Random-phase surface-wave solitons in nonlocal nonlinear media

We demonstrate, theoretically and experimentally, incoherent surface solitons in a noninstantaneous nonlocal nonlinear media. These incoherent surface waves are located at the interface between a nonlinear medium with long-range nonlocality and a linear dielectric medium (air).     

Noise correlations in three-terminal diffusive superconductor-normal-metal-superconductor nanostructures

We present measurements of current noise and cross correlations in three-terminal superconductor-normal-metal-superconductor (S-N-S) nanostructures that are potential solid-state entanglers thanks to Andreev reflections at the N-S interfaces. The noise-correlation measurements spanned from the regime where electron-electron interactions are relevant to the regime of incoherent multiple Andreev reflection. In the latter regime, negative cross correlations are observed in samples with closely spaced junctions.     

Optical characteristics of a multilayer photovoltaic cell for oblique incidence of light

Taking into account the contributions of interference and incoherent multiple reflections of light in the substrate, we have determined the distribution of the absorbed energy density Q in layers of a multilayer photovoltaic cell in the general case of oblique incidence of light on the cell. The relations obtained are expressed in terms of the Fresnel reflection and transmission coefficients for interfaces between media, which for oblique incidence are different for s and p polarization of the incident light. The energy absorbed by an active layer of the cell varies very slightly with the angle of incidence if the maximum in the Q distribution is located at a heterojunction. We carried out a numerical analysis for a five-layer cell based on a copper phthalocyanine-fullerene heterojunction. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 795–800, November–December, 2007.     

椭偏精确测定透明衬底上吸收薄膜的厚度及光学常数

椭偏仪难以精确测量透明衬底上吸收薄膜光学常数的原因:1)衬底的背面反射光为非相干光, 它的存在会极大的增加拟合难度; 2)衬底光学常数(折射率和消光系数)的差异会影响测量的准确性, 而且会在吸收薄膜的光学常数中表现出来, 需要单独测量其光学常数; 3)厚度与光学常数之间呈现强烈的关联性. 针对以上三个问题, 选择石英玻璃、载玻片、盖玻片和普通浮法玻璃作为研究对象. 采用折射率匹配法消除上述衬底背面反射光的影响. 结果显示, 折射率匹配法能够有效消除折射率在1.43-1.64、波长范围为190-1700 nm波段的石英、浮法玻璃等透明衬底的背面反射光. 之后, 通过拟合椭偏参数ψ和垂直入射时的透过率T₀ 分别得到以上衬底的折射率和消光系数. 拟合得到的结果与文献报道的趋势一致. 最后, 采用椭偏参数和透过率同时拟合的方法(SE+T法)得到类金刚石薄膜(沉积在石英玻璃上)和非晶硅薄膜(沉积在载玻片、盖玻片上)光学常数和厚度的准确解.     

One-dimensionally incoherent surface structures

Unusual surface structures of Na on Ni (110) occur in which evenly spaced Na atoms are positioned incoherently with respect to the Ni substrate atoms along troughs in the close packed direction of the substrate surface. In the first case considered for coverages between about 0.25 and 0.31 monolayers, alternate troughs on the Ni(110) surface contain incoherent rows of Na atoms. The rows are randomly out of phase with one another and in addition the interatomic spacing between Na atoms in these rows varies inversely with the coverage. The second case concerns coverages from about 0.64 to 0.71 monolayers where every trough contains an incoherent row of Na atoms and the rows are in phase with one another. The interpretation of the one-dimensionally incoherent sodium structures and their dependency on the two-fold symmetry of the substrate discussed in this study may have applicability to surface structures observed in other similar LEED adsorption studies.     

Noise and full counting statistics of incoherent multiple Andreev reflection

We present a general theory for the full counting statistics of multiple Andreev reflections in incoherent superconducting-normal-superconducting contacts. The theory, based on a stochastic path integral approach, is applied to a superconductor-double-barrier system. It is found that all cumulants of the current show a pronounced subharmonic gap structure at voltages V=2Delta/en. For low voltages V or =3. We show that this low-voltage result holds for a large class of incoherent superconducting-normal-superconducting contacts.     

基于脑模型控制器的红外背景预测算法

在分析云背景红外图像空间分布上存在混沌现象的基础上,提出一种基于脑模型控制器的红外背景预测算法.该方法利用混沌具有短时可预测性的特点,对云背景图像进行预测,并根据云背景杂波和运动目标的混沌特性差异修正预测模型.仿真结果表明,该算法能有效地提高云背景的预测准确度,预测残差符合白噪音特性,对云背景杂波具有良好的抑制效果,能显著提高目标的信杂比,从而改善目标的检测性能.     

