Nonlinear wave interactions in patterned Silica and AlGaAs waveguides

We study nonlinear interactions between discrete optical solitons that propagate in different regimes of diffraction, and the nonlinear scattering of dispersive waves by local optical potentials. It is well known in optics that when linear coherent waves meet, they interfere without interactions. Linear waves also scatter through local optical structures not exchanging any power with the guided modes of these structures. As a focusing Kerr nonlinearity is present, such linearly-inhibited phenomena can exist. Our studies are performed in silica and AlGaAs nonlinear waveguides, excited by ultra-short pulses in the near infrared. Presented at 9-th International Workshop on Nonlinear Optics Applications, NOA 2007, May 17–20, 2007, Świnoujście, Poland     

放电管直径和水含量对脂肪醚气相微波放电分解产生活泼自由基影响的ESR研究

本文用自旋捕捉技术与ESR相结合方法,系统研究了放电管直径及水含量对低压下脂肪醚气相微波放电分解产生自由基的影响。表明:随着放电管直径减小,放电时碳化现象加重,H·原子寿命变短;含水量加大,碳化剧烈。并根据其放电机理,对以上现象发生的原因进行一定的探讨。     

电极过程自由基中间体的ESR研究——取代苯基重氮盐的电解还原

本文用自由基捕捉剂苯亚甲基叔丁基氮氧化物(PBN)与ESR相结合的方法研究了十种取代苯基重氮盐RC₆H₄N₂⁺BF₄^-(R=F,Cl,Br,NO₂,OCH₃及CH₃)在乙腈中电解还原产生的活泼自由基。结果表明:1.RC₆H₄N₂⁺BF₄^-电解还原时产生RC₆H₄自由基,并能被捕捉剂PBN所捕捉,以形成稳定的自由基加合物[RC₆H₄-PBN]^·。2.由[RC₆H₄-PBN]^·ESR谱的超精细裂分常数算出的二面角θ_β值大小与处于不同位置的给定取代基R的关系为:θ_β(O-R) < θ_β(m-R) < θ_β(P-R)     

Influence of the electric characteristics of II–VI semiconductor material on the electroluminescence of lanthanide complex

The organic-inorganic combined structural device (ITO/PVK:Eu/ZnS/Al) is fabricated based on layered optimization scheme. II–VI semiconductor material ZnS is acted as an electron function (transporting and acceleration) layer. The hot electrons which have been accelerated in the ZnS layer directly impact excitation europium ions through resonant energy transfer and then recombine with injected holes to form excitons in PVK or EuTTA₂(N-HPA)Phen. Europium (Eu) ions may also be excited by intramolecular energy transfer from ligands. There are two kinds of excitation mechanisms: impacted excitation and injected recombination for the combined structural device. The electroluminescence (EL) intensity of the combined structural device is strongly improved and reaches up to 381 cd/m² at 20 V compared with the pure organic structural device. It may be an effective method to improve the EL intensity of the lanthanide complex by using electric characteristics of inorganic semiconductor materials.     

The unique carrier mobility of Janus MoSSe/GaN heterostructures

Heterostructure is an effective approach in modulating the physical and chemical behavior of materials. Here, the first-principles calculations were carried out to explore the structural, electronic, and carrier mobility properties of Janus MoSSe/GaN heterostructures. This heterostructure exhibits a superior high carrier mobility of 281.28 cm²·V⁻¹·s⁻¹ for electron carrier and 3951.2 cm²·V⁻¹·s⁻¹ for hole carrier. Particularly, the magnitude of the carrier mobility can be further tuned by Janus structure and stacking modes of the heterostructure. It is revealed that the equivalent mass and elastic moduli strongly affect the carrier mobility of the heterostructure, while the deformation potential contributes to the different carrier mobility for electron and hole of the heterostructure. These results suggest that the Janus MoSSe/GaN heterostructures have many potential applications for the unique carrier mobility.     

Setup of a dipole trap for all-optical trapping

Micromotion induced by the radio-frequency field contributes greatly to the systematic frequency shifts of optical frequency standards. Although different strategies for mitigating this effect have been proposed, trapping ions optically has the potential to provide a generic solution to the elimination of micromotion. This could be achieved by trapping a single ion in the dipole trap composed of a highpower laser field. Here, we present the setup of the dipole trap composed of a 532 nm laser at a power of 10 W aiming to optically trap a single ~(40)Ca~+ and we observe an AC-Stark shift of the fluorescence spectrum line of ～22 MHz caused by the 532 nm dipole beam. The beam waist of the dipole laser is several microns, which would provide a dipole potential strong enough for all-optical trapping of a single ~(40)Ca~+ ion.     

