Modeling light propagation and amplification efficiency in highly multimode, Yb-doped fiber amplifiers

Area of Science:

• Optical Engineering
• Laser Physics
• Fiber Optics

Background:

• Multimode fibers offer potential for high-power fiber amplifiers, but their analysis is complex.
• Previous research primarily focused on single-mode or few-mode fibers, limiting understanding of multimode systems.
• Nonlinear effects and amplified spontaneous emission (ASE) are critical challenges in power scaling fiber amplifiers.

Purpose of the Study:

• To develop a tractable numerical model for simulating light propagation in narrowband, highly multimode fiber amplifiers.
• To incorporate key physical phenomena including gain saturation, spatial hole-burning, pump depletion, and mode-dependent gain.
• To analyze the impact of amplified spontaneous emission (ASE) and spontaneous emission on amplifier efficiency.

Main Methods:

• A frequency domain, field-based numerical model was developed.
• The model incorporates gain-induced mode coupling and amplified spontaneous emission (ASE) from first principles.
• The model was applied to Ytterbium (Yb)-doped fiber amplifiers.

Main Results:

• The model successfully simulates light propagation in highly multimode fiber amplifiers.
• Identified operational regimes where spontaneous emission or ASE limits amplifier efficiency.
• Demonstrated the influence of mode-dependent gain and pump depletion on amplifier performance.

Conclusions:

• The developed numerical model provides a valuable tool for studying multimode fiber amplifiers.
• It enables quantitative analysis of nonlinearity mitigation and power scaling strategies.
• This work facilitates the design and optimization of high-power multimode fiber amplifier systems.