The Gouy phase shift of the highly focused radially polarized beam

The Gouy phase shift in the focal field of high-NA focused radially polarized beam has been investigated in detail. Analytical expression for the Gouy phase shift can be derived using tilted wave interpretation, which provides a reasonable prediction compared to vectorial diffraction numerical simulation. Using this method, irregular wave spacing in the vicinity of the focus can be revealed.     

Investigation of low energy pion-nucleus interaction using electrofission data for heavy nuclei at the pion threshold

A theoretical approach to describe electro- and photofission processes at intermediate energies was worked out. Photopion reabsorption mechanisms by two and three nucleons (2NA and 3NA) were incorporated in the calculations. The comparison with electrofission data for preactinides showed that a substantial 3NA component should be added in the pion absorption to fit the data near photopion threshold, in accordance with a recent theoretical estimate. It was also shown that the shape of the fission response curve is sensitive to detailed aspects of the pion mean free path. Received: 10 March 1998 / Revised version: 12 March 1999     

Orthogonal Aberration Functions for Microlithographic Optics

Newly developed orthogonal aberration functions are reviewed. The new functions can be utilized to express aberrations of a high NA and wide field optical system like a microlithographic projection lens. The new functions are orthogonal to each other and expressed by a simple combination of Zernike function(s) of pupil coordinates and Zernike function(s) of field coordinates.     

Transverse superresolution with extended depth of focus using binary phase filters for optical storage system

This paper reports the study of superresolution and extension of depth of focus (DOF) of three-zone binary phase filters (BPFs) under high numerical aperture (NA) focusing. Two three-zone BPFs (BPF1 and BPF2) are specially designed to achieve transverse superresolution and extension of DOF simultaneously for the optical disc system with an objective lens of NA = 0.65. Numerical simulations based on the vectorial diffraction theory indicate that the transverse focal spot size of this system can be as small as that of NA = 0.85 and its DOF is as large as that of NA = 0.6 with acceptable Strehl ratios (> 0.4 for BPF1 and > 0.35 for BPF2) and low side-lobe intensity ratios (< 10%) by using these BPFs. It suggests that the storage capacity of this optical storage system may be improved to the same as that of a system with an objective lens of NA = 0.85. Moreover, the strict requirement of the focusing servo system caused by decreasing wavelength or employing higher NA objective lens can be mitigated. Therefore, these BPFs presented in this paper should be highly interesting for applications of high density optical data storage.     

Peculiarities of filamentation of sharply focused ultrashort laser pulses in air

Peculiarities of the self-focusing and filamentation of high-power femtosecond laser pulses in air have been experimentally and theoretically studied under conditions of broad variation of the beam focusing parameter. The influence of the numerical aperture (NA) of the initial radiation focusing on the main characteristics of laser-induced plasma columns (characteristic transverse size, length, and concentration of free electrons) is considered. It is established that, for a rigid (NA > 0.05) initial laser beam focusing, the transverse size of the plasma channel ceases to decrease at a level of R _pl ≈ 2–4 μm as a result of strong refraction of radiation on the plasma formed at the focal waist, which prevents further contraction of the laser beam due to its focusing and self-focusing.     

Instability of layered quantum liquids: 5. Collective modes at low density

We calculate the plasmon dispersion of electron superlattices by taking into account many-body effects via the local-field correction. For small electron density we find a weak roton structure in the dispersion of optical plasmons. Landau damping is strongly enhanced by many-body effects, especially for acoustical plasmons. We compare with experimental results of high-T _c superconductors. Some experiments are suggested.     

Anomalies and proximity effect in high-T C tunnel junctions

Summary Some of the main anomalies in conductance characteristics of high-T _C tunnel junctions are considered. Mainly, the extreme, depression of gap structures, the presence of conductance peaks in corrispondence to the counterelectrode gap, and ?zero-bias anomalies? will be examined. The possibility of application of the proximity McMillan model to describe the behaviour in conductance of high-T _C junctions is considered. Discussion and preliminary comparison with experimental data on YBCO junctions are also reported.     

