Directly diode-pumped holmium fiber lasers

Sensitizer-free holmium-doped silica and fluoride mid-infrared fiber lasers are pumped using a high-power diode laser operating at 1148 nm. A maximum output power of 162 mW at 2.86 μm was produced at a slope efficiency of 24% using Ho³⁺, Pr³⁺-doped fluoride fiber. Using Ho ³⁺-doped silica fiber, a maximum output power of 55 mW at 2.1 pm was generated at a slope efficiency of 27%, a value limited by the presence of pump excited state absorption.