230 mW of blue light from a thulium-doped upconversion fiber laser

We demonstrate a powerful diode-pumped blue laser source, consisting of a 7-W diode at 807 nm that pumps a Nd:YAG laser giving 1.6 W with good beam quality at 1123 nm, and a thulium-doped upconversion fiber laser. The maximum output power achieved at 481 nm is 230 mW. We also describe the behavior of a reversible loss which is generated in the fluoride fiber during high power operation.