2014

• Record 421 of
  
  Title:Tunable terahertz Kerr switching based on nonlinear polarization rotation in silicon waveguide
  
  Author(s):Mou, Miaoli(1); Liu, Hongjun(1); N., Huang; Q., Sun; Z., Wang
  Source: Applied Optics  Volume:   Issue: 12  DOI: 10.1364/AO.53.002741  Published: April 20, 2014  
  Abstract:A compact and widely tunable terahertz (THz) all-optical Kerr switching using nonlinear polarization rotation generated by cross-phase modulation in a silicon waveguide is theoretically proposed. A switching efficiency of 83% is obtained when a -phase shift difference between the TE and TM polarization components of the continuous-wave THz signal is achieved. Moreover, the tuning range of the THz switching is from 7.69 to 10 THz through changing the pump power. This THz all-optical switching has potential applications in THz communications and other THz switchable devices. © 2014 Optical Society of America.
  Accession Number: 20142400001207
• Record 422 of
  
  Title:High-efficiency Terahertz-wave generation in silicon membrane waveguides
  
  Author(s):Liu, Hongjun(1); Wang, Zhaolu(1); Huang, Nan(1); Sun, Qibing(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 9199  Issue:   DOI: 10.1117/12.2060232  Published: 2014  
  Abstract:Terahertz (THz) wave generation via four-wave mixing (FWM) in silicon membrane waveguides is investigated with mid-infrared pump. The silicon membrane waveguides with width of 12 μm and heights varied from 14 μm to 17 μm, which can confine the THz-wave ranging from 7.5 THz to 10 THz due to the large refractive index contrast of the waveguide core and cladding, are designed to realize the collinear phase matching for THz-wave generation via FWM. Compared with the conventional parametric amplification or wavelength conversion based on FWM in silicon waveguides, which needs a pump wavelength located in the anomalous group-velocity dispersion (GVD) regime to realize broad phase matching, the pump wavelength located in the normal GVD regime is required to realize phase matching because of the large signal-pump frequency detuning. Phase matching for a tunable THz-wave ranging from 8.57 THz to 10 THz can be realized by tuning the pump wavelength from 4.2 μm to 4.4 μm in the silicon waveguide with rib height of 15 μm. Whilst, the phase matching bandwidth of THz-wave ranging from 7.7 THz to 10 THz can be achieved by tailoring the waveguide height from 14 μm to 17 μm when the pump wavelength is 4.3μm. Moreover, the conversion efficiency of the THz-wave generation is studied with different pump wavelengths and waveguide heights, the maximum conversion efficiency of 1.25 % at 9.2 THz can be obtained in a 6-mm long silicon waveguide when the pump wavelength is 4.3 μm and the waveguide height is 15 μm. © 2014 SPIE.
  Accession Number: 20150700530025
• Record 423 of
  
  Title:Wavelength conversion in highly nonlinear silicon - Organic hybrid slot waveguides
  
  Author(s):An, Linliang(1); Liu, Hongjun(1); Sun, Qibing(1); Huang, Nan(1); Wang, Zhaolu(1)
  Source: Applied Optics  Volume:   Issue: 22  DOI: 10.1364/AO.53.004886  Published: August 1, 2014  
  Abstract:Wavelength conversion based on four-wave mixing (FWM) in a silicon-organic hybrid slot waveguide is theoretically investigated in the telecommunication bands. Compared with vertical slot waveguides, the horizontal slot waveguide structure exhibits much flatter dispersion. The maximum nonlinearity coefficient γ of 1.5 × 107W-1km-1and the minimum effective mode area Aeffof 0.065 μm2are obtained in a horizontal slot waveguide with a 20-nm-thick optically nonlinear layer by controlling the geometric parameters. The wavelength conversion efficiency of 7.45 dB with a pump power of 100 mW in a 4-mm-long horizontal slot waveguide is obtained. This low power on-chip wavelength convertor will have potential applications in highly integrated optical circuits. © 2014 Optical Society of America.
  Accession Number: 20143200002774
• Record 424 of
  
