Reverse optical forces in negative index dielectric waveguide arrays

Nonconservative optical forces acting on dipolar particles are considered in longitudinally invariant optical fields. We demonstrate that the orientation of these forces is strictly dictated by the propagation vector associated with such field configurations. As a direct consequence of this, it is impossible to achieve a reversal of optical forces in homogeneous media. We show instead that translation invariant optical tractor fields can in fact be generated in the negative index environment produced in a special class of fully dielectric waveguide arrays.     

Step-profile measurement by backpropagation of multiple-wavelength optical fields

Multiple-wavelength optical fields on a detecting plane of an interferometer are generated from the interference signals detected for an object surface. The generated optical fields are backpropagated along the optical axis. An optical field along the optical axis is reconstructed by summing the backpropagated fields over the multiple wavelengths. The intensity and phase distributions of the reconstructed optical field provide the position of the object surface with an accuracy of a few nanometers.     

Remarks on degenerate theories of the conformal invariant quantum field theory

It is remarked that conformally invariant degenerate theories can be found along the current algebra approach to quantum field theory. The only input is the definition of the product of single-valued fields with other fields.     

Charged magnetoexcitons in two-dimensions: magnetic translations and families of dark states

We show that optical transitions of charged excitons in semiconductor heterostructures are governed in magnetic fields by a novel exact selection rule, a manifestation of magnetic translations. It is shown that the spin-triplet ground state of the quasi-two-dimensional charged exciton X--a bound state of two electrons and one hole-is optically inactive in photoluminescence at finite magnetic fields. Internal bound-to-bound X- triplet transition has a specific spectral position, below the electron cyclotron resonance, and is strictly prohibited in a translationally invariant system. These results allow one to discriminate between free and disorder-affected charged excitons.     

Nonlinear realization of <Emphasis Type="Italic">N</Emphasis>=2 superconformal symmetry and brane effective actions

Since there is an incompatibility of simultaneously nonlinear breaking the superconformal symmetry and the dilatation symmetry with the dilaton taken as the compensator field, in the present paper is shown an alternative mechanism of spontaneous breaking the N=2 superconformal symmetry to the N=0 case. By using the approach of nonlinear transformations one finds that it leads to a space-filling brane theory with Weyl scale W(1,3) symmetry. The dynamics of the resulting Weyl scale invariant brane, along with that of other Nambu–Goldstone fields, is derived in terms of the building blocks of the vierbein and the covariant derivative from the Maurer–Cartan one-forms. A general coupling of the matter fields localized on the brane world volume to these NG fields is also constructed.     

Mutual spatiotemporal coherence of optical fields in an amplitude-splitting interferometer

We have considered cross correlations of wave perturbations formed by optical fields at different points of space at the exit of an interferometer with the splitting of the amplitude of the initial wave field. Expressions for the longitudinal spatiotemporal cross-correlation function of perturbations on the optical axis of a Michelson interferometer have been obtained and analyzed. We have determined spatial and temporal intervals in which the wave fields excite mutually coherent perturbations in the exit channel of the interferometer in the free space and in the image space of the lens system. We have found that, in the free space, mutually correlated perturbations arise simultaneously in identical longitudinal intervals, whereas, in the image space, they arise at different times in spatial and temporal intervals varying along the optical axis of the lens. The influence of cross correlations of the wave fields on the interferometer signal has been analyzed.

     

Broadband focused waves with compensated spatial dispersion: transverse versus axial balance

We determine the constraints an ABCD optical system must verify to achieve, at the focal region, broadband waves with compensated spatial dispersion either along the optical axis, called on-axis isodiffracting fields, or in the lateral direction, here named in-plane isodiffracting beams. An optical configuration is identified for generating both types of achromatic broadband focused wave fields. An experimental verification is also provided.     

光学微操纵过程的轴平面显微成像技术

光学俘获技术利用光与物质相互作用产生的光势阱效应来实现对微粒的操控,已经成功应用于生物医学、材料科学等交叉领域.在对微粒进行三维俘获时,传统的宽场光学显微技术只能观测到某一平面内微粒的横向运动,对微粒沿轴向运动的观测受到很大限制.本文将轴平面显微成像技术引入光学微粒操控研究中,利用45?倾斜的反射镜把微粒的轴向运动信息转换到横向平面进行观测,与传统宽场显微成像技术相结合,实现了对二氧化硅小球俘获过程横向和轴向运动的同步观测.该成像方法无需扫描和数据重构,具有实时快速等优点,在新型光束光镊、厚样品三维观测和成像等领域具有潜在的应用价值.     

