2016

• Record 205 of
  
  Title:Growth of SiC nanowires by low pressure chemical vapor infiltration using different catalysts
  
  Author(s):Men, Jing(1); Liu, Yongsheng(1); Luo, Rong(1,2); Li, Weinan(2); Cheng, Laifei(1); Zhang, Litong(1)
  Source: Journal of the European Ceramic Society  Volume: 36  Issue: 15  DOI: 10.1016/j.jeurceramsoc.2016.04.004  Published: November 1, 2016  
  Abstract:SiC nanowires were synthesized by LPCVI using different catalysts, and the influences of input gas ratio (α) and catalysts were investigated. The average diameter firstly decreased and then increased with increasing α. Under Ni-based catalysis, SiC nanowires were long and thin, and increased with increasing concentration; under Fe-based catalysis, they were short and thick, and the influence of concentration could be neglected. The growth of SiC nanowires was controlled by vapor-liquid-solid (VLS) growth mechanism and the liquid-solid interface between nanowire and metal droplet was the growth plane. At same concentration, the diameter grown under Ni-based catalyst decreased with decreasing diameter of catalyst droplet, while under Fe-based catalyst, the diameters were not affected by catalyst droplet because of the high concentration. SiC nanowires were synthesized in 2D C/SiC composites and could enhance the mechanical properties effectively because of energy consuming from the fracture, pulled up and debond of SiC nanowires. © 2016 Elsevier Ltd
  Accession Number: 20161602262189
• Record 206 of
  
  Title:High power diode laser array development using completely indium free packaging technology with narrow spectrum
  
  Author(s):Hou, Dong(1); Wang, Jingwei(1); Gao, Lijun(1); Liang, Xuejie(1); Li, Xiaoning(1); Liu, Xingsheng(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 9730  Issue:   DOI: 10.1117/12.2213928  Published: June 30, 2016  
  Abstract:The high power diode lasers have been widely used in many fields. In this work, a sophisticated high power and high performance horizontal array of diode laser stacks have been developed and fabricated with high duty cycle using hard solder bonding technology. CTE-matched submount and Gold Tin (AuSn) hard solder are used for bonding the diode laser bar to achieve the performances of anti-thermal fatigue, higher reliability and longer lifetime. This array consists of 30 bars with the expected optical output peak power of 6000W. By means of numerical simulation and analytical results, the diode laser bars are aligned on suitable positions along the water cooled cooler in order to achieve the uniform wavelength with narrow spectrum and accurate central wavelength. The performance of the horizontal array, such as output power, spectrum, thermal resistance, life time, etc., is characterized and analyzed. © 2016 SPIE.
  Accession Number: 20163002634496
• Record 207 of
  
  Title:Waveguide fabrication in Yb3+ doped phosphate glass by 50 kHz repetition rate ultrafast laser
  
  Author(s):Liu, Xin(1,2); Bai, Jing(1); Zhao, Wei(1); Cheng, Guanghua(1)
  Source: Journal of Laser Micro Nanoengineering  Volume: 11  Issue: 3  DOI: 10.2961/jlmn.2016.03.0007  Published: 2016  
  Abstract:Waveguide (trace guiding type) inscription condition inside Yb3+ doped phosphate bulk glass was investigated under irradiating of 50 kHz repetition rate volume ultrafast lasers. We processed single trace and multi-core ones inside the bulk material, the captured near field mode pattern confirmed that both structures perform good guiding properties. Beam shaping technique was adopted during fabrication of the single trace in order to obtain a relative symmetric waveguide cross section. Waveguide lasing was achieved in the single line trace with a linear cavity configuration. The maximum laser output of 11 mW was obtained under mono-directional of 980 nm space light pumping, with ~2% corresponding slope efficiency. Guiding mode could be manipulated in the Expanded-core waveguide (ECW) by extra design freedom in the structure parameter, and ECW generally support larger effective mode area light transporting.
  Accession Number: 20164603012491
• Record 208 of
  
