Polarization properties of some materials at near millimeter wavelengths

The degree of polarization of some materials widely used as optical components in the submillimeter and millimeter region has been measured in the wavelength interval 0.5÷3 mm. The procedure used in the measurements allows to determine degress of polarization of the order of 10^–5.     

Effect of monomer-treated inorganic fillers on mechanical,rheological, and thermal properties of LLDPE nanocomposites

This article discusses the role of nanoscale calcium carbonate (nCC) surface treatment in affecting the mechanical, rheological, and thermal properties of linear low-density polyethylene (LLDPE). The mechanical tests indicated that nCC could simultaneously reinforce and toughen LLDPE. In addition, the composite sample with methacrylic acid (MA)-treated nanoparticles shows further increased mechanical properties as compared to unmodified nanoparticles. In the presence of dicumyl peroxide (DCP), a small amount of MA could increase markedly the mechanical properties of LLDPE/nCC composites. The results of rheological property analysis indicated that the viscosity increased with increasing amount of the filler, especially at low shear rates, but showed a substantial reduction with increasing concentration of the reactive monomer. The thermal behavior of these materials is evaluated by differential scanning calorimetry and thermogravimetric analysis. The addition of a small amount of MA and DCP enhances the stabilization of the blends.     

含特异材料光子晶体隧穿模的偏振特性

构造了由普通材料A(SiO₂)和电单负材料B组成的(AB)^N(BA)^N型一维光子晶体.数值计算表明原禁带的1907.3 nm处出现了一个十分尖锐的隧穿模. 入射角增加,该隧穿模的透射率和半峰全宽度均保持不变,但位置发生蓝移, 入射角在15°-65°的区间内,移动率的绝对值 |dλ/dθ| 较大.当B介质的磁导率μ_B 从5增加到10时,只是隧穿模的位置发生了红移. 介质的几何厚度增加时,隧穿模的透射率不变,但其位置红移明显,半峰全宽略有增加.     

High-resolution electron microscopy in structural studies of inorganic materials

A summary is given of the use of high-resolution electron microscopic imaging methods in structure determination, stressing their advantage over conventional diffraction methods, and the instrumental and specimen-dependent limitations on their applicability. Some examples of the use of this technique are given, both in systems where the unit-cell structure is known and only long-range order is lacking, and in cases of completely unknown phases.     

Effect of micro and nanoparticle inorganic fillers on the field emission characteristics of photosensitive carbon nanotube pastes

We successfully fabricated field emitter arrays of carbon nanotube (CNT) dots of 10 μm diameter with excellent field emission properties by using photosensitive CNT paste. The CNT paste was investigated in terms of morphologies, current-voltage properties, and luminous uniformities by varying the mixing ratios of micro and nanoparticle inorganic fillers and the amount of CNTs added into the paste. The 3:1 mixing of micro and nanoparticle fillers and the addition of 5% CNTs in the paste brought about the best field emission characteristics of dot-patterned CNT field emitter arrays.     

Optical switch and luminescence properties of sol–gel hybrid organic–inorganic materials containing azobenzene groups and doped with neodymium ions

TiO₂/γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane hybrid organic–inorganic material, which contains azobenzene groups and is doped with neodymium ions, was prepared by a low temperature sol–gel technique. The trans-cis-trans photoisomerization cycles of the hybrid film were investigated by a photoirradiation with UV light followed by visible light. An intense room-temperature upconversion emission at 397 nm was also measured from a hybrid film heated at a low temperature of 80 °C upon excitation with a xenon lamp at a wavelength of 580 nm. The mechanism of the upconversion is proposed and indicates that the sequential two-photon absorption process originating from the long-lived ⁴ F _3/2 excited state should be responsible for the up-conversion process. These results indicate that the prepared hybrid materials with multifunctional photonic properties are promising candidates for integrated optics and photonic applications, which would allow directly integrating onto a single chip, the upconversion device with the pump source, and optical data storage and optical switching devices. PACS 42.65.Pe; 78.66.Sq; 81.20.Fw; 82.50.Fv     