Spatial characterization of general partially polarized beams

The spatial characterization of light beams given in terms of intensity moments is extended to partially polarized beams by means of a generalization of the Stokes-Mueller formalism. A simple classification scheme of partially polarized fields is proposed, and laws of propagation through nonpolarizing and polarizing optical systems are provided. Some invariant parameters are also investigated.     

Cubic interaction vertices for fermionic and bosonic arbitrary spin fields

Using the light-cone gauge approach to relativistic field dynamics, we study arbitrary spin fermionic and bosonic fields propagating in flat space of dimension greater than or equal to four. Generating functions of parity invariant cubic interaction vertices for totally symmetric and mixed-symmetry massive and massless fields are obtained. For the case of totally symmetric fields, we derive restrictions on the allowed values of spins and the number of derivatives. These restrictions provide a complete classification of parity invariant cubic interaction vertices for totally symmetric fermionic and bosonic fields. As an example of application of the light-cone formalism, we obtain simple expressions for the Yang–Mills and gravitational interactions of massive arbitrary spin fermionic fields. For some particular cases, using our light-cone cubic vertices, we discuss the corresponding manifestly Lorentz invariant and on-shell gauge invariant cubic vertices.     

Bessel beam spectral-domain high-resolution optical coherence tomography with micro-optic axicon providing extended focusing range

Endoscopic imaging in tubular structures, such as the tracheobronchial tree, could benefit from imaging optics with an extended depth of focus (DOF) to accommodate the varying sizes of tubular structures across patients and along the tree within the same patient. Yet the extended DOF needs to be accomplished without sacrificing resolution while maintaining sufficient sensitivity and speed of imaging. In this Letter, we report on the measured resolution and sensitivity achieved with a custom-made micro-optic axicon lens designed to theoretically achieve an 8 mm DOF. A measured invariant resolution of approximately 8 microm is demonstrated across a 4 mm measured DOF using the micro-optic axicon while achieving an invariant sensitivity of approximately 80 dB with a 25 mW input power. Double-pass Bessel beam spectral-domain optical coherence tomography with an axicon micro-optic lens (i.e., <1 mm in diameter) is, for the first time to our knowledge, demonstrated in a biological sample demonstrating invariant resolution and signal-to-noise ratio across a 4 mm measured DOF, which is compared to Gaussian beam imaging.     

Transmission of Cerenkoverenkov radiation in optical fibers

Cerenkov radiation is generated as an unwanted background when optical fibers carrying signals pass through radiation fields. The angular dependence of the intensity of ? Cerenkov radiation transmitted in silica-core fibers was measured using 6 and 12 MeV electron beams from a Varian Clinic accelerator. These confirmed theoretical predictions that the angular variation of ? Cerenkov radiation transmitted along optical fibers depends only on the refractive index difference Dn between the core and the cladding, and that the peak intensity is proportional to the cube of the fiber core radius.     

RIGHT TRANSLATION INVARIANT METRICS AND VARIATIONAL PRINCIPLES ON A PRINCIPAL BUNDLE——TREATED AS THE UNION OF SPACE-TIME AND AN INTERNAL SPACE

In this paper, we discuss how to assign a metric on a principal bundle and howto rewrite the variational principles for a particle and for matter fields in an inva-riant from on the bundle in the principal-bundle formulation of gauge theories. Weshow that the right-translation invariant metric on the bundle must contain quantitieswhich transform exactly as gauge potentials, thus providing a new formalism for gaugefields. And we formulate the variational principle for a particle moving in the gaugefield as follows: The particle moves along a horizontal geodesic on the principalbundle. Starting from this we derive the Wong's equations of motion. Moreover, we elucidate the physical view-point which treats the bundle space asthe union of space-time and the internal space. Advantages of this viewpoint for un-derstanding the essentialities of gauge transformations and gauge invariance and forestablishing unified theories of gravitation and gauge fields are also discussed.     