Generation and propagation of undamped temperature waves under pulse action on a target surface

The physical mechanism of undamped temperature waves and the conditions of generation thereof in media with a finite time of local thermal relaxation are examined. The wave frequency depends on the relaxation time and the parameters of the pulse action on a medium, and the lowest frequencies correspond, in particular, to air. These effects can be used to identify and investigate this action. It is demonstrated that the character of wave reflection from the interface between different media depends on the state and the finish quality of the given surface. In particular, in the ideal case of a sharp interface between air and metal, temperature waves are totally reflected at the interface. On the contrary, if there is a “blurred” interface, reflections can be almost completely suppressed and waves not absorbed in air penetrate into another medium and are rapidly attenuated in it. Other combinations of media can also lead to an analogous phenomenon, which makes it possible to develop remote heating systems by which distant environments are warmed without thermal energy losses in the intermediate medium.     

Analysis of light out-coupling from microlens array

Microlens array has been known to be effective in enhancing the out coupling efficiency of LEDs, OLEDs and other thin film light emitting devices. However, mechanism of efficiency enhancement by use of microlens arrays is still ambiguous, apart from suggestions that it leads to randomization of photons. We have studied the photon dynamics in the presence of microlens arrays and the effect of various parameters e.g. microlens contact angle, absorption and substrate refractive index using ray tracing simulations. Microlens array leads to extraction of a portion of photons outside the escape cone at the cost of reduced extraction from within the escape cone. The reduced extraction from within the escape cone is compensated by multiple reflections from the back surface. Increase in microlens contact angle reduces the number of reflections required for out-coupling hence reducing the absorption in the device.     

Analysis and elimination of boundary reflections in transmission holograms

Elimination of reflections which occur at the glass–air interface of holographic plates is an important factor to be taken into account when recording transmission holograms. If these reflections are not eliminated, unwanted secondary gratings are stored due to interference of the object and reference beams with the beams reflected at the interface. This not only gives rise to an anti-aesthetic effect, but also produces a reduction in diffraction efficiency and an increase in noise. We present the results obtained using a method which eliminates these unwanted reflections. This method, instead of using liquids, makes use of a black self-adhesive PVC masking tape stuck on the glass side of the holographic plate. We carried out a qualitative analysis of the different results obtained for plates with and without black PVC tape and also quantitatively analyzed the effect of the tape on the reflectivity of the plates as well as the density of holographic gratings. The results obtained confirm the applicability of the method described for antihalation reduction and elimination of unwanted reflections that cause interference affecting the quality of the holographic image.     

Geometrical optics of lightguides with an oblique input end-face

The geometrical-optics relations between meridional rays of incidence and maximum aperture have been derived for the general case of a lightguide with an oblique input end-face. It is shown that the maximum angles of incidence are asymmetrical with respect to both the axis of the lightguide and the normal to the input end-face. A numerical comparison shows that for a light-guide with an oblique input end-face, in the meridional ray case, a greater or smaller angle of aperture may result, depending on the cutting angle, compared with that for a lightguide input end-face perpendicular to the optical axis. A greater angle of aperture is especially important since it means an improvement in the launching efficiency of incoherent light sources. Moreover, the maximum angle of aperture has been derived for the generalized light guide in which successive total internal reflections at the cladding/surroundings interface have been taken into account.     

在半导体-金属相变温度附近氧化钒薄膜光学性质的异常变动

在可见光—近红外波段的不同波长下,测量了半导体-金属相变过程中氧化钒薄膜样品的反射率和透射率.在薄膜相变过程中,不同波段的反射率曲线和透射率曲线表现出不同的变化趋势.利用非相干光在薄膜中的多级反射-透射模型,计算了相变过程中不同波长下氧化钒薄膜的折射率n和消光系数k随温度的变化.结果表明,在相变温度附近氧化钒薄膜光学性质的异常变动,其原因既有薄膜的折射率和消光系数随波长的变化趋势不同,也有在吸收性薄膜中存在探测光多次反射和透射的累加效应.     

Anisotropy induced in a silver-chloride emulsion by two incoherent and perpendicular light vibrations

After a report on the composition of two incoherent rectilinear vibrations with perpendicular polarizations, we suggest in this paper a method of extraction of the difference between two images in incoherent and polarized light. The images, perpendicularly polarized, are simultaneously recorded on a silver chloride emulsion H where an optical anisotropy is induced only in the areas where the incident intensity distributions are not identical. After exposure, H, observed between crossed polarizers, displays the difference between the two original images in its image plane. In addition, it is shown that the sign of this difference is retrieved by means of the dichroism of the plate.     