Polarization dependence of optical Kerr effect in metallophthalocyanine-doped inorganic-organic hybrid materials

Ultrafast optical Kerr effect of metallophthalocyanine-doped inorganic-organic materials was investigated using a femtosecond optical Kerr shutter at wavelength of 800 nm. Experimental results showed that the dependence of the Kerr signals on the polarization angle between the pump beam and the probe beam could be controlled by changing the pump-probe intensity ratio. The pump-intensity dependence of the polarization characters of the Kerr signals probably arose from the contribution of light induced transient grating (LITG) to the Kerr signals.     

Polarization wake of penetrating ions: oscillator model

The wake potential induced by a swift nonrelativistic ion has been studied theoretically for a random stopping medium consisting of quantal-harmonic-oscillator atoms. The primary purpose has been to study the influence of atomic binding on the frequently-studied wake potential in a Fermi gas. Quantitative comparisons at constant plasma frequency and increasing oscillator frequency show a gradual decrease in wavelength and a slight decrease in amplitude of the oscillatory part of the wake potential, as well as a systematic decrease in screening of the near-field next to the projectile. These findings can be expected on the basis of the Drude-Lorentz formula for the effective resonance frequency. We find a distinct dependence of the induced potential on the ion charge as long as the plasma frequency exceeds the oscillator frequency. In the opposite case of a dominating oscillator frequency we find little difference between the field induced by a point charge and that by a neutral atom. As an application area we briefly discuss the proximity effect in the energy loss of molecular ions. We find that the polarization wake modifies the proximity effect, in contrast to the frequently-expressed view that it causes the proximity effect.     

A laser-erosion collector for microspectral analysis of solid inorganic materials

To carry out a microspectral analysis of solid inorganic materials with preliminary laser sampling, we suggest a collector consisting of two thin graphite semidisks, which in sampling are installed on the specimen surface with a certain gap for passage of laser radiation. The specific features and analytical application of the collector are considered. Scientific-Research Institute of Chemistry at the Nizhni Novgorod State University, 23, bl. 5, Gagarin Ave., Nizhini Novgorod, 603600, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 839–842, November–December, 1998.     

Effective permittivity of materials containing graded ellipsoidal inclusions

We prove a generic theorem stating the equivalence between a graded dielectric ellipsoid (with gradation along a family of internal confocal ellipsoids) and an anisotropic homogeneous ellipsoid. We then describe a procedure to obtain the three principal permittivities of the effective ellipsoid for any given dielectric gradation profile. Finally, we apply a multiscale approach to homogenize dispersions of ellipsoidal graded particles.     

SIMS molecular cluster intensities of inorganic salts containing sulfur and nitrogen oxyanions

Secondary ion mass spectrometry (SIMS) is used to examine alkali sulfur oxyanion and nitrogen oxyanion salts. The secondary ion spectra, filtered about a nominal 1-eV kinetic energy, are measured in the dynamic SIMS mode using a 1—5 μA/cm² beam intensity of 1-keV Ar⁺ primary ions. Charge build-up on the sample surface is neutralized by thermal electrons. The positive (+) secondary ion spectra are dominated by cation species (M⁺, MO⁺, M₂⁺, M₂O⁺). The negative (−) secondary ion spectra include the anion central atom (A)—oxygen series (O⁻, A⁻, AO⁻, AO₂⁻, AO₃⁻, AO₄⁻). The relative ion intensity pattern of the (−) series shows a clear dependence on anion stoichiometry. For sulfur oxyanions and a 1-keV Ar⁺ ion beam, the pattern can be represented by a modified Poisson distribution if dissociation of AO₄^t- and AO₃⁻ is assumed for sulfate and sulfite, respectively. The Poisson distribution mean values for oxygen loss are found to be 4̃.5 for sulfate and sulfite and 3̃ for thiosulfate. The mean value for loss increases with increasing Ar⁺ ion energy in the range 0.5–2.0 keV. The nitrogen oxyanion intensifies are complicated by ion beam damage and by neutralization effects. Primary ion beam damage of the substrate is monitored by X-ray photoelectron spectroscopy (XPS).     

