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Applied Optics

Lincheng Li, Xin Yu, Shunli Zhang, Xiaolin Zhao, Li Zhang
Cost aggregation is one of the key steps in the stereo matching problem. In order to improve aggregation accuracy, we propose a cost-aggregation method that can embed minimum spanning tree (MST)-based support region filtering into PatchMatch 3D label search rather than aggregating on fixed size patches. However, directly combining PatchMatch label search and MST filtering is not straightforward, due to the extremely high complexity. Thus, we develop multiple MST structures for cost aggregation on plenty of 3D labels, and design the tree-level random search strategy to find possible 3D labels of each pixel...
April 20, 2017: Applied Optics
Timothy Doster, Abbie T Watnik
Orbital angular momentum (OAM) beams allow for increased channel capacity in free-space optical communication. Conventionally, these OAM beams are multiplexed together at a transmitter and then propagated through the atmosphere to a receiver where, due to their orthogonality properties, they are demultiplexed. We propose a technique to demultiplex these OAM-carrying beams by capturing an image of the unique multiplexing intensity pattern and training a convolutional neural network (CNN) as a classifier. This CNN-based demultiplexing method allows for simplicity of operation as alignment is unnecessary, orthogonality constraints are loosened, and costly optical hardware is not required...
April 20, 2017: Applied Optics
Bo Li, Youyou Hu, Yi Hu, Jiang Zhao
In this paper, a three folds spatial resonator composed of a triple-axicon retroreflector and four pieces of quarter wave phase retarder is demonstrated to directly output radially polarized beams in a fast axial flow (FAF) CO<sub>2</sub> laser system. The triple-axicon retroreflector serves as the azimuthally polarized beams' selective element, and the quarter wave phase retarders convert the azimuthally polarized beams to radially polarized beams. Finally, a stable 1.5 kW radially polarized beam is generated in this laser system...
April 20, 2017: Applied Optics
Mohammad R N Avanaki, Adrian Bradu, Adrian Podoleanu
In this paper we investigate a phase-correction method for compensation of the nonlinearity of conventional wavelength-swept laser sources based on a fiber Fabry-Perot tunable filter as a wavelength selective element. A triangular waveform signal is commonly used to drive the filter. We, however, extract the zero crossings from the interferograms and modify the shape of the triangular signal accordingly. This algorithm was tested for different values of the optical path length difference in the interferometer setup...
April 20, 2017: Applied Optics
Amir Hossein Farhadian, Masoud Kavosh Tehrani, Mohammad Hossein Keshavarz, Seyyed Mohammad Reza Darbani
In this study, for the first time to the best of our knowledge, a combination of the laser-induced breakdown spectroscopy (LIBS) technique and artificial neural network (ANN) analysis has been implemented for the identification of energetic materials, including TNT, RDX, black powder, and propellant. Also, aluminum, copper, inconel, and graphite have been used for more accurate investigation and comparison. After the LIBS test and spectrum acquisition on all samples in both air and argon ambient, optimized neural networks were designed by LIBS data...
April 20, 2017: Applied Optics
Ron Driggers
Editor-in-Chief Ron Driggers cautions authors to avoid using trademarked or copyrighted content in a journal publication.
April 20, 2017: Applied Optics
Alexandre S Shcherbakov, Adan Omar Arellanes
We present a principally new acousto-optical cell providing an advanced wideband spectrum analysis of ultra-high frequency radio-wave signals. For the first time, we apply a recently developed approach with the tilt angle to a one-phonon non-collinear anomalous light scattering. In contrast to earlier cases, now one can exploit a regime with the fixed optical wavelength for processing a great number of acoustic frequencies simultaneously in the linear regime. The chosen rutile-crystal combines a moderate acoustic velocity with low acoustic attenuation and allows us wide-band data processing within GHz-frequency acoustic waves...
April 20, 2017: Applied Optics
Jiading Wu, Jingcao Chu, Zefeng Zhang, Jiahui Huang, Huai Zheng, Sheng Liu
Due to the total internal reflection at the upper interface of the encapsulation layer, the light extraction efficiency (LEE) of chip-on-board packaging light-emitting diodes is attenuated significantly. It is well known that the LEE can be enhanced by patterning the encapsulation layer. In this study, a novel method of patterning the encapsulation layer, which is based on the interaction between the ionic wind and liquid encapsulation, is proposed and demonstrated. Two kinds of encapsulation patterns, namely dual stripe and meniscus, were fabricated successfully...
April 20, 2017: Applied Optics
Stefan Grottker, Wolfgang Viöl, Christoph Gerhard
In this work, we investigated the generation of particles during pure laser and plasma-assisted laser ablation of titanium. Experiments were performed using a NIR picosecond laser at a wavelength of 1030 nm and a pulse duration of 8 ps. For plasma-assisted ablation, an atmospheric pressure dielectric barrier discharge plasma was applied where the process gas was argon. Quantitative particle distributions at sizes from 10 nm to 10 μm were determined. In addition, we evaluated the amount of ablated material via laser scanning microscopy...
April 20, 2017: Applied Optics
A F Forughi, B Stoeber, S I Green
Optical transparency can be determined by passing light through an object and comparing the intensity of the transmitted light with the intensity of the incident light. This measurement needs optical access to both sides of the object for illumination and measurement. Optical access to both sides of the object may be restricted in some situations due to the presence of an opaque obstacle, lack of physical access, etc. A novel technique of transmittance measurement is presented that is able to determine the transparency of thin-film objects with optical access limited to just one side...
