ZnS Nanospheres for Optical Modulator in an Erbium-Doped Fiber Laser

Zinc sulfide (ZnS), which belongs to transition metal monochalcogenides, is a semiconductor material with wide direct band gap. It can potentially show some special applications (such as luminescence, phosphor, sensors, infrared window materials, photocatalysis) by changing the morphology, size, and crystal structure of semiconductor materials. However, ZnS nanospheres have not been studied as optical modulators until now. Herein, ZnS nanospheres are synthesized by the hydrothermal method and are used to realize optical modulators in an Er-doped fiber laser. The evanescent field effect is utilized to incorporate the ZnS nanospheres on a tapered fiber. Furthermore, with the increase in pump power, the modulation interval gradually decreases to a minimum of 34.36 ns corresponding to the modulation frequency of 29.1 MHz, which is the highest modulation frequency to our knowledge in a ring cavity all-fiber laser. These results demonstrate ZnS nanospheres together with the interaction of dispersion and nonlinearity in optical fibers can modulate the proposed lasers. This not only provides a new method for controlling the power and frequency of all optical modulators, but also marks an important step for ZnS materials in optics research and device applications.     

具有增强电荷转移驱动的磺酸基功能化g-C3N4光催化剂的设计合成及应用

随着全球环境问题日益严重以及能源需求的不断增长,人们对高效环境修复与能源转换技术的需求日益增强.以半导体材料为光催化剂,可将可再生的太阳能转化为化学能,有望成为解决人类面临的能源和环境问题的有效途径.其中,开发高效稳定的光催化剂是该技术得以实际应用的关键.近几十年,研究人员开发出多种半导体材料并应用于光催化研究.其中,具有可见光响应的有机非金属光催化剂石墨相氮化碳(g-C₃N₄)因其稳定的分子结构,较小的禁带宽度(~2.7 e V)以及合适的能带结构而备受关注.然而,与大多数半导体光催化剂相似,由于传统g-C₃N₄上的光生电子和空穴极易复合,表面催化活性位点较少,可见光响应范围较窄,使得其催化效率不高.基于g-C₃N₄独特的有机分子结构,通过引入功能化的特定基团以优化g-C₃N₄的电子能带结构,促进载流子传输,拓展可见光响应范围,是提高其光催化效率的有效途径.已有研究表明,在各种功能化官能团中,具有强电负性的含氧基团对g-C₃N₄的Melon单元优化是非常有效的.因此,本文通过g-C₃N₄与氨基磺酸间的简单固相热反应成功合成了磺酸基功能化的g-C₃N₄纳米片(SACN),并实现了同步增强的相互作用.根据固体强酸特性,氨基磺酸可以在热处理的辅助下对g-C₃N₄进行酸刻蚀,从而增加其比表面积以及表面催化活性位点.更重要的是,理论计算与实验表征结果表明,磺酸基团的吸电子诱导效应所产生的电荷驱动力可极大改善g-C₃N₄的电荷转移动力学,有效抑制了它们的再结合.此外,吸电子诱导效应还可促进g-C₃N₄的局域电子再分布,进而降低g-C₃N₄的导带电位,增强光诱导电子的还原能力.光催化性能测试结果表明,SACN-400样品(前驱体中氨基磺酸加入量为400 mg)在光催化分解水制备氢气以及光降解传统污染物领域展现出较好的性能,其在入射光波长为420±15 nm时的产氢表观量子效率为11.03%.综上,本文为设计合成具有较高产氢性能以及污染物降解效率的石墨相氮化碳基光催化剂提供了一种简便有效的策略.     

Suppression of multiple scattering by photon cross-correlation techniques

The effectiveness of cross-correlation schemes for suppressing multiple scattering in light scattering measurements has been demonstrated convincingly. Thus, measurements on turbid samples can be analysed as though the samples were transparent, i.e. exhibiting only single scattering. The methods are now being used for new research, particularly in the study of concentrated colloidal dispersions. This article reviews the current state of the field with emphasis on the two-colour and three-dimensional dynamic light scattering techniques. Although these methods were originally designed to suppress multiple scattering in dynamic light scattering, it has recently been recognised that they are also effective in static light scattering. The cross-correlation schemes are compared briefly with other light-scattering methods for studying turbid and opaque samples such as fibre-optic probes and diffusing wave spectroscopy.     