Multichannel filtering properties of photonic crystals containing single-negative materials

The multichannel filtering properties have been investigated by means of the transfer matrix method in photonic crystals containing two kinds of single-negative materials. Two sets of filtering channels appear simultaneously in the zero effective phase gaps. One is omnidirectional for TE polarization but angle-sensitive for TM polarization, while the other is angle-sensitive for TE polarization but omnidirectional for TM polarization. The resonance modes for different channels can be independently tuned. This structure provides an efficient way to fabricate omnidirectional multichannel filters with independently tunable polarization channels.     

Transmission properties of a double-periodic quasi-crystal containing single-negative materials

The transmission properties of a double-periodic quasi-crystal containing single-negative materials are investigated with the transfer matrix method and effective medium theory. It is shown that the double-periodic quasi-crystal has a single-negative band gap between the zeros of average permittivity and average permeability of the effective medium. These zeros are affected only by the filling factor of the structure, and are independent from the order of the double-periodic quasi-crystal. Moreover, we show that the periodic structure created by repeating the double-periodic quasi-crystal has some omnidirectional band gaps at the single-negative frequency region. The number of such omnidirectional band gap increases by increasing the order of double-periodic quasi-crystal. Then, the structure can be used as a multichannel filter.     

Periodic defect modes of one-dimensional crystals containing single-negative materials

The transmission properties of a one-dimensional (1D) photonic crystal containing two kinds of single-negative (permittivity or permeability negative) material with an inserted array of defects (RHM and LHM) were presented by the transfer matrix method (TMM). The dependence of the defect modes on the structure parameters was discussed by using the TMM. In contrast to the Bragg gaps, the properties (the central frequency and width of the gap) of zero effective phase (zero−φ_eff) and gap are invariant with a change in scale length and insensitive to the incident angles. The property of the periodic defect modes in the SNG host periodic structure was studied. It illustrates that the defect modes properties changed more by insert periodic defect than by single-media defect. The defect modes are sensitive to the parameters of the defect layers and the incident angle.     

Optical properties of one-dimensional photonic crystals containing graded materials

The optical properties of an one-dimensional photonic crystal containing graded materials are studied theoretically. The graded layers have space dispersive permittivity and magnetic permeability which vary along the direction perpendicular to the surface of the layer. The gradation profiles of permittivity are studied in detail. We show that the structure possesses forbidden band gaps in its transmission spectra and the gradation profiles of permittivity affect the band gaps significantly. For the exponential gradation profile ε₁(x) = α e^βx, the number of the band gaps increases and the total frequency region corresponding to the gaps becomes large with increasing parameter β. On the other hand, the position of band gaps can be changed by the adjustment of the gradation profiles even if possessing same volume-average permittivity in the graded layers. Therefore, we can achieve suitable photonic band gaps by choosing gradation profiles of permittivity.     

含特异材料的光量子阱频率特性研究

基于传输线加载集总元件的方法制备光量子阱. 对阱内物质为光子晶体和左手材料两种情况下的传输特性进行比对. 结果表明局域模个数与阱内物质的周期数相同; 左手材料情况下光量子阱具有尺度小、 便于调节的优点.实验结果与理论结果相符合.     

Polarization-sensitive effects of solgel materials containing various chiral media

The polarization-sensitive effects of solgel materials containing various chiral media were measured experimentally. The results show that the solgel material displays optical activity when it contains organic chiral molecules and manifests depolarization when it contains inorganic chiral microcrystals with a particle size of 70 microm. Solgel material containing glass powder that also has a particle size of 70 microm displays a polarization held characteristic (i.e., the polarization of the output light is the same as that of the input light).