Energy flow lines for the radiation emitted by a dipole

An oscillating electric dipole emits radiation, and the flow of energy in the electromagnetic field is represented by the field lines of the Poynting vector. In the most general state of oscillation the dipole moment vector traces out an ellipse. We have evaluated analytically the field lines of the Poynting vector for the emitted light, and it appears that each field line lies on a cone, which has its axis perpendicular to the plane of the ellipse. The field lines exhibit a vortex structure near the location of the dipole, and they approach a straight line in the far field. It is shown that due to the spiraling of the field lines near the source, the asymptotic limit of a field line is displaced as compared to a ray which would come directly out of the source. Both the spatial extent of the vortex in the near field and the magnitude of the displacement of the image in the far field are of nanoscale dimension.     

Propagation of the Lissajous singularity dipole through an astigmatic lens

The propagation was investigated of a pair of Lissajous singularities of opposite singularity index called the Lissajous singularity dipole (LSD) through an astigmatic lens. It is shown that after passing through the lens the positions of the singularities are inverted and more than two LSDs occur. Changes in the degree of polarization of the LSDs as well as in the shape of the Lissajous figures also occur. In addition, Lissajous singularities may take place at the focal plane, and a single Lissajous singularity may appear and vanish under certain conditions. The results are compared with those of previous work.     

Energy flow of electric dipole radiation in between parallel mirrors

We have studied the energy flow patterns of the radiation emitted by an electric dipole located in between parallel mirrors. It appears that the field lines of the Poynting vector (the flow lines of energy) can have very intricate structures, including many singularities and vortices. The flow line patterns depend on the distance between the mirrors, the distance of the dipole to one of the mirrors and the angle of oscillation of the dipole moment with respect to the normal of the mirror surfaces. Already for the simplest case of a dipole moment oscillating perpendicular to the mirrors, singularities appear at regular intervals along the direction of propagation (parallel to the mirrors). For a parallel dipole, vortices appear in the neighbourhood of the dipole. For a dipole oscillating under a finite angle with the surface normal, the radiating tends to swirl around the dipole before travelling off parallel to the mirrors. For relatively large mirror separations, vortices appear in the pattern. When the dipole is off-centred with respect to the midway point between the mirrors, the flow line structure becomes even more complicated, with numerous vortices in the pattern, and tiny loops near the dipole. We have also investigated the locations of the vortices and singularities, and these can be found without any specific knowledge about the flow lines. This provides an independent means of studying the propagation of dipole radiation between mirrors.     

Transmission electron microscopy study of dislocations and interfaces in CdTe solar cells

We report on our transmission electron microscopy study of dislocations and interfaces in CdTe solar cells. The atomic structure of dislocations formed inside CdTe grains have been determined by atomic-resolution transmission electron microscopy. We discuss the electronic properties of the dislocations and explore the effects of oxygen on the interdiffusion at CdS/CdTe interface. We find that the presence of oxygen in either CdS or CdTe suppresses the interdiffusion at the CdS/CdTe interface. We have further investigated interdiffusion at the CdS/Zn₂SnO₄ interface. We find that Zn diffuses into CdS from Zn₂SnO₄ and Cd diffuses into Zn₂SnO₄ from CdS. The possible effects of the interdiffusion are discussed. Finally, we have examined the distribution of intentionally introduced Cu at the CdTe/CdS junction, and we find that Cu is distributed uniformly in the CdS layer.     

Vectorial topological dipole in output radiation of a fiber optical coupler

It is experimentally and theoretically demonstrated that a vectorial topological dipole is formed in the radiation field of the main channel of a fiber optical coupler. The dipole consists of two polarization umbilics—of the star and lemon or the star and monstar types—and retains its structure in the course of radiation propagating along the fiber, whereby the topological index remains unchanged. Using a polarization filter, it is possible to select two identically charged vortices corresponding to these polarized umbilics.     