Photonic Alamouti encoder for unifying hybrid FSO/RF system

A unified hybrid free-space optical–radio-frequency (HFR) system based on photonic technology is proposed to simplify the system design and remove the restriction on the azimuth rotation for point-to-point wireless links between mobile platforms. The proposed system applies parallel channel coding techniques and photonic technology to unify the two channels. The principle of a photonic encoder for Alamouti codes is proposed and verified by simulations. A 10 Gbit/s data stream is correctly encoded with an acceptable waveform distortion. Photoelectronic integrated circuits for unified photonic codecs and transceivers could be developed based on this principle.     

Ag nanoparticles immobilized on guanidine modified-KIT-5 mesoporous nanostructure: Evaluation of its catalytic activity for synthesis of propargylamines and investigation of its antioxidant and anti-lung cancer effects

The current study involves the novel synthesis of Ag nanoparticles (Ag NPs) decorated biguanidine modified mesoporous silica KIT-5 following post-functionalization approach (KIT-5-bigua-Ag). The tiny Ag NPs were being stabilized over the in situ prepared biguanidine ligand. The high surface area material was characterized using advanced analytical methods like Fourier Transformed infrared (FT-IR) spectroscopy, N₂-adsorption–desorption isotherm, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction study (XRD). The material was having large pore cage like structure with pore diameter of 8–10 nm. TEM study displayed the particles size of deposited Ag NPs were 10–15 nm. The KIT-5-bigua-Ag nanocomposite had a significantly high surface area of 318 m²/g (BET analysis). Towards the chemical applications of the material, we headed the three-component reaction of aldehydes, amines and alkynes (A³ coupling) with good to excellent yields (70–98%) of diverse Propargylamines. The catalyst was easily isolable and reused in 8 cycles without any leaching and considerable change in its reactivity. In addition, the KIT-5-bigua-Ag nanocomposite was engaged in biological assays like study of anti-oxidant properties by DPPH mediated free radical scavenging test using BHT as a reference molecule. Thereafter, on having a significant IC50 value in radical scavenging assay, we extended the bio-application of the desired nanocomposite in anticancer study of A549 cell of human lung in-vitro conditions. In the cytotoxicity and anti-human lung studies, the nanocomposite was treated to lung cancer A549 cell line following MTT assay. The cell viability of malignant lung cell line reduced dose-dependently in the presence of KIT-5-biguanidine-Ag nanocomposite. IC50 values of the nanocomposite were observed to be 915.22 μg/mL against A549 cell line. So, these results suggest that KIT-5-bigua-Ag as a novel chemotherapeutic nanocomposite have a suitable anticancer activity against lung cell lines.     

Deformations of the spin currents by topological screw dislocation and cosmic dispiration

We study the spin currents induced by topological screw dislocation and cosmic dispiration. By using the extended Drude model, we find that the spin dependent forces are modified by the nontrivial geometry. For the topological screw dislocation, only the direction of spin current is bent by deforming the spin polarization vector. In contrast, the force induced by cosmic dispiration could affect both the direction and magnitude of the spin current. As a consequence, the spin-Hall conductivity does not receive corrections from screw dislocation.     

Analysis of polarization state in quantum key distribution via single-photon two-qubit states

An improved quantum key distribution scheme via single-photon two-qubit states is proposed. The input–output model of the polarization state is established. And the influence of the interferometers to the polarization state is analyzed. Quantum bit error rate of polarization coding caused by birefringent and coordinate system difference between incident light and the fast and slow axes in fiber interferometer is simulated. Furthermore, maintaining conditions of polarization state are given on this basis.     

基于第一性原理的固体界面摩擦学性能高通量计算研究

基于第一性原理提出了自动构建计算构型-自动提交计算任务-智能分析计算数据的固体界面摩擦性能自动化计算方法,并通过并发-并行同时计算约1 000个计算任务,实现了固体界面摩擦性能的高通量计算. 以石墨烯/石墨烯滑动体系为例,测试了高通量计算方法的可靠性. 结果表明:通过该方法计算的势能面与文献中使用传统方法计算的势能面一致,摩擦系数也与试验结果相符合,从而验证了该方法的可靠性. 该方法能够极大地节约科研人员使用第一性原理研究固体界面摩擦性能所需的时间.      

Attacking Quantum key distribution with GHZ state

A modified attack scheme base on GHZ state is proposed. The relationships among QBER, ratio of qubits which eavesdropped by Eve(eavesdropper) and average photon number in signal state were analysed. The simulation shows that when Eve attacks all of the multi-photons state pulses and the 43% of single-photon state pulses he can get about 46% original qubits which shared between Alice (sender) and Bob (receiver). And the average photon number of the signal state affect the QBER and the leaked information non-linearly.