Digital speckle interferometry for assessment of surface roughness

In this work, the principle of interferometry is used to assess the surface roughness of the machined surfaces. Interferometry produces an interference fringe pattern when two or more light waves interact with each other. It is one of the important tool for precision optical metrology and testing. Well-known advantages of the phase shifting interferometry include high measurement accuracy, rapid measurement, good result even with low contrast fringes and that the polarity of the wave front can be determined. In fringe projection techniques, a known optical fringe pattern is projected onto the surface of interest. The fringe pattern on the surface is perturbed in accordance with the profile of the test surface, thereby enabling direct derivation of surface profile.In this work, an attempt has been made to assess the surface roughness using a speckle fringe analysis method of five frame phase shift algorithm for machined surface (ground surface). As these fringes are too noisy, advanced filtering technique has been used so as to reduce noise and to get improved wrapped phase map from the phase shifted fringes. A phase unwrapping software has been developed using discrete cosine transform (DCT) to generate the three-dimensional (3-D) profiles. Finally, it is compared with R_a values measured using a mechanical stylus instrument, showing good agreement.     

Focal shift of cylindrical vector axisymmetric Bessel-modulated Gaussian beam with radial variance phase wavefront

Axisymmetric Bessel-modulated Gaussian beam with quadratic radial dependence (QBG beam) has attracted much attention recently. In this paper, the focal shift of the cylindrical vector QBG beam with radial variance phase wavefront is investigated theoretically by vector diffraction theory. Results show that focus shifts considerably by changing the phase parameter C that indicates the radial phase variance speed. Under condition of small beam parameter μ of cylindrical vector QBG beam, there is one focal peak that shifts far away from optical aperture on increasing C. When μ increases, there may occur two focal peaks that also shift remarkably on increasing C. And it was found that the dependence of focal shift distance on increasing phase parameter is linear. Phase parameter adjusts the focal shift distance, while, polarization angle does not affect focal shift obviously.     

Giant and negative bistable shifts for one-dimensional photonic crystal containing a nonlinear metamaterial defect

In this Letter, we investigate giant and negative bistable lateral shifts for a light beam transmitted through a one-dimensional photonic crystal containing a nonlinear metamaterial defect. It is shown that there exists a typical S-shaped curve of the normalized input-output intensity. The hysteresis of lateral shift, resulting from the reshaping effect (constructive and destructive interferences of each plane wave components undergoing different phase shifts) is dependent on the nonlinear defect, the incident intensity and incidence angle. Numerical simulations are also made for the validity of stationary phase approach. All these phenomena lead to potential applications in integrated optics and optical switches.     

Finite thickness lens model for self-focusing (defocusing) in Kerr medium

A “finite thickness lens” model for self-focusing (defocusing) in Kerr medium is presented. An on-axis normalization transmittance formula is presented for arbitrary nonlinear phase shift for the finite thickness Kerr medium by introducing a nonlinear ABCD-matrix for the transition of a Gaussian beam from linear to non-linear medium, without complex calculation for the beam radius at the far field aperture. The variation of the peak and valley transmittance difference is found to enhance linearly as the phase shift at the focus increases by increasing the thickness of the medium. If the ratio of the Rayleigh istance divided by the thickness of the medium (d/z0) is constant and small enough, the peak and valley transmittance difference stays constant. Finally, a qualitative formula is presented to express the relationship between the system parameters and the on-axis phase shift at the focus.      

Polarization interferometer as a proximity sensor

A simple interferometric phasemeter which can be used as a proximity sensor is described. It is based on the measurement of the phase shift between the p- and s- components of a field caused by the processes of attenuation in total internal reflection. The role of the interferometer is to restore the p- and the s- components from the resultant totally reflected field, with minimum amplitude and phase distortions and to let them interfere. The phase shift as a function of the attenuation of the total internal reflection can be determined from the interference signal. The interferometer is of a common path polarization shearing type, consisting of Rochon beamsplitter and a linear polarizer. An experiment for measuring the distance between glass plane surface and a plane attenuater made of Si mono-crystal is described. A good agreement between theory and experiment for separations less than 300 nm is observed. This device can be applied in research and metrology. After further modifications, the optical system could be used for proximity sensing, surface geometry control, variable optical retarders, contamination monitoring, etc.     

Quantum mechanical calculation of Suryan’s line broadening in nuclear magnetic resonance

The first quantum theory of the classical radiation damping in nuclear magnetic resonance is presented. Relaxation times and life times arising from the interaction of nuclear spin with the radio-frequency radiation field are calculated. Second-order line shifts are predicted and the existence ofI _z andI _z ² -type operators due to photons is pointed out. The predicted line shifts as well as relaxation are found to be measurably large. Numerical estimates are given for protons in water.     