电阻加载偶极天线阻抗带宽及脉冲辐射特性研究

分析了偶极天线电阻加载方面的若干问题，包括不同电阻加载方式阻抗频率特性比较，连续与离散串联集中电阻加载脉冲辐射特性比较，证明其它加载方式具有与Wu-King电阻加载相似的特性，与未加载偶极天线相比，阻抗带宽较宽，辐射脉冲失真较小。     

Experimental investigations of the radiation patterns of the dipole antennas of a mobile radio-communications system

The results of measurements of the radiation patterns of the dipole antennas of a mobile radio-communications system in the short-and ultrashort-wave bands are presented. The changes in the directional properties of the antennas due to their mutual influence when they are arranged compactly on the carrier are investigated. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 39–41, May, 2008.     

Propagation through the ocean's surface at shallow angles with a laser beam

Propagation through the ocean's surface at shallow angles with a laser has been successfully demonstrated experimentally in the ocean. A 6-mJ multipulse laser at a depth of 1.5 m in water with an attenuation coefficient of approximately 3.3 m(-1) was easily detected 600 m away on a sunlit day at an angle of 1 degree to the ocean's surface. The measured efficiency was 3.6 x 10(-2) (J/J)/sr (joules received per receiver steradian per joule transmitted). Statistical ray trace analysis and physical tank modeling produced equivalent efficiencies.     

Transmission of radiation energy through absorbing and dispersing materials irradiated by a parallel beam at some definite angle of incidence

Laws governing the transmission of radiation energy are established on the basis of which it is possible to calculate the distribution of flux density and absorbed energy over the thickness of an absorbing and dispersing layer irradiated from both sides at some definite angle of incidence.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 2, pp. 267–277, August, 1972.     

Transmission of light through magnetic nanocavities

The transmission of light through a metallic film stack on a transparent substrate, perforated with a periodic array of cylindrical holes/nanocavities, is studied. The structure is fabricated by using self-assembled nanosphere lithography. Since one layer in the film stack is made of a ferromagnetic metal (iron), exposure of the structure to a solution containing iron oxide nanoparticles causes nanoparticle accumulation inside the nanocavities. This changes the dielectric constant inside the nanocavities and thus affects the light transmission. Simulations are in good agreement with experiment, and show large sensitivity of the response to the amount of iron oxide nanoparticles deposited. This could be used in various sensor applications.     

Modelling of intercellular induction of apoptosis in oncogenic transformed cells and radiation effects on the phenomenon

The removal of transformed cells via induction of apoptosis through intercellular signalling by surrounding cells is supposed to represent an important control mechanism limiting carcinogenesis. Low doses of radiation influence the efficiency of this anti-carcinogenesis process, indicating possible beneficial effects of low doses of radiation mediated by intercellular communication ('non-targeted effects'). To quantitatively understand the signalling system involved and the effects of radiation and to assess the role of this phenomenon in radiation-induced carcinogenesis, multi-scale modelling studies have been started. The proposed kinetic model takes into account (i) triggering of the effector function in cells in the vicinity of transformed cells, (ii) intercellular signalling between effector and transformed cells and (iii) execution of apoptosis in attacked cells. The systems model without radiation perturbance is reviewed. First results accounting for radiation-induced modulations of the signalling schemes are presented.     

Precision pointing and tracking through random media by exploitation of the enhanced backscatter phenomenon

The active illumination of a target through a turbulent medium with a monostatic transmitter-receiver results in a naturally occurring conjugate wave caused by reciprocal scattering paths that experience identical phase variations. This reciprocal path-scattering phenomenon produces an enhanced backscatter in the retroverse direction (precisely along the boresight of the pointing telescope). A dual aperture causes this intensity enhancement to take the form of Young's interference fringes. Interference fringes produced by the reciprocal path-scattering phenomenon are temporally stable even in the presence of time-varying turbulence. Choosing the width-to-separation ratio of the dual apertures appropriately and utilizing orthogonal polarizations to suppress the time-varying common-path scattered radiation allow one to achieve interferometric sensitivity in pointing accuracy through a random medium or turbulent atmosphere. Computer simulations are compared with laboratory experimental data. This new precision pointing and tracking technique has potential applications in ground-to-space laser communications, laser power beaming to satellites, and theater missile defense scenarios.     

