Comparative study of continuous wave Tm3+-doped silica and fluoride fiber lasers

We compare Tm3+-doped silica and fluoride fiber lasers in continuous wave operation using the same experimental setup. For incident pump powers of up to 50 W, the fluoride fiber is shown to have higher output power and efficiency compared to silica and reaches a maximum output power of 20 W at 1.94 mu m. A slope efficiency of 49% (41%) and a maximum optical-to-optical efficiency of 45% (35%) at an incident pump power of 25 W (37 W) were determined for the fluoride (silica) fibers, respectively. These optical-to-optical efficiencies are the highest reported for directly diode-pumped Tm3+-based fiber lasers. We establish that in free-running mode, fiber lasers using fluoride glass are temporally more stable than fiber lasers using a silica host.