2013
2013
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Record 289 of
Title:De-noising and enhancement for terahertz imaging
Author(s):Xu, Limin(1,2); Fan, Wenhui(1); Liu, Jia(1,2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 42 Issue: 10 DOI: Published: 2013Abstract:Terahertz waves can be used as a tool of non-destruction detection and imaging for certain kinds of materials because of unique characteristics. Improvement of imaging quality is of great significance to the application of terahertz imaging system. Digital image processing is a very important solution to the enhancement of imaging quality. Based on terahertz transmission imaging experiments, investigation was made on the use of image de-noising and enhancement techniques in order to suppress the influence of experimental noise of the imaging system and ultra-short laser power jitter. The methods included spatial domain filtering, Gaussian smoothing, frequency -domain filtering and edge detection. Analysis on the choice of methods and the comparison of effects was also given. Results show that, through an integrated use of image de -noising and enhancement techniques, the definition and identifiability of terahertz images are improved enormously.Accession Number: 20135217144593 -
Record 290 of
Title:Positive-negative nonlocal lensless imaging based on statistical optics
Author(s):Yao, Yin-Ping(1,2); Wan, Ren-Gang(1); Xue, Yu-Lang(1,2); Zhang, Shi-Wei(1,2); Zhang, Tong-Yi(1)Source: Wuli Xuebao/Acta Physica Sinica Volume: 62 Issue: 15 DOI: 10.7498/aps.62.154201 Published: August 5, 2013Abstract:Based on correlated imaging with pseudo-thermal light, Wu and Meyers independently experimentally showed that both positive and negative images can be obtained by using a novel algorithm. With the theory of statistical optics, we construct the model of thermal light, and demonstrate the novel algorithm for image reconstruction. To deal with the data attained in the correlated imaging, we reorder the intensity recorded by the bucket detector according to the value of fluctuation. For a given fluctuation range with all the records above or below a specific value, we can obtain either positive or negative images by calculate the correlation between the selected records of the bucket detector and the reference detector. Nevertheless, without correlated calculations, positive or negative images can be also produced by directly averaging the corresponding records of the reference detector with positive or negative fluctuations. Meanwhile, the visibility of imaging is greatly enhanced. This correspondence imaging method further demonstrates the importance of intensity fluctuations in the nonlocal imaging with thermal light. We also experimentally show the images that obtained by the correlation method and the positive-negative correspondence imaging method, respectively. Our results indicate that this novel algorithm has a better visibility than that of the conventional correlated imaging. ? Chinese Physical Society.Accession Number: 20133616694039 -
Record 291 of
Title:Diode-pumped Yb:YAG thin disk laser with a novel multi-pass pump and cooling arrangement
Author(s):Song, Qiong Ge(1,2); Cheng, Guang Hua(1); Zhu, Jiang Feng(3)Source: Applied Mechanics and Materials Volume: 423-426 Issue: DOI: 10.4028/www.scientific.net/AMM.423-426.2074 Published: 2013Abstract:We demonstrate a Yb:YAG thin disk laser with multi-pass diode-pumped structure and direct water cooling device. In the pump system, four passes of the pump radiation are focused on the thin disk using a center-punched spherical lens. The thin disk serves as the window of a copper tank and is directly cooled with recycle water-contacted method. The thin disk laser has a low pump at the threshold of operation. We obtained 450 mW output power around 1030 nm in a simple F-P resonant cavity. ? (2013) Trans Tech Publications, Switzerland.Accession Number: 20134416915414 -
Record 292 of
Title:A space audio cummunication system based on X-ray
Author(s):Deng, Ning-Qin(1,2); Zhao, Bao-Sheng(1); Sheng, Li-Zhi(1); Yan, Qiu-Rong(1); Yang, Hao(1,2); Liu, Duo(1,2)Source: Wuli Xuebao/Acta Physica Sinica Volume: 62 Issue: 6 DOI: 10.7498/aps.62.060705 Published: March 20, 2013Abstract:In this paper, an X-ray communication program, which consists of a sender of grid controlled X-ray source and a receiver of X-ray single-photon detector based on micro-channel plate, is presented. With the detailed information about the signal modulation transmitter, the micro-channel-based X-ray single-photon detector as well as the signal receiving demodulator, a space audio communication system based on X-ray is built. The communication rate of more than 20 kbit/s is realized. According to the preliminary test result analyses of the X-ray space audio communication system test, the X-ray emission success rate restricts the communication speed by the influence of different X-ray intensities, signal shaping time and threshold settings respectively. Therefore, a scheme for further increasing X-ray communication performance is suggested. ? 2013 Chinese Physical Society.Accession Number: 20132016329276 -
