2011
2011
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Record 145 of
Title:All fiber supercontinuum light source using photonic crystal fibers pumped by nanosecond fiber laser pulses
Author(s):Zhu, S.L.(1,2); Gao, C.X.(1); He, H.D.(1); Feng, L.(1); Cao, Z.Y.(1)Source: Laser Physics Volume: 21 Issue: 9 DOI: 10.1134/S1054660X11150412 Published: September 2011Abstract:A novel compact supercontinuum (SC) source using the single mode photonic crystal fibers (PCF) pumped with an all fiber MOPA fiber laser is demonstrated experimentally. A bandwidth of 700 nm is achieved by operating the pumping fiber laser at a wavelength of 1064 nm, pulse duration of 10 ns, repetition rate of 50 kHz and peak power of 1 kW. The SC generation is initiated through modulation instability (MI) which breakups the nanosecond pump pulses into picosecond or femtosecond pulses, and further broadened through nonlinear effects of PCF. ? 2011 Pleiades Publishing, Ltd.Accession Number: 20114314447237 -
Record 146 of
Title:Parallel two-step phase-shifting microscopic interferometry based on a cube beamsplitter
Author(s):Gao, Peng(1,2); Yao, Baoli(1); Min, Junwei(1); Guo, Rongli(1); Zheng, Juanjuan(1); Ye, Tong(1)Source: Optics Communications Volume: 284 Issue: 18 DOI: 10.1016/j.optcom.2011.04.049 Published: August 15, 2011Abstract:Parallel two-step phase-shifting interferometry for microscopy is presented, and the recording condition for generalized two-step phase-shifting interferometry is discussed. A 45° tilted cube beamsplitter enables to replicate the orthogonally linear polarized object and reference waves into two parallel beams, respectively. As a consequence, two interferograms with quadrature phase shift are obtained along the two beams, and phase reconstructed with an improved algorithm. To reconstruct the phase distribution from the two-step phase-shifting interferograms, a certain recording condition should be satisfied. However, the recording condition has not ever been discussed before. In this paper, the recording condition for the two-step phase-shifting interferometry is derived and that is: the intensity of reference wave should be no less than two times object wave intensity. ? 2011 Elsevier B.V. All rights reserved.Accession Number: 20112414050864 -
Record 147 of
Title:Impact of dispersion profiles of silicon waveguides on optical parametric amplification in the femtosecond regime
Author(s):Wang, Zhaolu(1,2); Liu, Hongjun(1); Huang, Nan(1); Sun, Qibing(1); Wen, Jin(1,2)Source: Optics Express Volume: 19 Issue: 24 DOI: 10.1364/OE.19.024730 Published: November 21, 2011Abstract:The impact of dispersion profiles of silicon waveguides on femtosecond optical parametric amplification (OPA) is theoretically investigated. It is found that flat quasi-phase-matching, smooth temporal profiles and separable spectra for 200 fs pulses can be obtained by tailoring the cross-section of silicon rib waveguide. We achieve on-chip parametric gain as high as 26.8 dB and idler conversion gain of 25.6 dB for a low pump peak power over a flat bandwidth of 400 nm in a 10-mm-long dispersion engineered silicon waveguide. Our on-chip OPA can find important potential applications in highly integrated optical circuits for alloptical ultrafast signal processing. ? 2011 Optical Society of America.Accession Number: 20114814562991 -
Record 148 of
Title:High-power picosecond terahertz-wave generation in photonic crystal fiber via four-wave mixing
Author(s):Wu, Huihui(1,2); Liu, Hongjun(1); Huang, Nan(1); Sun, Qibing(1); Wen, Jin(1,2)Source: Applied Optics Volume: 50 Issue: 27 DOI: 10.1364/AO.50.005338 Published: September 20, 2011Abstract:We demonstrate picosecond terahertz (THz)-wave generation via four-wave mixing in an octagonal photonic crystal fiber (O-PCF). Perfect phase-matching is obtained at the pump wavelength of 1:55 μm and a generation scheme is proposed. Using this method, THz waves can be generated in the frequency range of 7:07-7:74 THz. Moreover, peak power of 2:55W, average power of 1:53mW, and peak conversion efficiency of more than .66:65 dB at 7:42THz in a 6:25cm long fiber are realized with a pump peak power of 2kW. ? 2011 Optical Society of America.Accession Number: 20113914366066 -
Record 149 of
Title:Single-image super-resolution via local learning