Effects of post-annealing on crystalline and transport properties of Bi_2Te_3 thin films

A well-established method is highly desirable for growing topological insulator thin films with low carrier density on a wafer-level scale. Here, we present a simple, scalable method based on magnetron sputtering to obtain high-quality Bi_2 Te_3 films with the carrier density down to 4.0 × 10~(13) cm~(-2). In contrast to the most-used method of high substrate temperature growth, we firstly sputtered Bi_2 Te_3 thin films at room temperature and then applied post-annealing. It enables the growth of highly-oriented Bi_2 Te_3 thin films with larger grain size and smoother interface. The results of electrical transport show that it has a lower carrier density as well as a larger coherent length(～ 228 nm, 2 K). Our studies pave the way toward large-scale, cost-effective production of Bi_2 Te_3 thin films to be integrated with other materials in wafer-level scale for electronic and spintronic applications.     

Molecular dynamics simulations of dopant effectson lattice trapping of cracks in Ni matrix

Molecular dynamic analysis was performed on pure and doped (by Re, Ru, Co or W) Ni at 300 K using the embedded-atom-method (EAM) potentials to understand the crack formation of the doped Ni matrix in the (010)[001] orientation. When Ni was doped with Re, Ru, and W, the matrix demonstrated increased lattice trapping limits and, as a result, improved the mechanical properties. Consequently, this prevented the bond breakage at the crack tips and promoted crack healing. The average atomic and surface energy values increased when Re, Ru, and W were added. Analysis of these energy increase helped us to understand the influence these elements had on the lattice trapping limits. The fracture strength of the Ni matrix at 300 K increased because of the formation of the stronger Ni-Re, Ni-Ru, and Ni-W bonds. At the same time, doping the Ni matrix with Co did not demonstrate any strengthening effects because of the formation of Co-Ni bonds, which are weaker than the Ni-Ni bonds. Out of all dopants tested in this work, Ni doping with W showed the best results.     

Partial atomic multipoles for internally consistent microelectrostatic calculations

An extension of the extant microelectrostatic methodologies, based on the concept of distributed generalized polarizability matrix derived from the Coupled Perturbed Hartree–Fock (CPHF) equations, is proposed for self‐consistent calculation of charge carrier and charge‐transfer (CT) state electrostatic energies in molecular solids, including the doped, defected and disordered ones. The CPHF equations are solved only once and the generalized molecular polarizability they yield enables low cost iterations that mutually adjust the molecular electronic distributions and the local electric field in which the molecules are immersed. The approach offers a precise picture of molecular charge densities, accounting for atomic partial multipoles up to order 2, which allows one to reproduce the recently reported large charge‐quadrupole contributions to CT state energies in low‐symmetry local environments. It is particularly well suited for repetitive calculations for large clusters (up to 300,000 atoms), and may potentially be useful for describing electrostatic solvent effects. © 2017 Wiley Periodicals, Inc.     

Nanoparticle enabled thermal control of ions in liquid crystals

Typically, ionic species in thermotropic liquid crystals are nearly fully ionised. Therefore, the concentration of mobile ions practically does not depend on the temperature. Interestingly, the same liquid crystals doped with nanoparticles exhibit totally different behaviour. The concentration of mobile ions become temperature dependent. This paper reports the effects of the temperature on the concentration of ions in liquid crystal nanocolloids. Liquid crystals doped with both 100% pure and contaminated nanoparticles are considered. Regardless the ionic purity of nanodopants, the concentration of mobile ions in liquid crystal nanocolloids increases towards the saturation as their temperature goes up. The magnitude of this saturation level equals the initial concentration of ions in liquid crystals doped with 100% pure nanoparticles. The temperature induced release of ions by contaminated nanoparticles in liquid crystals increases the above-mentioned saturation level. While the dispersion of 100% pure nanoparticles in liquid crystals leads to the temperature-dependent purification only, the use of contaminated nanoparticles results in the temperature-driven switching between the purification and contamination regimes enabling thermal control of ions.