Tightly focusing of linearly polarized vortex beams through a dielectric interface

Based on vectorial Debye theory, the tightly focusing properties of linearly polarized vortex beams through a dielectric interface are studied. Then the intensity distribution in the focal region is investigated in detail by numerical calculations. The focal shifts induced by the mismatch of the refractive indices across the interface has been found. And the dependence of focal shifts and spot size of the focused field on the probe depth and numerical aperture of the objective are presented. Furthermore, the characteristic of intensity pattern of the cross section of the focused field is illustrated, finding that the intensity pattern rotates with the propagation of beams.     

Tightly focusing of spirally polarized Quadratic Bessel Gaussian beam through a dielectric interface

Based on vector diffraction theory, the tight focusing properties of spirally polarized axisymmetric Bessel-modulated Gaussian beam through a dielectric interface on high numerical aperture (NA) are investigated theoretically. The optical intensity distribution in the focal region of high NA objective lens is investigated in detail by numerical calculations. The results show that the focal shift induced in the focal region is by mismatch of refractive indices across the dielectric interface. It is also found that the optical intensity in focal region of spirally polarized Quadratic Bessel Gaussian (QBG) beam can be altered considerably by changing spiral parameter C that indicates the polarization spiral degree of the incident beam.     

有平界面存在时时间反转法的自聚焦性能

时间反转法是一种具有独特优点的自适应聚焦方法,对超声成像中图象畸变的消除有重要价值。本文就声场中存在介质分平面时,对时间反转法实现自聚焦的声场给出了解析式;并运用所建立起来的时间反转成像实验系统进行了有平界面存在时的自聚焦实验,实验所得自聚焦增益与理论计算结果相符。     

双环径向偏振涡旋光束经介质界面的深聚焦

基于矢量德拜理论,研究了双环径向偏振涡旋光束经介质分界面的深聚焦特性。当选取适当的入射光束拦截比时(即透镜孔径半径与入射光束的束腰半径的比),在聚焦场中可以得到一个极小的局域空心光束。局域空心光束的大小不仅与透镜的数值孔径有关,还与聚焦场介质的折射率有关。另外,还研究了透镜的数值孔径、入射光束的拦截比以及探测深度对聚焦光束实际焦点位置的影响。通过对聚焦光束的实际焦点位置的计算发现:当选取一定的光束拦截比时,聚焦光束存在一个焦点开关。     

双环径向偏振涡旋光束经介质界面的深聚焦

基于矢量德拜理论,研究了双环径向偏振涡旋光束经介质分界面的深聚焦特性。当选取适当的入射光束拦截比时（即透镜孔径半径与入射光束的束腰半径的比）,在聚焦场中可以得到一个极小的局域空心光束。局域空心光束的大小不仅与透镜的数值孔径有关,还与聚焦场介质的折射率有关。另外,还研究了透镜的数值孔径、入射光束的拦截比以及探测深度对聚焦光束实际焦点位置的影响。通过对聚焦光束的实际焦点位置的计算发现：当选取一定的光束拦截比时,聚焦光束存在一个焦点开关。     

Propagation of plane waves through the interface between media with dislocations

The laws of propagation of plane waves in homogeneous media with dislocations in the presence of an interface are considered using the equations of the defect field theory. The reflection coefficients and the refractive indices of displacement waves and the waves of a defect field, which is characterized by a dislocation density tensor and a dislocation flux density tensor, are determined. The dependences of these quantities on the parameters of the adjacent media are analyzed.     

Interaction of superdislocations with a plane interface

Using the linear isotropic elasticity-theory approximation, an analysis is made of the splitting of linear superdislocations with an arbitrary Burgers vector near plane interfaces of different types as defined by Head [4].Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 9, pp. 11–15, September, 1971.     

Focal shifts in focused Hermite-cosh-Gaussian laser beams

A closed-form propagation equation of Hermite-cosh-Gaussian beams passing through an unapertured thin lens is derived. Focal shifts are analyzed by means of two different methods according to the facts that the axial intensity of some focused Hermite-cosh-Gaussian beams are null and that of some others are not null but the principal maximum intensity may be located on the axis or off the axis. Optimal focusing for the beams is studied, and the condition of optimal focusing ensuring the smallest beam width is also given.     

