Synchronized multi-wavelength soliton fiber laser via intracavity group delay modulation

Dong Mao,Heze Zhang,Zhiwen He,Zhipei Sun,Huaqiang Wang,Jianlin Zhao,Chao Zeng,Yueqing Du

doi:10.1038/s41467-021-26872-x

Dong Mao, Heze Zhang + Show 6 more

Open Access

https://doi.org/10.1038/s41467-021-26872-x

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Abstract

Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper. Frequency-resolved measurements fully retrieve the fine temporal structure of pulses, validating the direct generation of synchronized ultrafast lasers from two to five wavelengths with sub-pulse repetition-rate up to ~1.26 THz. Simulation results well reproduce and interpret the key experimental phenomena, and indicate that the saturable absorption effect automatically synchronize multi-wavelength solitons in despite of the small residual group delay difference. These results demonstrate an effective approach to create synchronized complex-structure solitons, and offer an effective platform to study the evolution dynamics of nonlinear wavepackets.

Highlights

Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses
For conventional multi-wavelength mode-locked lasers, the pulse velocities depend on the operating wavelengths due to the intracavity group delay dispersion (GDD)
When the GDD is negligible or the group delay difference is compensated, the pulses centered at different wavelength can be synchronized, generating a packet of ultrahigh-repetition-rate pulses (Fig. 1a)

Summary

Results

The fiber laser operates at a stable single-wavelength modelocked state before imparting group delay with the PPS, where conventional solitons are formed with the intrinsic balance between the anomalous group-velocity dispersion and self-phase modulation effect[33], as illustrated in Supplementary Note 1. After introducing a group delay difference of 3.5 ps (comparable with ~3.25 ps in the experiment) to compensate that of the cavity (red solid curve in Fig. 4a), a typical synchronized dual-wavelength mode-locking state is automatically established in the fiber laser with the assistance of the saturable absorber, despite the residual group delay difference of ~0.07 ps. It is indicated that the group delay compensation dominate the synchronization

20 Dispersion

Methods

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