Technological advances in Terahertz sources and sensors. Towards industrial transfer

Terahertz (THz) radiation is a promising candidate for industrial radiography and many NDT imaging applications, due to its many unique applications and interesting properties. In the electromagnetic spectrum, terahertz (THz) or submillimeter waves are located between infrared and microwaves. The terahertz (THz) band (or gap) extends from 100 GHz to 10 THz, corresponding to a wavelength of around 3 to 0.03 mm. This is very low-energy radiation (a few meV), which interacts with matter mainly through collective modes of vibration and molecular rotation. These rays have the property of being highly penetrating in dielectric or poorly conducting materials. This property makes it possible to obtain qualitative or quantitative information on materials, such as the presence of defects using imaging techniques, or their composition and dimensional control using spectroscopy. The advantages of terahertz technology are numerous: in-depth analysis of dielectric materials, sub-millimeter resolution, non-ionizing radiation (i.e. no danger to the operator), non-contact diagnosis (i.e. no alteration to the part or part surface), and a high capacity for detecting or measuring humidity.

However, the implementation of terahertz sources remains difficult due to the current limitations of silicon technology, and little research has been carried out. As a result, all these imaging systems are subject to incremental improvements that are linked to the dynamics of technological progress.

Thanks to laboratory research in the fields of ultra-high-frequency electronics and optoelectronics, the development of terahertz NDT systems is now possible, thanks in particular to improved technological building blocks and lower component manufacturing costs. Terahertz technology is applicable to a wide range of industrial sectors, including construction, transport and food processing.