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32Open InnovationTerahertz Technology Research Center The terahertz band refers to electromagnetic waves at frequencies ranging from roughly 100 GHz to 10 THz (3 mm to 30 µm in wavelength), which lies between so-called radio waves and light waves. Electromagnetic waves in this region have so far been diicult to generate and detect. As a result, the terahertz band remained unused and unexplored. However, due to trends such as the recent growth in demand for high capacity communication between wireless ter-minals, coupled with the increasing competition for microwave frequency resources that are already in use, there is a rapidly growing need for technology that can exploit new frequencies in the terahertz band. This situation has led to a rapid acceleration in the research and development of devices capable of operating in the terahertz band, as well as advances in basic measurement technology. Researchers are now starting to consider how this frequency band can be used for “active services” involving the generation of terahertz signals. To accelerate this trend, the Terahertz Technol-ogy Research Center has leveraged NICT’s diverse capabilities in R&D ranging from materials to systemization, and has driven forward with the research and development of cutting edge measurement technology to support the realization of terahertz wireless communication systems with a capacity of the order of 100 Gbit/s. In addition, by working with organizations such as the Terahertz Systems Consortium, we will promote joint studies with industry and academia and take part in discussions about standardization aimed at improving the environment so that the terahertz band can be used eectively (Fig.1).Core technology for terahertz radio test bedIn FY2007, we examined a method for generating optical frequency comb signals with low phase noise and high purity with the aim of generating terahertz signals with high spectral efficiency. Figure 2 shows an outline of an optoelectronic os-cillator incorporating an optical frequency comb oscillator built using this method. By using a highly pure microwave signal pro-duced by self-excitation of an optoelec-tronic resonator structure to directly gen-erate an optical frequency comb, we have Fig.1 : Overview of the Terahertz CenterResearch and Development