Measurement of Wave-Front Aberrations in Lithography Lenses with an Overlay Inspection Tool

Measurement methods using overlay inspection tools have been established for wave-front aberrations in optical lithography lenses used for integrated circuit manufacturing. Three-beam interferometry and asymmetric two-beam interferometry can transform the wave-front aberrations at selected points on the lens pupil to lateral image shifts for fine grating objects. A technique of overlapped exposures makes the image shifts of inner lines of the grating images optically measurable, even if the images are too fine to be resolved optically. These methods are available in the fields of integrated circuit manufacturing and lithography tool assembling. This paper sums up measurement methods for wave-front aberrations. It is experimentally estimated that the methods are equally matched with the phase measuring interferometry widely used in the tool assemblies respecting accuracy and precision.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15–17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

Phase shift analysis of pion-4He scattering by optimal polynomial expansion

A novel method of phase shift analysis for the scattering of charged pion from⁴He nuclei is proposed. The nuclear amplitudef _N (ϑ) has been parametrized in terms of a polynomial expansion in a conformally mapped variable, which is obtained by optimally exploiting the analytic property off _N . The method exhibits a significant reduction in the number of free parameters required for the fixed energy phase shift analysis of the differential cross-section data. The nuclear amplitude thus constructed is then used to obtain phase shifts and inelastic parameters of all possible orders. Reliable values of the real and imaginary parts of the forward amplitude are also obtained.     

二维热离子等离子体中离子声孤波的相互作用

通过使用推广的 Poincar-Lighthill-Kuo 摄动方法,研究了二维热离子等离子体中两个沿不同方向传播的离子声孤波的相互作用,得到了两个分别描述沿ξ和η方向传播的孤波的KdV方程以及两个孤波以任意夹角碰撞后的相移和轨道.同时还研究了离子温度比σ、热容比γ和碰撞夹角α对孤波相移的影响.研究表明,这些参量可以明显地改变孤波的相移,且在该系统中存在压缩型孤波. 关键词： 热离子等离子体 离子声孤波 Poincar-Lighthill-Kuo方法 相移     

Radiative Energy Shifts of an Atom Coupled to the Derivative of a Scalar Field near a Reflecting Boundary

We study the radiative energy level shifts of a two-level atom in dipole coupling to the derivative of a massless scalar quantum field in a spacetime with a perfectly reflecting boundary, and calculate the contributions of vacuum fluctuations and radiation reaction to the level shift. It is found that the energy level shift of the excited state is an oscillating function of the atom＇s distance from the boundary and it can either be positive or negative, while that of the ground state is always positive. The most remarkable feature is that the energy level shift of the ground state behaves like 1/z^4 when the atom＇s distance from the boundary, z, is very large as compared to the transition wavelength of the atom, while it behaves like 1/z^3 when z is very small     

利用声场频谱频率漂移监测内波的算法改进和实验验证

声场频谱的频率漂移曲线可以用来监测内波。由于简正波幅度剧烈起伏带来的干扰,目前尚无从实验数据中提取频移曲线的有效算法.提出了一种依据实测声学传播数据提取频移曲线的算法。借助于简正波过滤技术,该算法利用相关法从简正波相角之差中提取频率漂移曲线。利用该算法提取的频移曲线与内波导致的跃层起伏具有很高的相似性,这在2011年黄海实验中得到了验证。该算法的优点是可以保留简正波相位差变化导致的频移曲线信息,同时又能有效地抑制简正波幅度起伏带来的干扰,但是需要良好的接收阵阵型来保证简正波分离。      

Essai d'interprétation des déplacements et élargissements par la pression des raies du spectre de vibration-rotation des molécules diatomiques

An interpretation is given of the dependence on the rotational quantum number J of the pressure shift and broadening of the lines of the vibration-rotation band of a hydracide molecule perturbed by a noble gas. It is shown that, with the fundamental hypothesis of adiabatic collisions between the absorbing molecule and the noble gas atoms, the impact theory can describe the J dependence. This results from the fact that one introduces the average over the sine of the phase shift η, which is J dependent, and not the average of the phase shift itself which is vanishing. With a hard-sphere model good agreement is obtained between the calculated and the observed shifts. Further, a rough estimation of the breadth is made.     

Simulation study of solvent shifts of vibrational overtone spectra

Buckingham's theory of the solvent shift of vibrational spectral frequencies predicts that the shift of the v = 0 → n overtone transition is n times the shift of the fundamental v = 0 → 1. We test this prediction by molecular dynamics simulations using existing intermolecular potential models for liquid N₂ and dilute N₂ in liquid Ar, at standard state conditions. We extend Buckingham's theory by including additional intramolecular potential and perturbation terms which lead to solvent-induced anharmonicity, i.e. O(n ²) terms in the solvent shift. The simulations show that Buckingham's prediction is not accurate for N₂ at standard liquid state conditions. We find that at these conditions there is a significant positive O(n ²) contribution to the solvent shifts and that for n ～ 20 the shifts change sign from red to blue. Simulation results and indirect evidence from shock wave experiments with liquid N₂ show that Buckingham's prediction is more accurate for high-pressure high-temperature conditions, where the shifts are blue and only slightly nonlinear in n.     