Record 293 of
Title:Spatiotemporal shaping of terahertz pulses using conductive apertures of finite thickness
Author(s):Zou, Shengwu(1,2); Zhang, Tongyi(1)Source: Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams Volume: 25 Issue: 5 DOI: 10.3788/HPLPB20132505.1325 Published: May 2013Abstract:Terahertz (THz) pulses after spatiotemporal shaping have been widely applied to THz spectroscopy and imaging. We simulate the shaping effect of rectangular and circular apertures by employing the three-dimensional (3D) finite-difference-time-domain (FDTD) method. The simulation results show that we can realize effective shaping and filtering of THz pulses using rectangular and circular conductive apertures of finite thickness. When the long side of the rectangular aperture is perpendicular to the polarization direction of the incident wave, the rectangular aperture has a good influence on the shaping and filtering of THz pulses. However, when the long side of the rectangular aperture is parallel to the polarization direction of the incident wave, it almost has no obvious effect on the shaping and filtering of THz pulses. The circular aperture has more obvious effect on shaping of THz pulses than the rectangular aperture. Moreover, these simulation results can be interpreted qualitatively by the theory of planar waveguides.Accession Number: 20132016328399 -
Record 294 of
Title:Suppression of the fluctuation effect in terahertz imaging using homomorphic filtering
Author(s):Xu, Limin(1,2); Fan, Wenhui(1); Liu, Jia(1,2)Source: Chinese Optics Letters Volume: 11 Issue: 8 DOI: 10.3788/COL201311.081201 Published: August 2013Abstract:To suppress the fluctuation effect due to laser power instability and terahertz radiation fluctuation, a homomorphic filtering method is proposed to process the terahertz images obtained from a pulsed terahertz raster scanning imaging system. The physical model of homomorphic filtering for terahertz imaging is established. The mathematical expressions are given with the specific physical meaning in accordance with the imaging principle. To demonstrate the effectiveness of the method, a homomorphic filtering experiment based on two raw terahertz images selected from the literature using a continuous-wave (CW) terahertz source is also performed. The effect of the method is compared with those described in the literature, and the advantages of homomorphic filtering are discussed. The pulsed- and CW-terahertz image processing results both show that in addition to suppressing the fluctuation effect, the method can also enhance target imaging. ? 2013 Chinese Optics Letters.Accession Number: 20134917058257 -
Record 295 of
Title:Buried waveguide in neodymium-doped phosphate glass obtained by femtosecond laser writing using a double line approach
Author(s):Long, Xuewen(1,2); Bai, Jing(1,2); Liu, Xin(1,2); Zhao, Wei(1); Cheng, Guanghua(1)Source: Chinese Optics Letters Volume: 11 Issue: 10 DOI: 10.3788/COL201311.102301 Published: October 2013Abstract:We fabricate a buried channel waveguide in neodymium-doped phosphate glass using a double line approach by femtosecond laser writing. Raman spectra reveal an expansion of the glass network in the laser irradiated region. Given the stress-induced positive refractive index change, waveguiding between two separated tracks is demonstrated. The refractive index difference profile of the waveguide is reconstructed from the measured near-field mode. Propagation loss is measured by scattering technique. Microluminescence spectra reveal that the Nd3+ fluorescence property is not significantly affected by waveguide formation process, which indicates that the inscribed waveguide is a good candidate for active device. ? 2013 Chinese Optics Letters.Accession Number: 20135017073920 -
Record 296 of
Title:High-birefringence, low-loss porous fiber for single-mode terahertz-wave guidance
Author(s):Chen, Na-Na(1,2); Liang, Jian(1,2); Ren, Li-Yong(1)Source: Applied Optics Volume: 52 Issue: 21 DOI: 10.1364/AO.52.005297 Published: July 20, 2013Abstract:A new kind of polymer porous fiber with elliptical air-holes is designed for obtaining high birefringence in the terahertz (THz) frequency range in this paper. Using the finite element method, the properties of this kind of fiber are simulated in detail including the single-mode propagation condition, the birefringence, and the loss. Theoretical results indicate that the single-mode THz wave in the frequency range from 0.73 to 1.22 THz can be guided in the fiber; the birefringence can be enhanced by rotating the major axis of the elliptical air-hole and there exists an optimal rotating angle at 30°. At this optimal angle a birefringence as high as 0.0445 can be obtained in a wide frequency range. Low-loss THz guidance can be achieved owing to the effective reduction of the material absorption in such a porous fiber. This research is useful for polarization-maintaining THz-wave guidance. ? 2013 Optical Society of America.Accession Number: 20133116570590 -
