Research on a 1.7 μm all-fiber mode-locked Tm-doped fiber laser

The 1.7 μm ultrashort pulse fiber laser has received great attention for its promising applications in various fields, such as bioimaging and materials processing. We experimentally built a 1.7 μm all-fiber structure mode-locked Tm-doped fiber laser based on the nonlinear polarization rotation technique. The optical gain at the 1.7 μm waveband is effectively obtained by using a core-pumping scheme, and the ASE at long wavelengths is suppressed by a fiber-based bandpass filter in the cavity. The proposed fiber laser delivers an ultrashort pulse with a central wavelength of 1733 nm and a 3 dB bandwidth of 6.3 nm. The mode-locked pulse has a repetition frequency of 19.56 MHz and an average power of 1.4 mW. In addition, the evolution of the pulse inside the laser cavity is numerically simulated. The proposed 1.7 μm all-fiber mode-locked laser is beneficial to further improve the stability and integration of the 1.7 μm laser source, which could find important applications in fields such as bioimaging.