Optica Foundation initiatives use photonics to address wireless and bandwidth limitations

By Gina Rullo 

The Optica Foundation released more detailed information on data communications research funded by the 2023 Optica Foundation Challenge. Work from researchers Ahmed Dorrah, Harvard John A. Paulson School of Engineering and Applied Sciences, United States, and Ying Xue, The Hong Kong University of Science and Technology, Hong Kong, will demonstrate unique responses to emerging data and bandwidth limitations.

Both research efforts are supported by a $100,000 grant from the Optica Foundation, and Dorrah and Xue will use these funds to advance their work.

"As the demand for high-speed data transfer dramatically increases, communication networks need to accommodate such advances in an energy-efficient, safe, and cost-effective manner," said Alan Willner, chair of the Challenge Selection Committee. "Drs. Dorrah and Xue are attacking such fundamental issues from differing and highly innovative perspectives, including mitigating the limitations associated with free-space optics and photonic integrated circuits."

Free Space Optics' potential

Free space optics have revealed promise for wireless communications because they are not hindered by physical connections, which is why the global free space optical (FSO) communications market is projected to reach $7 billion by 2030 with a compound annual growth rate (CAGR) of 30 percent.

In this executive summary, Dorrah outlines the research on structured light generation and sensing with metasurfaces for THz communications.

Terahertz (THz) radiation, which offers a larger bandwidth than current wireless standards with minimal external effects, can potentially reinforce FSO communications. Still, it has been hindered by the shortage of affordable cameras with the correct attributes to detect and read light signals.

In his work, Dorrah seeks answers to these stopgaps. By developing efficient schemes for sensing and generating THz beams, Dorrah believes he can leverage them for FSO communications.

Dorrah proposes applying metasurfaces, or flat optics structures designed to control light, to convert any 1D THz power detector array to a full 2D wavefront camera for capturing light signals. Essentially, the metasurface performs a set of operations on incoming light and projects the result onto a power detector, enabling the full reading of the THz beam profile with high resolution and over broadband.

"The THz range has the potential to be hugely successful in free space because it holds a wider bandwidth than microwaves and can enable a new generation of wireless communications, including 6G," Dorrah said. "On an academic scale, I hope to inspire others who work with structured light in the visible regime to try to develop elegant and affordable techniques for structuring light in the THz regime."

As a first step, Dorrah and his collaborators will work to design and model the appropriate metasurface. After about six months, he expects they will begin testing the metasurface "camera" and its efficiency in a proof of concept that will advance the FSO movement.  

Addressing silicon bottlenecks 

By 2025, global data creation is expected to climb to more than 180 zettabytes, and this growth is creating a communication bottleneck in silicon-based integrated circuits and systems. In addition, solutions that have emerged to respond to these issues have been impeded by fabrication, production and economic constraints. 

However, new work from Ying Xue plans to respond to these issues by introducing a novel integration method called lateral aspect ratio trapping (LART). With LART, Xue can focus on placing high-performance lasers exactly where they are needed in a photonic integrated circuit in an efficient, scalable and low-cost manner. In addition, she will enable the integration of electronics and photonics on the same chip, supporting the next generation of data communications and telecom.

"This is complex work, but it will address the issues of integrated photonics delivering on the promises of silicon photonics," Xue said. "We are looking at the complete functionality of a photonic integrated circuit on silicon, enabling large bandwidth, low cost, and the integration of electronics on the same chip. It will open new opportunities in research and industry."

Xue reports her first step is to design the template on the substrate, including the laser structure and fabrication process. In six months, she anticipates running experiments on an initial template, fine-tuning and determining designs for electrically pumped lasers in silicon photonics.

In this executive summary, Xue discusses Monolithic III-V active devices in-plane coupled with Si for integrated Si-photonics.

These research initiatives were made possible through the Optica Foundation Challenge grants. This challenge was designed to engage early-career professionals in out-of-the-box thinking and provide seed money to investigate environmental, health and information hypotheses. Each recipient received $100,000 to explore their ideas and take steps toward addressing critical global issues. Recipients have begun working on these projects and expect to report initial results in 2024.

Gina Rullo is a freelance writer.

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