Graphene Q-switched distributed feedback fiber lasers with narrow linewidth approaching the transform limit

Area of Science:

• Photonics and Laser Technology
• Materials Science (Graphene Applications)

Background:

• Distributed Feedback Bragg-grating Fiber Lasers (DFB-FLs) typically operate with kHz linewidths.
• Graphene's unique optical properties enable its use as a saturable absorber in laser cavities.

Purpose of the Study:

• To demonstrate a compact, all-in-line graphene-based DFB-FL (GDFB-FL).
• To investigate the generation of passively Q-switched pulses using graphene as a saturable absorber.
• To characterize the performance of the GDFB-FL in terms of linewidth, pulse duration, energy, and peak power.

Main Methods:

• Integration of a graphene saturable absorber into a DFB-FL cavity.
• Pumping the laser system with a 980 nm continuous-wave laser.
• Characterization of the output laser pulses, including linewidth, duration, energy, and peak power.

Main Results:

• Achieved a compact, all-in-line GDFB-FL with a linewidth of hundreds of kHz.
• Generated high-quality, passively Q-switched pulses with ~1 μs durations and ~10 nJ pulse energies.
• Observed a peak power approximately 600 times higher than the original DFB-FL.
• Pulses approached the transform limit, indicating high quality.

Conclusions:

• The developed GDFB-FL offers significant improvements in peak power and pulse quality.
• Optimization predicts MHz repetition rates and sub-100 ns pulse durations.
• The laser's narrow linewidth, long coherence length, tunability, stability, compactness, and robustness make it suitable for optical communications, metrology, and sensing.