Efficient continuous-wave and short-pulse Ho3+-doped fluorozirconate glass all-fiber lasers operating in the visible spectral range

In this work, efficient visible Ho3+-doped fluorozirconate glass (Ho:ZBLAN) all-fiber lasers operating in continuous-wave (CW) and Q-switching regimes are experimentally demonstrated. The combination of a direct blue pump, a highly-doped Ho:ZBLAN fiber and the fiber end-facet mirrors contributes to a simple all-fiber configuration. A tunable laser emission in the green spectral range of 543-550 nm is achieved with >150 mW output power and a tunable deep-red laser around 754-758 nm is also obtained with about 16 mW output power. Interestingly, stable visible self-Q-switched operation was successfully observed. For the green Q-switched all-fiber laser, a maximum single pulse energy of 196 nJ is realized with a repetition rate of 97.66 kHz and a pulse duration of 605 ns. As the pump power is increased, the deep-red Q-switched all-fiber laser has the pulse repetition rate from 59.88 to 100.5 kHz and the pulse duration from 4.85 to 2.02 mu s, corresponding to the maximum pulse energy of 58 nJ. To the best of our knowledge, this work is the first demonstration of Ho:ZBLAN all-fiber lasers emitting in the visible spectral range (i.e., both green and deep-red wavelengths).