Hollow-Core Fiber: Breaking the Nonlinearity Limits of Silica Fiber in Long-Distance Green Laser Pulse Delivery

Hollow-core fiber (HCF), in which >99.99% of the light is guided in a central air (or vacuum) filled core, is a radically new fiber technology offering the potential to overcome the nonlinear limits associated with the delivery of high-brightness laser pulses over long distances in conventional solid-core fiber. Overcoming these limits is particularly challenging at visible wavelengths where the core sizes of single-mode fibers (SMFs) are reduced. In this work, the delivery of near-diffraction-limited, kilowatt-peak-power, sub-nanosecond laser pulses in the green wavelength range over hundred-meter scale lengths of a hollow-core anti-resonant fiber (HC-ARF) which offers broadband low-loss guidance in the visible is experimentally demonstrated. Substantially reduced nonlinearity-induced spectral broadening is observed relative to silica-core SMF. The simulation further confirms that the broadening observed (in the HC-ARF) is entirely due to the interaction of the light with the air in the core and thus can effectively be eliminated by evacuating the fiber. Moreover, access to lower-loss is noted, and visible guiding HC-ARFs (that are now becoming available) will improve the throughput efficiency and extend power delivery to kilometer distance scales. The results demonstrated here pave the way for future long-distance HCF pulse delivery applications, such as remote industrial e-mobility manufacturing.