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Zhancheng Li, Wenwei Liu, Hua Cheng, Jieying Liu, Shuqi Chen, Jianguo Tian
Optical metasurfaces consisting of single-layer nanostructures have immensely promising applications in wavefront control because they can be used to arbitrarily manipulate wave phase, and polarization. However, anomalous refraction and reflection waves have not yet been simultaneously and asymmetrically generated, and the limited efficiency and bandwidth of pre-existing single-layer metasurfaces hinder their practical applications. Here, a few-layer anisotropic metasurface is presented for simultaneously generating high-efficiency broadband asymmetric anomalous refraction and reflection waves...
October 20, 2016: Scientific Reports
Jakub Tomek, Rebecca A B Burton, Gil Bub
Cardiac arrhythmias are one of the most frequent causes of death worldwide. A popular biological model used to study arrhythmogenesis is the cultured cardiac cell monolayer, which provides a good trade-off between physiological relevance and experimental access. Excitation wave patterns are imaged using high-bandwidth detectors, producing large data sets that are typically analyzed manually. To make such analysis less time consuming and less subjective, we have designed and implemented a toolkit for segmentation and tracking of cardiac waves in optical mapping recordings...
October 18, 2016: Biophysical Journal
Ronald H Silverman
The use of focused ultrasound to obtain diagnostically significant information about the eye goes back to the 1950s. This review describes the historical and technological development of ophthalmic ultrasound and its clinical application and impact. Ultrasound, like light, can be focused, which is crucial for formation of high-resolution, diagnostically useful images. Focused, single-element, mechanically scanned transducers are most common in ophthalmology. Specially designed transducers have been used to generate focused, high-intensity ultrasound that through thermal effects has been used to treat glaucoma (via ciliodestruction), tumors, and other pathologies...
2016: Clinical Ophthalmology
Benjamin T Diroll, Peijun Guo, Robert P H Chang, Richard D Schaller
Epsilon-near-zero materials may be synthesized as colloidal nanocrystals which display large magnitude sub-picosecond switching of infrared localized surface plasmon resonances. Such nanocrystals offer a solution-processable, scalable source of tunable metamaterials compatible with arbitrary substrates. Under intraband excitation, these nanocrystals display a red-shift of the plasmon feature arising from the low electron heat capacities and conduction band non-parabolicity of the oxide. Under interband pumping, they show in an ultrafast blueshift of the plasmon resonance due to transient increases in the carrier density...
October 18, 2016: ACS Nano
Bo Wang, Baogang Quan, Jingwen He, Zhenwei Xie, Xinke Wang, Junjie Li, Qiang Kan, Yan Zhang
A wavelength de-multiplexing metasurface hologram composed of subwavelength metallic antennas is designed and demonstrated experimentally in the terahertz (THz) regime. Different character patterns are generated at the separated working frequencies 0.50 THz and 0.63 THz which determine a narrow frequency bandwidth of 130 GHz. The two working frequencies are around the central resonance frequency of the antennas where antennas behave strong wavefront modulation. Each antenna is fully utilized to control the wavefront of the metasurface at different frequencies by an optimization algorithm...
October 18, 2016: Scientific Reports
Gauthier Briere, Benoit Cluzel, Olivier Demichel
Although epsilon-near-zero (ENZ) metamaterials offer many unconventional ways to play with light, the optical impedance mismatch with surroundings can limit the efficiency of future devices. We report here on the improvement of the transmittance of an ENZ wavefront shaper. In this Letter, we first address the way to enhance the transmittance of a plane wave through a layer of ENZ material, thanks to a numerical optimization approach based on the transfer matrix method. We then transpose the one-dimensional approach to a two-dimensional case where the emission of a dipole is shaped into a plane wave by an ENZ device with a design that optimizes the transmittance...
October 1, 2016: Optics Letters
Sarah Moussa, Alois Dexl, Eva Maria Krall, Marie Dietrich, Eva-Maria Arlt, Günther Grabner, Josef Ruckhofer
PURPOSE: To evaluate and compare visual and refractive outcomes after laser-assisted in situ keratomileusis (LASIK) surgery for the correction of myopia or myopic astigmatism using 3 different treatment protocols. METHODS: We included 736 eyes of 369 patients (age 18-62 years) divided into 3 groups: 235 eyes of 118 patients (MEL80 group) undergoing LASIK using optimized aspheric ablation profiles (MEL80 excimer laser; Carl Zeiss Meditec), 248 eyes of 124 patients (Wavescan group) undergoing wavefront-guided (WFG) LASIK (STAR S4IR excimer laser + Wavescan aberrometer; Abbott Medical Optics), and 253 eyes of 127 patients (iDesign group) undergoing WFG LASIK (STAR S4IR excimer laser + iDesign system; Abbott Medical Optics)...
