Towards a 20W-level industrial-grade Er:ZBLAN fiber laser at 2.8μm

20 W of laser operation at around 2.8 m in an Er-doped fluoride fiber is reported using a simple and proven optical setup. Compared to experiments in the past, the efficiency was significantly increased that allowed doubling the output power. In the tested free run configuration, the wavelength shifts from 2790 nm to a maximum of 2855 nm when increasing the pump power from 1 watt to about 80 W at 975 nm. A long-term experiment showed oscillation at around 20 W output power for nearly 60 hours with an average rate of power decrease of the order of 0.1% per hour.