,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 materials 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 quantum 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 响应进行全面的分析。,信封中的“炭疽热”病菌粉末成像,T-射线 透视衣物？,牛仔裤: Route 66 毛衣: Mercury 羽绒大衣: Bossini 裤子: Great Land 毛巾: 414 内衣: Puma 衬衫: Basic Edition,如果是鞋子会怎么样?,为了加强执法力度?,T-射线 收发器,当警察需要从屋外确知人质、恐怖分子和武器的详细位置和状况的时候，我们可否使用THz收发器来帮忙?,T-射线收发器,THz 收发器,目标,T-射线 波,飞行时间 T-射线成像,T-ray imaging is fast being recognized as a powerful diagnostic technique.,一块火鸡骨头的T-射线 CT,刊登了我们T-射线 CT 研究的杂志有: 医学设备和诊断工业，高级专业成像与辐射疗法，工业电视 (旧金山)，每日邮报，光电子杂志，诊疗世界，医学设备和诊断新闻， RT 成像，商业周刊。,火鸡骨头,Reconstructed Image,一个球状物体(f=36 mm)的T-射线 CT成像,Photo,Reconstructed Image,在 Laser Focus World上发表的一篇图文, 5 月, 2002,2-, 4-, and 8-Level T-Ray Fresnel Lenses,2-Level,4-Level,8-Level,S. Wang, et al, OL, 27, 1183 (2002).,Tomography with a T-Ray Binary Lens,simultaneously image 3 targets at different frequencies,z,z,6 cm,3 cm,4 cm,7 cm,sensor,1.57THz,1.24THz,0.75THz,Fresnel lens,THz wave,z,Laser Focus World August issue,Future Work for T-Ray Imaging,Problems need to be solved: 1 Imaging Time should be from hours to less than one minute, with a target time of a few seconds. 2 Imaging Area should be from 2 cm to 20 cm, with a target area of 40 cm. 3 Imaging Resolution should be from 3 mm to sub-mm, with a target resolution of 0.1 mm. 4 Imaging Distance should be from 20 cm to 2 meter, with a target distance of a few hundred meters.,Tomographic imaging system offers cross-sectional information within a target, provides functional imaging.,Prof. Ci-Ling Pans THz Lab (Clean-Room),THz Lab at Capital Normal University of Beijing,THz Lab at National Normal University of Taipei,A fiber laser as a source,THz wave sensing system,Hurdles, Challenges and Opportunities,High water absorption (H2O: 150 cm-1) Limited acquisition speed Lack of real time signal processing Reflection mode imaging Low spatial resolution (1 mm) Low signal to noise ratio (1000) Irregularity of the objects Scattering of materials (Mie scattering) Lack of signature database Cost (US$100k),THz Imaging Lab at Rensselaer,August, 2000 in Denmark International Terahertz Workshop,Nov. 2001 in Leeds, UK 1st International Conference on Biomedical Imaging & Sensing Applications with THz waves,Center for Terahertz Research ,July 3, 2002,现在全世界有95个以上的研究小组在进行与THz 有关的研究项目 物理 生物 化学 生物制药 材料科学 电子工程 美国: 主要研究力量 欧洲: Teravision， Tera-bridge Teraview Ltd. 日本: Tera-photonics 台湾: Tera-photonics China: 新的 NSFC THz 项目,US News and World Report,Next Rays? T-Ray!,Tech TV on Terahertz Imaging,