October 10, 2016: European Journal of Ophthalmology
Xiaowei Zhang, Zhifeng Tang, Fuzai Lv, Xiaohong Pan
A wavefront analysis indicates that a flexural wave propagates at a helix angle with respect to the pipe axis. The expression for calculation of the helix angle for each flexural mode is given, and the helix angle dispersion curves for flexural modes are calculated. According to the new understanding of flexural guided waves, a helical comb magnetostrictive patch transducer (HCMPT) is proposed for selectively exciting a single predominant flexural torsional guided wave in a pipe and inspecting spiral welded pipes using flexural waves...
September 29, 2016: Ultrasonics
F Kuhr, A Schmidt, P Rehmann, B Wöstmann
OBJECTIVE: To evaluate a new method of measuring the real deviation (trueness) of full arch impressions intraorally and to investigate the trueness of digital full arch impressions in comparison to a conventional impression procedure in clinical use. METHODS: Four metal spheres were fixed with composite using a metal application aid to the lower teeth of 50 test subjects as reference structures. One conventional impression (Impregum Penta Soft) with subsequent type-IV gypsum model casting (CI) and three different digital impressions were performed in the lower jaw of each test person with the following intraoral scanners: Sirona CEREC Omnicam (OC), 3M True Definition (TD), Heraeus Cara TRIOS (cT)...
October 4, 2016: Journal of Dentistry
Yuan Zhao, Mingyu Sheng, Lin Huang, Shuo Tang
We have developed a fiber-optic multiphoton microscopy (MPM) system with handheld probe using femtosecond fiber laser. Here we present the detailed optical design and analysis of the handheld probe. The optical systems using Lightpath 352140 and 352150 as objective lens were analyzed. A custom objective module that includes Lightpath 355392 and two customized corrective lenses was designed. Their performances were compared by wavefront error, field curvature, astigmatism, F-θ error, and tolerance in Zemax simulation...
September 1, 2016: Biomedical Optics Express
Arun Kumar Jain, Chintan Malhotra, Anand Pasari, Pawan Kumar, Majid Moshirfar
PURPOSE: To compare the outcomes of topography-guided and wavefront-optimized treatment in patients having laser in situ keratomileusis (LASIK) for myopia. SETTING: Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India. DESIGN: Prospective contralateral-eye case study. METHODS: Patients had topography-guided LASIK in 1 eye and wavefront-optimized LASIK in the contralateral eye using the Customized Refractive Surgery Master software and Mel 80 excimer laser...
September 2016: Journal of Cataract and Refractive Surgery
Mark Rosenfield, Kenneth J Ciuffreda
PURPOSE: The SVOne is a portable, Hartmann-Shack wavefront aberrometer, which can be attached to a smartphone to determine the refractive error of the eye objectively. Previous results have shown the device to provide measurements equivalent to those of standard clinical techniques in young, healthy adults. The aim of the present study was to compare the findings of the SVOne with retinoscopy, subjective refraction, and two commercially available autorefractors (Retinomax-3 and WAM-5500) in a pediatric population...
September 23, 2016: Optometry and Vision Science: Official Publication of the American Academy of Optometry
Miguel Faria-Ribeiro, Rafael Navarro, José Manuel González-Méijome
PURPOSE: It has been hypothesized that central and peripheral refraction, in eyes treated with myopic overnight orthokeratology, might vary with changes in pupil diameter. The aim of this work was to evaluate the axial and peripheral refraction and optical quality after orthokeratology, using ray tracing software for different pupil sizes. METHODS: Zemax-EE was used to generate a series of 29 semi-customized model eyes based on the corneal topography changes from 29 patients who had undergone myopic orthokeratology...
