 2018: Optics Express
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