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Terahertz wave generation from ring-Airy beam induced plasmas and remote detection by terahertz-radiation- enhanced-emission-of-fluorescence: a review

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Frontiers of Optoelectronics 2019年第2期12卷 117-147页

作者： Kang LIU Pingjie HUANG Xi-Cheng ZHANG The Institute of Optics University of Rochester Rochester NY14627USA State Key Laboratory of Industrial control Technology College of Control Science and Engineering Zhejiang University Hangzhou 310027China The Beijing Advanced Innovation Centerfor Imaging Technology Capital Normal University Beijing 100037China

With the increasing demands for remote spectroscopy in many fields ranging from homeland security to environmental monitoring, terahertz (THz) spectroscopy has drawn a significant amount of attention because of its capability to acquire chemical spectral signatures non-invasively. However, advanced THz remote sensing techniques are obstructed by quite a few factors, such as THz waves being strongly absorbed by water vapor in the ambient air, difficulty to generate intense broadband coherent THz source remotely, and hard to transmit THz waveform information remotely without losing the signal to noise ratio, etc. In this review, after introducing different THz air-photonics techniques to overcome the difficulties of THz remote sensing, we focus mainly on theoretical and experimental methods to improve THz generation and detection performance for the purpose of remote sensing through tailoring the generation and detection media, air-plasma. For the THz generation part, auto-focusing ring-Airy beam was introduced to enhance the THz wave generation yield from two-color laser induced air plasma. By artificially modulated exotic wave packets, it is exhibited that abruptly auto-focusing beam induced air-plasma can give an up to 5.3-time-enhanced THz wave pulse energy compared to normal Gaussian beam induced plasma under the same conditions. At the same time, a red shift on the THz emission spectrum is also observed. A simulation using an interference model to qualitatively describe these behaviors has be developed. For the THz detection part, the results of THz remote sensing at 30 m using THz-radiation-enhanced-emission- of-fluorescence (THz-REEF) technique are demonstrated, which greatly improved from the 10 m demonstration last reported. The THz-REEF technique in the counter-propagation geometry was explored, which is proved to be more practical for stand-off detections than co-propagation geometry. We found that in the counter- propagating geometry the maximum amplitude

关键词： ultrafast terahertz (THz) techniques THz air- photonics ring-Airy beams THz-radiation-enhanced-emis- sion-of-fluorescence (THz-REEF) of air-plasma in co- propagation geometry THz-REEF of air-plasma in coun-ter-propagation geometry

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判定函数单调性的一个新方法

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平顶山学院学报 1996年第S1期13卷 15-16页

作者：王如鸿平顶山一高

判定函数单调性的一个新方法王如鸿（市高压开关厂技工学校）众所周知，判定复合函数的单调性可用求导法及定义法，但求导法需高等数学的知识，用定义需很高的数学技巧，推导极复杂．本文将用初等方法──分解法解决复合函数单调性判定... 详细信息

判定函数单调性的一个新方法王如鸿（市高压开关厂技工学校）众所周知，判定复合函数的单调性可用求导法及定义法，但求导法需高等数学的知识，用定义需很高的数学技巧，推导极复杂．本文将用初等方法──分解法解决复合函数单调性判定问题．定理设函数ｙ＝ｆ（ｕ）在Ｕ内...

关键词： Nonlinear co- Semigroup exitence stability

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