Design Employs Photonics to Overcome Physical and Technological Barriers

Physical and digital connectivity in urban neighborhoods is key to cities’ revival and quality of life. Small businesses and creative industries thrive on highly networked communities with immediate access to all the internet has to offer, on-demand and on-the-go. If only cities had a platform that could deliver extremely fast data and video downloads for a large number of smartphone users.

A research team in UVA’s Charles L. Brown Department of Electrical and Computer Engineering has a plan to turn this vision into a reality. Associate Professor Andreas Beling and Assistant Professors Xu Yi and Steven Bowers propose using light to make wireless millimeter wave communication possible. They have earned a four-year, $1.3 million National Science Foundation grant to address the need for large data capacity in future wireless communication systems, combining their expertise in integrated photonics, nonlinear optics and wideband integrated antennas.

“Our research focuses on high throughput, to send as much data as you would reasonably want, from the backbone of the internet to the users of mobile devices,” Bowers said. To fulfill this aim, the researchers need to overcome both physical and technological barriers.

The physical barrier is that the part of the electromagnetic spectrum devoted to wireless communications is finite. The solution is to design wireless networks that function at a higher frequency, to open additional spectrum that allows downloading more information at the same time and location.

Cellular networks operating at millimeter-wave frequencies will increase the required bandwidth of the base station—a radio receiver/transmitter that serves as the hub of a wireless network. Additionally, the base stations need to be placed closer together because wireless signals don’t travel far; the higher the frequency, the shorter its physical reach.

The technological barrier is that wireless communication systems built in traditional electronics tend to be bulky and power-hungry at these extremely high frequencies. This makes wide coverage difficult. Antenna remoting—to place the electronic equipment away from the antenna—is impossible over cable due to exorbitant loss in signal power.

Photonics—the science of light generation, detection, and manipulation—overcomes both barriers. “Photonics allows us to make very small, integrated systems on a chip. This is crucial to the growth and accessibility of wireless networks that operate at the millimeter-wave frequencies,” Beling said.

The team is exploring how to use light to generate and modulate information on the wireless signals, to produce very precise millimeter wave frequencies with very low noise. They envision a chip-sized system that can provide a vast array of wireless channels in the millimeter-wave spectrum—30 to 300 gigahertz—with terabit-per-second throughput. It promises faster, larger data downloads through a wireless network that works with the urban architecture. Instead of disrupting neighborhoods by building more cell towers, the network could run on miniaturized base stations placed discretely on light poles, for example. 

A diverse set of capabilities including photonics, electronics, and heterogeneous integration is required to design such a system. Beling is an expert in active photonic device development including ultra-high speed photodiodes and their heterogeneous integration, to deliver photodetectors with very high bandwidth. Yi is an expert in integrated nonlinear optics and microcombs that efficiently convert photons from single to multiple wavelengths and has designed an optical microresonator that generates very stable signals. Bowers is an expert in millimeter-wave and sub-terahertz integrated circuits and systems as well as integrated antennas. He is also well versed in protocols to test and validate the performance of integrated systems.

“By pooling our areas of expertise, we can tightly co-design multiple technologies across length scales to enable the next generation of integrated wireless communication systems,” Beling said. “We envision a hybrid technology with greater performance, functionality and applications than a single process could achieve, without driving up the cost.”

The National Science Foundation’s Division of Electrical, Communications and Cyber Systems awarded the grant under its ASCENT program, Addressing Systems Challenges through Engineering Teams. The UVA team’s project, ASCENT: Photonically Driven mm-Wave Communication Platform, aligns with the program’s mission to produce fundamental research leading to disruptive technologies and significant improvements in the environment, health, quality of life and national prosperity.