Dual square-wave pulse passively mode-locked fiber laser

Area of Science:

• Optics and Photonics
• Fiber Laser Technology

Background:

• Passively mode-locked fiber lasers are crucial for generating ultrashort optical pulses.
• Square-wave pulses (SWPs) offer unique characteristics compared to traditional solitons.
• Nonlinear amplifying loop mirrors (NALMs) are effective components for mode-locking fiber lasers.

Purpose of the Study:

• To investigate the generation and characteristics of square-wave pulses (SWPs) in a passively mode-locked fiber laser.
• To explore the behavior of SWPs under varying pump power conditions.
• To achieve stable dual SWP operation and analyze the underlying physical mechanisms.

Main Methods:

• Utilized a passively mode-locked fiber laser incorporating a nonlinear amplifying loop mirror (NALM).
• Employed a cavity with a net dispersion of approximately 0.68 ps².
• Systematically varied pump power to observe SWP characteristics and dual-pulse generation.

Main Results:

• Successfully realized a passively mode-locked fiber laser generating SWPs.
• Observed expansion of SWP duration and near-constant peak power with increasing pump power.
• Achieved stable dual SWP operation with a pulse interval of 41 ns at 800 mW pump power, and pulse widths of 1.5 ns.
• Demonstrated linear rise in output power with pump power and a stable dual-pulse interval.

Conclusions:

• The study demonstrates the feasibility of generating stable SWPs and dual SWPs in a fiber laser.
• The observed SWP breaking and vector nature are attributed to nonlinear cavity dynamics.
• The findings provide insights into controlling and optimizing SWP generation for potential applications.