10-watt diode-pumped red Pr:ZBLAN double-clad fiber laser.

We report on a continuous-wave (CW) praseodymium fluoride fiber laser delivering 10-watt level output power in the red spectral range. It employs a double-clad 0.8 mol% PrF-doped ZBLAN fiber as a gain medium and a high-power fiber-coupled 442-nm GaN laser diode module as a pump source. The CW Pr-laser delivers 9.1 W at 635 nm with a slope efficiency of 27.0% (versus launched pump power), a laser threshold of 1.32 W, and a single-mode output. In the quasi-continuous-wave regime, its output is further scaled to 10.32 W. The spectrum broadening in this laser is explained by four-wave mixing and is well described by the square root law. This result represents a new milestone in developing visible fluoride fiber lasers. The temperature-dependent spectroscopy of Pr ions in the ZBLAN glass is studied, and the limits for further power scaling of red fluoride fiber lasers are discussed.