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

Abstract 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.