All-solid antiresonant fiber design for high-efficiency three-level lasing in ytterbium-doped fiber lasers

We propose and investigate an all-solid ytterbium-doped antiresonant fiber (YbARF) design to inherently suppress four-level lasing with >20 dB/m of selective loss and achieve high-efficiency three-level lasing while maintaining near-diffraction-limited operation with an ultra-large mode area of approximately 3630 µm². The YbARF is designed such that the high-gain wavelengths corresponding to four-level lasing lie in the resonance band characterized by high confinement loss. This enables three-level lasing with high efficiency in a short (0.8-m-long) YbARF, making it a potential candidate for high-peak-power ultrafast lasers at 976 nm. We discuss fiber design considerations and detailed simulation results for three-level lasing performance in the YbARF, which promises >85% lasing efficiency in a single-pass pump configuration. These design concepts can be easily extended to suppress high-gain wavelengths in other rare-earth-doped (e.g., with thulium, erbium, and neodymium) fiber amplifiers or lasers.