3 W narrow-linewidth ultra-short wavelength operation near 1707 nm in thulium-doped silica fiber laser with bidirectional pumping

<p> We have developed an ultra-short wavelength operation of all-fiber Tm-doped laser system, in which the laser system was structured in a FBGs based linear cavity with FBG associated bidirectional pump mechanism at 1550 nm. The laser yielded 3.15 W of continuous-wave output at 1706.75 nm with a narrow-linewidth of similar to 50 pm. A high reflectivity FBG (HR-FBG) at 1550 nm was used to reflect the residual pump light and achieve the bidirectional pump mechanism. The maximum slope efficiency was improved from 23.2% without HR-FBG to 42.1% with HR-FBG at 1550 nm and the lowest pump threshold was reduced from 1.6 to 0.8 W accordingly. In the experiment, we have also investigated the dependencies of the slope efficiencies and pump threshold of the laser versus the length of active fiber and reflectivity of the output mirror (FBG) in detail. It is indisputable that the development of 1.7 mu m silicate fiber lasers with Watt-level output power will open up a number of promising application windows.