Group VIB transition metal dichalcogenides (TMDs) have been successfully demonstrated as saturable absorbers (SAs) for pulsed fiber lasers. For the group comprising IVB TMDs, applications in this field remain unexplored. In this work, ZrS₂-based SA is prepared by depositing a ZrS₂ nanostructured film onto the side surface of a D-shaped fiber. The nonlinear optical properties of the prepared SA are investigated, which had a modulation depth of 3.3% and a saturable intensity of 13.26 MW/cm². In a pump power range of 144–479 mW, the Er-doped fiber (EDF) laser with ZrS₂ can operate in the dual-wavelength Q-switching state. The pulse duration declined from 10.0 μs down to 2.3 μs. The single pulse energy reached 53.0 nJ. The usage of ZrS₂ as a SA for pulse generation in fiber lasers is presented for the first time. Compared to the experimental results of dual-wavelength Q-switched fiber lasers with two-dimensional (2D) materials, our laser performance was better. Our work indicates that the group comprising IVB TMD ZrS₂ has bright prospects for nonlinear optical applications.

Tantalum pentoxide (Ta₂O₅) has attracted intensive attention due to their excellent physicochemical properties. Ta₂O₅ films were synthesized via electron beam evaporation (EBE) and subsequently annealed at different temperatures ranging from 300 to 900 °C. X-ray diffraction (XRD) results show that amorphous Ta₂O₅ thin films form from 300 to 700 °C and then a phase transition to polycrystalline β-Ta₂O₅ films occurs since 900 °C. The surface morphology of the Ta₂O₅ films is uniform and smooth. The resulted Ta₂O₅ films exhibit excellent transmittance properties for wavelengths ranging from 300 to 1100 nm. The bandgap of the Ta₂O₅ films is broadened from 4.32 to 4.46 eV by annealing. The 900 °C polycrystalline film electrode has improved electrochemical stability, compared to the other amorphous counterparts.

Transition metal oxides (TMOs) have been successfully demonstrated as Q-switchers for pulsed fiber lasers. In this work, the ferroferric-oxide (Fe₃O₄) nanoparticles are synthesized via chemical co-precipitation. Filmy Fe₃O₄/polyvinyl alcohol (PVA) is adopted as the Q-switcher in a 1 μm region. The Fe₃O₄/PVA film has the modulation depth of 7.8% and saturable intensity of 71.32 MW/cm², respectively. By incorporating the Fe₃O₄/PVA film into Yb-doped fiber laser (YDF) cavity as a saturable absorber (SA), the stable Q-switching operation is obtained in 77-157 mW pump power range. At the pump power of 147 mW, the Q-switched YDF laser emits stable laser pulses with the maximum single pulse energy of 50.35 nJ and shortest pulse duration of 1.63 μs. The experimental results indicate that the zero-dimensional Fe₃O₄ nanoparticles have a bright prospect for nonlinear optics applications.