γ-MnO2-deposited photonic crystal fiber: Novel photonic devices for multi-state solitons generation

Transition metal oxides, especially MnO2 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 MnO2 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 MnO2-light interaction occurs due to enhanced evanescent-field strength (over 10 cm) of the SA could enable stable mode locking operation at 1.55 mu m region. By inserting a Sagnac fiber filter in the cavity, multi-state solitons are experimentally demonstrated with iden-tical layout, respectively, which greatly improves the versatility of this laser. This study proves that MnO2 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 appli-cations of photonics.