Record 297 of
Title:Experimental study on high eff iciency of Ti: sapphire laser to single-mode fiber coupling
Author(s):Liu, Jia(1,2); Fan, Wenhui(1)Source: Chinese Optics Letters Volume: 11 Issue: 5 DOI: 10.3788/COL201311.050605 Published: May 2013Abstract:We experimentally investigate an optimum scheme of coupling a collimated light from a Ti: sapphire laser source into a standard single-mode fiber (SMF). By adjusting the effective numerical aperture (NA) of coupling lens and eliminating the chromatic aberration, a coupling efficiency of around 70% is finally obtained. This result is close to the maximum value predicted by theoretical simulation. It is well demonstrated that high coupling efficiency between Ti:sapphire laser and SMF can also be obtained by optimizing certain parameters of a coupling lens, without employing any special optical components, or the specific fiber with complex structure. ? 2013 Chinese Optics Letters.Accession Number: 20132616449039 -
Record 298 of
Title:Experimental study on mode matching for preparation of squeezed light at 1064 nm
Author(s):Feng, Fei(1,2); Zhang, Tongyi(1); Qu, Wenyan(1,2); Song, Jiazheng(1)Source: Optical Engineering Volume: 52 Issue: 8 DOI: 10.1117/1.OE.52.8.086102 Published: August 1, 2013Abstract:The effect of mode matching on the preparation of the squeezed light at 1064 nm with periodically poled KTiOPO4 (PPKTP) crystal is reported. We can derive the desired mode by improving the spatial mode matching into optical cavities, including the beam from the laser mode matched to the optical parametric amplifier cavity and mode cleaning cavity; also it is useful for the stability of the locking systems. By increasing the fringe visibility between the squeezed light and the local oscillator beam, a squeezing level of -8.75 dB or even higher could be observed, even with the same experimental parameters as described elsewhere. ? 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) ? 2013 SPIE.Accession Number: 20151200649080 -
Record 299 of
Title:Theoretical study on balanced homodyne detection technique in preparation of squeezed states of light
Author(s):Qu, Wen-Yan(1,2); Feng, Fei(1,2); Song, Jia-Zheng(1); Zhang, Tong-Yi(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8912 Issue: DOI: 10.1117/12.2034576 Published: 2013Abstract:We analyze the balanced homodyne detection technique in the detection of squeezed light, which is controlled by dither locking scheme. We discuss how the balanced homodyne detection efficiency influences the detected degree of squeezing. Also, fluctuation in the relative phase between the local beam and the squeezed light is discussed, since a little phase fluctuation would decrease the detected degree of squeezing greatly. Then, the dither locking technique is studied in detail, which is used to lock the relative phase between the local beam and the squeezed light. The simulation experiments and theoretically results show that the balanced homodyne detection technique and the dither locking scheme are efficient methods to get more accurate degree of squeezing in the preparation of the squeezed states of light. ? 2013 SPIE.Accession Number: 20141317521667 -
Record 300 of
Title:Synthesis of a terpolymer containing fluorene, side chain conjugated thiophene and benzothiadiazole and its applications in photovoltaic devices
Author(s):Liu, Hongli(1); Qu, Bo(2); Chen, Jian(1); Cong, Zhiyuan(1); An, Zhongwei(1); Gao, Chao(1,3); Xiao, Lixin(2); Chen, Zhijian(2); Gong, Qihuang(2)Source: Journal of Applied Polymer Science Volume: 128 Issue: 5 DOI: 10.1002/app.38528 Published: June 5, 2013Abstract:A terpolymer (POTVTh-8FO-DBT) containing fluorene, side chain conjugated thiophene and 4,7-dithieny-2,1,3-benzothiadiazole was synthesized by palladium-catalyzed Suzuki coupling method. The polymer is soluble in common organic solvents. The thermal, absorption, and electrochemical properties of the polymer were examined. Photovoltaic properties of POTVTh-8FO-DBT were studied by fabricating the polymer solar cells (PSCs) based on POTVTh-8FO-DBT as donor and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as acceptor. With the weight ratio of POTVTh-8FO-DBT: PC61BM of 1: 1 and the active layer thickness of 80 nm, the power conversion efficiency (PCE) of the device reached 0.47% with Voc = 0.61 V, Jsc = 1.61 mA/cm2, and filled factor (FF) = 0.49 under the illumination of AM 1.5, 100 mW/cm2. The results indicated that this polymer was promising donor candidates in the application of PSCs. ? 2012 Wiley Periodicals, Inc.Accession Number: 20131116122166