On-Chip, Electronically Tunable Frequency Comb
March 19, 2019 | Harvard John A. Paulson School of Engineering and Applied SciencesEstimated reading time: 3 minutes
Lasers play a vital role in everything from modern communications and connectivity to bio-medicine and manufacturing. Many applications, however, require lasers that can emit multiple frequencies—colors of light—simultaneously, each precisely separated like the tooth on a comb.
Image Caption: A new integrated electro-optic frequency comb can be tuned using microwave signals, allowing the properties of the comb—including the bandwidth, the spacing between the teeth, the height of lines and which frequencies are on and off—to be controlled independently. It could be used for many applications including optical telecommunication. (Image courtesy of Second Bay Studios/Harvard SEAS)
Optical frequency combs are used for environmental monitoring to detect the presence of molecules, such as toxins; in astronomy for searching for exoplanets; in precision metrology and timing. However, they have remained bulky and expensive, which limited their applications. So, researchers have started to explore how to miniaturize these sources of light and integrate them onto a chip to address a wider range of applications, including telecommunications, microwave synthesis and optical ranging. But so far, on-chip frequency combs have struggled with efficiency, stability and controllability.
Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Stanford University have developed an integrated, on-chip frequency comb that is efficient, stable and highly controllable with microwaves.
“In optical communications, if you want to send more information through a small, fiber optic cable, you need to have different colors of light that can be controlled independently,” said Marko Loncar, the Tiantsai Lin Professor of Electrical Engineering at SEAS and one of the senior authors of the study. “That means you either need a hundred separate lasers or one frequency comb. We have developed a frequency comb that is an elegant, energy-efficient and integrated way to solve this problem.”
Loncar and his team developed the frequency comb using lithium niobite, a material well-known for its electro-optic properties, meaning it can efficiently convert electronic signals into optical signals. Thanks to the strong electro-optical properties of lithium niobite, the team’s frequency comb spans the entire telecommunications bandwidth and has dramatically improved tunability.
“Previous on-chip frequency combs gave us only one tuning knob,” said co-first author Mian Zhang, now CEO of HyperLight and formerly a postdoctoral research fellow at SEAS. “It’s a like a TV where the channel button and the volume button are the same. If you want to change the channel, you end up changing the volume too. Using the electro-optic effect of lithium niobate, we effectively separated these functionalities and now have independent control over them.”
This was accomplished using microwave signals, allowing the properties of the comb—including the bandwidth, the spacing between the teeth, the height of lines and which frequencies are on and off—to be tuned independently.
“Now, we can control the properties of the comb at will pretty simply with microwaves,” said Loncar. “It’s another important tool in the optical tool box.”
“These compact frequency combs are especially promising as light sources for optical communication in data centers,” said Joseph Kahn, Professor of Electrical Engineering at Stanford and the other senior author of the study. “In a data center—literally a warehouse-sized building containing thousands of computers—optical links form a network interconnecting all the computers so they can work together on massive computing tasks. A frequency comb, by providing many different colors of light, can enable many computers to be interconnected and exchange massive amounts of data, satisfying the future needs of data centers and cloud computing."
The Harvard Office of Technology Development has protected the intellectual property relating to this project. The research was also supported by OTD’s Physical Sciences & Engineering Accelerator, which provides translational funding for research projects that show potential for significant commercial impact.
This research was co-authored by Brandon Buscaino, Cheng Wang, Amirhassan Shams-Ansari, Christian Reimer and Rongrong Zhu. It was supported by the National Science Foundation, the Harvard University Office of Technology Development’s Physical Sciences and Engineering Accelerator, and Facebook, Inc.
Suggested Items
ASMC 2024 to Showcase AI, Smart Manufacturing and Sustainability to Advance Chip Industry Manufacturing Expertise
03/27/2024 | SEMIMore than 125 experts will offer insights into the latest semiconductor manufacturing strategies and methodologies as hundreds of industry stakeholders gather at the 35th annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC 2024), May 13-16 in Albany, New York.
IPC APEX EXPO 2024: LPKF—Debunking Depaneling Industry Perceptions
03/27/2024 | Nolan Johnson, I-Connect007In this audio interview, listen to Jake Benz discuss advances in laser depaneling at LPKF. Thanks to advances in laser technology, perceptions about laser depaneling are changing from a low-speed, specialized process to a high volume process suitable for production manufacturing. Benz elaborates on some of the development and engineering that went into creating their latest, most capable depaneling machines.
Seeking Employment: Meet Gary Turner
03/25/2024 | Barry Matties, I-Connect007Meet Gary Turner, a recent graduate from the University of Texas at Dallas with a bachelor’s degree in mechanical engineering and a master’s in material science and engineering. He is currently seeking employment in the industry. The following interview will allow you to learn about Gary and see if he might be a good candidate for a position you are looking to fill.
The Challenges, Opportunities, and Future Specialties of PCB Design
03/19/2024 | Stephen V. Chavez, Siemens EDAWhat were once specialties have become more generalized over time—PCB designers must learn about design automation, signal integrity (SI), electromagnetic compatibility (EMC), complex high-speed design, mechanical design, and manufacturability/producibility. Design engineers must learn about layout, simulation, and supply chains—and in their place new specialties have emerged, like multi-gigabit SerDes channel design, advanced manufacturing, IoT, and multi-physics system verification.
Siemens, NVIDIA Expand Collaboration on Generative AI for Immersive Real-time Visualization
03/19/2024 | PRNewswireSiemens announced that it will deepen its collaboration with NVIDIA to help build the industrial metaverse. Siemens is bringing immersive visualization powered by new NVIDIA Omniverse Cloud APIs to the Siemens Xcelerator platform, driving increased use of AI-driven digital twin technology.