マルチモードレーザダイオードを用いたテラヘルツ検査技術の開発

概要

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The femtosecond laser (fs laser) is generally used in order to transmit and receive the terahertz (THz) wave. But the fs laser is very expensive. The cost of equipment is an important factor to adopt inspection equipment. Therefore, we developed the terahertz time domain spectroscopy (THz-TDS) using laser diode (LD) which cheap laser. The measured samples are concretes and cables. Concretes and cables are generally inspected by X-rays or ultrasonic waves, and those inspections are required to inspect the measuring object by non-destructive and non-contact. We measured about the sample from which the diameter of glass spheres differed, and the sample which mixed glass spheres with cement. We disassembled the cable and measured the material separately. In THz-TDS using fs laser and LD, we confirmed correlation between transmission and the diameter of glass spheres, and correlation between transmission and the mixture ratio of cement and glass spheres. Moreover, we confirmed that we recognized the form of the conductor in the cable by transmission of the THz wave through the material of the cable. We compared the measurement result of having used fs laser with the measurement result of having used LD, and we validated that the equipment using LD is suitable for the inspection equipment.