A team led by University of Illinois engineer Milton Feng has introduced an upgrade to transistor lasers that could boost computer processor speeds. (Photo by L. Brian Stauffer)Computer processing speed is limited by the basic physics of electricity: electrons traveling through the tiny wires and switches on a computer chip can only go so fast. But engineers at the University of Illinois Urbana-Champaign are looking to the transistor laser, a device that draws upon the speed of light, to allow for much faster processing of information within computer chips.

The transistor laser was discovered in 2004 through groundbreaking research at the university by a team headed by Milton Feng and Nick Holonyak Jr. The researchers discovered that light – previously thought to be a byproduct of transistor electronics – could be harnessed as an optical signal.

The principle of bistability, or two stable energy states existing within a single system, figures into a recently-published study led by Feng. Bistability is found in devices as simple as a light switch: the switch lever is designed to rest in the "on" or "off" position, but not between the two. Bistability within a transistor allows the device to form an optical-electric switch, which is the primary building block for the development of optical logic – the language needed for future optical computer processors to communicate.

“Building a transistor with electrical and optical bistability into a computer chip will significantly increase processing speeds,” said Feng. “The devices can communicate without the interference that occurs when limited to electron-only transistors."

As published in the Journal of Applied Physics, the researchers describe how adding an optical element creates a feedback loop to control the transmission of light, using a process called electron tunneling.

The new transistor could enable new devices and applications that have not impossible with traditional transistor technology.

“This is a single device that provides bistability for both electrical and optical functions with one switch,” Feng said. “It is totally new, and we are working hard to find more new applications for the device.”