  Title:Compact Structure Hashing via Sparse and Similarity Preserving Embedding
  
  Author(s):Ye, Renzhen(1,2); Li, Xuelong(1)
  Source: IEEE Transactions on Cybernetics  Volume: 46  Issue: 3  DOI: 10.1109/TCYB.2015.2414299  Published: March 2016  
  Abstract:Over the past few years, fast approximate nearest neighbor (ANN) search is desirable or essential, e.g., in huge databases, and therefore many hashing-based ANN techniques have been presented to return the nearest neighbors of a given query from huge databases. Hashing-based ANN techniques have become popular due to its low memory cost and good computational complexity. Recently, most of hashing methods have realized the importance of the relationship of the data and exploited the different structure of data to improve retrieval performance. However, a limitation of the aforementioned methods is that the sparse reconstructive relationship of the data is neglected. In this case, few methods can find the discriminating power and own the local properties of the data for learning compact and effective hash codes. To take this crucial issue into account, this paper proposes a method named special structure-based hashing (SSBH). SSBH can preserve the underlying geometric information among the data, and exploit the prior information that there exists sparse reconstructive relationship of the data, for learning compact and effective hash codes. Upon extensive experimental results, SSBH is demonstrated to be more robust and more effective than state-of-the-art hashing methods. © 2015 IEEE.
  Accession Number: 20151700790687
• Record 209 of
  
  Title:Linearly, radially and azimuthally polarized femtosecond laser induced periodic surface structures on amorphous alloy
  
  Author(s):Li, Chen(1,2); Cheng, Guang-Hua(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 45  Issue: 8  DOI: 10.3788/gzxb20164508.0832001  Published: August 1, 2016  
  Abstract:The formation mechanism of Laser Induced Periodic Surface Structures (LIPSS) on the amorphous alloy Zr44Ti11Cu10Ni10Be25(at%) was investigated. In experiment, LIPSS on the amorphous alloy were produced by ultrashort laser pulses of 120 fs duration at 800 nm wavelength in three types of laser polarizations (linear, radial and azimuthal polarization). These LIPSS are comprised of Low-Spatial-Frequency LIPSS (LSFL) with the periodicity of 652~723 nm and macro-ripples with the periodicity of 1 304~1 765 nm. By Finite-Difference Time-Domain (FDTD) simulations, formation mechanism of macro-ripples can be explained by the interference between laser and modulated scattered electromagnetic wave induced by rough surface. In the condition of three types of laser polarizations (linear, radial and azimuthal polarization), FDTD simulation results agree with experimental results, proving the effectiveness of the macro-ripple formation mechanism. © 2016, Science Press. All right reserved.
  Accession Number: 20163402737302
• Record 210 of
  
  Title:Terahertz narrow-band filter based on rectangle photonic crystal
  
  Author(s):Lu, Yangang(1); Liu, Hongjun(1); Sun, Qibing(1); Huang, Nan(1); Wang, Zhaolu(1)
  Source: Journal of Modern Optics  Volume: 63  Issue: 3  DOI: 10.1080/09500340.2015.1073808  Published: February 4, 2016  
  Abstract:A terahertz filter with a channel drop cavity and a resonant reflection cavity in a two-dimensional photonic crystal is theoretically proposed. The channel drop cavity is used to trap photons at resonant frequency from the bus waveguide through coupling and emit them to a drop waveguide, while the resonant reflection cavity is used to realize wavelength selective reflection feedback in the bus waveguide. The transmission properties of the terahertz filter are simulated using the finite element method. It is found that a peak with the central frequency of 1.12 THz is existed in the transmission spectrum. The full width at half maximum of the passband is only 5 GHz, and the peak drop efficiency is up to 94.8%. © 2015 Taylor and Francis.
  Accession Number: 20153301176491
• Record 211 of
  
  Title:Multi-channel terahertz wavelength division demultiplexer with defects-coupled photonic crystal waveguide
  