September 23, 2016: Optometry and Vision Science: Official Publication of the American Academy of Optometry
Nektarios Koukourakis, Bob Fregin, Jörg König, Lars Büttner, Jürgen W Czarske
Imaging-based flow measurement techniques, like particle image velocimetry (PIV), are vulnerable to time-varying distortions like refractive index inhomogeneities or fluctuating phase boundaries. Such distortions strongly increase the velocity error, as the position assignment of the tracer particles and the decrease of image contrast exhibit significant uncertainties. We demonstrate that wavefront shaping based on spatially distributed guide stars has the potential to significantly reduce the measurement uncertainty...
September 19, 2016: Optics Express
Xiaoxia Huang, Dongxia Hu, Wei Zhou, Wanjun Dai, Xuewei Deng, Qiang Yuan, Qihua Zhu, Feng Jing
In direct drive ICF, optical zooming is an effective way to mitigate cross-beam energy transfer and increase the hydrodynamic efficiency, by reducing the spot size of the laser beams while target compressing. In this paper, a novel optical zooming scheme is proposed, which employs a focusing grating to focus the broadband laser pulse, changing the spot size on the target within single beamlet. Experimentally, a focusing grating with clean aperture of 40-mm × 40-mm placed after the collimated light successfully realized the peak-valley of defocusing wavefront distribution of 0...
September 19, 2016: Optics Express
Hongli Yu, Chengliang Yang, Zihao Xu, Peiguang Zhang, Huanyu Xu, Zhaoliang Cao, Quanquan Mu, Li Xuan
An effective method for reducing the sensitivity of phase diversity (PD) technique to Poisson noise is proposed. The denoising algorithm based on blocking-matching and 3D filtering is first introduced in the wavefront sensing field as a preprocessing stage. Then, the PD technique is applied to the denoised images. Results of the numerical simulations and experiments demonstrate that our approach is better than the traditional PD technique in terms of both the root-mean-square error (RMSE) of phase estimates and the structural similarity index metrics (SSIM)...
September 19, 2016: Optics Express
Sihao Ding, Siyang Cao, Yuan F Zheng, Robert L Ewing
We propose an approach to produce computer generated holograms (CGHs) from image pairs of a real-world scene. The ratio of the three-dimensional (3D) physical size of the object is computed from the image pair to provide the correct depth cue. A multilayer wavefront recording plane method completed with a two-stage occlusion culling process is carried out for wave propagation. Multiple holograms can be generated by propagating the wave toward the desired angles, to cover the circular views that are wider than the viewing angle restricted by the wavelength and pitch size of a single hologram...
September 20, 2016: Applied Optics
Johan Öhman, Mikael Sjödahl
Poor axial resolution in holographic particle imaging applications makes particle positioning in 3D space more complex since the positions are not directly obtained. In this paper we estimate the axial position of micrometer particles by finding the location where the wavefront curvature from the scattered light becomes zero. By recording scattered light at 90° using off-axis holography, the complex amplitude of the light is obtained. By reconstruction of the imaged scene, a complex valued volume is produced...
September 20, 2016: Applied Optics
Yan Yan, Long Li, Guodong Xie, Changjing Bao, Peicheng Liao, Hao Huang, Yongxiong Ren, Nisar Ahmed, Zhe Zhao, Zhe Wang, Nima Ashrafi, Solyman Ashrafi, Shilpa Talwar, Soji Sajuyigbe, Moshe Tur, Andreas F Molisch, Alan E Willner
Electromagnetic waves carrying orbital angular momentum (OAM) have been used for mode division multiplexing in free-space communication systems to increase both the capacity and the spectral efficiency. In the case of conventional wireless communication links using non-OAM beams, multipath effects caused by beam spreading and reflection from the surrounding objects affect the system performance. This paper presents the results of analysis, simulations, and measurements of multipath effects in a millimetre-wave communication link using OAM multiplexing at 28 GHz...
2016: Scientific Reports
Diego López-Alcón, Iván Marín-Franch, Vicente Fernández-Sánchez, Norberto López-Gil
The purpose of this work was to find plausible predictors among optical parameters that may explain the inter-individual differences in subjective amplitude of accommodation not explained by age. An exploratory multivariable regression analysis was carried out retrospectively on a dataset with 180 eyes from 97 subjects (ages ranged from 20 to 58years). Subjective amplitudes of accommodation were recorded with the use of a custom-made Badal system. A commercial aberrometer was used to obtain each eye's wavefront during the full range of accommodation...
September 14, 2016: Vision Research
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