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Record 229 of
Title:Autofocusing based on wavelength dependence of diffraction in two-wavelength digital holographic microscopy
Author(s):Gao, Peng(1); Yao, Baoli(1); Rupp, Romano(2); Min, Junwei(1); Guo, Rongli(1); Ma, Baiheng(1); Zheng, Juanjuan(1); Lei, Ming(1); Yan, Shaohui(1); Dan, Dan(1); Ye, Tong(1)
Source: Optics Letters Volume: 37 Issue: 7 DOI: 10.1364/OL.37.001172 Published: April 1, 2012
Abstract:An autofocusing method for two-wavelength digital holographic microscopy (TWDHM) based on the wavelength dependence of the diffraction process is proposed. Red and green lights are employed for the illumination of the TWDHM, and the generated holograms are recorded simultaneously by a color CCD camera. Due to the wavelength dependency of the diffraction process, the farther the reconstruction plane is from the image plane, the larger the difference is between the red and green light distributions. Thus, the image plane can be determined by finding the minimum of the variation between the red and green lights on their amplitude distributions. The feasibility of the proposed method is demonstrated by simulation and experiment. ? 2012 Optical Society of America.
Accession Number: 20121414925555
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Record 230 of
Title:Intense red upconversion emission of Yb/Tm/Ho triply-doped tellurite glasses
Author(s):Zhan, Huan(1,2); Zhou, Zhiguang(1,2); He, Jianli(1,2); Lin, Aoxiang(1,2)
Source: Applied Optics Volume: 51 Issue: 15 DOI: 10.1364/AO.51.003091 Published: May 20, 2012
Abstract:By conventional melting and quenching methods, 3Yb2O 3-0.2Tm2O3-xHo2O3 (wt%, x = 0.2 ～ 1.2) was doped into an easily fiberized tellurite glass with composition of 78TeO2-10ZnO-12Na2O (mol%) to form YTH-TZN78 glasses. Under 976 nm excitation, the direct sensitizing effect of Yb ions (Yb → Ho) and indirect sensitizing and self-depopulating effects of Tm ions (Yb → Tm → Ho) were found to present intense red upconversion emission at 657 nm (Red, Ho: 5F5 → 5I 8) and were responsible for the absence of the usually observed 484 nm emission (Blue, Tm:1G4 → 3H 6). Regardless of the dopant concentration of Ho ions, the intensity of the red emission at 657 nm (Red, Ho: 5F5 → 5I8) is about three times stronger than that of the green one at 543 nm (Green, Ho:5S2 → 5I 8). For this certain red emission at 657 nm, 0.4 wt% Ho 2O3-doped YTH-TZN78 glass was found to present the highest emission intensity and is therefore determined as a promising active tellurite glass for red fiber laser development. ? 2012 Optical Society of America.
Accession Number: 20122215062371
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Record 231 of
Title:Fluorescence volume imaging with an axicon: Simulation study based on scalar diffraction method
Author(s):Zheng, Juanjuan(1); Yang, Yanlong(1); Lei, Ming(1); Yao, Baoli(1); Gao, Peng(1); Ye, Tong(1,2)
Source: Applied Optics Volume: 51 Issue: 30 DOI: 10.1364/AO.51.007236 Published: October 20, 2012
Abstract:In a two-photon excitation fluorescence volume imaging (TPFVI) system, an axicon is used to generate a Bessel beam and at the same time to collect the generated fluorescence to achieve large depth of field. A slice-by-slice diffraction propagation model in the frame of the angular spectrum method is proposed to simulate the whole imaging process of TPFVI. The simulation reveals that the Bessel beam can penetrate deep in scattering media due to its self-reconstruction ability. The simulation also demonstrates that TPFVI can image a volume of interest in a single raster scan. Two-photon excitation is crucial to eliminate the signals that are generated by the side lobes of Bessel beams; the unwanted signals may be further suppressed by placing a spatial filter in the front of the detector. The simulation method will guide the system design in improving the performance of a TPFVI system. ? 2012 Optical Society of America.
Accession Number: 20124415633778
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Record 232 of
Title:Angular momentum characteristics of cylindrical vector beams
Author(s):Yang, Shuangyan(1); Wang, Tingting(1); Li, Chunfang(1,2)
Source: Guangxue Xuebao/Acta Optica Sinica Volume: 32 Issue: 6 DOI: 10.3788/AOS201232.0626002 Published: June 2012
Abstract:The representation theory of nonparaxial light beams is introduced. On the basis of this theory, the decomposition of angular momentum of nonparaxial light beams is well solved. The total angular momentum of an arbitrary free electromagnetic field is separated rigorously into spin and orbital parts, both of which are dependent on the state of polarization and polarization ellipticity. The angular momentum problem of cylindrical vector beams is mainly researched. Based on the expressions of cylindrical vector beams and angular momentum operators given both in momentum space and position space, it is shown that cylindrical vector beams with a helical phase structure are the eigenstates of total angular momentum in the propagation direction, and the eigenvalue of total angular momentum has no relationship with polarization ellipticity. This provides a new calculation of the angular momentum for this special kind of light beams.