太阳模拟器的拉赫不变量传递

介绍了太阳模拟器的组成及工作原理。在非成像光学的光学扩展量基础上,对照明系统和投影成像系统进行了光学匹配,并从拉赫不变量的角度分析了能量在整个系统中的传递情况,得出椭球聚光镜、光学积分器和准直物镜这三者的相对孔径相互之间的最佳匹配关系,即三者的相互之间的相对孔径值均为1／4时,满足光瞳衔接原理。计算得到了从物面到像面的拉赫不变量为0．45,验证了整个光学系统从物面到像面的拉赫不变量守恒,有效地利用了光学系统的光能。     

A local approach to dimensional reduction: I. General formalism

We present a formalism for dimensional reduction based on the local properties of invariant cross-sections (“fields”) and differential operators. This formalism does not need an ansatz for the invariant fields and is convenient when the reducing group is non-compact.

In the approach presented here, splittings of some exact sequences of vector bundles play a key role. In the case of invariant fields and differential operators, the invariance property leads to an explicit splitting of the corresponding sequences, i.e. to the reduced field/operator. There are also situations when the splittings do not come from invariance with respect to a group action but from some other conditions, which leads to a “non-canonical” reduction.

In a special case, studied in detail in the second part of this article, this method provides an algorithm for construction of conformally invariant fields and differential operators in Minkowski space.     

First- and second-order statistics of partially coherent, high-numerical-aperture optical fields

The intensity probability distribution as well as the cross-spectral density of partially coherent optical fields generated through high-numerical-aperture illuminations are analyzed, and novel effects, not apparent in paraxial optical fields, are described. It is shown that the intensity probability distribution significantly differs from what can be expected from a small-angle analysis, and the number of degrees of freedom for the distribution is higher. It is further shown that the cross-spectral density of a high-angle optical field is a function of the coordinate difference along the propagation direction of the field.     

基于多变量鉴别分析的光学畸变不变性图像识别

提出一种基于鉴别分析的光学畸变不变性图像识别方法：对包含各种畸变的训练图像集采用主成分分析得到若干本征图像,作为参考模式与测试图像做光学相关,利用本民输入图像的相关结果作为识别特征,采用最佳鉴别分析做了训练和识别,即可实现对输入图像的畸变为性快速识别。采用非相干光相关器为光学实现硬件,给出了实验结果。     

Some topological invariants for three-dimensional flows

We deal here with vector fields on three manifolds. For a system with a homoclinic orbit to a saddle-focus point, we show that the imaginary part of the complex eigenvalues is a conjugacy invariant. We show also that the ratio of the real part of the complex eigenvalue over the real one is invariant under topological equivalence. For a system with two saddle-focus points and an orbit connecting the one-dimensional invariant manifold of those points, we compute a conjugacy invariant related to the eigenvalues of the vector field at the singularities. (c) 2001 American Institute of Physics.     

First-order invariant Einstein-Cartan variational structures

A first-order invariant Einstein-Cartan structure is a Lagrangian structure on a differential manifold defined by a generally invariant Lagrangian depending on a metric field, a connection field, and the first derivatives of these fields. Moreover, it is assumed that the metric and connection fields satisfy the so-called compatibility condition. In this paper the problem of finding all such invariant Einstein-Cartan structures is discussed. It is shown that each Lagrangian of these structures depends only on certain tensors constructed from the metric and the connection fields, which means that all the Lagrangians can be described within the framework of the classical theory of invariants. The maximal number of functionally independent Lagrangians is determined as a function of the dimension of the underlying manifold.     

Binding of Resonant Dielectric Particles to Metal Surfaces Using Plasmons

Forces between dielectric particles induced by optical fields can bind them into new systems, varying from optical molecules to large aggregates. Here it is shown that surface plasmons can bind resonant dielectric particles to the waveguiding surfaces resulting in stable levitation of the particles by the optical forces alone. At the same time, the particles can be propelled efficiently along the surface. The predictions follow from solving the 3D electromagnetic problem of plasmon scattering on a dielectric microsphere near the metal surface. To tackle the problem, an accurate and fast hybrid approach is developed: the fields are expanded into 2D angular components which are calculated using finite-difference time-domain simulations. The rigorous numerical results are also explained qualitatively using an analytically solvable model in which a resonant magnetic dipole illuminated by a plasmon interacts with the surface. The particle binding to surfaces is a remarkable outcome of the strong optical interaction at nanoscale and it may offer new configurations for particle manipulations by guided waves, especially in chip-scale structures.