At the Frontier of the “Terahertz Gap”

By Lisa DeNike

Physics and Astronomy Professor N. Peter Armitage is quick to point out that many basic investigations aimed at understanding the fundamental nature of materials—such as the one he is conducting—have resulted in practical applications that have improved life in some way. Two good examples are the transistor radio and magnetic resonance imaging.

"These discoveries enabled technologies that transformed our world," says Armitage, a researcher in the Henry A. Rowland Department of Physics and Astronomy as well as the new Institute for Quantum Matter in the Krieger School of Arts and Sciences. "Even if those practical applications were not the original purpose of those studies, they are often the result."

It’s too early to say what practical applications might come of Armitage’s recent research project, a three-year study funded through a $2.2 million grant from the Gordon and Betty Moore Foundation. Armitage’s work involves the invention and development of new optical techniques and instruments to explore the characteristics of complex condensed matter such as superconductors, electronic gases, and quantum magnets.

"Specifically, we are developing low-energy optical spectroscopies in the so-called ‘terahertz gap,’ which is the experimentally difficult frequency region above that attainable with electronics but below that accessible with photonics," Armitage says, referring to the use of light to examine materials and their characteristics.

The terahertz frequency range is considered a frontier in optical and condensed matter research.

"It is hardly an exaggeration that most of what we know about physical systems, from the acoustics of a violin to the energy levels of atoms, comes from oscillating them at their natural frequencies," Armitage says, "and it’s staggering how many materials show natural frequency scales in the THz range. The community hasn’t been able to perform reliable measurements in this range until recently."

According to Armitage, these materials are tremendously important for both potential applications and fundamental science. "In the long run, the techniques we develop will be used as a basis for the development of even newer technologies, such as near-field THz microscopy and THz polarization sensors for nanoscale and biological systems," he says.