A ultrafast laser on a chip

Ultrafast lasers emit pulses lasting only a few hundred femtoseconds, or quadrillionths of a second. These flashes of light power applications from precision micromachining, eye surgery to optical frequency combs, the Nobel Prize-winning technology behind today's most precise optical atomic clocks. Yet despite more than two decades of effort, ultrafast lasers have largely remained bulky, expensive systems confined to optical tables.

Now a team led by Professor Tobias J. Kippenberg at EPFL has brought them onto a photonic chip. Publishing in Nature, the researchers report the first integrated ultrafast laser that rivals table-top femtosecond lasers, delivering 1.05 nanojoules in pulses as short as 147 femtoseconds.

Photonic chips guide and process light in microscopic channels called waveguides patterned on a wafer, much like how electronic microchips route electricity. Already widely used in telecommunications, photonic chips have miniaturized complex functions that once required much larger systems.

"For more than twenty years, a high-pulse-energy femtosecond laser on chip was widely regarded as a holy grail of integrated photonics,” says Kippenberg. "Our result shows that it is not only possible, but that it can be achieved with a surprisingly elegant architecture that the integrated-photonics community had overlooked."

An overlooked design

The EPFL team turned to a largely overlooked laser design known as the Mamyshev oscillator. In the laser cavity, a nonlinear waveguide sits between two optical filters that each let through a different slice of the color spectrum. When a strong pulse travels through the waveguide, it broadens into a wider range of colors, allowing part of it to pass through both filters and keep circulating. Weak light does not broaden enough and is rejected.

“This design is especially attractive because it does not require any component that is difficult to make on this erbium-doped silicon nitride chip,” explains Zheru Qiu, a co-leading author of the paper.

Another advantage, Qiu says, is that the Mamyshev oscillator is well suited to the tight confinement of light in photonic chips. When light is squeezed into tiny waveguides, it interacts strongly with itself. Too much of this nonlinear interaction can destabilize pulses in conventional designs, but the Mamyshev architecture is much less vulnerable to this problem.

Tiny laser, broad impact

On the chip, the 42-cm-long laser cavity can be folded into a space the size of a match head, far smaller than optical fiber-based lasers. Because these photonic chips can be manufactured at wafer scale, much like computer chips, more than 1000 laser cavities could be produced at once, opening a path toward much lower-cost ultrafast lasers for sensing, spectroscopy and metrology. "With kilowatt-level peak powers, the chip can drive demanding applications that have long depended on large, expensive laboratory lasers," says Qiu.

The result could lead to portable and affordable tools for detecting pollutants, revealing hidden defects and performing medical diagnostics, while opening a path toward compact optical atomic clocks for future communication and navigation.

Other contributors

EPFL Institute of Electrical and Microengineering

Helmholtz-Zentrum Dresden-Rossendorf (HZDR)

Reference

Zheru Qiu, Xuan Yang, Xurong Li, Jianqi Hu, Zhongshu Liu, Yichi Zhang, Xinru Ji, Jiale Sun, Grigory Lihachev, Zihan Li, Ulrich Kentsch, Tobias J. Kippenberg. High-pulse-energy integrated mode-locked laser using a Mamyshev oscillator. Nature 03 June 2026. DOI: 10.1038/s41586-026-10517-4