Integrated Mamyshev oscillator delivers nanojoule pulses on a chip

An integrated Mamyshev oscillator consisting of an erbium-ion-implanted silicon nitride waveguide and two waveguide Bragg gratings generates mode-locked pulses with nanojoule pulse energy.

Integrated mode-locked lasers have been extensively pursued over the past decades due to their compactness, wafer-scale manufacturability, and integration capability with other devices, but their pulse energies have remained stuck at the picojoule level—far too low to drive nonlinear processes such as supercontinuum generation. Now, Zheru Qiu and colleagues at Swiss Federal Institute of Technology Lausanne (EPFL) and other institutions demonstrated an integrated Mamyshev oscillator that breaks this barrier, producing nanojoule pulses directly from a photonic chip [1]. This is the first-time stable mode locking has been achieved on rare earth doped integrated waveguides.

The Mamyshev oscillator exploits self-phase modulation and offset spectral filtering to produce a nonlinear transfer function equivalent to a saturable absorber, thereby eliminating the need for a physical saturable absorber. This design tolerates large nonlinear phase shifts—a critical advantage in high-confinement integrated waveguides, where the effective nonlinearity (nonlinear coefficient) is three orders of magnitude stronger than in optical fibers. The reported laser cavity consists of a 42-cm Er:Si₃N₄ spiral waveguide sandwiched between two waveguide Bragg gratings with offset reflection bands. Self-seeded by temporary pump modulation, the oscillator produces a 175.5-MHz pulse train with ~1-nJ pulse energy from each output, two orders of magnitude higher than any previous integrated mode-locked laser. The pulses are predominantly linearly chirped and can be compressed to 147 fs. The laser also exhibits excellent coherence, with a 105-dB signal-to-noise ratio of the fundamental beat note, 59-fs integrated timing jitter and a 0.012-mHz Lorentzian linewidth of the repetition-rate beat note.

As application examples, the laser was used to directly drive a 1.5-octave-spanning supercontinuum in a separate Si₃N₄ waveguide, and powers a terahertz time-domain spectrometer (THz-TDS) achieving 5-THz bandwidth and 90-dB dynamic range. Non-contact thickness metrology and material identification were successfully demonstrated by the THz-TDS.

This work establishes a practical path toward chip-scale ultrafast lasers with performance approaching fiber-based systems, with implications for portable frequency combs, spectroscopy and terahertz imaging.

References

[1] Qiu , Z. , Yang , X. , Li , X. , Hu , J. , Liu , Z. , Zhang , Y. , Ji , X. , Sun , J. , Lihachev , G. , Li , Z. , Kentsch , U. , Kippenberg , T.J. : High-pulse-energy integrated mode-locked laser using a Mamyshev oscillator. Nature 654(8117), 57–63(2026)

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