Terahertz Non-destructive Imaging System Applied on Composite Materials Testing

Terahertz wave has been widely studied in material detection and material structural evaluation, due to its unique characteristics compared with other electromagnetic waves. However, there are some limitations in terahertz imaging systems, such as the power of the terahertz source is generally low, and the complex optical system increases the energy loss. In this paper, to improve the stability of the system and reduce the loss of propagation energy, we propose a new terahertz non-destructive testing imaging system with the advantages of low cost and high propagation efficiency. The quantum cascade laser terahertz source is applied for high output power, and the optical system is optimally designed for high propagation efficiency. Then, an experiment was conducted, and the internal defects of the composite materials with double-sided polyethylene embedded with a metal indium grid were detected. The experimental results show that the proposed system has good detection ability for the internal metal defects of the composite material.