Self-sweeping ytterbium-doped fiber laser based on a fiber saturable absorber

Generally speaking, the self-sweeping effect relies on the dynamical grating formed in a gain fiber. Here, the normal self-sweeping was generated in a pump-free ytterbium-doped fiber which serves as a fiber saturable absorber and is introduced to the laser cavity by a circulator in this experiment. The sweeping rate and the sweeping range alter as usual, both of which can be controlled by the pump power. Further, a new self-pulse signal is observed and discussed in this work, which shows the difference of the self-sweeping effects between active fiber and fiber saturable absorber

Discretized optical dynamics in one-dimensionally synthetic photonic lattice

Synthetic photonic lattice with temporally controlled potentials is a versatile platform for realizing wave dynamics associated with physical areas of optics and quantum physics. Here, discrete optics in one-dimensionally synthetic photonic lattice is investigated systematically, in which the light behavior is highly similar to those in evanescently coupled one-dimensional discrete waveguides. Such a synthetic dimension is constructed with position-dependent periodic effective gauge fields based on Aharonov-Bohm effect arising from the phase accumulations of the fiber loops. By tuning the phase accumulations and coupling coefficient of the coupler, the band translation and gap property can be modulated which further results in the impulse and tailored Gaussian wave packet responses as well as Talbot recurrences. In addition, Bloch oscillations and Anderson localization can also be obtained when the phase accumulations are linearly changed and weakly modulated in random, respectively. The periodic effective gauge fields configuration in our protocol enables SPL to be a research platform for one-dimensional dynamically modulated elements or even non-Hermitian waveguides

Narrow bandwidth Q-switched Erbium-doped fiber laser based on dynamic saturable absorption filtering effect

We proposed a narrow spectral bandwidth Erbium-doped fiber (EDF) laser Q-switched by a homemade saturable dynamic induced grating (SDIG) which is introduced via reforming the structure of a fiber saturable absorbers FSA with a piece of EDF and a fiber Bragg grating. The SDIG integrates both saturable absorption and spectral filtering effect simultaneously, which was confirmed through theoretical analysis and experimental results for the first time, to the best of our knowledge. Further study verified that the spectral width of the Q-switched emissions is decided by the length of the SDIG and the input power of the pump source. The Q-switched pulse with the narrowest spectral width of about 29.1 pm achieved in this work is the narrowest bandwidth pulse in the domain of the FSA Q-switched fiber lasers when the length of SDIG and pump power are 20 cm and 250 mW, respectively. Our method provides a simple way to obtain the Q-switched pulses with narrow bandwidths, which have promising applications for nonlinear frequency conversion, Doppler LIDAR and coherent beam combinations

A Novel Antifungal Plasma-Activated Hydrogel

Antifungal hydrogels with added antifungal drugs have received extensive attention from researchers due to their potential use in various applications, such as wound dressings and ultrasound gel pads. In this study, we proposed and designed an alternative antifungal hydrogel preparation strategy to obtain hydrogels with high antifungal abilities. We employed plasma-activated water (PAW) instead of water in the hydrogel polymerization process to prepare plasma-activated hydrogels (PAHs). Disc diffusion assay results revealed that PAH exhibits satisfactory antifungal activity. Interestingly, the oxidation–reduction potential (ORP) of the PAH was significantly lower than that of conventional polyacrylamide (PAAm) hydrogels, and we provided a possible reaction equation to explain the lower value of ORP in the PAH. Furthermore, using electron spin resonance (ESR) spectroscopy, the hydroxyl radical was detected in PAHs. Although the active ingredients in the hydrogel cannot be quantitatively measured, the hydroxyl radical and NO3– are speculated to be the main components of PAH with antifungal activity according to ESR spectroscopy and optical emission spectroscopy. Further experiments also showed that PAH has a longer antifungal lifetime than PAW. In summary, the proposed plasma-activated hydrogels can provide valuable preparation strategies for delivering antifungal capabilities and have many potential applications in biomedical fields

A Novel Antifungal Plasma-Activated Hydrogel

Antifungal hydrogels with added antifungal drugs have received extensive attention from researchers due to their potential use in various applications, such as wound dressings and ultrasound gel pads. In this study, we proposed and designed an alternative antifungal hydrogel preparation strategy to obtain hydrogels with high antifungal abilities. We employed plasma-activated water (PAW) instead of water in the hydrogel polymerization process to prepare plasma-activated hydrogels (PAHs). Disc diffusion assay results revealed that PAH exhibits satisfactory antifungal activity. Interestingly, the oxidation–reduction potential (ORP) of the PAH was significantly lower than that of conventional polyacrylamide (PAAm) hydrogels, and we provided a possible reaction equation to explain the lower value of ORP in the PAH. Furthermore, using electron spin resonance (ESR) spectroscopy, the hydroxyl radical was detected in PAHs. Although the active ingredients in the hydrogel cannot be quantitatively measured, the hydroxyl radical and NO3– are speculated to be the main components of PAH with antifungal activity according to ESR spectroscopy and optical emission spectroscopy. Further experiments also showed that PAH has a longer antifungal lifetime than PAW. In summary, the proposed plasma-activated hydrogels can provide valuable preparation strategies for delivering antifungal capabilities and have many potential applications in biomedical fields