  Title:High-precision method of machining taper holes of diesel engine nozzle with femtosecond laser
  
  Author(s):Wang, Feng(1,2); Luo, Jian-Jun(1); Li, Ming(2)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 43  Issue: 4  DOI: 10.3788/gzxb20144304.0414003  Published: April 2014  
  Abstract:Femtosecond laser processing has litle-thermal effects, high precision, and is not particular about materials. Aiming at the machining requirement for nozzle's spray holes, as a key part of the high pressure common rail injection system for diesel engine, a femtosecond laser processing apparatus with three-wedge scanning system was designed for technical research of taper holes' machining. Then tests of the taper holes' physical dimensions and the flow rate of the fuel jet nozzles were carried out with three coordinates measuring machine (measurement accuracy 1.2 μm) and high-pressure liquid flow test bench for the injector(measurement accuracy ±0.1%). The experimental results show that the designed apparatus can machine nozzles, and the performance is able to meet the application requirement of Euro V emission regulations. The technique has important significance for improving the level of automobile industry and domestic emission standard of diesel engined car.
  Accession Number: 20142117743318
• Record 425 of
  
  Title:Double-mode electrostatic dispersing prism for electron pulse time-domain compression
  
  Author(s):Wang, Chao(1); Kang, Yifan(2)
  Source: Optik  Volume: 125  Issue: 21  DOI: 10.1016/j.ijleo.2014.05.051  Published: November 1, 2014  
  Abstract:The generalized theory of double-mode electrostatic dispersing prism for time-domain compressing electron pulse is presented. The fundamental difference between the two modes of o mode and e mode lies in the dispersive dependence of electron's time of flight on its initial kinetic energy at prism entrance: the electrons with higher initial axial energy definitely have longer time of flight for o mode, while not the case for e mode, which results from the electron pulse's U-shaped motion in the prism. The dispersive dependence of time of flight constitutes the mechanism of electron pulse compression for each mode. An example is given to demonstrate the issue of parameter choosing for the prism and to verify its tunable performance of compression. © 2014 Elsevier GmbH.
  Accession Number: 20144400133743
• Record 426 of
  
  Title:Double-mode electrostatic dispersive prism for compressing electron pulse
  
  Author(s):Wang, C.(1); Kang, Y.(2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 9233  Issue:   DOI: 10.1117/12.2064943  Published: 2014  
  Abstract:The generalized theory of double-mode electrostatic dispersing prism for time-domain compressing electron pulse is presented. The fundamental difference between the two modes of o mode and e mode lies in the dispersive dependence of electron's time of flight on its initial kinetic energy at prism entrance: the electrons with higher initial axial energy definitely have longer time of flight for o mode, while not the case for e mode, which results from the electron pulse's Ushaped motion in the prism. The dispersive dependence of time of flight constitutes the mechanism of electron pulse compression for each mode. An example is given to demonstrate the issue of parameter choosing for the prism and to verify its tunable performance of electron pulse compression.
  Accession Number: 20150800545874
• Record 427 of
  
  Title:Methods of fault diagnosis in fiber optic current transducer based on Allan variance
  
  Author(s):Wang, Lihui(1,2); Chen, Gang(3); Ji, Jianfei(3); Sun, Jian(3); Qian, Jiabin(1); Liu, Xixiang(1)
  Source: Mathematical Problems in Engineering  Volume: 2014  Issue:   DOI: 10.1155/2014/831075  Published: 2014  
  Abstract:To ensure low failure and high reliability of fiber optic current transducers (FOCTs), it is urgent to study methods of condition monitoring and fault diagnosis in FOCT. Faults in FOCT have statistical characteristics. With the analyzing of time domain and frequency domain features in fiber optic current transformers' measurement data, we establish correspondence between the physical characteristics of key components in transformer and data features and then build diagnostic analysis model based on Allan variance. According to the Allan variance calculation results, we can diagnose fiber optic current transformer's health state and realize faults location. Experiment results show that diagnostic methods based on Allan variance are accurate and effective to identify fault features. © 2014 Lihui Wang et al.
  Accession Number: 20142917952693
• Record 428 of
  
