テラヘルツ検出デバイス開発, 社会実装に向けたアプリケーション開発 ： 非破壊検査から結晶成長まで

Non-destructive and non-contact measurement technology using terahertz waves is expected to solve social issues such as aging infrastructure facilities and promotion of plastic container recycling. However, devices capable of high-sensitivity detection at room temperature, which is necessary for social implementation, have not yet been commercialized, and our laboratory is constructing a terahertz wave measurement system with the aim of social implementation of nondestructive and non-contact inspection using terahertz wave devices. Focusing on materials, they are also developing device materials to increase the sensitivity of detection devices. In a study on nondestructive inspection of concrete structures, it was confirmed that the location and degree of corrosion of reinforcing steel bars at a cover thickness of 10 mm inside the concrete can be estimated by terahertz reflection measurement. In a study on non-contact identification of plastics, it was confirmed that transmission measurements in the sub-terahertz band around 0.3 THz and in the terahertz band above 1 THz can not only identify the type of plastic, but also provide information on additives in transmission measurements from 1 THz to 6 THz. As a result of material development, organic triglycine sulfate (TGS) crystals used as infrared detector elements were grown from saturated solution by solvent evaporation method and irradiated with 40 GHz electromagnetic waves in the sub-terahertz band during crystal growth. As a result, the crystal growth rate was doubled compared to the non-irradiated condition, and the crystal structure was further changed. The new result that crystal growth is promoted by irradiation of electromagnetic waves in the sub-terahertz band is expected to lead to the proposal of a new crystal growth method using electromagnetic waves in the terahertz band. The non-contact, nondestructive measurements and material development data outlined in this paper provide the basis for future terahertz applications.