Advances in high-energy ns-pulse laser beam delivery through optical fibers

We demonstrated that multimode optical fibers with a large cladding-to-core ratio achieve nearly 100% energy coupling efficiency and exhibit a high energy throughput of 16 mJ at a laser pulse width of 2 ns and a wavelength of 1064 nm, even when bent to a radius of 0.15 m. In addition, we explore the application of these fibers for spatial beam division in distributed rocket engine ignition systems. The primary limiting factors are analyzed, supported by simulations of pulse intensity propagation and distribution along the fiber and the experiment. We also discuss the formation of hot spots within the fiber as a function of both the fiber and input beam parameters.