2011
2011
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Record 277 of
Title:Rapid data acquisition in terahertz imaging
Author(s):Xue, Bing(1); Fan, Wenhui(1); Liang, Yuqing(1)Source: Chinese Optics Letters Volume: 9 Issue: SUPPL. 1 DOI: 10.3788/COL201109.S10501 Published: June 2011Abstract:A new data-acquisition method based on the less movement of the time-delay stage is designed. The method can clearly reduce the time used in the entire imaging process in terahertz pulse imaging. According to the experimental result, the quality of imaging remains the same as the normal method or even better. The applicability and limitation of the method are also discussed. ? 2011 Chinese Optics Letters.Accession Number: 20113214224383 -
Record 278 of
Title:Laser beam smoothing based on spherical circular grating
Author(s):Zhao, Xin(1); Xie, Yongjun(1)Source: Journal of Optoelectronics and Advanced Materials Volume: 13 Issue: 7 DOI: Published: July 2011Abstract:We propose a new method of beam smoothing based on spherical circular grating to reduce the perturbation in near field and focal plane. Our numerical simulation demonstrates that the smoothing effect using circular grating is better than that of 2D-SSD. The new method has potential application in inertial confinement fusion (ICF).Accession Number: 20203409072914 -
Record 279 of
Title:Thermal reaction of high power semiconductor laser with voids in solder layer
Author(s):Ding, Xiaochen(1); Zhang, Pu(2); Xiong, Lingling(2); Ou, Xiang(1); Li, Xiaoning(2); Xu, Zhongfeng(1); Wang, Jingwei(3); Liu, Xingsheng(2,3)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 38 Issue: 9 DOI: 10.3788/CJL201138.0902006 Published: September 2011Abstract:With the improvement of power, efficiency, reliability, manufacturability, and cost of high power semiconductor laser, many new applications are being enabled. Most of the semiconductor laser bars are packaged with the indium solder. However, some small voids are created during the packaging process, which will be gradually enlarged by the electromigration and electrothermal migration of the indium solder. Voids may cause local overheating near the facets of the laser. Therefore it is necessary to study the thermal behavior of semiconductor laser bars with voids in the solder layer. The thermal behavior of a single-bar CS-packaged 40 W 808 nm semiconductor laser with voids in the solder layer is studied and the relationship between temperature and voids size is analysed. The distribution of voids is predicted according to the space spectrum of a 40 W 808 nm semiconductor laser bar and the simulation results. It is found that the simulation results agree well with the measurement of the scanning acoustic microscope (SAM) image of solder layer.Accession Number: 20114914584138 -
Record 280 of
Title:Interaction and motion of solitons in passively-mode-locked fiber lasers
Author(s):Liu, Xueming(1)Source: Physical Review A - Atomic, Molecular, and Optical Physics Volume: 84 Issue: 5 DOI: 10.1103/PhysRevA.84.053828 Published: November 14, 2011Abstract:Interaction and motion of multiple solitons in passively-mode-locked (PML) fiber lasers are investigated numerically. Three types of relative motions of two solitons are found in PML fiber lasers. The numerical results show that the relative motion of solitons attributes to the phase shift, which corresponds to the instantaneous frequency at pulse peak to be nonzero. Different from the classical dynamics of billiard balls, the interaction of solitons is similar to the Feynman diagram which is a pictorial way to represent the interaction of particles. After solitons interact with one another, their shapes do not change, but their phases shift and relative motions change. The theoretical results demonstrate that the separation of neighboring solitons in the laser cavity is about several hundred picoseconds to several nanoseconds. The theoretical predictions are in good agreement with the experimental results. ? 2011 American Physical Society.Accession Number: 20114714546951 -
Record 281 of
Title:Multiple responses of TPP-assisted near-perfect absorption in metal/Fibonacci quasiperiodic photonic crystal
