Experimental observation of negative lateral displacements of microwave beams transmitting through dielectric slabs

It was theoretically predicted that when a beam of light travels through a thin slab of optically denser medium in the air, the emerging beam from the slab will suffer a lateral displacement that is different from the prediction of geometrical optics, that is, the Snell's law of refraction and can be zero and negative as well as positive. These phenomena have been directly observed in microwave experiments in which large angles of incidence are chosen for the purpose of obtaining negative lateral displacements. (C) 2005 Elsevier B.V. All rights reserved.

Negative lateral shift of a light beam transmitted through a dielectric slab and interaction of boundary effects

It is found that when a light beam travels through a slab of optically denser dielectric medium in air, the lateral shift of the transmitted beam can be negative. This is a novel phenomenon that is reversed in comparison with the geometrical optic prediction according to Snell's law of refraction. A Gaussian-shaped beam is analyzed in the paraxial approximation, and a comparison with numerical simulations is made. Finally, an explanation for the negativity of the lateral shift is suggested, in terms of the interaction of boundary effects of the slab's two interfaces with air.

Large positive and negative lateral displacements from total internal reflection configuration with a weakly absorbing dielectric film

It is theoretically shown that the simultaneously large positive and negative lateral displacements will appear when the resonant condition is satisfied for a TE-polarized light beam reflected from the total internal reflection configuration with a weakly absorbing dielectric film. Appearance of the enhanced negative lateral displacement is relative to the incidence angle, absorption of the thin Elm and its thickness. If we select an appropriate weakly absorbing dielectric film and its thickness, the simultaneously enhanced positive and negative lateral displacements will appear at different resonant angles. These phenomena may lead to convenient measurements and interesting applications in optical devices.

Large and negative lateral displacement in an active dielectric slab configuration

We investigate the large negative lateral displacements of TE polarized light beams reflected from or transmitted through an active slab surrounded by transparent medium. The large negative displacements can be achieved when the incidence angle of the beam is less than but close to the critical angle for total reflection. It is also shown that both the reflectivity and transmissivity of the beam that correspond to the large negative displacements can be enhanced by active medium. These phenomena may lead to convenient measurements and interesting applications in optical devices. (c) 2006 Elsevier B.V. All rights reserved.

Optical response in a quantum dot superlattice nanoring under a lateral electric field

The optical absorption of a GaAs/AlGaAs quantum dot superlattice nanoring (QDSLNR) under a lateral dc electric field and with magnetic flux threading the ring is investigated. This structure and configuration provides a unique opportunity to study the optical response of a superlattice under an inhomogeneous electric field, which is not easily realized for general quantum well superlattices (QWSLs) but naturally realized for QDSLNRs under a homogeneous lateral electric field. It has been shown that a lateral dc electric field gives rise to a substantial change of the optical absorption spectra. Under a low field, the excitonic optical absorption is dominated by a 1s exciton. And with the electric field increasing, the optical absorption undergoes a transition from 1s excitonic absorption to 0 excitronic WSL absorption. (The number of 0, and -1 and +1 below are WSLs index.) The -1 and the +1 WSLs corresponding to the maximum effective field can also be identified. Due to the inhomogeneity of the electric field, the peaks of the -1 and the +1 WSLs are diminished and between them there exist rich and complicated structures. This is in contrast to the general QWSLs under a homogenous electric field. The complicated structures can be understood by considering the inhomogeneity of the electric field along the ring, which results in the nearest-neighbor transition, the next-nearest-neighbor transition, etc., have a different value repectively, at different sites along the ring. This may give rise to multiple WSLs. We have also shown that the line shape of the optical absorption is not sensitive to the threading magnetic flux. The threading magnetic flux only gives rise to a slight diamagnetic shift. Thus the enhancement of the sensitivity to the flux allowing for observation of the excitonic Aharanov-Bohm effect in the plain nanoring is not expected in QDSLNRs.