  Author(s):Li, Shaopeng(1); Liu, Hongjun(1); Sun, Qibing(1); Huang, Nan(1)
  Source: Journal of Modern Optics  Volume: 63  Issue: 10  DOI: 10.1080/09500340.2015.1111457  Published: May 30, 2016  
  Abstract:Terahertz (THz) wavelength division demultiplexer based on a compact defects-coupled photonic crystal waveguide is proposed and demonstrated numerically. This device consists of an input waveguide that perpendicularly coupled with a series of defects cavities, each of which captures the resonance frequency from the input waveguide. Coupled-mode theory and finite element method are used to analyze the transmission properties of the structure. It is found that the transmission wavelength centered around 1 THz can be adjusted by changing the geometrical parameters of defects cavities, which equals to THz waves generated by optical methods such as difference frequency generation and optical rectification. Applications in this frequency range are urgently needed. Furthermore, the highest transmission efficiency of 0.94 can be achieved when a perfect wavelength-selective mirror is set in the output waveguide. © 2015 Taylor & Francis.
  Accession Number: 20154601557553
• Record 212 of
  
  Title:X-ray focusing optics and its application in X-ray communication system
  
  Author(s):Liu, Duo(1,2); Qiang, Peng-Fei(1); Li, Lin-Sen(1,2); Su, Tong(1); Sheng, Li-Zhi(1); Liu, Yong-An(1); Zhao, Bao-Sheng(1)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 65  Issue: 1  DOI: 10.7498/aps.65.010703  Published: January 5, 2016  
  Abstract:X-ray communication, which was first introduced by Keith Gendreau in 2007, is potential to compete with conventional communication methods, such as microware and laser communication, against space surroundings. Researchers have spent much time and effort on the mission making the initial idea into reality in recent years. Eventually, the X-ray communication demonstration system based on the grid-controlled X-ray source and single-photon detection technique can deliver both audio and video information in a 6-meter vacuum tunnel, and the bit-error-rate performance of the communication system is analyzed. But it is difficult to implement applications in industries. The point is to find a way to reduce the signal divergence geometrical attenuation and increase the distance of the communication which can be regarded as an important foundation of future deep-space X-ray communication applications. Therefore, it is urgent to study the X-ray communication system. By using a nested X-ray focusing optics as transmitting and receiving antennas of the communication system, the signal gain and the distance of X-ray communication can be greatly improved. Specifically, the nested X-ray focusing optics is similar to the Wolter type I telescope, which is widely used in the field of X-ray astronomy. The difference between them is that the Wolter type I optics is originally proposed based on a paraboloid mirror and a hyperboloid mirror, but X-ray focusing optics, the simplified Wolter type I optics, provides a single reflection by a conical approximation mirror, and it is more suitable for X-ray communication. In this paper, aiming at the future demand of X-ray communication, the optimization and analysis of the nested X-ray focusing optics are carried out, and the recurrence relations between the layers of mirrors are derived. Reasonable initial structural parameters and structure of the optics are designed. In addition, the theoretical effective collection area is calculated. Feasibility of using the X-ray focusing optics as transmitting and receiving antennas is analyzed, and the theory and structural design of the X-ray focusing optical are discussed. Signal divergence of transmitting antenna, effective area of receiving antenna, the focal spot size, and the signal gain properties are preliminary studied. The results show that the signal divergence is about 3 mrad, and the transmit gain is 23 dB; the effective area of receiving antenna is 5700 mm2 at 1.5 keV. Moreover, the focal spot diameter and the receive gain are 4.5 mm and 25 dB, respectively, and the total gain of this communication system can reach up to 48 dB. © 2016 Chinese Physical Society.
  Accession Number: 20160601889252
• Record 213 of
  
  Title:Accelerating incoherent hollow beams beyond the paraxial regime
  
  Author(s):Yang, Yanlong(1,2); Yan, Shaohui(1); Yu, Xianghua(1); Li, Manman(1,2); Yao, Baoli(1)
  Source: Optics Express  Volume: 24  Issue: 24  DOI: 10.1364/OE.24.027683  Published: November 28, 2016  
  Abstract:We propose a non-paraxial hollow accelerating beam, which is formed by incoherently superposing two well-designed coherent accelerating beams. Very interestingly, this incoherent superposition does not hamper the acceleration dynamics pertaining to the coherent ones, but results in a hollow intensity pattern in the cross section transverse to the circular accelerating trajectory. By a simple optimization, this hollow cross section pattern can be effectively extended to an angle close to 90°. The magnitude and the phase of the angular spectrum of the beam are given followed by a suggested scheme to generate the beam in practice. Such highly self-bending hollow beams may find applications in some fields such as optical manipulation. © 2016 Optical Society of America.
  Accession Number: 20164903093516
• Record 214 of
  
