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991.
992.
P. Zhang S.-L. Zhang Y.-D. Tan Z.-Q. Zhao Z.-L. Zeng 《Applied physics. B, Lasers and optics》2012,106(3):657-662
The output responses of phase, amplitude, and polarization of light intensity of a He–Ne laser with the birefringent external cavity are presented. All phenomena are observed in two orthogonal directions related to the birefringent element’s orientation, and are studied under weak optical feedback. Experiments are carried out in five available detecting positions. It is found that laser intensities are modulated in the two orthogonal directions simultaneously, with a phase difference dominated by the phase retardation of the birefringence element. The modulation amplitudes are different in the two directions. A special polarization phenomenon is also observed and discussed. This research may provide a potential novel measuring principle for transparent birefringent materials. 相似文献
993.
We present a high power red-green-blue (RGB) laser light source based on cascaded quasi-phasematched wavelength conversions in a single stoichiometric lithium tantalate. The superiority of the experimental setup is: the facula of the incident beam is elliptical to increase interaction volume, and the cavity was an idler resonant configuration for realizing more efficient red and blue light output. An average power of 2 W of quasi-white-light was obtained by proper combination of the RGB three colors. The conversion efficiency for the power of the quasi-white-light over pump power reached 36%. This efficiency and powerful RGB laser light source has potential applications in laser-based projection display et al. 相似文献
994.
Yanlu Li Xian Zhao Weiliu Fan Honggang Sun Xiufeng Cheng 《Journal of nanoparticle research》2012,14(3):739
Semiconductor nanowires (NWs) exhibit tunable physical properties intrinsically related to their reduced dimensionality, quantum
size effect, morphology, and surface effects. By using density functional theory, we investigated the cross-sectional effect
on the electronic structure of Ag-doped ZnO NWs. Three types of NWs have been considered: hexagonal cross-sectional ZnO NWs
with zigzag and armchair surfaces, respectively, and triangular cross-sectional ZnO NW with zigzag surface. The results show
that Ag prefers to substitute surface Zn atoms and induces typical p-type characteristic for all kinds of NWs. Moreover, single
Ag doping could create a much shallower acceptor with a smaller hole effective mass in triangular ZnO NW than in the two hexagonal
ZnO NWs. With the increase of Ag concentration, the p-type doping becomes much less effective overall. However, double Ag
substituting in the zigzag surface of triangular ZnO NW improves the p-type properties, while substituting in the angle site
seriously damage the p-type conduction. As the triangular ZnO NWs and prismatic ZnO nanoparticles have been synthesized recently,
on the basis of our results, we expect that effective p-type could be achieved via incorporating Ag in triangular ZnO NWs
experimentally. 相似文献
995.
A compact achromatic quarter-wave retarder (QWR) operating in reflection mode is designed for using in terahertz region. It
is a composite device utilizing form birefringence and Fabry–Pérot (FP) interference. Under illumination of plane waves with
incidence angle of 45°, from 1.8 THz to 2.8 THz, the QWR achieved only ±2° variation around 90° phase retardation, enlarging
the working bandwidth of ordinary QWR greatly. An analytical model combining transmission-line (TL) theory with effective
medium theory (EMT) is presented and results agree well with the time-consuming numerical calculation. The 38 μm thick construction
is simple and easy for fabrication by the existing lithographic technique and a promising application in terahertz or other
frequency region is believed. 相似文献
996.
基于氙灯的非相干宽带腔增强吸收光谱系统, 并将其应用于痕量气体及气溶胶消光系数的测量. 该系统的探测灵敏度通过测量NO2在520—560 nm波长范围内的吸收得到验证, 最小可探测灵敏度为1.8× 10-7cm-1 (1σ, 0.12 s积分时间, 50次平均), 对应的NO2探测极限~33 nmol/mol. 结合标准气溶胶粒子发生系统, 测量了不同浓度的单分散硫酸铵气溶胶粒子在532 nm波长处的消光系数, 得到粒径为600 nm的硫酸铵气溶胶的消光截面为1.12× 10-8cm2, 与文献报道值1.167× 10-8cm2相一致, 验证了气溶胶测量的可行性和准确性. 相似文献
997.
Zhiqiang Nie Yanpeng Zhang Yan Zhao Chenzhi Yuan Changbiao Li Rui Tao Jinhai Si Chenli Gan 《Journal of Raman spectroscopy : JRS》2011,42(1):1-4
We demonstrate the enhancement and suppression of four‐wave mixing (FWM) in an electromagnetically induced transparency (EIT) window in Y‐type 85Rb atomic system. The generated two‐photon FWM signal can be selectively enhanced and suppressed via an EIT window. The EIT of probe as well as the enhancement and suppression of FWM signals can be modified by the sequential‐cascade double dressing. The influence of different probe polarization configurations is also studied. Different polarization states of the probe laser can select different transitions among Zeeman sublevels and different dressing strengths. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
998.
This paper is concerned with a stabilized finite element method
based on two local Gauss integrations for the two-dimensional
non-stationary conduction-convection equations by using the lowest
equal-order pairs of finite elements. This method only offsets the
discrete pressure space by the residual of the simple and symmetry
term at element level in order to circumvent the inf-sup condition.
The stability of the discrete scheme is derived under some
regularity assumptions. Optimal error estimates are obtained by
applying the standard Galerkin techniques. Finally, the numerical
illustrations agree completely with the theoretical expectations. 相似文献
999.
提出了一个闭环自调频混沌系统, 对压控振荡器输出进行采样, 采样值经非线性变换后产生控制压控振荡器下一时刻频率的调频码. 利用一维分岔图、二维分岔图和Lyapunov指数等研究了该系统的动力学行为; 并利用峰值均值功率比、频谱以及输出信号的相关函数等分析了该系统的应用特性. 研究表明, 该系统有复杂的动力行为, 展现分岔、多稳态和混沌等现象, 产生的信号具有低峰值均值功率比和宽频带的特性. 同时还讨论了利用调频码实现系统同步的可能性, 证实了简单的控制器可以实现自调频系统的同步. 在电路实验中, 压控振荡器用数字频率合成技术实现, 实验结果与理论分析一致.
关键词:
混沌
多稳态
峰值均值功率比
同步 相似文献
1000.