Accession Number: 20124215567442
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Record 233 of
Title:All-fiber normal-dispersion single-polarization passively mode-locked laser based on a 45-tilted fiber grating
Author(s):Liu, Xianglian(1,2,4); Wang, Hushan(1); Yan, Zhijun(3); Wang, Yishan(1); Zhao, Wei(1); Zhang, Wei(1); Zhang, Lin(3); Yang, Zhi(1); Hu, Xiaohong(1); Li, Xiaohui(1,2); Shen, Deyuan(1); Li, Cheng(1); Chen, Guangde(2)
Source: Optics Express Volume: 20 Issue: 17 DOI: 10.1364/OE.20.019000 Published: August 13, 2012
Abstract:An all-fiber normal-dispersion Yb-doped fiber laser with 45- tilted fiber grating (TFG) isto the best of our knowledgeexperimentally demonstrated for the first time. Stable linearly-chirped pulses with the duration of 4 ps and the bandwidth of 9 nm can be directly generated from the laser cavity. By employing the 45 TFG with the polarization-dependent loss of 33 dBoutput pulses with high polarization extinction ratio of 26 dB are implemented in the experiment. Our result shows that the 45 TFG can work effectively as a polarizerwhich could be exploited to singlepolarization all-fiber lasers. ? 2012 Optical Society of America.
Accession Number: 20123615400646
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Record 234 of
Title:Two-dimensional optical lattice solitons in photovoltaic-photorefractive crystals
Author(s):Guo, Jian-Bang(1); Lu, Ke-Qing(1,2); Niu, Ping-Juan(2); Yu, Li-Yuan(2); Xing, Hai-Ying(2)
Source: Chinese Physics Letters Volume: 29 Issue: 8 DOI: 10.1088/0256-307X/29/8/084212 Published: August 2012
Abstract:We study two families of two-dimensional bright lattice solitons in photovoltaic-photorefractive crystals. It is shown that self-focusing and self-defocusing lattice solitons are possible only when their power level exceeds a critical threshold. It is found that self-focusing lattice solitons exist not only in the semi-infinite band gap, but also in the first band gap, whereas self-defocusing lattice solitons exist only in the first band gap. The structures of these lattice solitons are also analyzed. Our results indicate that a self-focusing lattice soliton in the semi-infinite band gap is more confined than in the first band gap so its tails in the first band gap occupy many lattice sites; when a self-defocusing lattice soliton is close to the second band, the self-defocusing lattice soliton is more confined so its tails occupy a few lattice sites. ? 2012 Chinese Physical Society and IOP Publishing Ltd.
Accession Number: 20220711662373
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Record 235 of
Title:Simulation of incoherently coupled multicomponent solitons on MATLAB
Author(s):Li, Kehao(1,3); Chen, Weijun(2); Wang, Chunxiang(2); Hui, Juanli(2); Lu, Keqing(1,2)
Source: Proceedings of 2nd International Conference on Computer Science and Network Technology, ICCSNT 2012 Volume: Issue: DOI: 10.1109/ICCSNT.2012.6526189 Published: 2012
Abstract:We show that incoherently coupled multicomponent beam evolution equations in the low-amplitude regime in biased photorefractive-photovoltaic crystals can exhibit the analytical solutions of multicomponent solitons, which are due to both the spatially nonuniform screening of the external electric field and the photovoltaic effect. These multicomponent solitons can be obtained for N self-trapped mutually incoherent optical beams, where N is an arbitrary whole number. When the photovoltaic effect is neglected, their nonlinear evolution equations change into that for multicomponent screening solitons, and these multicomponent solitons change into multicomponent screening solitons. When the external bias field is absent, their nonlinear evolution equations change into that for multicomponent photovoltaic solitons in closed and open circuits, and these multicomponent solitons change into multicomponent photovoltaic solitons in closed and open circuits. ? 2012 IEEE.
Accession Number: 20133016524923
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Record 236 of
Title:Intense 2.7 μm emission of Er3+-doped water-free fluorotellurite glasses
Author(s):Zhan, Huan(1,2); Zhou, Zhiguang(1); He, Jianli(1,2); Lin, Aoxiang(1)
Source: Optics Letters Volume: 37 Issue: 16 DOI: 10.1364/OL.37.003408 Published: August 15, 2012
Abstract:By physical and chemical dehydration techniques, a group of Er3+-doped water-free fluorotellurite glasses with a composition of 60TeO2 -30ZnF2 -10NaFTZNF60; mol% + x Er2O3wt%; x 0 ? 1.5 were fabricated. Under 978 nm excitation, the 4I11 / 2 ? 4I13 / 2 emission of Er3+ ions in TZNF60-glass was investigated: tf is of 1.07 ? 1.93 ms and emission bandwidth is about 163 nm at 2.71 μm, which benefits from the absence of OH groups and the decreased phonon energy with the addition of fluorides. In contrast, 1.25Er-TZNF60 glass is proposed to be a promising material for mid-infrared fiber lasers at around 2.7 μm. ? 2012 Optical Society of America.
