Laser array of coherent beam combination system revisited: angular domain perspective and fractal-based optimization

TL;DR

This paper revisits the theory of coherent beam combination in laser arrays from an angular domain perspective, introducing fractal-based optimization to improve system performance and offering new insights into far-field interference patterns.

Contribution

It presents a novel angular domain theoretical model for laser array CBC systems and proposes a fractal-based configuration for enhanced beam combining performance.

Findings

Angular harmonic representation elucidates mainlobe and sidelobe formation.

Orbital angular momentum spectrum analysis provides insight into interference patterns.

Fractal-based array configuration improves beam combining efficiency.

Abstract

Coherent beam combination (CBC) of fiber lasers holds promise for achieving high brightness laser systems, which have given rise to widespread applications such as particle accelerator, space debris removal, and industrial fabrication. The emitting laser array of CBC systems offers intriguing features in terms of agile beam steering, flexible beam shaping, and high scalability for output power and array elements. However, the theoretical model of the laser array in CBC systems is less well explored beyond the routine angular-spectrum method, where methods for optimizing the laser array configuration are more limited. Here, we explore the theory for the laser array of CBC systems in the view of angular domain. The laser array is represented by the composition of angular harmonics, the orthogonal basis over the azimuthal plane, and we elucidate the formation of mainlobe and sidelobes of the far-field interference pattern by using the orbital angular momentum spectrum analysis and azimuthal decomposition. Based on our findings, a fractal-based laser array configuration is proposed to enhance the performance of the combining system. Our work offers a deeper insight into the theoretical study and application of laser beam combination and opens opportunities for the further optimization of CBC implementations.