2017
2017
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Record 253 of
Title:Chiral long-period gratings: Fabrication, highly sensitive torsion sensing, and tunable single-band filtering
Author(s):Kong, Xudong(1,2); Ren, Kaili(1,2); Ren, Liyong(1); Liang, Jian(1,2); Ju, Haijuan(1,2)Source: Applied Optics Volume: 56 Issue: 16 DOI: 10.1364/AO.56.004702 Published: June 1, 2017Abstract:A promising technology for fabricating chiral long-period gratings (CLPGs) is demonstrated using a commercial fusion splicer. The key aspect of this technology is the incorporation of a fully automatic program we designed for the fusion splicer. High-quality CLPGs are successfully fabricated from single-mode fibers, which have very flat surfaces and low insertion loss. We also investigate the tuning characteristics of the transmission spectrum with the mechanical twist rate in CLPGs for torsion sensing application. The torsion sensitivity is improved and the shift in resonance wavelength versus the mechanical twist rate shows an almost perfect linear relationship. In addition, by choosing appropriate fabrication parameters, the fabricated CLPGs can be used as tunable single-band-rejection filters in a broad wavelength range. ? 2017 Optical Society of America.Accession Number: 20172403756324 -
Record 254 of
Title:Complementary normalized compressive ghost imaging with entangled photons
Author(s):Liu, Dawei(1,2); Li, Lifei(1)Source: arXiv Volume: Issue: DOI: Published: March 13, 2017Abstract:We demonstrate a compressive normalized ghost imaging system with entangled photons employing complementary compressive imaging (CCI) technique. The quantum ghost image reconstruction was achieved at only 19.53% sampling ratio of raster scanning. With the special +1/-1 type sensing matrix and appropriate optimal algorithm, the photon utilization efficiency and robustness of the imaging system is enhanced significantly. Our results reveal the great potential of CCI technique applied in quantum imaging and other quantum optics field such as quantum charactering and quantum state tomography to use the information loaded in each photon with high efficiency. Copyright ? 2017, The Authors. All rights reserved.Accession Number: 20200053039 -
Record 255 of
Title:Theoretical study on core-mode to radiation-mode coupling in chiral fiber long-period gratings
Author(s):Ren, Kaili(1,2); Ren, Liyong(1); Wang, Yingli(1); Lin, Xiao(1); Liang, Jian(1,2); Xu, Yiping(1); Ju, Haijuan(1,2)Source: Optics and Laser Technology Volume: 92 Issue: DOI: 10.1016/j.optlastec.2017.01.022 Published: July 1, 2017Abstract:The chiral fiber long-period gratings (CLPGs) could be fabricated by twisting a high-birefringence (Hi-Bi) fiber. However, when it is immersed into a material whose refractive index (RI) is higher than that of the cladding, there exists a complicated coupling between the core modes and the radiation ones. In this paper, for the first time to our knowledge, we theoretically investigate the mode coupling characteristics in such a CLPG. It is found that, owing to a strong mode transfer from the co-handed core mode to continuous radiation ones under the phase-matching condition, the CLPG can be regarded as a broadband circular polarizer since only the cross-handed circularly polarized light is left when a linearly polarized light is injected. Furthermore, the influence of the RI of the surrounding medium on the bandwidth and extinction ratio of this circular polarizer is investigated in detail. As a result, a broadband all-fiber circular polarizer can be constructed. Considering its simple configuration, it might have some potential applications, such as filters, broadband polarizers, and sensors. ? 2017 Elsevier LtdAccession Number: 20170703354900 -
Record 256 of
Title:Joint Dictionary Learning for Multispectral Change Detection
Author(s):Lu, Xiaoqiang(1); Yuan, Yuan(1); Zheng, Xiangtao(1)Source: IEEE Transactions on Cybernetics Volume: 47 Issue: 4 DOI: 10.1109/TCYB.2016.2531179 Published: April 2017Abstract:Change detection is one of the most important applications of remote sensing technology. It is a challenging task due to the obvious variations in the radiometric value of spectral signature and the limited capability of utilizing spectral information. In this paper, an improved sparse coding method for change detection is proposed. The intuition of the proposed method is that unchanged pixels in different images can be well reconstructed by the joint dictionary, which corresponds to knowledge of unchanged pixels, while changed pixels cannot. First, a query image pair is projected onto the joint dictionary to constitute the knowledge of unchanged pixels. Then reconstruction error is obtained to discriminate between the changed and unchanged pixels in the different images. To select the proper thresholds for determining changed regions, an automatic threshold selection strategy is presented by minimizing the reconstruction errors of the changed pixels. Adequate experiments on multispectral data have been tested, and the experimental results compared with the state-of-the-art methods prove the superiority of the proposed method. Contributions of the proposed method can be summarized as follows: 1) joint dictionary learning is proposed to explore the intrinsic information of different images for change detection. In this case, change detection can be transformed as a sparse representation problem. To the authors' knowledge, few publications utilize joint learning dictionary in change detection; 2) an automatic threshold selection strategy is presented, which minimizes the reconstruction errors of the changed pixels without the prior assumption of the spectral signature. As a result, the threshold value provided by the proposed method can adapt to different data due to the characteristic of joint dictionary learning; and 3) the proposed method makes no prior assumption of the modeling and the handling of the spectral signature, which can be adapted to different data. ? 2017 IEEE.Accession Number: 20161402198767 -
