Sate-of-the-Art of Terahertz Science and Technology
Terahertz (THz) science and technology is now globally attracting increasing interest, because explorations in the THz frequency range have become to play an important role in a very diverse field of applications, such as materials, devices, and imaging s
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Sate-of-the-Art of Terahertz Science and Technology Masayoshi Tonouchi
8.1 Introduction Terahertz (THz) science and technology is a new research field. THz refers to the frequency gap between the infrared and microwaves, typically the frequency range from 100 GHz to 30 THz. In fact, studies in the THz range have long been conducted in fields such as astronomy and analytical science. However, recent innovations in THz technologies are leading to a wide variety of applications in the field of Information and communications technology (ICT); biology and medical sciences, THz nondestructive evaluation (THz-NDE); homeland security, quality control of food and agricultural products; global environmental monitoring, and ultrafast computing, among others [1–3]. Why is the THz science and technology so important? The reasons are that it provides a novel sensing technique for spectroscopy and imaging in the THz frequency range; secondary, innovative fundamentals are for massive information and communication technology in future generations; as third, one can expect new science; in addition, we need standard measure for application. As for the sensing, THz waves are characterized by their low photons energy close to biofluctuation level. Besides, the THz waves are harmless in comparison with X-ray beam. The THz waves have relatively high transmittance of the matters compared with optical beam, and have smaller resolution for the imaging compared with micrometer waves, which enable us to distinguish specific materials buried in different. One of the important research trends in the field of electronics is to develop ultra-high-speed devices operative at THz frequency range, following to logic circuits at a clock rate over 100 GHz and wireless communication technology with 10 Gbps bit rate being achieved. For electronic devices in next generation, one has also to know basic/dielectric properties of the materials at a THz frequency range for high speed device development. Another M. Tonouchi (B) Institute of Laser Engineering, Osaka University, 2-6 Yamada-Oka, Suita, Osaka 565-0871, Japan e-mail: [email protected] K. Shudo et al. (eds.), Frontiers in Optical Methods, Springer Series in Optical Sciences 180, DOI: 10.1007/978-3-642-40594-5_8, © Springer-Verlag Berlin Heidelberg 2014
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interest is to study ultrafast phenomena in physical matters. Femtosecond (fs) lasers have opened new research field to pursue transient response in those. Especially THz waves probes low energy dynamics, which gives essential information of many materials such as electron scattering in semiconductors, molecular vibrations in biomaterials, and so on. Such transient low energy dynamics is unexplored area of research. Realistic application requires standards of THz waves and regulation for Electro Magnetic Compatibility (EMC). Above frequencies around 300 GHz, the waves are not allocated for commercial use. We also need to discuss environmental and astronomical use of THz waves. From a viewpoint of above interests, scie
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