• Low-dimensional materials is introduced into photonics for more than a decade. However, few reports about metal oxide nanoparticles' integration into photonic devices have been reported till now. • In this manuscript, manganese dioxide (MnO 2) nanoparticles are employed to make a robust and reliable saturable absorber for ultrafast fiber lasers. Due to their small band gap of 0.7 eV, tinier size and strong absorption in near-infrared wavelength range, MnO 2 nanoparticles show excellent nonlinear optical properties in the proposed femtosecond lasers. • The combination of nanomaterials and hollow photonic crystal fiber provides a simple and reliable approach to optimize compact photonic devices design, which could pave a novel way for its applications in the field of supercontinuum generation, nonlinear applications and fiber sensing. • By inserting a tunable Sagnac filter, conventional solitons, switchable noise-like pulses, soliton molecules and dip-type sidebands solitons could be obtained with identical configuration, which could greatly increase versatility of the proposed fiber laser. Transition metal oxides, especially MnO 2 nanoparticles, are often used as cathode of dry batteries and catalysts. They are also promising materials for ultrafast laser applications due to their strong absorption in visible light and near-infrared wavelength range. In this work, high-concentration MnO 2 nanoparticles dispersions embedded in the hole cladding of dual-hole photonic crystal fiber is fabricated as a saturable absorber with a modulation depth of 4 % and a saturation intensity of 25 MW/cm2. Strong MnO 2 -light interaction occurs due to enhanced evanescent-field strength (over 10 cm) of the SA could enable stable mode locking operation at 1.55 μm region. By inserting a Sagnac fiber filter in the cavity, multi-state solitons are experimentally demonstrated with identical layout, respectively, which greatly improves the versatility of this laser. This study proves that MnO 2 nanoparticles possess excellent nonlinear optical properties in the near-infrared band. The simple in-line structure of the proposed nanoparticles-deposited device could pave a way for high power and all-fiber applications of photonics. [ABSTRACT FROM AUTHOR]