PORTLAND, Ore. – Massachusetts Institute of Technology (MIT) researchers have sandwiched high-mobility graphene sheets between two ferroelectric materials, resulting in terahertz (THz) frequency operation that can directly operate on optical signals.

MIT predicts that the new material stack will lead to memories that are 10-times denser than today and to electrical devices that can directly operate on optical signals.

“Our work opens up exciting new areas for transmitting and processing optical signals,” said post-doctoral researcher Dafei Jin in a press statement. Jin is working with professors Nicholas Fang and Jun Xu, along with doctoral candidates Anshuman Kumar Srivastava and former post-doc researcher Kin-Hung Fung (now at Hong Kong Polytechnic University).

The researchers were inspired by ferroelectric-gated memories and transistors, to which they added the graphene material to improve performance. As they characterized the resulting hybrid devices, they discovered that two-dimensional plasmons form in the graphene that strongly couple with the phonon-polaritons in the ferroelectric materials. As a result, the devices were able to operate at terahertz frequencies with very low power dissipation.

Terahertz optical memories boost density 10-times by sandwiching high-mobility graphene between two layers of ferroelectric materials.

The researchers went on to pattern the materials into compact domains, which acted as terahertz frequency plasmonic waveguides with negligible cross-talk, even when packed as closely as 20 nanometers. As a result, the researchers predict their new material stack will be able to realize plasmonic waveguides that operate at extremely low power by harnessing the ferroelectric memory effect.

The new material stack may also provide a new way of translating optical-to-electrical signals, and vice versa, leading to a predicted 10-times density gain for these types of devices.

Funding for the project was provided by the National Science Foundation and the Air Force Office of Scientific Research.