Asymptotic theory of a large fiber-laser array passive phase locking

Area of Science:

• Optics and Photonics
• Laser Physics
• Nonlinear Optics

Background:

• Coherent laser beam combining offers a route to surpass single-mode fiber laser brightness limitations.
• Passive phase locking (PPL) simplifies systems by eliminating the need for external management.
• Fiber lasers exhibit significant optical path differences, posing challenges for PPL scalability.

Purpose of the Study:

• To investigate the impact of nonlinearity on beam-combining efficiency in two distinct fiber laser array architectures.
• To determine the ultimate limit for phase-locked laser-array size under PPL.
• To compare the performance of two globally coupled fiber-laser array configurations.

Main Methods:

• Development of a semi-analytical approach utilizing probability theory.
• Calculation of efficiency probability density as a function of system parameters.
• Analysis of two architectures: (I) amplifiers in a ring resonator with filtered feedback, and (II) lasers with external feedback.

Main Results:

• Nonlinearity positively influences beam-combining efficiency in both investigated fiber laser array architectures.
• Type II fiber laser arrays, featuring external feedback, exhibit enhanced characteristics compared to type I.
• The study provides insights into scaling limitations for PPL-based laser arrays.

Conclusions:

• Globally coupled fiber-laser arrays can achieve high combining efficiency through nonlinear effects.
• Type II arrays demonstrate superior scalability and performance for increasing array sizes.
• The findings contribute to understanding the fundamental limits and optimization strategies for high-brightness laser systems.