Single-Frequency Dy:ZBLAN Fiber Laser Tunable in the Wavelength Range From 2.925 to 3.250 $\mu$m

We report on an in-band-pumped Dy-doped ZBLAN fiber laser with tunable emission wavelength in the mid-IR range from 2.925 to 3.250
$\mu$
m and single-frequency operation. Using the combination of an intracavity germanium etalon and a reflective diffraction grating, we demonstrate the selection of single-frequency operation with emission linewidth narrower than 110 kHz, maximum output power of
$\sim 40$
mW, and relative intensity fluctuations at a level of 0.9% over an integration bandwidth from 1 Hz to 10 MHz.