Positioning photonic crystal cavities to single InAs quantum dots

We have investigated the optical properties of planar photonic crystal cavities formed by removing a single hole from a two-dimensional square lattice of air holes etched through a thin GaAs slab. We have demonstrated cavity resonances with quality factors (Q’s) as high as 8500, using an internal light source provided by an ensemble of InAs quantum dots (QDs) grown by molecular beam epitaxy (MBE). The high-Q modes are confined to a very small mode volume, V = 0.7(λ/n)³, making them attractive to study in the context of cavity quantum electrodynamics with single QDs, where a high is needed to observe the strong coupling between an electronic state of the dot and the optical cavity mode. To this end, we have developed an accurate and robust alignment technique that positions a photonic crystal cavity to a single QD with 25 nm resolution. We present the details of this new technology and demonstrate its effectiveness by strategically positioning a number of QDs within photonic crystal cavities at points where the electric field intensity is high.     

Plasmonic slow light waveguide and cavity

In this work, we present a detailed analysis of optical properties of metal–insulator and metal–insulator–metal (MIM) structure-based surface-plasmon waveguides and cavities. It is shown from the dispersion relation, the field distribution, the quality factor Q, and the transmission spectrum that the MIM structure can be designed as a high-Q cavity, supporting slow light with tolerable pulse distortion and lower propagation loss in the axial direction.     

高k介质在新型半导体器件中的应用

当CMOS器件特征尺寸缩小到45 nm以下, SiO₂作为栅介质材料已经无法满足性能和功耗的需要, 用高 k材料替代SiO₂是必然选择. 然而, 由于高 k材料自身存在局限性, 且与器件其他部分的兼容性差, 产生了很多新的问题如界面特性差、 阈值电压增大、 迁移率降低等. 本文简要回顾了高 k栅介质在平面型硅基器件中应用存在的问题以及从材料、 结构和工艺等方面采取的解决措施, 重点介绍了高k材料在新型半导体器件中的应用, 并展望了未来的发展趋势.     

Azimuthal correlations with high-pT multi-hadron cluster triggers in Au+Au collisions at ?{sNN } \sqrt {s_{NN} } = 200 GeV from STAR

Di-hadron correlation measurements have been used to probe di-jet production in heavy ion collisions at RHIC. A strong suppression of the away-side high-p _T yield in these measurements is direct evidence that high-p _T partons lose energy as they traverse the strongly interacting medium. However, since the momentum of the trigger particle is not a good measure of the jet energy, azimuthal di-hadron correlations have limited sensitivity to the shape of the fragmentation function. We explore the possibility to better constrain the initial parton energy by using clusters of multiple high-p _T hadrons in a narrow cone as the ‘trigger particle’ in the azimuthal correlation analysis. We present first results from this analysis of multi-hadron triggered correlated yields in Au+Au collisions at $ \sqrt {s_{NN} } $ \sqrt {s_{NN} } = 200 GeV from STAR. The results are compared with measurements in d + Au collisions and Pythia calculations, and the implications for energy loss and jet fragmentation are discussed.     

高k栅介质对肖特基源漏超薄体SOI MOSFET性能的影响

研究了高k栅介质对肖特基源漏超薄体SOI MOSFET性能的影响.随着栅介质介电常数增大,肖特基源漏(SBSD) SOI MOSFET的开态电流减小,这表明边缘感应势垒降低效应(FIBL)并不是对势垒产生影响的主要机理.源端附近边缘感应势垒屏蔽效应(FIBS)是SBSD SOI MOSFET开态电流减小的主要原因.同时还发现,源漏与栅是否对准,高k栅介质对器件性能的影响也不相同.如果源漏与栅交叠,高k栅介质与硅衬底之间加入过渡层可以有效地抑制FIBS效应.如果源漏偏离栅,采用高k侧墙并结合堆叠栅结构,可以提高驱动电流.分析结果表明,来自栅极的电力线在介电常数不同的材料界面发生两次折射.根据结构参数的不同可以调节电力线的疏密,从而达到改变势垒高度,调节驱动电流的目的. 关键词： k栅介质')" href="#">高k栅介质 肖特基源漏(SBSD) 边缘感应势垒屏蔽(FIBS) 绝缘衬底上的硅(SOI)     

Complex conductivity in high-Tc single crystal superconductors

The electromagnetic surface impedance of single crystal high-T_c superconductors has been examined within the framework of the two-fluid model and the hypothesis that the e m field modulates the partial concentrations of both normal and condensate fluids. A comparison with experimental data is reported.     

Possible mechanism for high-T c superconductivity

Based on recent experiments and numerical simulations on the glass behaviour of the new high-T _c superconductors, a microscopic mechanism is proposed. Disorder is found to play an important role. Pairing of holes and subsequent bose condensation on an antiferromagnetic background is proposed as a basic mechanism for high-T _c superconductivity.     