A novel proposal for enhancement of light extraction efficiency in WOLEDs based on optimized photonic crystal structures

In this paper we propose a framework to enhance light extraction efficiency in white organic light emitting diodes (WOLED) using photonic crystal (PhC) structures sandwiched between indium tin oxide (ITO, n_ITO = 1.8+0.01i) and glass (n_glass = 1.51) substrate, according to the high refractive index contrast of these two layers almost 50% of the generated light inside WOLED gets trapped in the mentioned interface. The main purpose of this article is to suggest a method to intentionally optimize PhC structures to reduce total internal reflections (TIR) happening at ITO/glass interface. Here three different patterns are considered including rectangular, hexagonal and circular lattices. Using Finite Difference Time Domain (FDTD) method and the presented framework for choosing structural parameters the portion of 50% trapped light in ITO was reduced to 20% which is a large enhancement in extraction efficiency of WOLED. Also far-field results before and after adding PhCs are investigated.     

半色调双面图像的色彩预测Clapper-Yule模型

为了准确地预测印刷图像的光谱反射率,在假定油墨是非散射介质以及油墨的折射率与纸张的折射率近似相等的近似下,利用考虑光在纸基内多次内反射的Clapper-Yule理论和描述多重内反射的网状结构分析模型,建立了同色不同加网周期双面墨像的光谱反射色彩预测模型.同时给出了包含纸基的向下体反射和反面纸基-空气构成界面定向反射作用的单面墨像Clapper-Yule色彩预测修正新模型.     

Electrical and structural characterization of inhomogeneously doped semiconductors by infrared spectroscopy

An optical method is presented for thenon-destructive electrical and structural characterisation of multilayer structures. The presented concept yields the complex refractive index profiles within an arbitrary composed layer system by using the symmetrical transmission and the asymmetrical reflectivity caused by the optical inhomogeneity of a material. This method includes the superimposition of coherent multiple reflections within the refractive index profile as well as incoherent multiple reflections within the whole wafer. This analysis yields the spacial distribution of free carrier density profiles within the sample as well as the transitions between different crystal phases by using the least squares fit procedures. The results of the optical analysis are compared with other methods used to quantitatively determine density profiles and phase transitions such as SIMS, spreading resistance, stripping Hall and RBS.     

The surface cracking behavior in air plasma sprayed thermal barrier coating system incorporating interface roughness effect

The objective of this work is to understand the effect of interface roughness on the strain energy release rate and surface cracking behavior in air plasma sprayed thermal barrier coating system. This is achieved by a parameter investigation of the interfacial shapes, in which the extended finite element method (XFEM) and periodic boundary condition are used. Predictions for the stress field and driving force of multiple surface cracks in the film/substrate system are presented. It is seen that the interface roughness has significant effects on the strain energy release rate, the interfacial stress distribution, and the crack propagation patterns. One can see the completely different distributions of stress and strain energy release rate in the regions of convex and concave asperities of the substrate. Variation of the interface asperity is responsible for the oscillatory characteristics of strain energy release rate, which can cause the local arrest of surface cracks. It is concluded that artificially created rough interface can enhance the durability of film/substrate system with multiple cracks.     

Full counting statistics of multiple Andreev reflections in incoherent diffusive superconducting junctions

We present a theory for the full distribution of current fluctuations in incoherent diffusive superconducting junctions, subjected to a voltage bias. This theory of full counting statistics of incoherent multiple Andreev reflections is valid for an arbitrary applied voltage. We present a detailed discussion of the properties of the first four cumulants as well as the low and high voltage regimes of the full counting statistics. The work presented here is an extension of the results of Pilgram et al. [31]. PACS 73.23.-b; 02.50.-r; 05.40.-a; 72.70.+m     

The 2.5-dimensional equivalent sources method for directly exposed and shielded urban canyons

When a domain in outdoor acoustics is invariant in one direction, an inverse Fourier transform can be used to transform solutions of the two-dimensional Helmholtz equation to a solution of the three-dimensional Helmholtz equation for arbitrary source and observer positions, thereby reducing the computational costs. This previously published approach [D. Duhamel, J. Sound Vib. 197, 547-571 (1996)] is called a 2.5-dimensional method and has here been extended to the urban geometry of parallel canyons, thereby using the equivalent sources method to generate the two-dimensional solutions. No atmospheric effects are considered. To keep the error arising from the transform small, two-dimensional solutions with a very fine frequency resolution are necessary due to the multiple reflections in the canyons. Using the transform, the solution for an incoherent line source can be obtained much more efficiently than by using the three-dimensional solution. It is shown that the use of a coherent line source for shielded urban canyon observer positions leads mostly to an overprediction of levels and can yield erroneous results for noise abatement schemes. Moreover, the importance of multiple facade reflections in shielded urban areas is emphasized by vehicle pass-by calculations, where cases with absorptive and diffusive surfaces have been modeled.