Record 257 of
Title:Effect of Two-color Laser Wavelength on Intense Terahertz Generation
Author(s):Chen, Ze-You(1,2); Fan, Wen-Hui(1); Chen, Xu(1,2); Ding, Ling(1,2); Song, Chao(1,2)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 46 Issue: 12 DOI: 10.3788/gzxb20174612.1214003 Published: December 2017Abstract:The effect of the two-color laser wavelength on intense terahertz generation was studied based on the transient photocurrent model. Theoretical calculation proves that the terahertz signal will increase with the increase of laser wavelength, and this trend will not vary with the variation of the pulse intensity, the pulse duration, the laser phase and the intensity ratio of the two-color laser. The distribution of terahertz spectrum will not change with the variation of the laser wavelength. Furthermore, the influence of laser wavelength on terahertz generation is analyzed, and the physical mechanism of this effect is explained by the free electron density and the drift current density. ? 2017, Science Press. All right reserved.Accession Number: 20180404664652 -
Record 258 of
Title:Polarization control methods in structured illumination microscopy
Author(s):Zhao, Tian-Yu(1,2); Zhou, Xing(1); Dan, Dan(1); Qian, Jia(1); Wang, Zhao-Jun(1); Lei, Ming(1); Yao, Bao-Li(1)Source: Wuli Xuebao/Acta Physica Sinica Volume: 66 Issue: 14 DOI: 10.7498/aps.66.148704 Published: July 20, 2017Abstract:Structured illumination microscopy (SIM) is one of the most promising super-resolution techniques, owing to its advantages of fast imaging speed and weak photo bleaching. The quality of the SIM image is greatly dependent on the contrast of the sinusoidal fringe illumination patterns. Low fringe contrast illumination will seriously affect the super-resolution result and lead to additional artifacts. The generation of fringe patterns with high contrast is the key requirement in hardware for the SIM technique. This can be done by the interference of two laser beams diffracted from the phase gratings addressed on a spatial light modulator. Meanwhile, for maximal interference contrast, precise polarization control to maintain s-polarization for different fringe orientations is critical. In this paper, we review several typical polarization control methods in SIM, and propose a new method by using a zero-order vortex half-wave retarder (VHR). Compared with the other methods, the presented VHR-based polarization control method is very efficient in terms of simple system configuration, ease of use, and high light energy utilization efficiency near to 100%. ? 2017 Chinese Physical Society.Accession Number: 20173804179887 -
Record 259 of
Title:High-sensitive torsion sensing based on chiral long-period gratings
Author(s):Kong, Xudong(1,2); Ren, Kaili(1,2); Ren, Liyong(1); Liang, Jian(1,2); Ju, Haijuan(1,2)Source: ICOCN 2017 - 16th International Conference on Optical Communications and Networks Volume: 2017-January Issue: DOI: 10.1109/ICOCN.2017.8121548 Published: November 27, 2017Abstract:High-reproducible chiral long-period gratings (CLPGs) are achieved, which are fabricated from normal single mode fibers. To explore torsion sensing application, we investigate the response trend of transmission spectrum versus mechanical twist rate in CLPGs. High torsion sensitivity is achieved, a perfect linear relationship between the resonance wavelength shift and the mechanical twist rate is displayed. ? 2017 IEEE.Accession Number: 20181104902481 -
Record 260 of
Title:Three-dimensional characterization of tightly focused fields for various polarization incident beams
Author(s):Cai, Yanan(1,2); Liang, Yansheng(1,2); Lei, Ming(1); Yan, Shaohui(1); Wang, Zhaojun(1,2); Yu, Xianghua(1); Li, Manman(1,2); Dan, Dan(1); Qian, Jia(1,2); Yao, Baoli(1)Source: Review of Scientific Instruments Volume: 88 Issue: 6 DOI: 10.1063/1.4989519 Published: June 1, 2017Abstract:Tightly focused vectorial optical beams have found extensive applications in variety of technical fields like single-molecule detection, optical tweezers, and super-resolution optical microscopy. Such applications require an accurate measurement and manipulation of focal optical fields. We have developed a compact instrument (with dimensions of 35 × 35 × 30 cm3) to rapidly measure the intensity distribution in three dimensions of the focused fields of vectorial beams and any other incident beams. This instrument employs a fluorescent nanoparticle as a probe to scan the focal region to obtain a high spatial resolution of intensity distribution. It integrates a liquid-crystal spatial light modulator to allow for tailoring the point spread function of the optical system, making it a useful tool for multi-purpose and flexible research. The robust applicability of the instrument is verified by measuring the 3D intensity distributions of focal fields of various polarization and wavefront modulated incident beams focused by a high NA (=1.25) objective lens. The minimal data acquisition time achievable in the experiment is about 8 s for a scanning region of 3.2 × 3.2 μm2 (512 × 512 pixels). The measured results are in good agreement with those predicted by the vectorial diffraction theory. ? 2017 Author(s).Accession Number: 20172703873676 -
