Researcher Develops Faster Terahertz Imaging for Medicine, Aerospace, Art

One day, terahertz cameras could scan an airplane wing made of fiber-reinforced composite material and detect damage caused by repeated stress. A terahertz camera could be used by doctors to look inside the body without the ionizing radiation risks associated with X-ray imaging. It could even detect skin cancer before any visual evidence appears. 

Junliang Dong, a U of A assistant professor of electrical engineering and computer science, received a prestigious NSF CAREER Award for $500,000 to develop the terahertz imaging technology for applications in healthcare, aerospace, and archaeology and art history. Dong is also developing high-speed terahertz cameras that could record rapid changes as short as one-billionth or one-quadrillionth of a second, such as material changing from one state to another or as light moves through a material. 

The CAREER Awards support early-career faculty with the "potential to serve as academic role models in research and education," according to the NSF. 

"This NSF CAREER Award demonstrates the quality of his research, and it is only the start of his professional achievements," said Jia Di, head of the Department of Electrical Engineering and Computer Science. 

A New Way to See 

The terahertz range is part of the electromagnetic spectrum between microwaves and infrared light. It used to be known as the "terahertz gap" because scientists had difficulty producing and detecting these waves. Devices that could emit terahertz waves were first developed in the 1970s, but generating and detecting the waves at room temperature did not become practical until the 1990s and 2000s. 

Like X-rays and microwaves, terahertz waves can see into some opaque objects. But unlike X-rays, terahertz waves are non-ionizing, so they do not have the same risk of damaging human DNA. Terahertz waves are shorter than microwaves, which enables higher resolution. 

To create terahertz waves, an ultrafast laser shines on a polymer lens. Today, that equipment is bulky. A terahertz imaging system could fill half a room. Dong hopes to reduce its size enough to sit on a table. 

"Then it can be portable. I can take it to a real application scenario," he said. 

Currently, technically mature terahertz cameras do not exist. To create an image, a sample must be scanned pixel by pixel. That process can work in labs and industrial applications, but it is too slow for medical use. 

"We cannot ask our patients to hold on under the machine and wait for 20 minutes to finish scanning," Dong said. 

Dong is working to combine the optical hardware with computational methods to overcome this limitation. Speeding up the imaging will also allow him to capture ultrafast phenomena. That could help scientists understand fundamental mechanisms in physics, chemistry and biology. 

Beyond the Surface 

Terahertz imaging has several unique characteristics compared with other imaging techniques. The waves are sensitive to water, and cancer cells contain higher water content than normal cells. That would let a terahertz camera detect skin cancer early, before it becomes visible, allowing patients to be treated before the cancer spreads. 

Terahertz waves are also well suited for examining multilayered structures. Strong and lightweight fiber-reinforced carbon composites used on aircraft and spaceships are made of layers. A terahertz camera could look inside the material for manufacturing defects or damage from fatigue that could lead to structural failure. 

During his doctoral work, Dong applied terahertz imaging to a 17th-century Italian painting. By uncovering each layer of paint on the canvas, he could understand the artist's style and how the work was created. 

"Terahertz can achieve something that other modalities cannot," he said.