Author(s):Tang, Yi(1); Yan, Pingkun(1); Yuan, Yuan(1); Li, Xuelong(1)Source: International Journal of Machine Learning and Cybernetics Volume: 2 Issue: 1 DOI: 10.1007/s13042-011-0011-6 Published: March 2011Abstract:Nearest neighbor-based algorithms are popular in example-based super-resolution from a single image. The core idea behind such algorithms is that similar images are close in the sense of distance measurement. However, it is well known in the field of machine learning and statistical learning theory that the generalization of the nearest neighbor-based estimation is poor, when complex or high dimensional data are considered. To improve the power of the nearest neighbor-based algorithms in single-image based super-resolution, a local learning method is proposed in this paper. Similar to the nearest neighbor-based algorithms, a local training set is generated according to the similarity between the training samples and a given test sample. For super-resolving the given test sample, a local regression function is learned on the local training set. The generalization of nearest neighbor-based algorithms can be enhanced by the process of local regression. Based on such an idea, we propose a novel local-learning-based algorithm, where kernel ridge regression algorithm is used in local regression for its well generalization. Some experimental results verify the effectiveness and efficiency of the local learning algorithm in single-image based super-resolution. ? 2011 Springer-Verlag.Accession Number: 20111313859598 -
Record 150 of
Title:Synthesis of a side chain conjugated polythiophene copolymer and its photovoltaic property
Author(s):Gao, Chao(1,2); Qu, Bo(3); Jiang, Zhongliang(1); Tian, Di(1); Liu, Hongli(1); Chen, Zhijian(3); Xiao, Lixin(3); Gong, Qihuang(3)Source: Synthetic Metals Volume: 161 Issue: 9-10 DOI: 10.1016/j.synthmet.2011.02.014 Published: May 2011Abstract:A new soluble polythiophene copolymer with phenylene-vinylene conjugated side chain (PEHOPVTh-Th) was synthesized. Polymer photovoltaic solar cells using PEHOPVTh-Th as donor and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61BM) as acceptor was demonstrated. The absorption spectrum of the PEHOPVTh-Th showed strong absorption in the visible region and a 55 nm red-shift in comparison with that of its homopolymer (PEHOPVTh). By adjusting the ratio of PEHOPVTh-Th to PC61BM, the polymer solar cells based on PEHOPVTh-Th showed a power conversion efficiency of 0.37% under 100 mW/cm 2 AM 1.5G simulated sunlight when the weight ratio of the polymer to PC61BM equals to 1:3. ? 2011 Elsevier B.V.Accession Number: 20111913971850 -
Record 151 of
Title:Compression of electron pulses in temporal domain
Author(s):Tian, Jin-Shou(1); Lei, Xiao-Hong(1,2); Wen, Wen-Long(1); Xu, Xiang-Yan(1); Wang, Jun-Feng(1)Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 19 Issue: 10 DOI: 10.3788/OPE.20111910.2379 Published: October 2011Abstract:The compression of electron pulses in the temporal domain is a core technique to improve the temporal resolution of ultrafast diagnosis instruments, such as streak cameras and ultrafast electron diffraction systems. In this paper, a time focusing technique is adopted to potentially improve the physical temporal resolutions of streak cameras and ultrafast electron diffraction systems. This method uses a time-dependent acceleration field to greatly compensate the temporal dispersion between photocathode and anode to accelerate the slow electrons and decelerate the fast electrons, relatively. As a result, the temperal dispersion due to an initial energy spread can be compensated to a large extent at the output of time focusing region. Tracing and simulating a large number of photoelectrons through Monte-Carlo and finite difference methods shows that the electron pulse with a 300 fs can be compressed to 50 fs, which lays a powerful foundation for developing the streak cameras and ultrafast electron diffraction systems with better than 100 fs temporal resolution.Accession Number: 20114714541765 -
Record 152 of
Title:Generation of 10-GHz duty-cycle tunable square optical pulse in an SOA-based mode-locked fiber laser
Author(s):Luo, D.(1,2); Yan, S.Y.(1); Xie, X.P.(1); Zhao, W.(1)Source: Laser Physics Volume: 21 Issue: 11 DOI: 10.1134/S1054660X11190224 Published: November 2011Abstract:We demonstrate the generation of 10-GHz optical square pulses by injecting a picosecond pulse train into an SOA-based mode-locked fiber laser. The novel scheme exploits nonlinear effects and gain saturation phenomenon in the semiconductor optical amplifier (SOA). This technique uses gain-compression dynamics between the input pulses and the generated ones in gain-saturated SOA to form square pulses. The center wavelength of the generated optical square pulse can be tuned from 1530 to 1570 nm by adjusting the center wavelength of the optical band pass filter (OBPF) in the SOA-based mode-locked fiber ring laser. The duty cycle of the output pulse can be tuned from 12.7 to 88.4%, which strongly depends on the input power and intra-cavity power. ? Pleiades Publishing, Ltd., 2011.Accession Number: 20120314700444 -
