Short single-frequency self-pulsing Brillouin-Raman distributed feedback fiber laser

Area of Science:

• Fiber laser technology
• Nonlinear optics
• Laser physics

Background:

• Distributed feedback Raman fiber lasers are crucial for various optical applications.
• Stimulated Brillouin scattering (SBS) is a nonlinear optical phenomenon that can influence laser dynamics.
• Understanding and controlling laser pulsing is essential for applications requiring pulsed light sources.

Purpose of the Study:

• To investigate the self-pulsing behavior of a distributed feedback Raman fiber laser utilizing stimulated Brillouin scattering.
• To characterize the key parameters of the self-pulsed laser output, including repetition rate, pulse width, and peak power.
• To explore the correlation between Raman and Brillouin lasing processes and their impact on output characteristics.

Main Methods:

• Experimental setup of a 250 mm long distributed feedback Raman fiber laser.
• Utilizing a bespoke grating for lasing at 1119 nm.
• Investigating the laser output under varying conditions to observe self-pulsing.
• Employing a phenomenological model to analyze the Raman-Brillouin interaction and predict pulsing behavior.

Main Results:

• Demonstrated self-pulsing with repetition rates up to 7 MHz, pulse widths of 25 ns, and peak powers of 1.2 W.
• Achieved low lasing threshold (0.55 W), peak slope efficiency of 14%, and maximum average output of 0.25 W.
• Showed high correlation between pure Raman and Raman-pumped Brillouin lasing, resulting in single-frequency CW and near transform-limited pulsed operation.

Conclusions:

• The stimulated Brillouin scattering in a distributed feedback Raman fiber laser cavity naturally leads to self-pulsing behavior.
• The demonstrated laser design is adaptable to various wavelengths due to the relative nature of Raman and Brillouin gain regions.
• The findings provide insights into controlling and optimizing pulsed fiber laser outputs for potential applications.