Hybridized surface-plasmon resonances of platinum colloid-adsorbed gold nanospheres

The surface-plasmon resonances of gold nanospheres dispersed in water split into two bands and shift to the red with the adsorption of colloidal platinum. These spectral changes are quite different from both the calculated and the experimental spectral variations of gold nanospheres with the thickness of coating platinum. Thus, these spectral changes have been attributed to the elementary plasmon interactions of the core gold and the adsorbed colloidal platinum as well as to the modification of the medium refraction index of the gold nanospheres. A simple and intuitive picture has been drawn to describe the hybridization plasmon interactions of a platinum colloid-adsorbed gold nanosphere.     

Magneto-optical resonances in periodic dielectric structures magnetized in plane

We studied the magneto-optical properties of a magnetized diffractive structure composed of a binary diffraction grating and a homogeneous layer. The structure is magnetized in-plane and the magnetization vector is perpendicular to the grating slits. By the electromagnetic modeling, the structure is shown to produce magneto-optical effects in the form of the resonant change of transmittance and reflectance in response to changing magnetization. The said resonant effects are found to occur both for TE- and TM-polarization of the incident wave. The dispersion curves for the structure eigenmodes have been derived by calculating the complex poles of the scattering matrix. Analysis of the dispersion curves shows that frequencies of the magneto-optical resonances coincide with those of the structure eigenmodes. We studied in which way the dispersion curves vary when the structure material is being magnetized. We propose a classification of magneto-optical resonances based on their relation with the symmetry of eigenmodes excited in the structure.     

Geometrically enhanced morphology-dependent resonances of a dielectric sphere

The effect that geometrical resonances of orbiting internally reflecting rays have on the morphology-dependent resonances of microspheres is investigated heuristically and numerically using generalized Lorenz-Mie theory. Angularly resolved off-axis Gaussian beam elastic scattering spectra are presented. The results obtained show that the elastic scattering intensity of morphology-dependent resonances is noticeably enhanced in the vicinity of the geometrical resonance scattering angles.     

Spectroscopic analysis of dipole interaction of metallic nanoparticles in dielectric multilayer dielectric thin film

Using electron beam gun PVD system, the thin film with multiple alternative layers of SiO₂ + Ag (300 nm)/SiO₂ (10-60 nm) was deposited on silica substrate. Annealing test was undertaken for optical absorption analysis. The annealing agglomerated metallic nanoparticles in each layer has enhancement effect for plasmon resonance absorption, these precipitated nanoparticles also cause absorption peak red shift. When the thickness of alternative dielectric layer becomes small enough, there is a coupling phenomenon between the electric dipoles of nanaoparticles in the alternative metallic particle doped layers.     

Cascades of Fano resonances in light scattering by dielectric particles

Fano lineshapes are fundamental spectroscopic signatures that quantitatively characterize the structural and dynamic properties of physical objects, from nuclei to three-dimensional solids and liquids. The study of cascades of Fano resonances is a fresh approach to the classical problem that greatly expands our knowledge and the scope of practical applications. Here it is demonstrated that in solid state physics cascades of Fano resonance can be considered as a general property of light scattering by dielectric particles with the Mie and Fabry-Perot manifold of narrow photonic eigenmodes. A general picture of Fano resonance cascades in the spectra of all basic elementary scatterers (spheres, cylinders, rings, split rings, rectangular cuboids) is presented. For rings, split rings, and cuboids, the scattering spectrum is divided into separate spectral regions, which begin with a broad transverse resonance of the Lorentz-type or Fano-type lineshape, genetically related to the modes of the disk that generates the ring, and continue with a gallery of longitudinal modes with exponentially increasing Q factors. The alternation of a cascade of transverse modes in a strict sequence of Lorentz-Fano-Lorentz-Fano-… is shown theoretically, as well as experimentally in the case of a ring. This picture opens the door to new fundamental phenomena and extended functionality of dielectric elementary scatterers due to the highly asymmetric controllable shape of the Fano line, periodically repeating in the scattering spectrum.     

Estimation of magnetic dipole detection parameters

Expressions are derived for describing the potential characteristics of magnetic dipole detection by geophysical system receivers with magnetometer- and gradiometer-type detectors. The characteristics are compared with the capabilities of correlation receivers to detect a completely known signal. Relations for estimating the accuracy of measurement of detection parameters and for optimizing the design of geophysical receivers in the “location—measurement” operating mode are given. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 52–55, July, 1997.     