Author(s):Gong, Yongkang(1); Liu, Xueming(1); Wang, Leiran(1); Lu, Hua(1); Wang, Guoxi(1)Source: Optics Express Volume: 19 Issue: 10 DOI: 10.1364/OE.19.009759 Published: May 9, 2011Abstract:Absorption properties in one-dimensional quasiperiodic photonic crystal composed of a thin metallic layer and dielectric Fibonacci multilayers are investigated. It is found that a large number of photonic stopbands can occur at the dielectric Fibonacci multilayers. Tamm plasmon polaritons (TPPs) with the frequencies locating at each photonic stopband are excited at the interface between the metallic layer and the dielectric layer, leading to almost perfect absorption for the energy of incident wave. By adjusting the length of dielectric layer with higher refractive-index or the Fibonacci order, the number of absorption peaks can be tuned effectively and enlarged significantly. ? 2011 Optical Society of America.Accession Number: 20112013982352 -
Record 282 of
Title:Dual-wavelength step-like pulses in an ultra-large negative-dispersion fiber laser
Author(s):Mao, Dong(1); Liu, Xueming(1); Wang, Leiran(1); Lu, Hua(1); Duan, Lina(1)Source: Optics Express Volume: 19 Issue: 5 DOI: 10.1364/OE.19.003996 Published: February 28, 2011Abstract:We report on experimental observation of dual-wavelength step-like pulses delivered from an erbium-doped fiber laser operating in ultra-large negative-dispersion regime. The step-like pulses consist of two rectangular pulses with different energies, durations as well as optical spectra, and are distinct from the conventional multi-solitons or bound-state solitons in that each pulse holds the same property. We find the weaker (or stronger) rectangular pulse in step-like pulses is more sensitive to the backward (or forward) pump while is less sensitive to the forward (or backward) pump. Our results demonstrate that the dual-wavelength operation results from the combination of fiber dispersion, fiber birefringence, as well as cavity filtering effect, and the intensity difference between rectangular pulses can be attributed to different gain characteristics of the forward and backward pump. ? 2011 Optical Society of America.Accession Number: 20111013714593 -
Record 283 of
Title:Low-frequency vibrational modes of benzoic acid investigated by terahertz time-domain spectroscopy and theoretical simulations
Author(s):Yan, Hui(1); Fan, Wen-Hui(1); Zheng, Zhuan-Ping(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8195 Issue: DOI: 10.1117/12.900322 Published: 2011Abstract:In this paper, the low-frequency vibrational modes of crystalline benzoic acid (BA) have been investigated by terahertz time-domain spectroscopy (THz-TDS) and theoretical simulations based on the linearity combination of atomic orbital within the Density Functional Theory (DFT) as well as ab initio molecular orbital method at second-order M?ller-Plesset Perturbation Theory (MP2) level for single molecule and dimer. Experimentally, a series of prominent absorption features of pure benzoic acid relevant to intra- and inter-molecular vibrational modes have been obtained below 4 THz at room temperature. For the theoretical simulations, geometry-optimization results of bond lengths and dihedral angles in both BA monomer and dimer are very close to experimental neutron diffraction measurements. Furthermore, the simulation results demonstrate absorption profile centered at 1.89 THz contains low-frequency modes of Ph-COOH twisting due to intramolecular motion and cogwheel owing to intermolecular motion. All the intra- and inter-molecular vibrational modes measured have also been assigned. ? 2011 SPIE.Accession Number: 20113614296191 -
Record 284 of
Title:Induced transparency in nanoscale plasmonic resonator systems
Author(s):Lu, Hua(1); Liu, Xueming(1); Mao, Dong(1); Gong, Yongkang(1); Wang, Guoxi(1)Source: Optics Letters Volume: 36 Issue: 16 DOI: 10.1364/OL.36.003233 Published: August 15, 2011Abstract:An optical effect analogous to electromagnetically induced transparency (EIT) is observed in nanoscale plasmonic resonator systems. The system consists of a slot cavity as well as plasmonic bus and resonant waveguides, where the phase-matching condition of the resonant waveguide is tunable for the generation of an obvious EIT-like coupled resonator-induced transparency effect. A dynamic theory is utilized to exactly analyze the influence of physical parameters on transmission characteristics. The transparency effect induced by coupled resonance may have potential applications for nanoscale optical switching, nanolaser, and slow-light devices in highly integrated optical circuits. ? 2011 Optical Society of America.Accession Number: 20113414251230 -
Record 285 of
