The next frontier of integration and miniaturization in semiconductors will be in the field of photonics, substantially increasing functionality, reliability and efficiency. A research team at the University of Virginia’s School of Engineering has set out to prove that a complex photonic integrated circuit is achievable and commercially viable. They have joined a team led by Quintessent, which has earned a research grant from the Defense Advanced Research Projects Agency’s LUMOS program. Quintessent is a start-up company spun out of the University of California Santa Barbara to commercialize quantum dot-based lasers and photonic integrated circuits for optical connectivity.
Four faculty members in UVA’s Charles L. Brown Department of Electrical and Computer Engineering have a role in Quintessent’s team — associate professor Andreas Beling, assistant professor Steven M. Bowers, assistant professor Xu Yi, and Joe Campbell, Lucien Carr III Professor of electrical and computer engineering. The quartet combines expertise in photonics, and devices and circuits, two of the department’s research strengths. Commercial partners Morton Photonics, X-celeprint, and Tower Semiconductor mirror these strengths — each firm plays an integral role in this research project, officially named PATRONUS.
To meet DARPA’s expectations for high performance, the team will need to design an integrated circuit that produces gain. Whereas the transistor does this well for electronic integrated circuits, achieving gain in photonic integrated circuits has proven elusive.
“Gain is tricky in the optical domain,” Bowers said. The standard practice is to produce light through a laser that is coupled onto rather than embedded in the photonic integrated circuit. “If we can get the light source and the high-speed components on the same chip, we can create systems that are much more complex and have added functionality.”
Amplification is a related challenge. On the electronics side, a transistor can output more signal power than it takes in, drawing additional energy from the battery. Due to the specialized materials required for lasers and optical amplifiers, most photonic integrated circuit platforms lack the ability to increase optical power, limiting the total number of devices per chip to tens or hundreds of devices.