A Novel Antifungal Plasma-Activated Hydrogel

Antifungal hydrogels with added antifungal drugs have received extensive attention from researchers due to their potential use in various applications, such as wound dressings and ultrasound gel pads. In this study, we proposed and designed an alternative antifungal hydrogel preparation strategy to obtain hydrogels with high antifungal abilities. We employed plasma-activated water (PAW) instead of water in the hydrogel polymerization process to prepare plasma-activated hydrogels (PAHs). Disc diffusion assay results revealed that PAH exhibits satisfactory antifungal activity. Interestingly, the oxidation–reduction potential (ORP) of the PAH was significantly lower than that of conventional polyacrylamide (PAAm) hydrogels, and we provided a possible reaction equation to explain the lower value of ORP in the PAH. Furthermore, using electron spin resonance (ESR) spectroscopy, the hydroxyl radical was detected in PAHs. Although the active ingredients in the hydrogel cannot be quantitatively measured, the hydroxyl radical and NO3– are speculated to be the main components of PAH with antifungal activity according to ESR spectroscopy and optical emission spectroscopy. Further experiments also showed that PAH has a longer antifungal lifetime than PAW. In summary, the proposed plasma-activated hydrogels can provide valuable preparation strategies for delivering antifungal capabilities and have many potential applications in biomedical fields

Preparation of Ultrasmall Goethite Nanorods and Their Application as Heterogeneous Fenton Reaction Catalysts in the Degradation of Azo Dyes

The discharge of azo dyes causes great harm to humans and the environment. Azo dyes can be degraded by a heterogeneous Fenton reaction catalyzed by α-FeOOH nanorods. However, because of the large size of conventional goethite nanorods, the reaction rate of the heterogeneous Fenton reaction is limited. In this study, we proposed a template method strategy for synthesizing ultrasmall α-FeOOH nanorods (SFNs) and investigated their use for catalyzing the degradation of an azo dye, methyl orange (MO). Transmission electron microscopy results suggested that the sizes of SFNs are much smaller than those of conventional nanorods (LFNs), and the catalytic efficiency of SFNs is 7.4 times higher than that of LFNs. This can be explained by the higher specific surface area and more catalytic sites of the catalyst. The degradation rate of MO increases with an increase in the concentrations of hydrogen peroxide (H2O2) and SFNs. Moreover, the MO degradation rate can reach 98% under the appropriate parameters after 60 min of reaction. In addition, reuse experimental results suggest that SFNs manufactured using our proposed approach achieved satisfied reusability, indicating that SFNs have potential application prospects in the degradation of azo dyes by catalyzing the heterogeneous Fenton reaction

Surfactants Improving the Wetting Behavior and Adhesion Mechanism of Pesticide Dilution Droplets on Jujube Leaf Surfaces

Fruit tree leaves have different chemical compositions and diverse wax layer structures that result in different patterns of wetting and pesticide solution spreading on their surface. Fruit development is a time when pests and diseases occur, during which a large number of pesticides are needed. The wetting and diffusion properties of pesticide droplets on fruit tree leaves were relatively poor. To solve this problem, the wetting characteristics of leaf surfaces with different surfactants were studied. The contact angle, surface tension, adhesive tension, adhesion work, and solid–liquid interfacial tension of five surfactant solution droplets on jujube leaf surfaces during fruit growth were studied by the sessile drop method. C12E5 and Triton X-100 have the best wetting effects. Two surfactants were added to a 3% beta-cyfluthrin emulsion in water, and field efficacy tests were carried out on peach fruit moths in a jujube orchard at different dilutions. The control effect is as high as 90%. During the initial stage when the concentration is low, due to the surface roughness of the leaves, the surfactant molecules adsorbed at the gas–liquid and solid–liquid interfaces reach an equilibrium, and the contact angle on the leaf surface changes slightly. With increasing surfactant concentration, the pinning effect in the spatial structure on the leaf surface is overcome by liquid droplets, thereby significantly decreasing the contact angle. When the concentration is further increased, the surfactant molecules form a saturated adsorption layer on the leaf surface. Due to the existence of a precursor water film in the droplets, surfactant molecules on the interface continuously move to the water film on the surface of jujube tree leaves, thus causing interactions between the droplets and the leaves. The conclusion of this study provides theoretical guidance for the wettability and adhesion of pesticides on jujube leaves, so as to achieve the purpose of reducing pesticide use and improving pesticide efficacy

Observation of Q-switched and continuous wave regimes with mode-hopping in Er-doped fiber lasers incorporating a dynamic population grating

Dynamic population gratings (DPGs) in rare-earth doped fibers are prevalent devices in fiber lasers for the production of single-longitudinal-mode emission, Q-switched pulses, and wavelength self-sweeping regimes. This study presents a transition from Q-switched state to continuous wave (CW) state, accompanying irregular mode-hopping, in an erbium-doped fiber laser with a heavily-doped DPG centered at 1549.95 nm. Our results demonstrate that the transition between these two states can be achieved by adjusting the pump power. The repetition frequency of the Q-switched pulse increases monotonically with the increasing pump power, while the pulse duration initially narrows and then expands because the reduced peak intensity weakens the nonlinear effect. Additionally, modulation peaks are evident on both the Q-switched pulse train and the CW background, which are induced by the irregular mode-hopping caused by the DPG. Furthermore, we observe that the central wavelength fluctuates within a range of 0.05 nm. These results provide valuable insight into the DPG effect in heavily-doped fibers