We experimentally demonstrated the passively Q-switched Nd:YAG laser based on the Mo ₂ C film as a saturable absorber.

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.

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.

Group IVB (Hf) transition metal dichalcogenides (TMDs) have attracted significant interest in photoelectronics due to their predictable superior physical characteristics. In this work, the liquid phase exfoliation method is used to prepare the hafnium diselenide (HfSe₂)/polyvinyl alcohol (PVA) saturable absorber (SA) device. The modulation depth (ΔT) is measured to be 6.65%. By using HfSe₂/PVA as a Q-switcher, application in the fiber laser with the Q-switching state is demonstrated experimentally. The maximum single pulse energy is 167 nJ is and the slope efficiency is 7.7%. To our best knowledge, this is the first report of the use of HfSe₂ as SA for large energy pulse generation. The experimental results prove that, because of its excellent nonlinear optical absorption properties, HfSe₂ could promote the development of Hf-based TMDs in the field of ultrafast photonics.

Molybdenum carbide (Mo₂C) is a two-dimensional (2D) MXene material which makes it a promising photoelectric material. In this study, reflective type MXene Mo₂C thin films were coated on a silver mirror by a magnetron sputtering method and were subsequently used in a passively Q-switched solid-state pulsed laser generator at the central wavelengths of 1.06 and 1.34 μm, respectively. The fabricated thin films of reflective type MXene Mo₂C exhibited large modulation depth of 6.86% and 5.38% at the central wavelengths of 1064 and 1342 nm, respectively. By inserting the Mo₂C saturable absorbers (SAs) into V-shaped Nd:YAG laser, short pulses were generated having a pulse duration, pulse energy, and average output power of 254 ns, 2.96 μJ, and 275 mW, respectively, at a wavelength of 1.06 μm. Similarly, shorter laser pulses were obtained in Nd:YVO₄ laser at 1.34 μm. Our results illustrated potential of the 2D MXene Mo₂C films for laser applications.