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We investigate the impact of 405 nm radiation on photodarkening evolution in Yb-doped fiber. Simultaneous photodarkening and photobleaching effects induced by 976 nm and 405 nm radiations respectively were investigated in a 1070 nm laser.

We demonstrate a double-clad fiber laser operating at 910 nm with a record power of 20 W. Laser emission on the three-level scheme is enabled by the combination of a small inner cladding-to-core diameter ratio and a high brightness pump source at 808 nm. A laser conversion efficiency as high as 44% was achieved in CW operating regime by using resonant fiber Bragg reflectors at 910 nm that prevent the lasing at the 1060 nm competing wavelength. Furthermore, in a master oscillator power-amplifier scheme, an amplified power of 14.8 W was achieved at 914 nm in the same fiber.

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