Single-Frequency 336 W Spliceless All-Fiber Amplifier Based on a Chirally-Coupled-Core Fiber for the Next Generation of Gravitational Wave Detectors

Specialty fibers such as chirally-coupled-core fibers show a high potential for further power scaling of single-frequency fiber amplifiers. For the first time, we demonstrate a spliceless all-fiber amplifier, where all optical components are directly integrated in a single Yb $^{3+}$ -doped 3C-fiber. Such a spliceless laser design enables a compact and robust architecture using specialty fibers, while maintaining excellent beam properties. At an output power of 336 W operating at 1064 nm, a fundamental mode content of 90.4% at a polarization extinction ratio above 13 dB was measured without any impact of transverse mode instabilities or other parasitic effects. This work emphasizes the field of applications of 3C-fibers in high-power laser systems.