Ruonan Han seeks to push the limits of electronic circuits.
Ruonan Han’s research is driving up the speeds of microelectronic circuits to enable new applications in communications, sensing, and security.
Han, an associate professor who recently earned tenured in
The terahertz region of the electromagnetic spectrum, which lies between microwaves and infrared light, has largely eluded researchers because conventional electronic devices are too slow to manipulate terahertz waves.
“Traditionally, terahertz has been unexplored territory for researchers simply because, frequency-wise, it is too high for the electronics people and too low for the photonics people,” he says. “We have a lot of limitations in the materials and speeds of devices that can reach those frequencies, but once you get there, a lot of amazing things happen.”
For instance, terahertz frequency waves can move through solid surfaces and generate very precise, high-resolution images of what is inside, Han says.
Radio frequency (RF) waves can travel through surfaces, too — that’s the reason your Wi-Fi router can be in a different room than your computer. But terahertz waves are much smaller than radio waves, so the devices that transmit and receive them can be smaller, too.
Han’s team, along with his collaborator Anantha Chandrakasan, dean of the School of Engineering and the Vannevar Bush Professor of Electrical Engineering and Computer Science, recently demonstrated a terahertz frequency identification (TFID) tag that was barely 1 square millimeter in size.
“It doesn’t need to have any external antennas, so it is essentially just a piece of silicon that is super-cheap, super-small, and can still deliver the functions that a normal RFID tag can do. Because it is so small, you could now tag pretty much any product you want and track logistics information such as the history of manufacturing, etc. We couldn’t do this before, but now it becomes a possibility,” he says.
A simple radio inspired Han to pursue engineering.
As a child in Inner Mongolia, a province that stretches along China’s northern border, he pored over books filled with circuit schematics and do-it-yourself tips for making printed circuit boards. The primary school student then taught himself to build a radio.
“I couldn’t invest a lot into those electronic components or spend too much time tinkering with them, but that was where the seed was planted,” he says. “I didn’t know all the details of how it worked, but when I turned it on and saw all the components working together it was really amazing.”
Han studied microelectronics at Fudan University in Shanghai, focusing on semiconductor physics, circuit design, and microfabrication.
Rapid advances from Silicon Valley tech companies inspired Han to enroll in a U.S. graduate school. While earning his master’s degree at the