Transmission of light waves through normal shocks

We seek to characterize light waves transmitted through normal shock waves. The investigation is motivated by the need for a theory to support a shadowgraph experiment for flow in a convergent-divergent nozzle. In this experiment light beams are passed through the nozzle transverse to the direction of the flow in which a shock has formed in the vicinity of the throat. We present a formulation and an approximation that yield calculations of the intensity of transmitted waves. We also present experimental results to support the theory. The patterns predicted by the theory compare well with the patterns observed in experiments.     

Transmission of radiation by a medium in two-dimensional problems

General formulas for the transmission characteristics of a medium for the simplest two-dimensional systems with an exponential law of absorption are given. These characteristics are the coefficients of irradiation, the coefficients of spatial distribution of the incident flux, and the coefficient of utilization of a point source. The emission characteristic of real surfaces is expressed by a cosine power series.     

Transmission grating filtering of 52-140-nm radiation

Filtering extreme UV radiation by gold freestanding transmission gratings was studied experimentally in the 52-140-nm wavelength range. Computer simulations are in good agreement with experimental results.     

Far field thermal radiation through nanoholes and apertures

Thermal radiation through a nanohole or a nanoaperture is calculated in this paper. Results show that for aperture size < dominant wavelength of thermally excited photons, heat flux deviates significantly from the well-known Planck blackbody expression of sigmaT4, where sigma is the Stefan-Boltzmann constant and T is the temperature. The heat flux through a nanohole is proportional to T8 and a4, where a is the radius of the hole. Finally it is shown that for aT < 10(6), where a is expressed in nm and T is expressed in K, radiative heat flux through the hole is proportional to T8 and for aT > 10(6) radiative heat flux is equal to the Planck blackbody heat flux; i.e., it is proportional to T4.     

Consideration on calibration and correction factors of an Hp10 chamber for different radiation qualities and angles of incidence

This paper presents the characterisation performed at IRSN (France) of an H(p)(10) chamber in terms of calibration coefficient and correction factors for the radiation qualities of ISO narrow spectrum series. The chamber response, expressed in H(p)(10) using conversion coefficients h(p)(K)(10; N, alpha) listed in ISO 4037-3 in the energy range from 30 to 1250 keV and for angles of incidence between 0 and 70 degrees, was found to be within approximately 10%. However, for photon energies <30 keV, an overresponse of the chamber that could reach 100% was observed. Nevertheless, this overresponse was reduced to 25% using the conversion coefficients estimated at Physikalisch-Technische Bundesanstalt (PTB). This implies that the X-ray spectra produced by the IRSN X-ray units are very similar to those produced by PTB, both containing a little bit more high-energy photons than the spectra used in ISO 4037-3. The dose rate dependence of the chamber tested by gamma radiation from (60)Co sources was found to be within 2% in the range of 0.3 mSv h(-1) to 1 Sv h(-1). The H(p)(10) chamber can measure directly the conventional true value of H(p)(10) after calibration by a reference laboratory, and can be used for transferring H(p)(10) reference quantities from a reference laboratory.     

梁结构耦合点处的振动功率传输关系

不同形式的波在结构中传输时携带着不同的振动能量。作为复杂结构的基本组成部分 ,以任意角度耦合的二叉梁、三叉梁等典型的梁结构 ,其中的波动在梁臂的交点 (耦合点 )处将产生转变。本文从波动的角度讨论了在这些典型梁结构中的振动功率传输特性 ,得到了一些有价值的结论 ,对于振动控制和结构优化设计具有重要的意义     

Transmission through the band-gap states in Schottky-barrier carbon nanotube transistors

We have studied the minimum off-state leakage current of ultrascaled Schottky-barrier carbon nanotube transistors (SBCNTs) with midgap Schottky-barrier source/drain contacts. The off-state leakage current is separated into two parts: thermal emission around the top of the Schottky barrier and tunneling through the evanescent band-gap states. Because the transmission through deep band-gap states makes a dominant contribution for ultrascaled SBCNTs, the off-state minimum leakage current increases exponentially with decreasing scaling length of SBCNTs.