Record 261 of
Title:Study of the interaction between graphene and planar terahertz metamaterial with toroidal dipolar resonance
Author(s):Chen, Xu(1,2); Fan, Wenhui(1)Source: Optics Letters Volume: 42 Issue: 10 DOI: 10.1364/OL.42.002034 Published: May 15, 2017Abstract:A planar terahertz metamaterial consisting of square split ring resonators is proposed, and the excitation of toroidal dipolar resonance is demonstrated. Moreover, we theoretically investigate the strong interaction between graphene and toroidal dipolar resonance of the metamaterial. By varying its Fermi energy, the simulations show that graphene can actively modulate the transmission amplitude of toroidal dipolar resonance and even switch it off. The interaction of the toroidal dipolar resonance with monolayer graphene further highlights the ultrasensitive sensing characteristic of the planar metamaterial, which can be utilized for other graphene-like two-dimensional materials. These intriguing properties of the proposed metamaterial may have potential applications in terahertz modulators and ultrasensitive sensors. ? 2017 Optical Society of America.Accession Number: 20172003675076 -
Record 262 of
Title:Transverse spinning of particles in highly focused vector vortex beams
Author(s):Li, Manman(1,2); Yan, Shaohui(1); Liang, Yansheng(1,2); Zhang, Peng(1); Yao, Baoli(1)Source: Physical Review A Volume: 95 Issue: 5 DOI: 10.1103/PhysRevA.95.053802 Published: May 1, 2017Abstract:Transverse spin angular momentum, which appears locally in the structured optical fields, has attracted much attention, owing to its extraordinary properties and potential applications. We show theoretically that, by highly focusing a vector vortex beam with azimuthally varied polarization, it is possible to trap multiple particles simultaneously and manipulate the particles' spin along the azimuthal direction. Both the direction and the magnitude of the spin angular momentum, so the spin torque on the particle, can be varied by changing the state of the input beams. Moreover, the magnitude of the spin torque can be manipulated further by changing the characteristics of the particles. Such results may be exploited in practical optical manipulation, especially for optically induced rotations. ? 2017 American Physical Society.Accession Number: 20171903641246 -
Record 263 of
Title:Survey of Spatio-Temporal Interest Point Detection Algorithms in Video
Author(s):Li, Yanshan(1); Xia, Rongjie(1); Huang, Qinghua(2,3,4); Xie, Weixin(1); Li, Xuelong(5)Source: IEEE Access Volume: 5 Issue: DOI: 10.1109/ACCESS.2017.2712789 Published: 2017Abstract:Recently, increasing attention has been paid to the detection of spatio-temporal interest points (STIPs), which has become a key technique and research focus in the field of computer vision. Its applications include human action recognition, video surveillance, video summarization, and content-based video retrieval. Amount of work has been done by many researchers in STIP detection. This paper presents a comprehensive review on STIP detection algorithms. We first propose the detailed introductions and analysis of the existing STIP detection algorithms. STIP detection algorithms are robust in detecting interest points for video in the spatio-temporal domain. Next, we summarize the existing challenges in the STIP detection for video, such as low time efficiency, poor robustness with respect to camera movement, illumination change, perspective occlusion, and background clutter. This paper also presents the application situations of STIP and discusses the potential development trends of STIP detection. ? 2013 IEEE.Accession Number: 20173504101693 -
Record 264 of
Title:Large sparse cone non-negative matrix factorization for image annotation
Author(s):Tao, Dapeng(1); Tao, Dacheng(2); Li, Xuelong(3); Gao, Xinbo(4)Source: ACM Transactions on Intelligent Systems and Technology Volume: 8 Issue: 3 DOI: 10.1145/2987379 Published: April 2017Abstract:Image annotation assigns relevant tags to query images based on their semantic contents. Since Non-negative Matrix Factorization (NMF) has the strong ability to learn parts-based representations, recently, a number of algorithms based on NMF have been proposed for image annotation and have achieved good performance. However, most of the efforts have focused on the representations of images and annotations. The properties of the semantic parts have not been well studied. In this article, we revisit the sparseness-constrained NMF (sNMF) proposed by Hoyer [2004]. By endowing the sparseness constraint with a geometric interpretation and sNMF with theoretical analyses of the generalization ability, we show that NMF with such a sparseness constraint has three advantages for image annotation tasks: (i) The sparseness constraint is more 0-norm oriented than the 1-norm-based sparseness, which significantly enhances the ability of NMF to robustly learn semantic parts. (ii) The sparseness constraint has a large cone interpretation and thus allows the reconstruction error of NMF to be smaller, which means that the learned semantic parts are more powerful to represent images for tagging. (iii) The learned semantic parts are less correlated, which increases the discriminative ability for annotating images. Moreover, we present a new efficient large sparse cone NMF (LsCNMF) algorithm to optimize the sNMF problem by employing the Nesterov's optimal gradient method. We conducted experiments on the PASCAL VOC07 dataset and demonstrated the effectiveness of LsCNMF for image annotation. ? 2017 ACM.Accession Number: 20171703612839