Cladding-pumped bismuth-doped fiber laser.

For the first time, to the best of the authors' knowledge, a cladding-pumped bismuth-doped fiber laser (BDFL) is demonstrated. A "home-made" Bi-doped germanosilicate fiber with a 125 µm circular outer cladding made of fused silica and coated by a low refractive index polymer is used as an active medium pumped by commercial multimode laser diodes with a total output power of 25 W at 808 nm. We find that the BDFL with a free-running cavity (when feedback is provided by ≈4% back reflection from two bare right-angle cleaved fiber ends) composed of a 100-m-long bismuth-doped fiber is capable of emitting at a wavelength of 1440 nm.