InP quantum dots (QDs) are emerging as promising materials for replacing cadmium‐based QDs in view of their heavy metal‐free and tunable luminescence. However, the development of InP QD materials still lags due to the expensive and flammable phosphorus precursors, and also the unsatisfactory repeatability caused by the fast nucleation rate. Adopting lowly reactive P precursor aminophosphine can overcome this issue, but their low photoluminescence quantum yield (PLQY) and widening line widths do not apply to the practical application. Through engineering, the core‐shell structure of QD, significantly promoted green emissions of QDs were obtained with PLQY of 95% and full width and half maximum (FWHM) of 45 nm, which demonstrated the highest PLQY record obtained from the aminophosphine system. Moreover, due to the residue halogen atoms on the QD surface as inorganic ligands to prevent further oxidization, these InP QDs demonstrated the ultra‐long operational lifetime (over 1000 h) for QDs based color enhancement film. By optimizing the device structure, an inverted green InP quantum dot light‐emitting diode (QLED) with external quantum efficiency (EQE) of 7.06% was also demonstrated, which showed a significant promise of these InP QDs in highly effective optoelectronic devices.

The novel vertically standing PtSe 2 film on transparent quartz was prepared by selenization of platinum film deposited by the magnetron sputtering method, and an Nd:LuVO 4 passively mode-locked solid-state laser was realized by using the fabricated PtSe 2 film as a saturable absorber. The X-ray diffraction pattern and Raman spectrum of the film indicate its good crystallinity with a layered structure. The thickness of PtSe 2 film is measured to be 24 nm according to the cross-section height profile of the atomic force microscope image. Highresolution transmission electron microscopy images clearly demonstrate its vertically standing structure with an interlayer distance of 0.54 nm along the c-axis direction. The modulation depth (ΔT ) and saturation fluence (Φ s ) of PtSe 2 film are measured to be 12.6% and 17.1 μJ∕cm 2 , respectively. The obtained mode-locked laser spectrum has a central wavelength of 1066.573 nm, with a 3 dB bandwidth of 0.106 nm. The transform limited pulse width of the mode-locked laser was calculated to be 15.8 ps. A maximum average output power of 180 mW with a working repetition rate of 61.3 MHz is obtained. To the best of our knowledge, this is the first report of the generation of ultrafast mode-locked laser pulses by using layered PtSe 2 as a saturable absorber.

Vertically standing SnS 2 film on transparent quartz was prepared by sulfuration of Sn film deposited by magnetron sputtering method. X-ray diffraction pattern and Raman spectrum of the film indicate its good crystallinity with a layered structure. Scanning electron microscope images of the film clearly demonstrate its vertically standing structure. The thickness of a single SnS 2 nanosheet is measured to be 18.4 nm according to the cross-section height profile of the atomic force microscope image. The nonlinear optical response of SnS 2 nanosheet film is investigated by using the open aperture Z-scan technology with a femtosecond pulsed laser (400 fs) working at 1064 nm. The modulation depth (α s ) and saturable absorption intensity (I sat ) of SnS 2 film are measured to be 11.7% and 1.9 MW cm −2 , respectively. The Z-scan results reveal that the SnS 2 nanosheet film exhibits strong saturable absorption behavior to the femtosecond laser, making it have potential applications in mode-locked lasers for femtosecond pulses generation.

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In this study, red light emitting InP/ZnSeS/ZnS quantum dots (QDs) are prepared by thermal injection method. The results show that the InP/ZnSeS/ZnS QDs saturable absorbers (SA) have good nonlinear saturable absorption properties with modulation depth of 24.2% and saturation intensity of 0.08 KW cm−2. Then the QD SAs are applied to the erbium‐doped fiber laser (EDFL) ring cavity system, and a mode‐locked laser pulse with a pulse width of 635 fs is generated. In addition, the pulse width is determined by the carrier recovery time, which is closely related to the defect density in the material. A large number of defects are eliminated in the QDs by hydrogen fluoride (HF) treatment, and the pulse width is reduced from 635 to 450 fs. Results of time‐resolved photoluminescence and ultrafast transient absorption spectroscopy (TAS) show that HF treatment indeed reduces defects in InP/ZnSeS/ZnS QDs, indicated by the decrease of the carrier recovery time. This is different from the reported 2D SA materials, which usually reduce the carrier recovery time by increasing the defect density. This study will inspire new applications of QDs in ultrafast photonics and nonlinear optics.

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