2.2 kW Single-Mode Narrow-Linewidth Laser Delivery Through a Hollow-Core Fiber

Antiresonant hollow-core fibers (AR-HCFs) have opened up exciting possibilities for high-energy and high-power laser delivery, thanks to their exceptionally low nonlinearities and high damage thresholds. While these fiber designs offer great potential for handling kilowatt-class powers, it is crucial to understand their fundamental limitations by investigating their performance at multi-kW power levels. Until now, efforts to deliver a narrow-linewidth single-mode laser at multi-kW power levels through a hollow core fiber have been unsuccessful. Here, we demonstrate the successful delivery of a record 2.2 kW laser power with a spectral linewidth of 84 GHz, centered at 1080 nm, while maintaining over 95% efficiency. This was achieved using a 6.25 m long AR-HCF with low-loss properties. Furthermore, we show power delivery of 1.7 kW with a spectral linewidth as narrow as 38 GHz. Our results could lead to a new generation of fiber-based laser beam delivery systems with applications in precision machining, nonlinear science, and directed energy.