Performance Scaling of Polygonal Chirally-Coupled-Core (CCC) Fibers for Coherently Combined Fiber Laser Arrays

PASSCODE: CCCfiber

Coherently combined ultrashort-pulse fiber laser arrays promise to enable next-generation multi-kW power laser drivers of high energy particle and radiation sources, needed for transformative impacts in multiple areas such as material science, medicine, biology, industrial processing, and high energy frontier (lepton colliders). These laser arrays must use novel types of fibers, which produce diffraction-limited output beams from large cores for accessing high energies and powers, and are also compatible with monolithic integration for the compactness and robustness of the system. Chirally-Coupled-Core (CCC) fibers with helically rotating polygonal index-guiding cores enable new degrees of freedom in controlling mode interactions via optical-angular-momentum-assisted quasi-phase matching, and have properties that are well suited for coherently-combined fiber laser arrays.

This dissertation presents the latest advances in CCC fibers. First, a new theoretical framework based on core-shape Fourier series decomposition is developed to explain the operation principle of CCC fibers and explore their core size scalability. Second, experimental progress is reported in high energy and average power scaling of 85μm core Yb-CCC fiber amplifiers with single mode output. Third, numerical models are developed to analyze the average power and energy storage potential of CCC fiber amplifiers. Last, a novel conceptual fiber design is proposed based on helical non-Hermitian gain and refractive index modulations, that enable new regimes of mode-control in large cores, such as selective mode amplification and unidirectional energy flows. These contributions are important for realizing high-energy and high-power coherently combined fiber laser systems.

CHAIR: Professor Almantas Galvanauskas