High-quality black phosphorus (BP) saturable absorber mirror (SAM) was successfully fabricated with few-layered BP (phosphorene). By employing the prepared phosphorene SAM, we have demonstrated ultrafast pulse generation from a BP mode-locked bulk laser for the first time to our best knowledge. Pulses as short as 6.1 ps with an average power of 460 mW were obtained at the central wavelength of 1064.1 nm. Considering the direct and flexible band gap for different layers of phosphorene, this work may provide a possible method for fabricating BP SAM to achieve ultrafast solid-state lasers in IR and mid-IR wavelength region.

Rhenium disulfide (ReS 2 ), a member of group VII transition metal dichalcogenides (TMDs), has attracted increasing attention because of its unique distorted 1T structure and electronic and optical properties, which are much different from those of group VI TMDs (MoS 2 , WS 2 , MoSe 2 , WSe 2 , etc.). It has been proved that bulk ReS 2 behaves as a stack of electronically and vibrationally decoupled monolayers, which offers remarkable possibilities to prepare a monolayer ReS 2 facilely and offers a novel platform to study photonic properties of TMDs. However, due to the large and layer-independent bandgap, the nonlinear optical properties of ReS 2 from the visible to midinfrared spectral range have not yet been investigated. Here, the band structure of ReS 2 with the introduction of defects is simulated by the ab initio method, and the results indicate that the bandgap can be reduced from 1.38 to 0.54 eV with the introduction of defects in a suitable range. In the experiment, using a bulk ReS 2 with suitable defects as the raw material, a few-layered broadband ReS 2 saturable absorber (SA) is prepared by the liquid phase exfoliation method. Using the as-prepared ReS 2 SA, passively Q-switched solid-state lasers at wavelengths of 0.64, 1.064, and 1.991 μm are investigated systematically. Moreover, with cavity design, a femtosecond passively modelocked laser at 1.06 μm is successfully realized based on the as-prepared ReS 2 SA for the first time. The results present a promising alternative for a rare broadband optical modulator and indicate the potential of ReS 2 in generating Q-switched and mode-locked pulsed lasers. It is further anticipated that this work may be helpful for the design of 2D optoelectronic devices with variable bandgaps.

A compact saturable absorber mirror (SAM) based on few-layer molybdenum disulfide (MoS 2) nanoplatelets was fabricated and successfully used as an efficient saturable absorber (SA) for the passively Q-switched solid-state laser at 1 μm wavelength. Pulses as short as 182 ns were obtained from a ytterbium-doped (Yb:LGGG) bulk laser Q-switched by the MoS 2 SAM, which we believe to be the shortest one ever achieved from the MoS 2 SAs-based Q-switched bulk lasers. A maximum average output power of 0.6 W was obtained with a slope efficiency of 24%, corresponding to single pulse energy up to 1.8 μJ. In addition, the simultaneous dual-wavelength Q-switching at 1025.2 and 1028.1 nm has been successfully achieved. The results indicate the promising potential of few-layer MoS 2 nanoplatelets as nonlinear optical switches for achieving efficient pulsed bulk lasers.

A novel two-dimensional (2D) material member in the transition metal dichalcogenides family, few-layered rhenium disulfide (ReS) was prepared by liquid phase method successfully. By using the open-aperture Z-scan method, the saturable absorption properties at 2.8 μm were characterized with a saturable fluence of 22.6  μJ/cm and a modulation depth of 9.7%. A passively Q-switched solid-state laser at 2.8 μm was demonstrated by using the as-prepared ReS saturable absorber successfully. Under an absorbed pump power of 920 mW, a maximum output power of 104 mW was obtained with a pulse width of 324 ns and a repetition rate of 126 kHz. To the best of our knowledge, this is the first demonstration of applying ReS in an all-solid-state laser. Moreover, this represents the shortest pulses in Q-switched MIR lasers based on a 2D material as the saturable absorber, which demonstrated the superiority of ReS acting as an optical modulator for generating short-pulsed lasers. The results well prove that 2D ReS is a reliable optical modulator for MIR solid-state lasers.

Using high-quality single-layer graphene as a saturable absorber, Tm:YAlO₃ (Tm:YAP) crystal as the gain medium, we demonstrated a laser-diode-pumped, compact, passively Q-switched (PQS) solid-state laser in the 2 μm region. The maximum average output power was 362 mW, with the corresponding largest pulse repetition rate and pulse energy of 42.4 kHz and 8.5 μJ, respectively. Under the same pump power, the pulse width of 735 ns was obtained, which is, to our best knowledge, the shortest pulse width among Tm-doped solid-state PQS lasers using graphene saturable absorber mirrors.

A high-quality black phosphorus (BP) saturable-absorber mirror (SAM) was successfully fabricated with the multi-layered BP, prepared by liquid-phase exfoliation (LPE) method. The modulation depth and saturation power intensity of BP absorber were measured to be 10.7% and 0.96 MW/cm(2), respectively. Using the BP-SAM, we experimentally demonstrated the mid-infrared (mid-IR) pulse generation from a BP Q-switched Cr:ZnSe laser for the first time to our best knowledge. Stable Q-switched pulse as short as 189 ns with an average output power of 36 mW was realized at 2.4 μm, corresponding to a repetition rate of 176 kHz and a single pulse energy of 205 nJ. Our work sufficiently validated that multi-layer BP could be used as an optical modulator for mid-IR pulse laser sources.

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In this Letter, a high-quality, few-layered black phosphorus (BP) saturable absorber (SA) was fabricated successfully, and a femtosecond solid-state laser modulated by BP-SA was experimentally demonstrated for the first time, to the best of our knowledge. Pulses as short as 272 fs were achieved with an average output power of 0.82 W, corresponding to the pulse energy of 6.48 nJ and peak power of 23.8 MW. So far, these represent the shortest pulse duration and highest output power ever obtained with a BP-based mode-locked solid-state laser. The results indicate the promising potential of few-layered BP-SA for applications in solid-state femtosecond mode-locked lasers.