Wide tunable random fiber laser with sub-kHz narrow linewidth based on a disordered fiber Bragg grating array

Area of Science:

• Photonics and Optics
• Laser Physics
• Materials Science

Background:

• Random fiber lasers (RFLs) offer unique properties but often suffer from broad linewidths and high noise.
• Achieving wide tunability while maintaining narrow linewidth and low noise is a significant challenge in RFL development.

Purpose of the Study:

• To demonstrate a wide-tunable random fiber laser (RFL) with narrow linewidth and low noise.
• To investigate the role of a disordered fiber Bragg grating array (FBGA) in achieving these performance metrics.

Main Methods:

• Fabrication of a disordered FBGA using femtosecond laser direct writing with varied random distances and grating periods.
• Combining the FBGA for random feedback with an erbium-doped fiber (EDF) for gain.
• Characterization of the RFL's tunability, linewidth, noise, and power stability.

Main Results:

• Demonstrated a single-mode RFL tunable over 35.9 nm with a minimum linewidth of 470 Hz.
• FBGA-based RFL exhibited over 4 times lower power fluctuation compared to random fiber grating (RFG)-based RFL.
• Achieved relative intensity noise (RIN) below -110 dB/Hz beyond 100 kHz, a ~17 dB suppression compared to RFG-based RFL.

Conclusions:

• The disordered FBGA provides critical random feedback with narrow reflection peaks, enabling wide tunability, narrow linewidth, and low noise in RFLs.
• The developed RFL shows superior performance in terms of power stability and noise suppression.
• This wide-tunable RFL with sub-kHz linewidth is suitable for advanced telecommunications and sensing applications.