Insider Summary

• Rice University researchers’ investigation into optical technology in the “new terahertz gap” could lead to quantum materials that help quantum electronics operate closer to room temperature.
• The team used the strong interaction of strontium titanate to pave the way for this approach.
• The research was conducted at the Emerging Quantum and Ultrafast Materials Laboratory.
• Image courtesy of Zhu lab/Rice University.

PRESS RELEASE — Visible light is only a small part of electromagnetic spectrumand the manipulation of light waves at frequencies beyond human vision have made technologies such as cell phones and mobile phones possible CT scans.

Rice University researchers have plans to tap into previously unused portions of the spectrum.

“There is a stark gap in the middle and farinfrared lightapproximately 5-15 terahertz frequencies and wavelengths ranging from 20-60 micrometers, which exist no good commercial product compared to higher optical frequencies and lower radio frequencies,” said Rui Xua third-year doctoral student at Rice and lead author at an article published in Advanced Materials.

This research conducted in Emerging Quantum and Ultrafast Materials Laboratory from co-authors Han Yu ZhuWilliam Marsh Rice Chair and assistant professor of materials science and nanoengineering.

“Optical technology in this frequency region ⎯ is sometimes called the ‘new terahertz gap’ because it is much more difficult to access than other 0.3-30 terahertz ‘gaps’ ⎯ can be very useful for studying and developing quantum materials for quantum electronics closer to room temperature, as well as sensing functional groups in biomolecules for medical diagnosis,” said Zhu.

The challenge the researchers face is identifying the right materials to carry and process the light in the “new terahertz gap”. Such light strongly interacts with the atomic structure of most materials and is quickly absorbed by it. The Zhu Group has turned the strong interaction to its advantage strontium titanateA oxide from strontium And titanium.

“The atoms coupled with terahertz light so strongly that they formed a new particle called phonon-polaritonwhich is confined to the surface of the material and is not lost within it,” said Xu.

Unlike other materials which support phonon-polariton in higher frequencies and usually in a narrow range, strontium titanate acts over the entire 5-15 terahertz gap due to a property called quantum paraelectric. The atoms show a large size quantum fluctuations and vibrates randomly, thus capturing light effectively without being trapped by captured light, even at zero degrees Kelvin.

“We proved the concept of a phonon-polariton strontium titanate device in the 7-13 terahertz frequency range by designing and building an ultrafast field concentrator,” Xu said. “The device squeezes light pulses into a volume that is smaller than the wavelength of light and maintains a short duration. Thus, we achieve strong transients electric field almost a gigavolt per meter.”

The electric field is so strong that it can be used to change the structure of materials to create new electronic properties, or to create new properties. nonlinear optics the response of a trace amount of a particular molecule that can be detected by a common optical microscope. Zhu said the design and fabrication methodology developed by his group is applicable to many commercially available materials and can enable photonic devices in the 3-19 terahertz range.

The paper’s other co-authors are Xiaotong Chen, a postdoctoral researcher in materials science and nanoengineering; Elizabeth Blackert and Tong Lin, doctoral students in materials science and nanoengineering; Jiaming Luo, third year doctoral student in applied physics; Alyssa Moon, now at Texas A&M University and previously enrolled at Rice in Nanotechnology Research Experience for Undergraduate Programs; and Khalil JeBailey, a senior in materials science and nanoengineering at Rice.

This research is supported by the National Science Foundation.