Some types of dark soliton interactions in inhomogeneous optical fibers

Dark solitons are the subject of intense theoretical and experimental studies in nonlinear optics due to their unique characteristics compared with bright solitons. In this paper, the variable coefficient high-order nonlinear Schrödinger equation in the inhomogeneous optical fiber is investigated. Via the Hirota bilinear method and symbolic computation, the analytic dark two-soliton solutions are obtained. With the suitable choices of functions and coefficients for the obtained dark two-soliton solutions, some new phenomena are presented for the first time. The influences on phases and amplitudes of soliton interactions are detailed analyzed. Moreover, sets of double-triangle structures and methods of changing the propagation direction of dark solitons are introduced. Finally, by choosing suitable functions of the fourth-order dispersion parameter, the arch-structure and M-structure interactions are revealed. Results may be potentially useful in designing all-optical switches and optical fibers.     

Supercontinuum generation with femtosecond optical pulse compression in silicon photonic crystal fibers at 2500 nm

In this paper, femtosecond optical pulses compression and supercontinuum generation in a triangular silicon photonic crystal fiber at 2500 nm are investigated. A region of large minimum anomalous group velocity dispersion, negligible higher order dispersions and unique nonlinearity of silicon are used to demonstrate compression of 100 fs initial input optical pulses to 2.5 fs and ultra-broadband supercontinuum generation with very low input pulse energy over short distances of the fiber.     

Injection-locked range and linewidth measurements at different seed-laser linewidths using a Fabry–Pérot laser-diode

In this paper we experimentally examine the dependence of the injection-locked range magnitude of a Fabry–Pérot (FP) laser on the linewidth of a seed laser. We measure the enhancement of the incident-power-dependent injection-locked range when changing the seed-light linewidth in three different ranges, starting with tens of GHz, then hundreds of MHz, and up to a few hundred kHz. We notice the progressive shrinkage of the locking range with an increase in the linewidth of the seed source. Simultaneously, the linewidth of a FP laser was measured and the cancellation of multiple longitudinal operating modes as well as a great reduction of linewidth are observed with a self-homodyne measurement.     

Quest towards ultimate performance in superconducting nanowire single photon detectors

正In 2007,superconducting nanowire single photon detectors(SSPD or SNSPD)[1]made an outstanding impact in the field of quantum information technology by demonstrating quantum key distribution(QKD)over a 200-km optical fiber with a 42-dB optical loss using a practical SNSPD system[2].This successful demonstration was realized thanks to its extremely     

The effect of anodising time on the electrochemical behaviour of the Ti/TiO<Subscript>2</Subscript> NTs/IrO<Subscript>2</Subscript>-RuO<Subscript>2</Subscript>-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> anode

Nowadays, mixed metal oxide (MMO) anodes are a superior alternative to lead alloys in electrowinning processes. Passivation of titanium substrate is the most common mechanism of deactivation in these anodes. In this research, titanium oxide nanotubes have been utilised as an interlayer between the substrate and a mixed metal oxide coating in order to improve the anode electrochemical behaviour and life via retardation of titanium passivation. Anodising of the substrate was done in 0.5 wt% hydrofluoric acid for 30, 60 and 240 min. The samples were subsequently coated with a coating composed of IrO₂-RuO₂-Ta₂O₅. The microstructure of different samples was observed by scanning with an electron microscope, and the electrochemical behaviour of the samples was studied by accelerated life test, cyclic voltammetry and electrochemical impedance spectroscopy. The studies showed that formation of titanium oxide nanotubes with anodising times of 60 and 240 min increases the life of the anode through the provision of a compact coating. The life of the anode which was anodised for 240 min lasted about 20% longer than the sample which had a substrate without any anodised layer.     

Fabrication of urchin-like NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> microspheres assembled by using SDS as soft template for anode materials of Lithium-ion batteries

In this paper, the urchin-like NiCo₂O₄ microspheres assembled by using sodium dodecyl sulfate (SDS) as soft template are successfully fabricated by a facile procedure including microemulsion-solvothermal reaction and subsequent calcination at 400 °C for 4 h. The structure and morphology of synthesized NiCo₂O₄ particles are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It has been clearly revealed that the prepared three-dimensional urchin-like NiCo₂O₄ microspheres are constituted by one-dimension nanowires. As it is applied to anode for lithium-ion batteries (LIBs), the initial coulombic efficiency is up to 75.7%, and the specific reversible capacity retains up to 1034.2 mAh/g even after 40 cycles at a current density of 100 mA/g. Furthermore, as the current density gradually increases to 800 mA/g, it still delivers the reversible capacity of 895.4 mAh/g. The high reversible specific capacity, perfect cyclability, and rate performance are attributed to the unique urchin-like NiCo₂O₄ microspheres, which can alleviate the volume expansion and shorten the diffusion path of ions and electrons during lithiation/delithiation process. The self-standing urchin-like NiCo₂O₄ microspheres may be a very promising candidate in place of the commercial graphite-based anode materials for high-performance LIBs.     

