fascinating physical and chemical properties. At present, two dimensional (2D) materials with brilliant nonlinear optical (NLO) properties play an key role in modern photonics since the appearance of graphene. [15] However, GDY, as a 2D allotrope of graphene, is still in the primary stage of its application in photonic fields. [16,17] On the basis of previous research results, the advantages of GDY as a NLO material for photonic devices are obvious. First, it is essentially different from the zero-band gap of graphene. GDY has a tunable direct band gap of 0.46-1.10 eV (according to different simulated methods), [18][19][20] which shows that GDY has great potential in the application of photonic devices based on optical switch function. Besides, in the structure of GDY, the alkyne bonds and sub-nanopore, provide a large number of reaction sites for its functionalization. In this context, the optical energy gap of the original GDY can be tuned in a wide range of wavelengths by controlling the type and amount of doped atoms (e.g., boron, nitrogen, phosphorus, and sulfur), [21][22][23] which makes GDY a more compatible NLO material. Recently, we used the method of spatial self-phase modulation to demonstrate the strong broadband Kerr nonlinearity and large nonlinear refractive index (in the order of ≈10 −5 cm 2 W −1 ) of GDY, [24] which indicates that GDY can be widely used in multi-functional photonic devices. Compared with the unstable black phosphorus (BP), the GDY material can remain stable up to 1000 K and its service life at room temperature is extremely long. [25] The excellent stability of GDY prevents it from photooxidation and photo degradation under high strong light irradiation, which is of crucial significance for the development of photonic devices that can be used for a long term. In view of this, the research and development of advanced multifunctional photonics devices (e.g., detector, photonic diode, switcher, sensors, and modulator) based on GDY is not only of great significance to fully understand the optical performance of all-carbon nanomaterials, but also promotes the development of photonic devices based on 2D materials.Ultrafast lasers which can be passively generated using saturable absorption of 2D materials play a pivotal role in various cutting-edge technologies such as micromachining, [26] hyperfine medical surgery, [27] and ultrafast information processing. [28] However, up to now, most of the ultrashort pulse generation Graphdiyne (GDY) is a novel 2D all-carbon nanomaterial, which has an intransic band gap, strong light-matter interaction, and large optical absorption in the infrared region, indicating that it has great potential in the field of mid-infrared ultrafast photonics. Here, a Z-scan method is used to demonstrate the broadband and strong nonlinear optical (NLO) response of GDY, and its performance in the application of mid-infrared ultrafast photonics is explored for the first time. The experimental results demonstrate that its nonlinear parameters are superior to the current...

As a two-dimensional material, MXene has accordion-like structures and possesses highly tunable and tailorable electro-optical capabilities, which suggests that it can be extensively used for electro-photonics devices. Here, we investigate the performances of 2D Ti 3 C 2 T x MXene in the nonlinear optical application of ultrafast photonics spanning the near-infrared (NIR) and mid-infrared (MIR) ranges. Interestingly, by utilizing the combined effects of nonlinear saturable absorption and high nonlinearity properties of the Ti 3 C 2 T x photonic device based on a microfiber, rogue waves with a high pulse energy in a fiber laser at 1.55 μm are first obtained. Additionally, by virtue of the Ti 3 C 2 T x saturable absorber, high-power ultrashort pulses are generated in a 2 μm fiber laser. Besides, a Ti 3 C 2 T x Q-switched fiber laser at 2.8 μm is also realized, which can deliver stable pulse trains with a 640 ns pulse width and a 122.9 kHz repetition rate, corresponding to a 1.8 μJ pulse energy and a 2.89 W peak power. The results suggest that as a promising nonlinear optical material, MXene has pioneered a way for the development of ultrafast nonlinear photonic devices in the NIR and MIR ranges.

The electronic emission characteristics of 13 gas-phase PAHs, ranging from phenlylacetylene to rubicene, were investigated to diagnose laser-induced fluorescence (LIF) spectra of PAHs in flame by DFT, TD-DFT, and premixed flame modeling methods. It was found that the maximum emission wavelengths of the PAHs with five-membered ring are located in visible region and insensitive to the number of C atoms. However, the fluorescence wavelengths of the PAHs without five-membered rings increase with the number of C atoms due to the reduced HOMO-LUMO gap. In addition, the fluorescence wavelength of the PAHs without five-membered rings with linear arrangement is longer than that of PAHs with nonlinear arrangement. According to the Franck-Condon principle, the vibrationally resolved electronic fluorescence spectra were obtained. The results show that fluorescence bandwidth of the PAHs with five-membered rings is much broader than that of the PAHs without five-membered rings. The concentration of PAHs was calculated by using the premixed flat-flame model with KM2 mechanism. On the basis of the fluorescence bandwidth and the concentration of the PAHs, the potentially fluorescence distribution of PAHs in flame was mapped. One can distinguish the specific PAHs according to the mapped fluorescence distribution of PAHs in this study. It was found that naphthalene should be responsible for the fluorescence located in the 312-340 nm region in the flame. 1-Ethynylnaphthalene is the most possible candidate to emit the fluorescence located in the 360-380 nm region. The fluorescence signals with the wavelength longer than 500 nm are likely emitted by the PAHs with five-membered rings. This study contributes to enhance the selectivity of PAHs in LIF technology, especially in the visible region.

Tin selenide (SnSe) nanosheets, as 2D materials, exhibit many excellent optical and electronic properties and can be widely utilized in various potential applications, such as photodetectors, photovoltaic cells, optical sensors, and nonlinear optical devices. Herein, the 2D SnSe nanosheets are synthesized by the method combining lithium ion intercalation and sonication‐assisted liquid phase exfoliation. The morphology, structures, and chemical composition of as‐prepared 2D SnSe sample are systemically analyzed. Interestingly, the 2D SnSe nanosheets are successfully fabricated as a saturable absorber (SA) by depositing on a microfiber, which shows excellent nonlinear absorption property in a wide band. By incorporating SnSe‐based SA into the fiber lasers, stable mode‐locked pulses can be realized at 1.5 and 2 µm with a pulse duration of 0.542 and 2.12 ps, respectively. Additionally, harmonic mode locking of bound solitons is generated in the 1.5 µm fiber laser. Furthermore, dual‐wavelength mode‐locked pulses at 1897.3 and 1910.5 nm are also obtained in the 2 µm fiber laser. These results validate that 2D SnSe materials show great potential in nonlinear photonic devices for broadband ultrafast photonics.

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