  Title:Theoretical and static experiment research on all optical solid state streak camera
  
  Author(s):Liang, Ling-Liang(1,2,3); Tian, Jin-Shou(1); Wang, Tao(1); Li, Fu-Li(3); Gao, Gui-Long(1,2,3); Wang, Jun-Feng(1); Wang, Chao(1); Lu, Yu(1); Xu, Xiang-Yan(1); Cao, Xi-Bin(1); Wen, Wen-Long(1); Xin, Li-Wei(1); Liu, Hu-Lin(1); Wang, Xing(1)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 63  Issue: 6  DOI: 10.7498/aps.63.060702  Published: March 20, 2014  
  Abstract:All optical solid state streak camera is to carry out the process of deflecting and scanning of the signal light which is coupled into the core of the waveguide, with spatially-modulated pump pulse exciting the light deflector, through precisely controlling the time delay between signal light and pump light. Not only can it solve the problems existing in the traditional photoelectron streak camera such as the decrease of the dynamic range caused by space charge effect and incapability of detecting the infrared light signal for photoelectric cathode, but also it has the advantages of simple structure, systemic stability. And the theoretical temporal resolution can reach up to picosecond scale even sub picosecond scale. For the AlxGa1-xAs/GaAs/ AlxGa1-xAs planar waveguide light deflector, we discuss in detail the change of the refractive index of the GaAs with time under the common influences of band filling, band gap shrinkage and free carrier absorption effect; when the change of the refractive index is on the order of 0.01 and the ratio of the signal spot size to the width of the waveguide p = 0.5, the theoretical temporal resolution can reach 2 ps; finally, the theoretical spatial resolution is calculated to be 17 lp/mm according to the condition of static experiment, while the experimental results show that spatial resolution is 9 lp/mm. © 2014 Chinese Physical Society.
  Accession Number: 20141317524077
• Record 429 of
  
  Title:Alternatively constrained dictionary learning for image superresolution
  
  Author(s):Lu, Xiaoqiang(1); Yuan, Yuan(1); Yan, Pingkun(1)
  Source: IEEE Transactions on Cybernetics  Volume: 44  Issue: 3  DOI: 10.1109/TCYB.2013.2256347  Published: March 2014  
  Abstract:Dictionaries are crucial in sparse coding-based algorithm for image superresolution. Sparse coding is a typical unsupervised learning method to study the relationship between the patches of high-and low-resolution images. However, most of the sparse coding methods for image superresolution fail to simultaneously consider the geometrical structure of the dictionary and the corresponding coefficients, which may result in noticeable superresolution reconstruction artifacts. In other words, when a low-resolution image and its corresponding high-resolution image are represented in their feature spaces, the two sets of dictionaries and the obtained coefficients have intrinsic links, which has not yet been well studied. Motivated by the development on nonlocal self-similarity and manifold learning, a novel sparse coding method is reported to preserve the geometrical structure of the dictionary and the sparse coefficients of the data. Moreover, the proposed method can preserve the incoherence of dictionary entries and provide the sparse coefficients and learned dictionary from a new perspective, which have both reconstruction and discrimination properties to enhance the learning performance. Furthermore, to utilize the model of the proposed method more effectively for single-image superresolution, this paper also proposes a novel dictionary-pair learning method, which is named as two-stage dictionary training. Extensive experiments are carried out on a large set of images comparing with other popular algorithms for the same purpose, and the results clearly demonstrate the effectiveness of the proposed sparse representation model and the corresponding dictionary learning algorithm. © 2014 IEEE.
  Accession Number: 20141017433607
• Record 430 of
  
