Spectral filtering effect on the ultrafast mid-infrared Er³⁺-doped ZBLAN fiber laser

We investigate the spectral filtering effect on the mid-infrared ultrafast Er³⁺-doped ZBLAN fiber laser based on nonlinear polarization evolution (NPE). A broad wavelength tuning range from 2720 nm to 2800 nm is achieved using a diffraction grating as the narrowband filter. Furthermore, numerical simulations are also carried out so that, by inserting a highly nonlinear fiber combined with an appropriate spectral filter in the laser system, a 329 nm ultra-broadband spectrum with a Fourier transform limit pulse as short as 47 fs can be achieved. Our results are conducive to understanding the spectral filtering effect on the lasing performance of mid-infrared ultrafast fiber lasers.