Wideband saturable absorption in metal-organic frameworks (MOFs) for mode-locking Er- and Tm-doped fiber lasers

We fabricate a metal-organic framework (MOF) saturable absorber (SA) based on a microfiber. Nonlinear optical absorption of the MOF SA is characterized systematically. The modulation depth is found to be 6.57% and 14.25% at 1.5 and 2 μm spectral ranges, respectively. We report ultrashort pulse generation in both Er- and Tm-doped fiber lasers by using the same microfiber-based MOF SA, operating at 384 fs and 1.3 ps pulse duration at 1563 nm and 1882 nm, respectively. To the best of our knowledge, this is the first report of a MOF-based fiber laser at near infrared spectral ranges. Our findings validate the applicability of MOFs as a broadband SA in ultrafast photonics.