All-normal-dispersion nonlinear polarization rotation mode-locked Tm:ZBLAN fiber laser

We demonstrated an all-normal-dispersion nonlinear polarization rotation mode-locked Tm:ZBLAN fiber laser in the 2 μm wavelength band. All fibers in the experiment were ZBLAN fibers with normal dispersion in the wavelength band. An average power of 63 mW with a characteristic cat-ear shaped optical spectrum of an ANDi laser was obtained. The center wavelength and the spectral bandwidth were 1880 nm and ~80 nm, respectively. The repetition rate was 70.6 MHz and the corresponding pulse energy was 0.9 nJ. The pulse duration directly from the oscillator was 860 fs and it was compressed to 107 fs.