April 20, 2017: Applied Optics
Olav Gaute Hellesø
Optical forces on a particle can be calculated using numerical methods and by integrating the Maxwell stress tensor over the surface of the particle. It is shown that this gives considerable numerical noise for the radiation force on particles with refractive index close to that of the surrounding medium and that a large number of mesh elements are necessary. It is found preferable to calculate the force from the local optical pressure, as this gives considerably less noise and requires significantly fewer mesh elements...
April 20, 2017: Applied Optics
Jian Wang, Hongyan Wu, Bo Jia
Real-time sound source localization has been widely realized by the conventional microphone array for the present. In addition, fiber-optic microphones have many advantages over conventional microphones. In the present work, an all-fiber-optic acoustic array system with a wavelength-division multiplexing scheme is proposed, which has a high sensitivity and significant superiority in high-frequency signal detection and can be applied in harsh environments. The system also has the advantages of simple construction and low cost...
April 20, 2017: Applied Optics
Wanzhuo Ma, Tianshu Wang, Yan Zhang, Peng Liu, Yuwei Su, Qingsong Jia, Mingzhe Bi, Peng Zhang, Huilin Jiang
We propose and experimentally demonstrate a widely tunable mode-locked thulium-doped fiber laser. The laser can operate at both continuous-wave and mode-locked states at different pump power levels. A classic nonlinear polarization rotation structure is employed to obtain the passive mode-locked laser. A birefringence Lyot filter as a fiber comb filter is used to expand the tuning range. Thanks to the filtering component, the tuning range of the continuous-wave laser can reach 127 nm (1823-1950 nm). The tuning ranges of the single-wavelength and dual-wavelength mode-locked lasers are 94 nm (1835-1929 nm) and 87 nm (1831-1918 nm), respectively, with a 3...
April 20, 2017: Applied Optics
Pengfei Wu, Zi Liang, Xing Zhao, Lei Su, Lipei Song
The need to image objects through light-scattering materials is common in a range of applications. Different methods have been investigated to acquire the image of the object when diffusers are presented. In this paper, we demonstrate the object reconstruction with single-shot imaging based on the correlography principle and phase retrieval algorithm with coherent illumination. We prove the possibility of reconstructing positive and negative objects in both transmission and reflection modes with collimated and scattered light...
April 20, 2017: Applied Optics
Naema Othman, Pierre Berini
We propose and investigate a Schottky contact detector where the contact metal is a nanoscale metal stripe waveguide supporting surface plasmons with strong localization along the Schottky contact. We consider Au for the metal stripe, p-doped silicon for the semiconductor, operation in the infrared (at λ<sub>0</sub>=1550  nm), and internal photoemission as the sub-bandgap detection mechanism. We find that the main surface plasmon mode of operation of the Au stripe exhibits diverging real and imaginary parts of n<sub>eff</sub> with decreasing stripe dimensions, commensurate with increasing confinement...
April 20, 2017: Applied Optics
Zhe Guang, Michelle Rhodes, Rick Trebino
Ultrashort pulses emerging from multimode optical fibers are spatiotemporally complex, because inside these fibers the modes have different spatial intensity patterns and experience different propagation velocities and dispersions. To determine the spatiotemporal field from multimode fibers, we applied a technique for the complete measurement of the output pulses called a spatially and temporally resolved intensity and phase evaluation device: full information from a single hologram. It yields the complete electric field over space and time from multiple digital holograms, simultaneously recorded at different frequencies on a single camera frame...
April 20, 2017: Applied Optics
Yaran Li, Baozhong Mu, Qing Xie, Yanan He, Zhiqiang Chen, Zhanshan Wang, Zhurong Cao, Jianjun Dong, Shenye Liu, Yongkun Ding
This article presents the development of an x-ray eight-image Kirkpatrick-Baez diagnostic system to be used at China's Shenguang-III (SG-III) laser facility in aspects of the optical design, multilayers, and online/offline tests. Six pieces of concave spherical substrates are used for constituting a special optical structure. Dual-periodic tungsten/carbon (W/C) multilayers are used for high reflectivity and large angular bandwidth of ∼0.1°. The global spatial resolution is ∼5  μm in the ±100  μm range...
April 20, 2017: Applied Optics
Travis W Sawyer, Ryan Petersburg, Sarah E Bohndiek
Optical fiber technology is found in a wide variety of applications to flexibly relay light between two points, enabling information transfer across long distances and allowing access to hard-to-reach areas. Large-core optical fibers and light guides find frequent use in illumination and spectroscopic applications, for example, endoscopy and high-resolution astronomical spectroscopy. Proper alignment is critical for maximizing throughput in optical fiber coupling systems; however, there currently are no formal approaches to tolerancing the alignment of a light-guide coupling system...
April 20, 2017: Applied Optics
D M Capps
The near and far fields of a finite conductivity metallic grating with symmetrical triangular facets, used in Littrow mount, are studied. A new Green's function approach, based on the Hertz vector, is introduced and used to propagate throughout a two-dimensional domain. The field quantity of primary interest is Poynting's vector; however, the stored power is also calculated. In assessing the fields generated by the propagator, a quasi-periodic dependence of output characteristics on the grating depth to period ratio, discussed in the literature, is also found in the present study...
April 20, 2017: Applied Optics
Tianying Chang, Xiansheng Zhang, Xiaoxuan Zhang, Hong-Liang Cui
Interactions of terahertz (THz) electromagnetic radiation with polymer materials have been studied recently with increasing depth and breadth, for purposes of both using polymers in fabricating THz optical components such as lenses, waveplates, waveguides, and sample holders/containers, and employing THz spectral imaging as a new tool for nondestructive testing of polymer composite structures. Either endeavor cannot even begin without a quantitative knowledge of the complex dielectric permittivity, i.e., the propagation and attenuation properties of such polymers in the requisite wave band...
April 20, 2017: Applied Optics
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