Title:Analysis of nanoplasmonic wavelength demultiplexing based on metal-insulator-metal waveguides
Author(s):Lu, Hua(1); Liu, Xueming(1); Gong, Yongkang(1); Mao, Dong(1); Wang, Guoxi(1)Source: Journal of the Optical Society of America B: Optical Physics Volume: 28 Issue: 7 DOI: 10.1364/JOSAB.28.001616 Published: July 1, 2011Abstract:Nanoplasmonic wavelength demultiplexing (WDM) structures based on metal-insulator-metal waveguides are designed and investigated numerically. The WDM structures possess a series of resonator-based channel drop filters near a bus waveguide. The demultiplexing wavelength of each channel can be tuned by adjusting the geometrical parameters and refractive index of the resonator. The numerical results based on the finite-difference time-domain method can be accurately explained by the resonant theory. Meanwhile, the transmission characteristics of the drop waveguide are influenced by the coupling distance between the resonator and drop/bus waveguides, which can be exactly analyzed by the temporal coupled-mode theory. Additionally, it is found that the drop efficiencies can be improved by a factor of more than 1.8 when a reflection feedback is introduced in the bus waveguide. ? 2011 Optical Society of America.Accession Number: 20112814130573 -
Record 286 of
Title:Unidirectional manipulation of surface plasmon polariton by dual-nanocavity in a T-shaped waveguide
Author(s):Gong, Yongkang(1); Liu, Xueming(1); Wang, Leiran(1); Zhang, Yani(1)Source: Optics Communications Volume: 284 Issue: 3 DOI: 10.1016/j.optcom.2010.09.074 Published: February 1, 2011Abstract:A structure of two dimensional T-shaped metal-insulator-metal waveguide with dual-nanocavity is proposed. The two nanocavities located at each side of the slit on the lower metallic surface, act as band rejection filters and are capable of stopping the surface plasmon polaritons (SPPs) at the resonant wavelengths. The Fabry-Perot interferometry theory and the Finite-Difference- Time-Domain method are utilized to investigate the proposed waveguide. The numerical results demonstrate the realization of miniaturized photonic devices for effectively switching the SPPs propagation between the left and right waveguides in one direction. ? 2010 Elsevier B.V. All rights reserved.Accession Number: 20104813434063 -
Record 287 of
Title:Image enhancement techniques used for THz imaging
Author(s):Liang, Yuqing(1); Fan, Wenhui(1); Xue, Bing(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8195 Issue: DOI: 10.1117/12.900775 Published: 2011Abstract:Terahertz (THz) radiation has been widely applied in the areas of spectroscopy, sensing and imaging. With the advancement of THz technologies, THz imaging has been progressed significantly and has huge potential applications in medical diagnosis, environmental control, chemical and biological identification. In the past, people mainly focused on overcoming the obstacles in the hardware, such as the limitation of resolution, accuracy and speed in THz imaging system. In this paper, image enhancement techniques are employed to enhance the contrast and get the better profile of THz image. Our results clearly demonstrate that digital image processing techniques can suppress noise effectively, extract target edges robustly, and therefore improve the quality of THz image. ? 2011 SPIE.Accession Number: 20113614296242 -
Record 288 of
Title:Coexistence of unequal pulses in a normal dispersion fiber laser
Author(s):Mao, Dong(1); Liu, Xueming(1); Wang, Leiran(1); Lu, Hua(1); Duan, Lina(1)Source: Optics Express Volume: 19 Issue: 17 DOI: 10.1364/OE.19.016303 Published: August 15, 2011Abstract:We experimentally demonstrate unequal pulses delivered from an erbium-doped fiber (EDF) laser with net-normal dispersion. Two types of pulses with different durations, energies, and spectra coexist in the same ring cavity. The output spectrum exhibits a broadband base that corresponds to the main pulse and a small rectangular lump that corresponds to the additional satellite pulse. With the enhancement of pump power, the intensity of main pulse almost keeps unchanged while the satellite pulse nearly increases linearly. Based on experimental results, it is indicated that two different pulse shaping mechanisms coexist in laser cavity, where the nonlinear polarization rotation (NPR) and spectral filtering (SF) effect contribute to the formation of main pulse and satellite pulse, respectively. ? 2011 Optical Society of America.Accession Number: 20113414251890