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Lead sulfide (PbS) is a nanomaterial with excellent optical and chemical properties, such as a narrow bandgap (0.37 eV), high thermal damage threshold, and high stability. Obviously, it is appropriate as a saturable absorber (SA) device for ultrafast photonics. However, PbS nanoparticles (NPs) as the SA of ultrashort harmonic mode‐locked pulse still haven't been demonstrated at present. In this paper, the PbS NPs are made into an SA‐device‐based microfiber by optical deposition method and connected in an integrated Erbium‐doped fiber laser. And both characteristics and nonlinear optical properties of PbS NPs have been systemically investigated. A fundamental frequency mode‐locked pulsed laser is proposed, whose central wavelength is 1560 nm, and the pulse width is 1 ps. In addition, high repetition rate operations are achieved, with a maximum repetition rate of 833 MHz. This is the first time that PbS NPs are used to generate 96th‐order harmonic mode‐locking, and the corresponding pulse duration is 987 fs. It is demonstrated that PbS NPs are a kind of SA photonic material with excellent performance. It can improve the communication capacity by applying fiber communication, and it has potential application value even in material processing and optical comb. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) materials are widely used in optoelectronics, thermodynamics and ultrafast fiber lasers because of their excellent nonlinear optical properties. Silver sulfide (Ag2S) is a kind of 3D material with a unique cubic structure and large absorption coefficient. In this paper, a double-balance detection system is used to measure the saturation absorption intensity of Ag2S as 226.6 MW cm−2 and the modulation depth as 13.9%. In the ring fiber laser, Ag2S is used as a saturable absorber (SA) to obtain a stable dual-wavelength mode locking. The center wavelengths of the mode locking are 1536.9 and 1544.5 nm, and the corresponding 3 dB bandwidths are 1.3 and 1.5. nm. By adjusting the polarization controller, a tuning process from two wavelengths to multiple wavelengths is realized, and the tunable width is 13.1 nm. This phenomenon is due to the combined effect of birefringence and nonlinear effects in the cavity. To our knowledge, this is the first report of a multiplexed fiber laser with Ag2S as a SA. The emergence of this result provides a valuable reference information for the multifunctional compact fiber laser, and the formed system can be applied in the fields of fiber sensing, telecommunications and optical communication. [ABSTRACT FROM AUTHOR]

As a rising star of transition metal oxides (TMOs), cuprous oxide (Cu2O) has a relatively narrow direct bandgap and features strong light–matter interaction, large optical absorption, large minority carrier diffusion lengths and high exciton binding energy, indicating its broad prospects in the field of photonics and optoelectronics. Herein, novel uniform Cu2O nanocubes are successfully prepared by liquid-phase reduction. However, the nonlinear optical (NLO) properties of Cu2O nanocubes and their applications in ultrafast photonics are rarely explored. The modulation depth (12.2%) and saturation intensity (65.8 MW cm−2) of Cu2O nanocubes are demonstrated experimentally, which indicates the excellent potential of Cu2O nanocubes in photonics among the emerging novel NLO materials. Meanwhile, the surface morphology, photoluminescence (PL) characteristics and chemical composition of Cu2O nanocubes have been systematically investigated. More importantly, a high repetition rate (HRR) of a ≈1 GHz ultrashort pulse laser with a 682 fs pulse width is obtained based on the Cu2O nanocubes as a saturable absorber (SA) in the telecommunications band for the first time. Considering the outstanding NLO properties and relatively narrow direct bandgap, these studies pave the way towards advanced photonics based on the Cu2O nanocube material. [ABSTRACT FROM AUTHOR]

In recent years, two‐dimensional materials have been widely used in the field of optics due to their unique nonlinear optical properties, broadband saturation absorption and ultrafast recovery time. MXene Ti3C2Tx is a kind of emerging two‐dimensional materials with large modulation depth, high damage threshold, and excellent electrical conductivity with near zero bandgap structure. However, MXene has seldom been applied in ultrafast photonics, especially the generation of ultrastable soliton molecules. In this paper, MXene is prepared and applied in the erbium‐doped fiber laser. The nonlinear optical properties of MXene Ti3C2Tx are studied experimentally. The center wavelength, 3‐dB bandwidth, fundamental frequency and the pulse duration of the conventional soliton are 1566.1 nm, 1.21 nm, 6.09 MHz and 993 fs, respectively. By adjusting the polarization state and pump power, the soliton molecules can be obtained in the laser cavity. Especially, two kinds of soliton molecules with CW peak and without CW peak are observed, respectively. Experimental results show that MXene saturable absorber (SA) can bear a high pump power. This work demonstrates that MXene Ti3C2Tx can be used as an excellent SA. Hence, we believe that this kind of optical material has many applications such as optical communication, optical logic gates and nonlinear devices, etc. [ABSTRACT FROM AUTHOR]

As a member of the 2D transition metal chalcogenides (TMCs), 2D Ag2S with large absorption coefficient, broadband optical response, extraordinary metal‐like ductility, high plastic deformation strain, unique layered structure, and very low solubility has offered a platform for achieving tremendous success in various fields. Great achievements have been made in exploring the linear optical, mechanical, and photoelectric properties of 2D Ag2S nanosheets. However, the nonlinear optical properties of 2D Ag2S nanosheets and their applications in ultrafast photonics have not been studied. The saturable absorption property of 2D Ag2S nanosheets is experimentally illustrated at the telecommunication band with a large optical modulation depth of 15.5% and a low saturable intensity of 250.4 MW cm−2. Moreover, the 229th harmonic soliton molecule with repetition rate of 1.1 GHz based on 2D Ag2S saturable absorber is realized at the telecommunication band for the first time to the authors' knowledge. Thankfully, 2D Ag2S nanosheets display excellent nonlinear optical properties suggesting that this may open a new door for advanced photonic devices based on 2D Ag2S nanosheets. [ABSTRACT FROM AUTHOR]

A series of Ce-Cu-SSZ-13 catalysts were synthesized by the ion exchange method based on the Cu-SSZ-13 prepared via a one-pot method and investigated for the selective catalytic reduction by NH3. Compared with Cu-SSZ-13, the catalytic activity and sulfur resistance of Ce-Cu-SSZ-13 were enhanced by modifying with cerium. XRD, N2-BET, MP-AES, XPS, H2-TPR and in situ DRIFTS were carried out to characterize the catalysts. XPS results suggested that more active sites on the surface of Ce-Cu-SSZ-13 catalysts. H2-TPR showed that the redox capacity of the Cu-SSZ-13 catalyst was enhanced after doping with Ce. In situ DRIFTS results demonstrated that the synergistic effect existing between copper and cerium species enhanced the adsorption performance of NH3 and NO + O2 on the catalyst surface. All of the above factors played important roles for achieving the high NH3-SCR performance. [ABSTRACT FROM AUTHOR]

MXene Nanosheets: Harmonic Mode-Locked Er-Doped Fiber Laser by Evanescent Field-Based MXene Ti3C2Tx (T = F, O, or OH) Saturable Absorber (Ann. MXenes, as a legendary family of two-dimensional (2D) van der Waals nanosheets materials, have been extensively studied due to their unique characteristics of broadband nonlinear optical response. In article number 1900437, Xiaohui Li, Han Zhang, and co-workers characterize MXene nanosheets systemically, and successfully apply MXene nanosheets in an Er-doped fiber laser to achieve harmonic mode-locking with a repetition frequency of 218.4 MHz. [Extracted from the article]