Accession Number: 20123615394913
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Record 237 of
Title:Prototype design of an all-reflective non-coaxial optical zooming system for space camera application without moving elements based on deformable mirror
Author(s):Zhao, Hui(1,2); Fan, Xuewu(1); Zou, Gangyi(1,3); Pang, Zhihai(3); Wang, Wei(1); Ren, Guorui(1); Su, Yu(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8557 Issue: DOI: 10.1117/12.981931 Published: 2012
Abstract:Based on optical zooming used to capture images with variable resolution and field of view (FOV), an all-reflective non-coaxial optical zooming system without moving elements is designed for space camera application. In this prototype design, a deformable mirror (DM) whose curvature radius can be changed is introduced. By carefully selecting the optical power of conventional reflective mirrors surrounding the DM, the overall focal length of the imaging system can be greatly changed with slight variation of curvature radius of DM. The focal length of the system can be changed from 48mm to 192mm and the system performance is approaching diffraction-limited with diverse criteria and the maximum stoke of DM is still within its physical limits at the same time. The experimental results prove the effectiveness of DM based optical zooming and will provide a new routine for new type of space camera design in the future. ? 2012 SPIE.
Accession Number: 20132916515060
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Record 238 of
Title:Selecting key poses on manifold for pairwise action recognition
Author(s):Cao, Xianbin(1,2); Ning, Bo(1); Yan, Pingkun(3); Li, Xuelong(3)
Source: IEEE Transactions on Industrial Informatics Volume: 8 Issue: 1 DOI: 10.1109/TII.2011.2172452 Published: February 2012
Abstract:In action recognition, bag of visual words based approaches have been shown to be successful, for which the quality of codebook is critical. In a large vocabulary of poses (visual words), some key poses play a more decisive role than others in the codebook. This paper proposes a novel approach for key poses selection, which models the descriptor space utilizing a manifold learning technique to recover the geometric structure of the descriptors on a lower dimensional manifold. A PageRank-based centrality measure is developed to select key poses according to the recovered geometric structure. In each step, a key pose is selected from the manifold and the remaining model is modified to maximize the discriminative power of selected codebook. With the obtained codebook, each action can be represented with a histogram of the key poses. To solve the ambiguity between some action classes, a pairwise subdivision is executed to select discriminative codebooks for further recognition. Experiments on benchmark datasets showed that our method is able to obtain better performance compared with other state-of-the-art methods. ? 2006 IEEE.
Accession Number: 20120514734323
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Record 239 of
Title:Luminescence properties of Nd3+-doped LaF3 nanocrystals with a long lifetime in organic solvents
Author(s):Sun, Wenxiu(1); Cui, Xiaoxia(2); Wang, Zhongyue(1); Wei, Wei(1,2); Peng, Bo(1,2)
Source: Journal of Materials Chemistry Volume: 22 Issue: 14 DOI: 10.1039/c2jm15891d Published: April 14, 2012
Abstract:A kind of monodisperse LaF3:Nd nanocrystal with a small size and long lifetime in solvent was synthesized via a hydrothermal process. The crystalline phase, morphology, and luminescence properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), emission spectroscopy as well as dynamic decays. The results indicated that LaF 3:Nd nanocrystals with a size below 30 nm have great dispersity in various solvents. An excellent lifetime of 359 μs was detected in a transparent DMSO-tetrabromoethane dispersion. It suggested that these nanocrystals could have great applications in biological and optical amplification fields. ? The Royal Society of Chemistry 2012.
Accession Number: 20121314898659
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Record 240 of
Title:Lens design for uniform illumination with LED
Author(s):Li, Lin(1); Wang, Guangzhen(1); Wang, Lili(1); Kong, Depeng(1); Ji, Jiangjun(1); Zhang, Yajun(2)
Source: Guangxue Xuebao/Acta Optica Sinica Volume: 32 Issue: 2 DOI: 10.3788/AOS201232.0222002 Published: February 2012
Abstract:A new method that the target plance is uniformly illuminated with aspheric lens is proposed. Based on the energy conservation law, it can be figured out the angle between the light source and the target surface, and the macro language of Zemax is used to make the lens meet the above mentioned relation, simulating and optimizing the result in the non-sequential mode and respectively simulating the three cases of the front surface. It is proposed and simulated a spherical LED array, and analysised the effect of the illumination uniformity of the angle and distance offsets. The result shows that the uniform illumination in a distance of 1 m and 0.25 m in diameter of the plane is achieved, with the uniformity of 96% or more. The spherical array meets the application requirements of shadowless lighting and the depth of illumination up to 1 m.
Accession Number: 20121014841971
