Topological Nanophotonic Wavelength Router Based on Topology Optimization

The topological nanophotonic wavelength router, which can steer light with different wavelength signals into different topological channels, plays a key role in optical information processing. However, no effective method has been found to realize such a topological nanophotonic device. Here, an on-chip topological nanophotonic wavelength router working in an optical telecom band is designed based on a topology optimization algorithm and experimentally demonstrated. Valley photonic crystal is used to provide a topological state in the optical telecom band. The measured topological wavelength router has narrow signal peaks and is easy for integration. This work offers an efficient scheme for the realization of topological devices and lays a foundation for the future application of topological photonics.

NMR study of Au/Al nanosytems in solution

Nuclear magnetic resonance spectroscopy (NMR) 1H, 35Cl, 27Al and 13C was applied to study underlying processes at the various stages of the synthesis of Au/Al nanoparticles. 35Cl spectrum was downfield shifted by 2.6 ppm as to the reference signal of the hydrated Cl− ion in NaCl solution. The evolution of the NMR spectra points to the formation of the stabilized shell around the gold containing nucleus. The shell restricts the supply of the reducing agents, which is the condition for the formation of Au2+ state at the concentration range in question. The electron paramagnetic resonance (EPR) spectra reveal formation of both Au2+ (g = 2.17) and Au+ (g < 2) intermediates incompletely reduced as well as Au0 clusters (g = 2.062) with odd number of atoms. The latter is coupled in many cases by the narrow signal with g = 2.0048 attributed to the radical in the supporting surrounding (tannin containing matrix in our case).

Bidirectional Nonnegative Deep Model and Its Optimization in Learning

Nonnegative matrix factorization (NMF) has been successfully applied in signal processing as a simple two-layer nonnegative neural network. Projective NMF (PNMF) with fewer parameters was proposed, which projects a high-dimensional nonnegative data onto a lower-dimensional nonnegative subspace. Although PNMF overcomes the problem of out-of-sample of NMF, it does not consider the nonlinear characteristic of data and is only a kind of narrow signal decomposition method. In this paper, we combine the PNMF with deep learning and nonlinear fitting to propose a bidirectional nonnegative deep learning (BNDL) model and its optimization learning algorithm, which can obtain nonlinear multilayer deep nonnegative feature representation. Experiments show that the proposed model can not only solve the problem of out-of-sample of NMF but also learn hierarchical nonnegative feature representations with better clustering performance than classical NMF, PNMF, and Deep Semi-NMF algorithms.

EPRInvestigation of Synthetic, Doped FeS2 and RuS2 Single Crystals

Synthetic FeS2 and RuS2 single crystals were prepared by the flux method using PbCl2, bismut, and tellurium as different solvents. FeS2 and some RuS2 samples were doped with elementary vanadium, other RuS2 crystals with manganese and nickel. The EPR spectra revealed Mn2+ in the low-spin state and Ni2+. The lineshape of the Mn sextet turned out to be asymmetrical. In some RuS2 samples we detected an isotropic structureless rather narrow signal with a linewidth down to 0.05 mT and attributed it to the conductivity. Its lineshape becomes symmetrical and Lorentzian by grinding the samples to a polycrystalline powder. The EPR parameters of appropriate spin-Hamiltonians were determined. The intensities of the allowed and forbidden lines depended very differently on the microwave power due to different degrees of saturation.

Electronic Conduction in Polymers. III. Electronic Properties of Polypyrrole

The electron spin resonance absorption and electrical resistivity have been measured under rigorous conditions for a series of polypyrroles prepared over the temperature range 120-500�. When plotted as a function of pyrolysis temperature the resistivity shows a maximum in the region 200-300�. Although the resistivity of the polymers prepared at 120� and 500� is roughly similar, their e.s.r. behaviour is quite different. The low-temperature polymer, containing much complexed iodine, shows a very broad signal arising from an excited state probably associated with a polypyrrole-iodine charge-transfer complex; the high temperature polymer, containing no iodine, shows a strong narrow signal arising from the ground state of the polymer. The changes in conductivity of the polymers following the adsorption of electron acceptor or donor molecules have been measured. It is concluded that, depending on the relative amounts of electron donating or attracting chemisorbed species in relation to the concentration of donor nitrogen atoms in the polypyrrole, the polymer may behave as an intrinsic or extrinsic semiconductor with n- or p-type characteristics. Charge-transfer complexes of strength sufficient to cause partial ionization induce extrinsic behaviour by changing the ratio of the number of electrons to the number of holes. Substituent groups such as the hetero atoms which interact with the π-electron system inductively or through resonance affect only the relative mobility of the charge carriers and induce intrinsic behaviour.