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Plasmonic nanocomposites have been extensively studied for over 3 decades. According to early theoretical studies, a large enhancement of nonlinear response has been predicted. Nonetheless, the promised enhancement of coherent or Kerr‐type nonlinearities incurs major limitations related to strong absorption and saturation effects. Accordingly, diffraction‐limited interactions and long‐scale propagation in ultrafast timescales are undermined despite nanoscale‐localized electronic field enhancement. Seemingly only nanometric devices operating at low intensity regimes are benefitted from the foresaid effect. Nonetheless, numerous studies have still exploited configurable properties of the nonlinear response of plasmonic nanocomposites, such as nonlinear absorption, high‐order nonlinearities, and diffusive nonlinearities for the development of novel processes within the framework of nonlinear wave propagation described by effective medium properties. In this review, the most recent developments on the understanding of the nonlinear response of metals and plasmonic nanocomposites in various temporal regimes are presented. Furthermore, a synthesis of their experimentally determined third‐order properties obtained by various experimental techniques, along with practical considerations, is provided. Computational models used for the formulation of nonlinear wave propagation in plasmonic nanocomposites are subsequently presented, corresponding to applicable concepts. Most recent related applications are concisely summarized, indicating the directions of increasing interest in the field, and outlining shortcomings. [ABSTRACT FROM AUTHOR]

The tellurium (Te)‐doped Ag60‐xSe40Tex (x = 0%, 5%, 10%, 15%) thin films of thickness ∼800 nm were prepared from the bulk sample by thermal evaporation method on a glass substrate. The X‐ray diffraction study revealed the amorphous nature of the films whereas the change in vibrational modes was noticed from the Raman spectroscopy. The composition of the films was verified by energy dispersive X‐ray analysis and the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in optical properties (linear and non‐linear) with Te addition were studied from UV‐Visible spectroscopy data and related empirical formulas. The addition of Te reduced the bandgap values significantly and the reduction in transmission resulted in the increase of the linear refractive index. The decrease in optical bandgap is due to an increase in disorder while the width of the tail in the gap increased with Te%. The optical density, dispersion energy, extinction coefficient, carrier concentration, dielectric constant, oscillator wavelength increased while the oscillator energy, oscillator strength, optical electronegativity decreased with Te content. The electrical susceptibility increased with Te content. The non‐linear susceptibilities and the non‐linear refractive index increased which is good for the nonlinear photonic devices. [ABSTRACT FROM AUTHOR]

The properties of crystalline materials can be described mathematically by tensors whose components are generally known as property constants. Tabulations of these constants in terms of the independent components are well known for common material properties (e.g. elasticity, piezoelectricity etc.) aptly described by tensors of lower rank (e.g. ranks 2–4). General relationships between constants of higher rank are often unknown and sometimes reported incorrectly. A computer program is developed here to calculate the property constant relationships of a property of any order, represented by a tensor of any rank and point group. Tensors up to rank 12, e.g. the tensor of sixth‐order elastic constants , can be calculated on a standard computer, while ranks higher than 12 are best handled on a supercomputer. Output is provided in either full index form or a reduced index form, e.g. the Voigt index notation common to elasticity. As higher‐order tensors are often associated with nonlinear material responses, the program provides an accessible means to investigate the important constants involved in nonlinear material modeling. The routine has been used to discover several incorrect relationships reported in the literature. [ABSTRACT FROM AUTHOR]

A conventional ceramic processing method was applied to manufacture high‐density 20‐nm ZnO‐Bi2O3‐Mn2O3 varistor ceramics. Different cooling rates in the range of 135–540°C/h led to a relatively slight influence on the microstructure, varistor voltage, and leakage current. In contrast, these rates strongly affected the nonlinear exponent. The specific surface area of the 20‐nm ZnO nanoparticle may have led to an intense solid‐state reaction even at a low cooling rate. Superior nonlinearity, with 59.7 μA nonlinear current leakage and 273.5 μA leakage current, was achieved at the 135°C/h cooling rate. The differences in the cooling rates led to a remarkable change in the material's stability under direct current (DC)‐accelerated aging stress in the following order: 135°C/hr ˃ 270°C/hr˃405°C/hr ˃ 540°C/hr. [ABSTRACT FROM AUTHOR]

Owing to mixed‐integer and non‐linear properties, the distribution network reconfiguration (DNRC) problem has been widely addressed with meta‐heuristic algorithms. To accelerate the solution process, two essential components of meta‐heuristic algorithms are investigated in this study: solution representation and fitness evaluation. Instead of the popular binary and integer numbers, decimal encoding is employed. Decoding is based on the proposed probability‐based loop destruction strategy. The fitness evaluation is based on the power flow calculation of radial network. Different from backward/forward sweep method, the advantageous direct solution technique is utilised, where the matrix generation process has been accelerated. Both improvements are based on the graph theory and fully explained with illustrative examples. Case studies are implemented on five benchmark systems. The superiority of the proposed methods over their advanced counterparts has been established with intensive comparisons. Finally, these methods are integrated into a standard particle swarm optimisation framework for the solution of DNRC. Results indicate that the proposals significantly improve the solution efficiency without the loss of quality. [ABSTRACT FROM AUTHOR]

Abstract: Alkali metals (Li, Na, K) doped anthracene high quality organic crystals were grown by slow evaporation at ambient environment. The relative occupancy of dopants and its influence of AN lattice phonons has been probed using elemental and diffraction analysis respectively. These alkali metal ions act as an efficient optically active sites, thereby projecting enhancement in UV region and photoluminescence studies. The nonlinear susceptibility (χ(3)) have been evaluated for doped crystals from Z ‐ scan technique and the values of these parameters found to be 10−2 esu which was higher than reported organic crystals. The incorporation of the alkali metal ions progressively alters melting point, overtone vibrational bands, mechanical strength and nonlinear optical properties for the grown crystals. The improved thermal, mechanical, linear and nonlinear optical properties of doped crystals make it as a better candidate for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotubes (MWCNTs) were successfully incorporated inside silica aerogel matrix. Solid composite materials were investigated by high-resolution transmission microscopy, scanning electron microscopy, optical spectroscopy. MWCNTs in the form of small bundles and individual tubes get locked inside the aerogel between its pores resulting in the local solution-free environment for nanotubes. Optical transmission of the composite material can be modified by the amount of the added MWCNTs. Nonlinear optical properties were studied by a Z-scan technique. Composite materials demonstrate saturable absorption for femtosecond laser pulses at 515 nm wavelength that are attributed to the properties of embedded nanotubes. Silica aerogels possess significantly better thermal stability compared to polymer matrices, hosts that are frequently used for saturable absorption applications of carbon nanotubes. Solid and lightweight silica aerogels with embedded nanotubes can be used as optical elements for various photonic devices. Photo of silica aerogel with embedded MWCNTs. Normalized Z-scan transmittance of silica aerogel with nanotubes for two different on-focus intensities. [ABSTRACT FROM AUTHOR]