  Title:Optical trapping force and torque on spheroidal Rayleigh particles with arbitrary spatial orientations
  
  Author(s):Li, Manman(1,2); Yan, Shaohui(1); Yao, Baoli(1); Liang, Yansheng(1); Han, Guoxia(1); Zhang, Peng(1)
  Source: Journal of the Optical Society of America A: Optics and Image Science, and Vision  Volume: 33  Issue: 7  DOI: 10.1364/JOSAA.33.001341  Published: July 1, 2016  
  Abstract:We investigate the spatial orientation dependence of optical trapping forces and intrinsic torques exerted on spheroidal Rayleigh particles under irradiation of highly focused linearly and circularly polarized beams. It is revealed that the maximal trapping forces and torques strongly depend on the orientation of the spheroid, and the spheroidal particle is driven to be stably trapped at the beam focus with its major axis perpendicular to the optical axis. For a linearly polarized trapping beam, the optical torque is always perpendicular to the plane containing the major axis and the polarization direction of the incident beam. Therefore, the spheroid tends to rotate its major axis along with the polarization direction. However, for a circularly polarized trapping beam, the optical torque is always perpendicular to the plane containing the major axis and the optical axis. What is different from the linear polarization case is that the spheroid tends to have the major axis parallel to the projection of the major axis in the transverse plane. The optical torque in the circular polarization case is half of that in the linear polarization case. These optical trapping properties may be exploited in practical optical manipulation, especially for the nonspherical particle's trapping. © 2016 Optical Society of America.
  Accession Number: 20163102664178
• Record 215 of
  
  Title:Theoretical analysis of the electromagnetic field inside an anomalous-dispersion microresonator under synthetical pump
  
  Author(s):Xu, Xin(1,2); Hu, Xiaohong(1,2); Feng, Ye(1,2); Liu, Yuanshan(1); Zhang, Wei(1); Yang, Zhi(1); Zhao, Wei(1); Wang, Yishan(1)
  Source: Chinese Physics B  Volume: 25  Issue: 3  DOI: 10.1088/1674-1056/25/3/034208  Published: January 18, 2016  
  Abstract:We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato-Lefever equation. Unlike the traditional single continuous wave (CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted. The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field. © 2016 Chinese Physical Society and IOP Publishing Ltd.
  Accession Number: 20161202137778
• Record 216 of
  
  Title:Action recognition by joint learning
  
  Author(s):Yuan, Yuan(1); Qi, Lei(1); Lu, Xiaoqiang(1)
  Source: Image and Vision Computing  Volume: 55  Issue:   DOI: 10.1016/j.imavis.2016.04.001  Published: November 1, 2016  
  Abstract:Due to the promising applications including video surveillance, video annotation, and interaction gaming, human action recognition from videos has attracted much research interest. Although various works have been proposed for human action recognition, there still exist many challenges such as illumination condition, viewpoint, camera motion and cluttered background. Extracting discriminative representation is one of the main ways to handle these challenges. In this paper, we propose a novel action recognition method that simultaneously learns middle-level representation and classifier by jointly training a multinomial logistic regression (MLR) model and a discriminative dictionary. In the proposed method, sparse code of low-level representation, conducting as latent variables of MLR, can capture the structure of low-level feature and thus is more discriminate. Meanwhile, the training of dictionary and MLR model are integrated into one objective function for considering the information of categories. By optimizing this objective function, we can learn a discriminative dictionary modulated by MLR and a MLR model driven by sparse coding. The proposed method is evaluated on YouTube action dataset and HMDB51 dataset. Experimental results demonstrate that our method is comparable with mainstream methods. © 2016 Elsevier B.V.
  Accession Number: 20161902345640