New atomic data for Kr XXXV useful in fusion plasma

Energy levels and emission line wavelengths of high-Z materials are useful for impurity diagnostics due to their potential application in the next generation fusion devices.For this purpose,we have calculated the fine structural energies of the 67 levels belonging to the 1s 2,1s2l,1s3l,1s4l,1s5l,and 1s6l configurations of Kr XXXV using GRASP(general purpose relativistic atomic structure package) code.Additionally,we have reported the transition probabilities,oscillator strengths,line strengths,and transition wavelengths for some electric dipole(E1) transitions among these levels.We predict new energy levels and radiative rates,which have not been reported experimentally or theoretically,forming the basis for future experimental work.     

Anisotropic distributions of electrical currents in high-<Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> grain-boundary junctions

We developed a self-consistent method for the calculation of spatial current distributions in high-T _c grain-boundary junctions. It is found that crystallographic anisotropy of high-T _c superconducting electrodes results in the effects, which previously were not taken into account for interpretations of experimental data. Among them is a significant redistribution of electrical currents in superconducting electrodes in the vicinity of a grain boundary. In particular in the case of [100]-tilt bicrystal junctions, this current redistribution results in a substantial focusing to the top or bottom part of a thickness of the grain boundary, depending on “roof”- or “valley”-type of the grain boundary. This redistribution is accompanied by generation of vortex currents around the grain boundary, which leads to self-biasing of grain-boundary junctions by magnetic field nucleated by these vortex currents. It is shown that twinning or variation of geometrical shape of the high-T _c electrode may also result in intensive redistribution of electrical currents and nucleation of local magnetic fields inside a high-T _c superconducting electrodes.     

Binding effects in the optical potential of pionic atoms

We calculate the contribution from nucleon binding to the coefficient Re B₀ in the optical potential of pionic atoms. The relevant Feynman graphs are deduced for nuclear matter. They depend on off-shell values for pion-nucleon scattering lengths a_πN and for the nucleon-binding potential V_NA. Off-shell effects are found to be very important: A pole model for a_πN, extrapolated off-shell, increases binding effects by a factor of three over the use of on-shell values. Two simple models are proposed for the off-shell continuation of V_NA. One leads to attractive, the other to repulsive contributions to Re B₀.     

Trapping Rayleigh particles using highly focused higher-order radially polarized beams

The optical trapping characteristics of highly focused higher-order radially polarized beams (R-TEM_p1*) acting on a Rayleigh particle are studied theoretically. Numerical results show that as the order p of beam increases and the numerical aperture NA_o of the objective decreases, the axial trap distance increases but the trap depth and maximum restoring force decreases. In a limit of NA_o = 1, three higher-order R-TEM_p1* beams of p = 1, 2, 3, like the fundamental lowest-order radially polarized beam of p = 0, can three-dimensionally trap a particle to the focus but the axial trap stiffness decreases with the increase of p. When NA_o = 0.95, the focus is still a stable trap point for the two beams of p = 0 and 1 but it becomes an unstable trap point for the two beams of p = 2 and 3. The trap stability is also discussed for higher-order radially polarized beam illumination.     

Resonance fluorescence of a two-level atom excited by a superposition of coherent states, and the instability of the average atomic dipole moment

We find the evolution of average atomic variables in the resonance fluorescence of a two-level atom excited by a superposition of coherent states shifted in phase by π. A new effect is predicted, the quantum instability of the average atomic dipole moment, with a strong correlation between atom and field being the reason. We propose different ways of verifying the effect in experiments involving high-Q optical and microwave cavities. Zh. éksp. Teor. Fiz. 111, 1174–1189 (April 1997)     

The vortex-like excitations detected by Nernst signals in high-Tc superconductors

The nature of the pseudogap state and its relation to the d-wave superconductivity in high-T _c superconductors is still an open issue. The vortex-like excitations detected by the Nernst effect measurements exist in a certain temperature range above superconducting transition temperature T _c, which strongly support that the pseudogap phase is characterized by finite pairing amplitude with strong phase fluctuations and imply that the phase transition at T _c is driven by the loss of long-range phase coherence. We first briefly introduce the electronic phase diagram and pseudogap state of high-T _c superconductors, and then review the results of Nernst effect for different high-T _c superconductors. Related theoretical models are also discussed.