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.

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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.

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.

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The depression of the current global oil market makes the majority of chemical EOR projects worldwide nearly unprofitable, especially in China. Therefore, economic alternative methods and technologies must be quickly developed. This proof of concept research evaluates a chemical flooding method using pre-formed mild O/W emulsions, which were produced by saponification between a low-cost alkali (NaOH) and a petroleum acid-rich oil. Our focus was first given to the dynamics of the saponification with an aim to quantify alkali consumption. Afterward, the composition of the crude oil before and after the reaction was characterized using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) to determine the preferred compounds in saponification. The physiochemical properties of the generated emulsions were further investigated through direct measurements of rheology, morphology, particle size distribution, and stability. Particular attention was placed on the oil displacement mechanisms of the emulsions at pore level. The results showed that fatty acids, naphthenic acids, and aromatic acids were clearly partitioned on the FT-ICR MS spectra of the crude oil, while the C16 and C18 fatty acids (DBE = 1, DBE represents equivalent double bond number) were predominantly saponified, which accordingly produced mild O/W emulsions (pH ≈ 7.0). The viscosity, morphology, and stability of the emulsions were found to strongly depend on the oil–water ratio. The displacement dynamics of three stable emulsions observed in a visual micromodel revealed that the O/W emulsion flooding can enlarge the sweep area and also notably reduce the residual oil saturation when employed as an EOR mode. Emulsification/entrainment, blocking, and stripping were three dominant pore level driving forces for this emulsion flooding. Phase inverse from O/W to W/O occurred when the emulsion of O/W = 3:7 was used and finally caused injectivity issue.

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