Mode structure evolution of a modeless multiwavelength Raman fiber laser

Area of Science:

• Optics and Photonics
• Laser Physics
• Fiber Lasers

Background:

• Multiwavelength Raman fiber lasers (MRFLs) are crucial for various applications.
• The longitudinal mode structure of MRFLs directly influences the temporal properties of laser radiation.

Purpose of the Study:

• To demonstrate a modeless multiwavelength Raman fiber laser (MRFL).
• To investigate the role of a low-reflection Sagnac loop mirror (SLM) in achieving a modeless state and stable temporal intensity distribution.

Main Methods:

• Utilizing a low-reflection Sagnac loop mirror (SLM) within the laser cavity.
• Analyzing the evolution of longitudinal mode structure with varying pump power.

Main Results:

• At low pump power, the MRFL shows a discrete multi-longitudinal mode structure.
• Increasing pump power causes mode broadening, overlap, and decoherence.
• The low-reflection SLM effectively promotes the transition to a modeless state.
• The modeless MRFL demonstrates a highly stable temporal intensity distribution.

Conclusions:

• A novel modeless MRFL design based on a low-reflection SLM is presented.
• The SLM facilitates the control of longitudinal mode structure, leading to enhanced temporal stability.
• This work offers a pathway to stable, modeless operation in multiwavelength fiber lasers.