in the field of ultrafast photonics. Since the successful demonstration of graphene-based saturable absorber (SA) for ultrafast pulsed lasers, [7,8] 2D layered materials including black phosphorus, topological insulators, and transition metal dichalcogenides (TMDs), have recently been extensively investigated in nonlinear optical devices for the generation of ultrafast pulses via passive modelocking operation. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] In particular, the recent advancements in the development of TMDs with unique electronic and optical attributes have explored many potential applications in electronics and photonics. [24,25] The TMDs with layered structure can be exfoliated into atomic-thin layers, which advance the development of wider applications as high-performance transistors, photodetectors and nonlinear optical devices owing to their widespread bandgaps from the visible to the nearinfrared region. [24][25][26][27][28][29][30][31] Currently, nonlinear optical devices based on group VIB TMDs have been fully studied using as saturable absorbers (SA) for the successful generation of short pulses in broadband region. [17][18][19][20][21][22][23][32][33][34][35][36] Despite the previous efforts, it is still possible to optimize the SA devices toward ultrafast photonics for the admired purposes of generating laser pulse with shorter pulse width and greater output power, which can be anticipated by exploring other members of TMDs. In comparison with intensively studied group VIB TMDs, group IVB TMDs which are theoretically predicted to have superior physical properties to group VIB TMDs, have rarely been investigated yet. [37,38] For instance, single-layered HfS 2 is expected to possess much higher carrier mobility (≈1800 cm 2 V −1 s −1 ) and smaller bandgap (≈1.2 eV) than that of MoS 2 . [38,39] Owing to superior electronic properties, ultrathin HfS 2 fabricated by mechanically exfoliation or chemical vapor deposition methods presents significant potential in phototransistors and field-effect transistors. [40][41][42][43][44][45][46][47] However, to our knowledge, the nonlinear optical properties of HfS 2 and its application in ultrafast photonics remain unknown.In this contribution, we demonstrate a new function of multilayered HfS 2 nanosheets (NSs) with nonlinear optical absorption for development of ultrafast photonic devices. We prepared HfS 2 NSs via a modified liquid exfoliation approach using isopropanol (IPA) as solvent. HfS 2 dispersions are precisely deposited onto a microfiber to form a SA device by using a photonic crystal fiber (PCF) assisted deposition method. The HfS 2 SA device is found to show excellent nonlinear absorption Group IVB transition metal dichalcogenides (TMDs) have attracted significant interests in photoelectronics due to their predictable superior physical properties compared to group VIB (Mo and W) TMDs. However, the nonlinear optical properties and ultrafast photonic devices based on group IVB TMDs remained unexplored so far. Herein, the nonlinear ...

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With the magnetron-sputtering deposition method, α phase indium selenide (α-InSe) was developed into a saturable absorber (SA) with wideband saturable absorption property at 800, 1560, and 1930 nm. After inserting the α-InSe SA into erbium-doped fiber laser (EDFL) and thulium-doped fiber laser (TDFL) systems, we can easily obtain stable soliton pulse trains. The pulse duration/pulse energy/slope efficiency for EDFL and TDFL were 276 fs/2.03 nJ/15.8% and 1.02 ps/7.1 nJ/23.5%, respectively. These results showed that the MSD-grown α-InSe could be regarded as high efficiency material to be applied in ultrafast photonics.

Ramp metering is an effective measure to alleviate freeway congestion. Traditional methods were mostly based on fixed-sensor data, by which origin-destination (OD) patterns cannot be directly collected. Nowadays, trajectory data are available to track vehicle movements. OD patterns can be estimated with weaker assumptions and hence closer to reality. Ramp metering can be improved with this advantage. This paper extracts OD patterns with historical trajectory data. A validation test is proposed to guarantee the sample representativeness of vehicle trajectories and then implement coordinated ramp metering based on the contribution of on-ramp traffic to downstream bottleneck sections. The contribution is determined by the OD patterns. Simulation experiments are conducted under real-life scenarios. Results show that ramp metering with trajectory data increases the throughput by another 4% compared with traditional fixed-sensor data. The advantage is more significant under heavier traffic demand, where traditional control can hardly relieve the situation; in contrast, our control manages to make congestion dissipate earlier and even prevent its forming in some sections. Penetration of trajectory data influences control effects. The minimum required penetration of 4.0% is determined by a t-test and the Pearson correlation coefficient. When penetration is less than the minimum, the correlation between the estimation and the truth significantly drops, OD estimation tends to be unreliable, and control performance becomes more sensitive. The proposed approach is effective in recurrent freeway congestion with steady OD patterns. It is ready for practice and the analysis supports the real-world application.