Dynamical, bidirectional model for coherent beam combining in passive fiber laser arrays

Area of Science:

• Optics and Photonics
• Laser Physics
• Fiber Optics

Background:

• Coherent beam combining in passive fiber laser arrays is crucial for high-power laser systems.
• Previous models did not account for transient gain dynamics or counterpropagating waves.
• Understanding these factors is essential for optimizing experimental conditions.

Purpose of the Study:

• To generalize existing models for coherent beam combining in fiber laser arrays.
• To incorporate transient gain dynamics and counterpropagating waves into the model.
• To analyze the impact of these factors and nonresonant nonlinearity on combining efficiency.

Main Methods:

• Generalization of a previously proposed model for coherent beam combining.
• Inclusion of transient gain dynamics and counterpropagating wave effects.
• Analysis of the influence of population relaxation, backward propagating waves, and nonresonant nonlinearity.

Main Results:

• Coherent beam combining is not significantly affected by population relaxation or backward propagating waves.
• These factors contribute to gain co-saturation.
• Nonresonant nonlinearity reduces coherent combining efficiency at higher power levels.
• The fiber laser array operates at frequencies with minimal overall losses.

Conclusions:

• The generalized model provides a more accurate representation of experimental conditions in fiber laser arrays.
• Transient gain and counterpropagating waves do not impede coherent beam combining.
• Nonresonant nonlinearity poses a limitation for high-power beam combining.
• The array's frequency selection is governed by minimizing total losses.