Roadmap Unveiled for Engineering Light Combs

Harvard researchers develop new model for designing compact, programmable electro-optic microcombs on thin-film lithium niobate chips.

Mar. 17, 2026 at 1:24am

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Optical frequency combs are powerful laser sources used in precision measurement, telecommunications, and other applications. Engineers at Harvard's School of Engineering and Applied Sciences have pioneered shrinking these combs onto photonic chips to create "microcombs" that are smaller and more energy-efficient. New research led by Professor Marko Lončar describes a generalized model for designing highly programmable and compact electro-optic microcombs on thin-film lithium niobate, a material with strong electro-optic properties. This work could make electro-optic microcombs more practical and easier to design for diverse applications.

Why it matters

Optical frequency combs are foundational tools for precision measurement, found in applications ranging from optical clocks to exoplanet detection. Shrinking these powerful laser sources onto photonic chips as "microcombs" could enable next-generation telecommunications and other uses. This new research provides a roadmap for designing highly customizable and energy-efficient electro-optic microcombs, which could significantly advance the practical applications of these compact optical frequency comb generators.

The details

The research team, led by Professor Marko Lončar, engineered long, racetrack-shaped resonators out of thin-film lithium niobate with embedded electro-optic modulators. This allowed them to explore modulation depths that are difficult to achieve in bulkier systems. By systematically mapping the new comb behaviors and pulse patterns they observed, the team developed a detailed, quantitative model for describing resonant electro-optic microcombs. This enabled them to expand the operation of their microcombs to use multiple microwave signal inputs, generating a broadband frequency comb that covers a greater range of light spectra.

  • The research is published in the journal Nature Physics.

The players

Marko Lončar

The Tiantsai Lin Professor of Electrical Engineering and Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and the leader of the research team.

Yunxiang Song

A graduate student in Lončar's lab and the first author of the published paper.

Harvard University Center for Nanoscale Systems

A member of the National Nanotechnology Coordinated Infrastructure Network, which supported the device fabrication in this work through NSF award No. ECCS-2025158.

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What they’re saying

“Using this on-chip platform, we were able to dive deep into the high modulation depth regime of EO microcombs, and comprehensively explore the types of combs, and correspondingly, pulses, that can be supported.”

— Yunxiang Song, Graduate student

What’s next

The breakthrough in expanding the operation of electro-optic microcombs to use multiple microwave signal inputs could lead to microcombs that can reach larger ranges of unknown optical frequencies, useful for metrology and other applications.

The takeaway

This new research provides a detailed roadmap for designing highly customizable and energy-efficient electro-optic microcombs on thin-film lithium niobate chips, which could significantly advance the practical applications of these compact optical frequency comb generators in telecommunications, precision measurement, and other fields.