Absorption of ultrashort electromagnetic pulses by metal nanospheres in a dielectric medium

The absorption of ultrashort electromagnetic pulses on silver nanosphere embedded into glass in vicinity of plasmon resonance is studied theoretically in the frame of perturbation theory. The calculations are made for corrected Gaussian shape of incident pulse which enables us to consider both the short duration and the long duration regimes. Analysis based on numerical calculations reveals the specific features of considered process so as the change of absorption spectra for different pulse length and nonlinear dependence of absorbed energy upon pulse duration.     

Facile synthesis of Cu--In--Zn--S alloy nanospheres for fast photoelectric detection across the visible spectrum

Fast and broadband photoelectric detection is a key process to many photoelectronic applications, during which the semiconductor light absorber plays a critical role. In this report, we prepared Cu–In–Zn–S (CIZS) nanospheres with different compositions via a facile hydrothermal method. These nanospheres were ~200 nm in size and comprised of many small nanocrystals. A photodetector responded to the visible spectrum was demonstrated by spraying the solution processed nanospheres onto gold interdigital electrodes. The photoelectric characterization of these devices revealed that CIZS nanospheres with low molar ratio of n(Cu)/n(In) exhibited improved photoelectric response compared to those with high n(Cu)/n(In), which was attributed to the reduced defects. The relatively large switching ratio (I_on/I_off), fast response and wide spectral coverage of the CIZS-based photodetector render it a promising potential candidate for photoelectronic applications.     

Evanescent waves in the magnetic field of an electric dipole

The magnetic field of radiation emitted by an electric dipole contains travelling and evanescent waves when represented as an angular spectrum. The evanescent waves decay exponentially away from the xy-plane, and will therefore not contribute to the detectable radiation in the far field, in general. It is well known, however, that in a small region around the z-axis the evanescent waves of the electric field do end up in the far zone. We have studied the corresponding magnetic evanescent waves, and we have found that the evanescent waves of the magnetic field do not contribute to the far zone in the neighbourhood of the z-axis. When considering the neighbourhood of the xy-plane, it appears that both the electric and magnetic evanescent waves end up in the far field, and the travelling and evanescent waves contribute equally to the radiation in the far zone. Close to the dipole the radiation field diverges, and we have shown that this is entirely due to the evanescent waves.     

Determination of the dipole magnetic moment of a product

Described is the determination of the dipole magnetic moment of a product by measuring the magnetic induction vectors between two selected points in space laying on a single line that passes through the product, e.g., through its geometrical center. The systematic error of the determined parameter, due to the effect of higher-order magnetic moments, is estimated and recommendations are given on the distance between magnetic transducers used to measure the magnetic dipole moment.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 39–41, June, 1994.     

Investigation of Fano resonances in the optomechanical cavity via a magnetic field

We theoretically investigate Fano resonances in a single-cavity optomechanical system, which is driven by an external force arisen from a passed current through one end of a mirror in a magnetic field. It is revealed that the asymmetric Fano shape in the optomechanical system strongly depended on the strength of the magnetic field and current intensity. Further, we study the phase of the transmitted probe light and find a tunable switch from slow to fast light and vice versa via manipulating the magnetic field.     

Facile hydrothermal synthesis and characterization of LaFeO3 nanospheres for visible light photocatalytic applications

LaFeO₃ nanospheres were synthesized by hydrothermal method followed by calcination. Citric acid was found to be key factor to the purity and the surface morphology of the LaFeO₃ nanospheres. The obtained nanospheres have been structurally characterized by XRD which confirms the single crystalline orthorhombic structure. The structural information of the nanosphere was also confirmed from the Raman spectrum. HRSEM and AFM revealed that the prepared sample has been composed of spherical like morphology with an average size of about 45 nm. From XPS analysis, the chemical state of the LaFeO₃ nanospheres was confirmed. Magnetic measurement indicates the products shows weak magnetic behaviour. The UV–Vis spectroscopy analysis shows strong absorption at 466 nm which confirms that the obtained material has excellent visible light absorption ability. Furthermore, the photocatalytic experiment demonstrates that the prepared LaFeO₃ nanospheres exhibit well and stable photocatalytic activity for decomposition of methyl orange under visible-light irradiation.     