Phase shift analysis of hyperon-nucleon elastic scattering using optimized polynomial expansion techniques

A relatively stable method of phase shift analysis of hyperon-nucleon scattering proposed by us is applied to Σ⁺ p and Λp scattering. The analytic cutt-planes of analyticity of the helicity amplitudes are mapped into the interior of unifocal ellipses. The helicity amplitudes are then expressed as accelerated convergent expansions in the mapped variable. A definite economy is observed in the number of free parameters for fixed energy phase shift analysis of Σ⁺ p and Λp scattering at 40 and 100 MeV and 100 MeV respectively. Twenty six more phase shifts and coupling parameters corresponding to higherJ values are also predicted.     

The Dobrushin-Shlosman phase uniqueness criterion and applications to hard squares

The rigorous Dobrushin-Shlosman phase uniqueness criterion is reviewed, then applied to the hard square model to prove that only a single phase exists at activityz=1.185. The criterion is violated (for a five-site by five-site lattice cell) atz=1.35557, but this does not imply phase nonuniqueness. This work complements that of Dobrushin, Kolafa, and Shlosman, who proved phase uniqueness for allz1. Certain experimentally discovered regularities are presented as conjectures: one for a more general problem and two for the application to hard squares. Even with these regularities, however, substantial further improvements in the algorithmic implementation of the criterion will be required before it can become a practical tool for locating phase transitions.     

Image displacement sensing (NDSE) for achieving overlay alignment

In this paper we discuss the application of NDSE [1] (Hewlett Packards nanoscale displacement sensing and estimation technology) as an overlay metrology tool. We describe a method where nanoscale displacement sensing forms the basis of a precision alignment measurement. We will then provide a review of experiments performed to assess the accuracy of one particular NDSE algorithm, tracking silicon targets as they translate on a piezoelectric stage under an optical microscope. We conclude by describing upcoming experiments which will incorporate NDSE as an alignment sensor in a nanoimprint lithography application.Current methods of overlay metrology and many methods of displacement metrology require precise alignment targets, such as symmetric geometric figures or extremely high-Q diffraction gratings. Such patterns are expensive to produce and/difficult to fabricate consistently. On the other hand, NDSE provides displacement sensing by tracking totally arbitrary patterns. As long as the patterns remain fixed, NDSE can provide extraordinary precision. We extend this advantage into a method for alignment sensing, which retains displacement sensing as the key underlying measurement. Hence, as with displacement sensing, the alignment targets need not be held to any absolute standard, pattern asymmetries caused by process variations are not an issue, and precision gratings are not required. PACS 06.30.Bp; 06.60.Sx; 81.16.-c; 81.16.Nd     

First-Order Phase Transitions in One-Dimensional Steady States

The steady states of the two-species (positive and negative particles) asymmetric exclusion model of Evans, Foster, Godrèche, and Mukamel are studied using Monte Carlo simulations. We show that mean-field theory does not give the correct phase diagram. On the first-order phase transition line which separates the CP-symmetric phase from the broken phase, the density profiles can be understood through an unexpected pattern of shocks. In the broken phase the free energy functional is not a convex function, but looks like a standard Ginzburg–Landau picture. If a symmetry-breaking term is introduced in the boundaries, the Ginzburg–Landau picture remains and one obtains spinodal points. The spectrum of the Hamiltonian associated with the master equation was studied using numerical diagonalization. There are massless excitations on the first-order phase transition fine with a dynamical critical exponent z = 2, as expected from the existence of shocks, and at the spinodal points, where we find z = 1. It is the first time that this value, which characterizes conformal invariant equilibrium problems, appears in stochastic processes.     

Systematic reduction of the permanent exciton dipole for charged excitons in individual self-assembled InGaAs quantum dots

The nature of the few particle wavefunctions for neutral and positively charged excitons is probed in individual InGaAs quantum dots using Stark-effect perturbation spectroscopy. A systematic reduction of the vertical component of the permanent excitonic dipole (p_z) is observed as additional holes are added to the dot. A comparison with calculations reveals that this reduction (Δp_z/e15–20%) is accompanied by a significant lateral expansion of the hole (2 nm) and contraction (1 nm) of the electron wavefunctions. We suggest that this lateral redistribution of the charged exciton wavefunctions provides an optical means to probe the lateral composition profile of the dot.     

原子力显微术轻敲模式中探针样品接触过程及相位衬度研究

借助简单的有阻尼受迫振子模型，研究了原子力显微术轻敲模式中探针与样品接触时间t_c、样品的表面形变D_z和相位衬度对探针设置高度z_c及样品杨氏模量E_s的依赖关系.结果发现,t_c与D_z均随E_s及z_c的增大而减小，同时探针与样品作用过程伴随很小的能量耗散.对轻敲过程中相移量φ的研究表明，E_s较大的样品有较小的φ，且φ随 关键词： 原子力显微术 轻敲模式 相位衬度