Focal shifts in diffracted converging spherical waves

It is known from a number of publications that when a converging, monochromatic spherical wave is diffracted at a circular aperture, the point of maximum intensity of the diffracted wave may not be at the geometrical focus of the incident wave, but may be located closer to the aperture. In the present note we show that when the incident wave is uniform and the angular semi-aperture is small, the ratio of such a shift Δ? of the point of maximum intensity to the distance ? between the geometrical focus and the plane of the aperture depends only on the Fresnel number N of the aperture when viewed from the geometrical focus. The effect becomes significant when N ? 5. When N = 1, for example, |Δ?| ≈ 0.4 ? and the maximum intensity is approximately twice as large as the intensity at the geometrical focus.     

Focal shifts in diffracted converging spherical waves

It is known that when a converging, monochromatic, spherical wave is diffracted at a circular aperture, the point of maximum intensity may not be at the geometric focus of the incident wave, but may be located closer to the aperture. In the present note this effect is calculated using somewhat simpler mathematical procedures than have been used in previous publications. The result is interpreted as the combined effect of diffraction and the inverse square law.     

Electromagnetic focusing through a tilted dielectric surface

Focusing through a tilted dielectric interface is studied, and an explicit expression for the electric field in the focal region is found. In the case of small tilt angles, only a simple aberration term remains.     

Electromagnetic field focusing by a plane multilayer structure with a Veselago medium

The focusing properties of a system of plane layers of a Veselago medium divided by vacuous intervals are investigated by the coordinate transformation method. The role of real and virtual foci in the mechanism of focusing by a multilayered lens is considered.     

余弦-高斯光束的焦平面及其位置

在余弦_高斯光束通过薄透镜聚焦系统的光场分布函数的基础上,利用二阶矩定义导出了聚焦余弦_高斯光束的光斑函数的解析表达式,由此求得束腰宽度及位置,进而给出了余弦_高斯光束的相对焦移的解析表达式。分析了光学系统参数以及光束参数对实际焦平面位置的影响并作了数值计算。     

聚焦部分相干涡旋光束的焦移

基于部分相干光的传输理论获得了部分相干涡旋光束被光阑透镜聚焦后的传输方程。基于这些方程研究了部分相干涡旋光束的焦移现象。研究结果表明,部分相干涡旋光束的焦移不仅依赖于菲涅耳数,而且依赖于光束的相干长度和涡旋光束的拓扑荷数。菲涅耳数越小,焦移量越大;部分相干涡旋光束的相干长度越小,焦移量越大;涡旋光束的拓扑荷数越大,焦移量越大。     

部分相干电磁光束的焦移

 基于有效菲涅耳数的概念,给出一种简单的表达式来评估部分相干电磁光束经圆形光阑透镜后所产生的相对焦移,对部分相干电磁光束经透镜聚焦的情况进行了研究。结果表明:当交叉谱密度函数的非对角元素为零时,有效菲涅耳数不仅依赖于真实的菲涅耳数大小,而且依赖于光束的偏振分布和入射部分相干电磁光束两个偏振分量的空间相干长度;相对焦移量仅由等效菲涅耳数决定。将此方法与数值积分法进行的比较表明,等效菲涅耳数可以简单、准确地评估焦移。     

Reflection of plane Beltrami waves from a plane interface in an isotropic chiral medium

The reflection of plane electromagnetic waves of circular polatization from a flat, ideally conducting screen limiting an isotropic chiral-medium half-space is examined. The equations relating the reflection coefficients with the common angle of incidence and material parameters of the medium are discussed.__________This revised version was published online in May 2005 with a correction on affiliation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 23–26, November, 2004.     

High aperture focusing through a spherical interface: Application to refractive solid immersion lens (RSIL) for subsurface imaging

The effects of on-axis spherical aberration and defocus on focusing across a spherical interface between two materials of mismatched refractive index are discussed. A vectorial integral representation for high aperture focusing in this configuration is formulated and an analytical expression for the spherical aberration function is derived. Numerical simulations are performed to analyse the effects of the spherical interface on both the transverse and axial intensity profiles. The results from these numerical simulations are important industrially in understanding the resolution enhancements from solid immersion lens technology, as well as being of more fundamental interest in calculating the distribution at the focal plane under different solid immersion lens configurations.     

Spin angular momentum of a field interacting with a plane interface

The quantization of the spin angular momentum S of a field interacting with a plane boundary is investigated. When a good set of modes is chosen, the component of S along the momentum P is formally the same as that for a free field. In the case of the presence of an evanescent wave the good modes are the same ones that appear in the filtering of the polarisation states by total reflection. But terms due to the discontinuity appear in the expressions. Although they are clearly related to the interaction field-interface, their interpretation is not obvious.