Record 153 of
Title:Effect of polarization on the evolution of electromagnetic hollow Gaussian Schell-model beam
Author(s):Long, Xuewen(1,2); Lu, Keqing(1); Zhang, Yuhong(1,2); Guo, Jianbang(1,2); Li, Kehao(1,2)Source: Optics Communications Volume: 284 Issue: 3 DOI: 10.1016/j.optcom.2010.09.078 Published: February 1, 2011Abstract:Based on the theory of coherence, an analytical propagation formula for partially polarized and partially coherent hollow Gaussian Schell-model beams (HGSMBs) passing through a paraxial optical system is derived. Furthermore, we show that the degree of polarization of source may affect the evolution of HGSMBs and a tunable dark region may exist. For two special cases of fully coherent and partially coherent δxx = δyy, normalized intensity distributions are independent of the polarization of source. ? 2010 Elsevier B.V. All rights reserved.Accession Number: 20104813434067 -
Record 154 of
Title:Analysis and comparison of pulse broadening caused by atmospheric turbulence and dispersion
Author(s):Lu, Hong-Qiang(1,2); Zhao, Wei(1); Xie, Xiao-Ping(1)Source: Binggong Xuebao/Acta Armamentarii Volume: 32 Issue: 4 DOI: Published: April 2011Abstract:The temporal broadening of optical pulses in satellite-earth laser communication systems. The expression of turbulence-induced pulse width broadening was given, in which the turbulent atmosphere index-of-refraction structure constant, propagation distance, zenith angle and original pulse width were considered. Based on the measured datum of atmospheric parameters, the refractive index in 1.55μm was derived and the relationship of dispersion-induced pulse broadening to the spectral width, propagation distance, zenith angle, original pulse width and the wavelength of optical signal was obtained. The simulation results show that the turbulence-induced pulse broadening can be neglected for the pulse width greater than 0.5 ps, however, the dispersion-induced pulse broadening can be neglected for the pulse width larger than 20 ps. The received pulse width and maximum achievable bandwidth are calculated in this paper under certain conditions.Accession Number: 20112013987704 -
Record 155 of
Title:Video-rate wide-field coherent anti-Stokes Raman scattering microscopy with collinear nonphase-matching illumination
Author(s):Lei, Ming(1,2); Winterhalder, Martin(1); Selm, Romedi(1); Zumbusch, Andreas(1)Source: Journal of Biomedical Optics Volume: 16 Issue: 2 DOI: 10.1117/1.3533707 Published: February 2011Abstract:A simple scheme for video-rate wide-field coherent anti-Stokes Raman scattering (CARS) microscopy is presented. The method is based on collinear nonphase-matching illumination. The mechanisms leading to CARS signal generation are investigated. We find that refraction-mediated phase-matching is the main effect. Video-rate wide-field CARS microscopy of polystyrene beads and CARS wide-field images of C. elegans embryos are shown, and the capabilities and the limitations of the scheme are discussed. ? 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).Accession Number: 20114514495620 -
Record 156 of
Title:Analytical vectorial structure of non-paraxial four-petal Gaussian beams in the far field
Author(s):Long, Xuewen(1,2); Lu, Keqing(1); Zhang, Yuhong(1,2); Guo, Jianbang(1,2); Li, Kehao(1,2)Source: Optik Volume: 122 Issue: 16 DOI: 10.1016/j.ijleo.2010.09.028 Published: August 2011Abstract:Abstract: The analytical vectorial structure of non-paraxial four-petal Gaussian beams (FPGBs) in the far field has been studied based on vector angular spectrum method and stationary phase method. In terms of analytical electromagnetic representations of the TE and TM terms, the energy flux distributions of the TE term, the TM term, and the whole beam are derived in the far field, respectively. According to our investigation, the FPGBs can evolve into a number of small petals in the far field. The number of the petals is determined by the order of input beam. The physical pictures of the FPGBs are well illustrated from the vectorial structure, which is beneficial to strengthen the understanding of vectorial properties of the FPGBs. ? 2010 Elsevier GmbH. All rights reserved.Accession Number: 20112814129539