Spray pyrolysis-deposited TiO<Subscript>2</Subscript> thin films as high-performance lithium ion battery anodes

Focusing on additive-free electrodes, thin films are of typical interest as electrodes for lithium ion battery application. Herein, we report the fabrication of TiO₂ thin films by spray pyrolysis deposition technique. X-ray diffraction and transmission electron microscopic analysis confirms the formation of anatase TiO₂. Electrochemical evaluation of these sub-micron TiO₂ thin films exhibits high-rate performance and long cycling stability. At 1C rate (1C?=?335 mA/g), the electrode delivered discharge capacity of 247 mAh/g allowing about 0.74 lithium into the structure. The electrodes also delivered specific capacities of 122 and 72 mAh/g at 10 and 30C rates, respectively. Without conductive additives, this excellent performance can be attributed to the nanosize effect of TiO₂ particles combined with the uniform porous architecture of the electrode. Upon cycling at high rates (10 and 30C), the electrode exhibited excellent cycling stability and retention, specifically only <?0.6% capacity loss per cycle over 2500 cycles.     

Autaptic modulation-induced neuronal electrical activities and wave propagation on network under electromagnetic induction

Based on an improved HR neuron model, the effects of electrical and chemical autapses on the firing activities of single neurons are studied, and the wave propagation in forward feedback neural network is also discussed by considering autapstic regulation under different intensities of electromagnetic induction. It is found that the electrical activities of single neuron can be changed by exerting excitatory or inhibitory of electrical and chemical autapses. With different feedback gains of electromagnetic induction current, membrane potential shows the oscillatory solutions and steady states. Under the condition of different autapse or electromagnetic induction, the propagation of electrical activities caused by the central neuron is transformed in the forward feedback network. Moreover, the spatial synchronization of the network will be changed by choosing different coupling intensities and feedback gains. It is proved that the electrical and chemical autapses play a significant role in firing modes of single neuron and the wave propagation of the forward feedback networks under the electromagnetic induction.     

The perception of entropy in rapidly moving sparse dot arrays: a nonlinear dynamic perspective

In visual fields composed of dots spatially randomly distributed but moving rigidly, the percept of coherent motion is lost once D_max is exceeded, resulting in an incoherent, random percept. We have investigated this transition both from a psychophysics perspective and in the development of a dynamic model of the visual system based on a spatially coupled array of nonlinear damped mass-springs cells. We present results of experiments using rigidly moving arrays of dots of different levels of sparseness and differing displacement magnitudes. Results show that the perception of randomness can be reliably judged and displays a transition from coherent to non-coherent motion as the motion amplitude is increased. Using standard psychophysical just noticeable difference (JND) judgements, we noted that the threshold JND was a function of displacement magnitude and sparseness and could not be explained by extant spatiotemporal filtering models. Our model qualitatively explains the important features of the data, reproducing the experimental D_max and entropy perception effects with increased stimuli motion amplitude at different spatial sparseness levels. We have then performed some numerical simulations of the model when the masses in the array are randomly distributed. Results show that sparseness plays different role if close or far from D_max in terms of motion coherence discrimination.     

Understanding the enhanced synchronization of delay-coupled networks with fluctuating topology

We study the dynamics of networks with coupling delay, from which the connectivity changes over time. The synchronization properties are shown to depend on the interplay of three time scales: the internal time scale of the dynamics, the coupling delay along the network links and time scale at which the topology changes. Concentrating on a linearized model, we develop an analytical theory for the stability of a synchronized solution. In two limit cases, the system can be reduced to an “effective” topology: in the fast switching approximation, when the network fluctuations are much faster than the internal time scale and the coupling delay, the effective network topology is the arithmetic mean over the different topologies. In the slow network limit, when the network fluctuation time scale is equal to the coupling delay, the effective adjacency matrix is the geometric mean over the adjacency matrices of the different topologies. In the intermediate regime, the system shows a sensitive dependence on the ratio of time scales, and on the specific topologies, reproduced as well by numerical simulations. Our results are shown to describe the synchronization properties of fluctuating networks of delay-coupled chaotic maps.