A monolithic microlens for an ytterbium-doped microstructured optical fiber amplifier

Ytterbium-doped microstructured optical fibers have many advantages for fiber amplifiers. Due to air-hole structures in the cladding of ytterbium-doped microstructured optical fibers, high-power microstructured optical fiber laser systems require stricter treatment of the fiber end than conventional ytterbium-doped double-cladding fiber laser systems. Here, we fabricated a fiber microlens in an ytterbium-doped double-cladding microstructured optical fiber for a fiber amplifier by CO2-laser fusion. The microlens can combine the end-cap scheme, pump coupling and beam shaping. This end face processing technology is useful for high mechanical stability, good reproducibility and miniaturization of laser systems.