Poly(3,4-ethylenedioxythiophene) nanospheres synthesized in magnetic ionic liquid

The synthesis of poly(3,4-ethylenedioxythiophene) nanospheres with their size ranging around 60 nm has been achieved by simply adding monomers into a magnetic ionic liquid, bmim[FeCl₄]. The ionic liquid leads to the formation of uniform nanospheres with a relatively narrow size distribution confined to submicrometer-sized domains. The polymers produced in this magnetic ionic liquid system are compared to those synthesized in conventional solution and emulsion polymerizations.     

纳米纤维素/磁性纳米球的原位合成及表征

利用实验室自制芦苇浆纳米纤维素原位合成纳米纤维素/磁性纳米球.通过原子力显微镜、透射电子显微镜、环境扫描电子显微镜、固含量、孔隙率、傅里叶变换红外光谱以及X射线衍射测试分析,结果表明磁性粒子为纳米Fe3O4,纳米Fe3O4与纳米纤维素通过化学键合和物理吸附使得纳米Fe3O4充分分散在纳米纤维素中,形成纳米纤维素/磁性纳米球;纳米纤维素浓度为1.0％,搅拌速度为500r/min,总铁离子浓度为0.0065mol/L(磁性粒子理论质量相对于纳米纤维素质量分数为5％)最佳制备条件下,原位合成纳米纤维素/磁性纳米球,经真空冷冻干燥,所得纳米纤维素/磁性纳米球具有磁化强度73.39A·m2/kg(以每克灰分计)、矫顽力1599.96A/m的磁特性.     

Extending "color constancy" outside the visible region

In this paper, the results of an investigation of the possibility of extending "color constancy" to obtain illuminant-invariant reflectance features from data in the near-ultraviolet (UV) and near-infrared (IR) wavelength regions are reported. These features are obtained by extending a blackbody-model-based color constancy algorithm proposed by Ratnasingam and Collins [J. Opt. Soc. Am. A27, 286 (2010)] to these additional wavelengths. Ratnasingam and Collins applied the model-based algorithm in the visible region to extract two illuminant-invariant features related to the wavelength-dependent reflectance of a surface from the responses of four sensors. In this paper, this model-based algorithm is extended to extract two illuminant-invariant reflectance features from the responses of sensors that cover the visible and either the near-UV or near-IR wavelength. In this investigation, test reflectance data sets are generated using the goodness-fitness coefficient (GFC). The appropriateness of the GFC for generating the test data sets is demonstrated by comparing the results obtained with these data with those obtained from data sets generated using the CIELab distance. Results based upon the GFC are then presented that suggest that the model-based algorithm can extract useful features from data from the visible and near-IR wavelengths. Finally, results are presented that show that, although the spectrum of daylight in the near UV is very different from a blackbody spectrum, the algorithm can be modified to extract useful features from visible and near-UV wavelengths.     

Compact diode pumped cw solid-state lasers in the visible spectral region

This paper reviews recent advances in diode pumped cw solid-state lasers in the visible spectral region. Such lasers are based on rare earth doped materials. Visible wavelengths can be generated by frequency conversion of near IR-lasers or by up-conversion pumped rare earth ion lasers.     

Radiative frequency shift and linewidth of an atom dipole in the vicinity of a dielectric microsphere

Abstract

The frequency shift and linewidth variation of an oscillator placed next to a dielectric microsphere are found within the framework of the classical approach. Both the frequency shift and the linewidth are shown to be substantially dependent on the location of the atom and the size of the microsphere and are capable of reaching very high values near the surface of the microsphere under resonance conditions. Near microsphere resonance, a blue frequency shift is predicted, leading to repulsive forces between the atom and the dielectric microsphere.     

Electroluminescence of Ti- and Ca-doped YAlO3 crystals in the visible region

The electroluminescence (EL) of perovskite-type YAlO₃ single crystal thin slabs doped with Ti and Ca was investigated. The thin slabs were prepared from rod-shaped single crystals grown in a reducing atmosphere by the floating-zone method. Samples of 0.1% Ti-doped YAlO₃, 1% Ti-doped YAlO₃ and 0.1% Ca-doped YAlO₃, on which Au and Al electrodes were deposited, showed green EL when electric fields greater than ± 1 × 10⁶ V/m were applied, with drive frequencies between 0.2 Hz and 1 kHz and a bipolar symmetrical drive waveform. The strongest EL band with narrow widths (FWHM = 3–4 nm) appeared at the same peak wavelength (546 nm) for all three samples. This gives rise to possible uses of Ti- and Ca-doped YAlO₃ crystals in EL devices that emit monochromatic green light.