Passive all-optical synchronization for polarization-maintaining mode-locked fiber lasers

Area of Science:

• Photonics
• Laser Physics
• Optical Engineering

Background:

• Mode-locked fiber lasers are crucial for various scientific applications.
• Achieving precise pulse synchronization between lasers is challenging, especially in robust, all-optical systems.
• Existing synchronization methods often require active feedback or are not fully optical.

Purpose of the Study:

• To propose and implement a passive, all-optical pulse synchronization technique for polarization-maintaining fiber lasers.
• To demonstrate robust and stable synchronization with high tolerance to cavity length mismatch.
• To enable long-term, stable operation without environmental stabilization.

Main Methods:

• A master-slave configuration using two independent Yb-doped and Er-doped mode-locked fiber lasers.
• Injection of master pulses into the slave laser cavity containing a nonlinear amplifying loop mirror.
• Utilizing the nonlinear amplifying loop mirror as a fast intensity modulator via nonreciprocal phase difference.

Main Results:

• Achieved robust and tight timing synchronization with a relative timing jitter of 26 fs (1-MHz bandwidth).
• Demonstrated high tolerance to cavity mismatch (800 µm).
• Confirmed long-term stable operation (>12 hours) without temperature stabilization or vibration isolation.

Conclusions:

• The developed passive, all-optical synchronization is a significant advancement for fiber laser systems.
• The system's robustness and stability open doors for applications requiring precise timing.
• Potential applications include pump-probe microscopy, two-color spectroscopy, and nonlinear frequency mixing.