  Title:Efficient optical Kerr gating property of fluorotellurite glass
  
  Author(s):Xiong, Yaobing(1); Yan, Lihe(1); Zhou, Zhiguang(2); Yi, Wenhui(1); Lin, Aoxiang(2); Si, Jinhai(1); Chen, Feng(1); Hou, Xun(1)
  Source: Optik  Volume: 125  Issue: 3  DOI: 10.1016/j.ijleo.2013.09.016  Published: 2014  
  Abstract:We investigated the ultrafast optical Kerr effect of the fluorotellurite glass (Ft glass), the nonlinear response time of which was measured to be less than 230 fs, while the nonlinear refractive index was estimated to be 9.62 × 10-16 cm2/W. Using optical Kerr gate (OKG) technique with Ft glass as Kerr medium, we obtained narrow-bandwidth and symmetric gated spectra from a supercontinuum (SC) generated by a femtosecond laser. Experimental results indicated that Ft glass was a good candidate for an OKG medium due to its fast response time, large nonlinearity, and high transparency. © 2013 Elsevier GmbH. All rights reserved.
  Accession Number: 20144500158382
• Record 431 of
  
  Title:A general approach for fabrication of nitrogen-doped graphene sheets and its application in supercapacitors
  
  Author(s):Wang, Dewei(1); Min, Yonggang(1); Yu, Youhai(1); Peng, Bo(1)
  Source: Journal of Colloid and Interface Science  Volume: 417  Issue:   DOI: 10.1016/j.jcis.2013.11.021  Published: March 1, 2014  
  Abstract:In this paper, a general and efficient strategy has been developed to produce nitrogen-doped graphene sheets (NGs) based on hard and soft acids and bases (HSAB) theory. Under hydrothermal conditions, any salt with amphiprotic character have a strong tendency to hydrolysis, it is possible to provide reducing agent and nitrogen source simultaneously. It is worth noting that, NGs can be prepared under hydrothermal conditions by using some common ammonium salts with hard acid-soft base pairs as nitrogen-doping agents. The morphology, structure and composition of the as-prepared NGs were studied in detail. The results demonstrated that large amount of nitrogen was incorporated into the nanocarbon frameworks at the same time as the graphene oxide (GO) sheets were reduced. The electrochemical behavior of the synthesized NGs as supercapacitor electrodes was evaluated in a symmetric two-electrode cell configuration with 1M H2SO4 as the electrolytes. It was found that the nitrogen groups making the as-prepared NGs exhibited remarkably enhanced electrochemical performance when used as electrode materials in supercapacitors. The supercapacitor based on the NGs exhibited a high specific capacitance of 242Fg-1 at a current density of 1Ag-1, and remains a relatively high capacitance even at a high current density. This work will put forward to understand and optimize heteroatom-doped graphene in energy storage systems. © 2013 Elsevier Inc.
  Accession Number: 20135217145337
• Record 432 of
  
  Title:Visible light driven photocatalytic reactor based on micro-structured polymer optical fiber preform
  
  Author(s):Li, Dong-Dong(1,2); She, Jiang-Bo(2); Wang, Chang-Shun(3); Peng, Bo(2)
  Source: Chinese Physics Letters  Volume: 31  Issue: 5  DOI: 10.1088/0256-307X/31/5/054206  Published: May 1, 2014  
  Abstract:A novel visible light driven photocatalytic reactor with 547 pieces of Ag/AgBr-film-modified capillaries is reported and it is derived from a microstructured polymer optical fiber (MPOF) preform. The MPOF preform not only plays the role of a light-transmitting media, but it is also a Ag/AgBr supporting and waste-water pipe to supply the photocatalytic degradation of dyes solute. The photocatalytic reactor has such a large surface area for Ag/AgBr loading, which is a visible light driven photocatalyst that photodegradation efficiency is enhanced. © 2014 Chinese Physical Society and IOP Publishing Ltd.
  Accession Number: 20220711659922