A new take on traditional gauges and imaging systems could more efficiently harness THz frequencies that have long eluded detectors. Researchers at the University of Michigan have created a transducer that makes light-to-sound conversion possible — the new device turns THz light (t-rays) into ultrasound waves, and then transmits them. A new detector turns THz light into ultrasound waves. Courtesy of University of Michigan. While such detectors are old hat, the new device is more sensitive, according to Jay Guo, lead researcher and a professor of electrical engineering, computer science, mechanical engineering and macromolecular science and engineering at UM. Just a few millimeters in size, the detector looks like a microring resonator. The transducer was created using a mixture of polydimethylsiloxane (PDMS) and carbon nanotubes. The nanotubes absorb the THz light when it reaches the transducer, turning it into heat. The heat is passed on to the PDMS, which then expands and creates an outgoing ultrasound wave at frequencies more than 1,000 times what human ears can detect. The new detector can provide THz imaging in real time, Guo said, noting that it has demonstrated a response speed of about 0.1 µs. It responds to the energy of individual THz light pulses, making it resistant to outside temperature variations. This makes the new transducer better suited for applications such as weapons and chemical detection as well as medical imaging and diagnosis. It could also help astronomers study planets in other solar systems. The work was funded by the National Science Foundation and the U.S. Air Force Office of Scientific Research. The research is published in Nature Photonics. For more information, visit www.umich.edu.