Lateral shift of the transmitted light beam through a left-handed slab

It is reported that when a light beam travels through a slab of left-handed medium in the air, the lateral shift of the transmitted beam can be negative as well as positive. The necessary condition for the lateral shift to be positive is given. The validity of the stationary-phase approach is demonstrated by numerical simulations for a Gaussian-shaped beam. A restriction to the slab's thickness is provided that is necessary for the beam to retain its profile in the traveling. It is shown that the lateral shift of the reflected beam is equal to that of the transmitted beam in the symmetric configuration.

Analysis of the lateral displacement and optical path difference in wide-field-of-view polarization interference imaging spectrometer

The mechanism of beam splitting and principle of wide-field-of-view compensation of modified Savart polariscope in the wide-field-of-view polarization interference imaging spectrometer (WPIIS) are analyzed and discussed. Formulas for the lateral displacement and optical path difference (OPD) produced by the modified Savart polariscope are derived by ray-tracing method. The theoretical and practical guidance is thereby provided for the study, design, modulation, experiment and engineering of the polarization interference imaging spectrometers and other birefringent Fourier-transform spectrometers based on Savart polariscopes. (c) 2006 Elsevier B.V. All rights reserved.

土壤干旱对2个种源野生酸枣幼苗生长和生理特性的影响

以采自陕西杨陵和安塞的2个1年生酸枣幼苗为材料,采用盆栽称重控水法研究了中度和重度土壤干旱胁迫对它们生长和生理特性的影响。结果表明,不同程度的水分胁迫均使2种源酸枣新生侧枝长度受到极显著抑制,其苗高和基径也受到一定程度抑制,同时分别使叶片相对含水量和水分饱和亏有一定程度的降低和升高;2种源酸枣叶片的叶绿素a含量在各水分胁迫均极显著降低,它们的总叶绿素含量也在重度干旱下显著降低;随土壤干旱胁迫时间的延续,2种源酸枣叶片保护酶SOD、CAT、APX活性上下波动,其脯氨酸和可溶性糖含量逐渐升高,而超氧阴离子含量在较低水平下波动,丙二醛含量逐渐降低。杨陵酸枣在土壤水分较好的条件下表现良好,而安塞酸枣则具有更强的适应旱生能力。研究发现,在不同程度的土壤干旱胁迫下,2个种源酸枣的生长均受到一定程度的抑制,但它们均能调节自身的保护酶系统活性和渗透调节物质含量来减轻干旱伤害,维持植物体的正常生理代谢功能,表现出较强的抗旱耐旱能力。

SIMULATION OF LATERAL CONFINEMENT IN VERY NARROW CHANNELS

A theoretical study is presented of the lateral confinement potential (CP) in the very narrow mesa channels fabricated in the conventional two-dimensional (2D) electron gas in GaAs-AlxGa1-xAs heterostructures. The ID electronic structures are calculated in the framework of the confinement potential: V(x) = m* omega0(2)x2/2 for Absolute value of x

A NOVEL ODOR SENSOR COATED WITH A LIPID-MEMBRANE

In this paper, an interdigital electrode lipid film odour sensor (ILOS) is designed, fabricated and tested. It is made from a microfabricated chemiresistor coated with a synthetic multibilayer film. Nine odorants in gas phase at room temperature have been detected using the odour sensor. For most of the odorants, the relation between the response of the ILOS and odorant concentration obeys Stevens' power law, and there is a good correlation between the minimum odorant concentrations that give rise to a change of the sensor's conductance and human olfactory thresholds.

ELECTRONIC-STRUCTURES OF QUANTUM WIRES FORMED BY LATERAL STRAIN

The electronic structures of quantum wires formed by lateral strain are studied in the framework of the effective-mass envelope-function method. The hole energy levels, wave functions, and optical transition matrix elements are calculated for the real quantum-wire structure, and the results are compared with experiment. It is found that one-dimensional confinement effects exist for both electronic and hole states related to the n (001) = 1 state. The lateral strained confinement causes luminescence-peak redshifts and polarization anisotropy, and the anisotropy is more noticeable than that in the unstrained case. The variation of hole energy levels with well widths in the [110] and [001] directions and wave vector along the [110BAR] direction are also obtained.