Advances in terahertz imaging

A terahertz image taken with the newly developed terahertz imaging set-up. The image size is 2 mm × 2 mm and the structure was hidden behind a silicon wafer.

TERAHERTZ imaging, which exists between the microwave and infrared wavelengths, has recently attracted attention for its ability to “see through” everyday objects. Among other things, it has been used to detect defects in space shuttle panels and uncover the material composition and substructure of paintings and murals. Current terahertz devices remain inherently slow, invasive, and better suited to non-biological materials. Besides, they are extremely expensive to manufacture. The British scientist Rayko Stantchev and associates have devised a new type of apparatus that could spur the development of cheaper, easier-to-manufacture terahertz imaging systems. Their technology relies on spatially controlling terahertz radiation in order to selectively illuminate parts of an object. The apparatus then measures the terahertz wavelengths transmitted through the selected parts of the object. The work was published in a recent issue of the journal Science Advances.

The scientists demonstrated the capability of the new technique using a circuit board hidden on the underside of a silicon wafer, showing that it was possible to see very tiny fissures in the circuit board. While they acknowledged the system used in this experiment would be difficult and expensive to manufacture commercially, the principles investigated here (photomodulation, near-field imaging and single pixel detection) have potential use in broader applications, including for other terahertz imaging systems.