Gold nanorods (GNRs) were used as a saturable absorber (SA) for passive mode-locking at 1 µm wavelength. The GNR-SA film was fabricated by mixing GNRs with sodium carboxymethylcellulose. The longitudinal surface plasmon resonance absorption of GNRs was used to induce mode-locking. By using the GNR-SA film, stable passive mode-locking at 1039 nm was experimentally demonstrated in an ytterbium-doped fiber laser cavity pumped by a 980 nm laser diode. The laser produced ∼440 ps pulses with a repetition rate of 36.6 MHz and an average output power of ∼1.25 mW for a pump power of ∼82 mW.
This study shows the ability of sodium-glucose co-transporter-2 inhibitors to lower atrial natriuretic peptide levels and improve glycaemic control, which may benefit the cardiovascular system.
Recently, theoretical studies show that layered HfTe5 is at the boundary of weak & strong topological insulator (TI) and might crossover to a Dirac semimetal state by changing lattice parameters. The topological properties of 3D stacked HfTe5 are expected hence to be sensitive to pressures tuning. Here, we report pressure induced phase evolution in both electronic & crystal structures for HfTe5 with a culmination of pressure induced superconductivity. Our experiments indicated that the temperature for anomaly resistance peak (Tp) due to Lifshitz transition decreases first before climbs up to a maximum with pressure while the Tp minimum corresponds to the transition from a weak TI to strong TI. The HfTe5 crystal becomes superconductive above ~5.5 GPa where the Tp reaches maximum. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. Crystal structure studies indicate that HfTe5 transforms from a Cmcm phase across a monoclinic C2/m phase then to a P-1 phase with increasing pressure. Based on transport, structure studies a comprehensive phase diagram of HfTe5 is constructed as function of pressure. The work provides valuable experimental insights into the evolution on how to proceed from a weak TI precursor across a strong TI to superconductors.
We numerically investigated widely tunable femtosecond solitons spanning from 4.1 to 7.2 µm in designed chalcogenide fibers with two rings of air holes. The core was made of Ge 15 Sb 15 Se 70 glass and the cladding glass was composed of Ge 20 As 15 S 65 . By using a 4.1 µm fiber laser with a pulse width of 100 fs as the pump light and 1 m long chalcogenide microstructured fibers as the nonlinear media, widely tunable femtosecond solitons spanning from 4.1 to 7.2 µm were observed, and the pulse width of these tunable Raman solitons remained below 150 fs. The efficiencies of the mid-infrared soliton could be up to over 80%, ranging from 4.1-6.8 µm. Through numerical simulations, we also observed red-shifted dispersive waves varying from 10.2 to 8.9 µm. Our simulated results show that the designed chalcogenide microstructured fibers are promising nonlinear media for generating tunable mid-infrared light sources.
We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.
We report the experimental observation of breathing solitons and a third harmonic in a tapered fluorotellurite photonic crystal fiber (PCF) pumped by a 1560 nm femtosecond fiber laser. The PCF has a core diameter that varies continuously along its length, resulting in a zerodispersion wavelength that moves from 1325 nm to 906 nm over the transition region. By finely controlling the dispersion map of the tapered PCF and increasing the order of the optical solitons, their breathing behavior is observed in the frequency domain and the number of breaths goes up to 9. Furthermore, the breathing behavior of the optical soliton is transferred to the third harmonic through inter-modal phase-matched processes in the tapered PCF, and the third harmonic also breathes with an increase in the pump power.
Oxygen Vacancy (OVs) and carbon doping of the photocatalyst body will significantly enhance the photocatalytic efficiency. However, synchronous regulation of these two aspects is challenging. In this paper, a novel C@TiO2‐x photocatalyst was designed by coupling the surface defect and doping engineering of titania, which can effectively remove rhodamine B (RhB) and has a relatively high performance with wide pH range, high photocatalytic activity and good stability. Within 90 minutes, the photocatalytic degradation rate of RhB by C@TiO2‐x (94.1 % at 20 mg/L) is 28 times higher than that of pure TiO2. Free radical trapping experiments and electron spin resonance techniques reveal that superoxide radicals (⋅O2−) and photogenerated holes (h+) play key roles in the photocatalytic degradation of RhB. This study demonstrates the possibility of regulating photocatalysts to degrade pollutants in wastewater based on an integrated strategy.
Synopsis
Transition metal dichalcogenides have recently attracted great interest as an important class of two-dimensional semiconductors because of their distinctive electronic, optical and catalytic properties. Here we demonstrate the first experimental study on ultrafast excited state dynamics of few-layered molybdenum disulfide under high pressure by means of broadband transient absorption spectroscopy combined with diamond anvil cell devices.
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