Researchers at the University of Texas at Dallas (UT Dallas) have designed an imager chip that could let cameras and mobile phones see through walls, wood, plastics, paper, and other objects. What makes this possible is the imager’s sensitivity to specific frequencies of electromagnetic waves.
Kenneth O, professor of electrical engineering at UT Dallas, and his team created a complimentary metallic-oxide semiconductor (CMOS) sensor similar to the type used in cameras and cell phones, except it works in the terahertz (THz) region of the electromagnetic spectrum. The terahertz frequencies, or T-waves as they’re called, have frequencies higher than microwaves but lower than infrared light. They have characteristics similar to both radio and light waves, which makes developing an imaging sensor for these frequencies difficult. Like radio waves, T-waves can penetrate certain materials. The degree of penetration depends on the material and the frequency of the terahertz light source. This lets researchers use the safe, nonionizing radiation of the terahertz wavelengths as a form of X-ray to see into and through objects.
Dr. O states, “We’ve created approaches that open a previously untapped portion of the electromagnetic spectrum for consumer use and life-saving medical applications. The terahertz range is full of unlimited potential that could benefit us all.”
The biggest challenge holding back terahertz use has been to develop an imaging sensor that doesn’t need a laboratory full of equipment to work. Current CMOS imagers are sensitive to visible light and form the “camera” element of many consumer devices including computers, smartphones, and game consoles. By using a new CMOS manufacturing technique, the UT group was able to create a CMOS imager sensitive to terahertz frequencies.
“CMOS is affordable and can be used to make lots of chips,” Dr. O said. “The combination of CMOS and terahertz means you could put this chip and receiver on the back of a cell phone, turning it into a device carried in your pocket that can see through objects.” Right now the focus is on limiting the range of the device to 4 in. or less to meet privacy concerns. But even that limited distance opens doors for new medical and health applications, industrial quality control, environmental monitoring, and high-speed communications.
“There are all kinds of things you could be able to do that we just haven’t yet thought about,” said Dr. O.