太赫兹科学与技术进展-张希成
32页1、,X.-C. Zhang (张希成) Center for THz Research Rensselaer Polytechnic Institute, USA,Recent Progress for THz Science & Technology,THz Group at Rensselaer,International Symposium of Ultrafast Phenomena and Terahertz Radiation,NRC Report: Harnessing Light,“A particularly novel and unexpected application of femtosecond light pulses is the generation of terahertz radiation, or T-rays. T-rays in the wavelength range of 0.05 to 1 mm provide a new technology for imaging hidden items and some invisible mate
2、rials properties.” - 1998,Waves Nature: Diffraction,single hole,Diffraction from a Hole (f=1.8 mm),Waves Nature: Diffraction,double holes,Youngs Experiment,T-ray,a pair of slits,Frequency Dependent T-ray Youngs Interference,Diffraction from Youngs T-Ray Interference,T-射线 的一些重要特性,T-射线 具有较低光子能量 (4 meV 1 THz) ,不会在生物组织中产生有害的光致电离。 很多有机分子由于偶极子的旋转和震动跃迁, 在 GHz 到 THz 频段,都具有很强的吸收和色散;分子的这些光谱特征使得T-射线 鉴别成为可能。 相干T-射线 信号瞬时电场的强度和相位可以同时被测量; 这样我们就可以通过对T-射线 进行时域探测,获得THz 吸收光谱和色散光谱。 THz 时域光谱提供了非常高的信噪比,而且对黑体辐射 (热背景)不
3、敏感。,The Breadth of T-Ray Applications,collated from several leading journals in past 5 years,Research Highlights in Year 2002,Solid state THz laser (Italy and UK) High power THz source from Jefferson Lab (US) T-ray tomographic imaging (US) THz resonant structure for label-free DNA detection (Germany) T-ray for biological and chemical agents sensing and imaging (US) THz radiation from semiconductor under strong B field (Japan) Nonlinear THz wave spectroscopy (US) THz wave quantum optics and quant
4、um computing (US) THz wave for medical application (Europe and US),T-Ray Imaging and Tomography,Why T-ray imaging modality? Functional imaging! T-ray imaging with standard x-y scan Transmission and reflection mode Tomography T-ray computed tomography (CT) T-ray diffractive tomography (DT) Tomography with a binary lens and a broadband pulse,T-Ray Image of A Letter Contains Powders,Image a letter,It contains powders,T-射线用于对抗生物恐怖主义,Thurengiensis 杆状菌 孢子被放入信封中。 THz像中其吸收/ 散射清晰可见, 但是为了准确地辨别,需要对样品的THz 响
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