磁场中双折射光纤的琼斯矩阵等效模型

采用延迟器与旋光器的串联模型, 研究磁场中双折射光纤的偏振传输特性, 将它们的琼斯矩阵按照两种不同的顺序级联相乘, 导出了两种等效模型中等效相位延迟量、等效快轴方向和等效旋光角的解析表达式。研究发现, 当光纤同时具有线双折射和圆双折射时, 单位长度的等效相位延迟量并不等于其固有的线双折射, 等效旋光角也不等于其法拉第旋转角, 它们同时都与光纤的固有线双折射和磁场引起的圆双折射相关联。且在不同级联顺序的两种等效模型中, 等效相位延迟器的快轴方向都不与光纤的双折射主轴重合, 而是分别向两个相反的方向偏移一定的角度, 偏移角为等效旋光角的一半。     

Derivation of the General Case Sagnac Result Using Non-Time-Orthogonal Analysis

The Sagnac time delay and fringe shift dependency on angular velocity and enclosed area are derived from the rotating reference frame using non-time-orthogonal (NTO) tensor analysis. NTO analysis differs from traditional approaches by postulating that the continuous and single valued nature of physical time constrains simultaneity in a rotating frame to be unique (and thus not a matter of convention.) This implies anisotropy in the physical, local speed of light and invalidity of the hypothesis of locality for NTO frames. The Sagnac relationship for the most general case, in which the area enclosed is not circular and does not have the axis of rotation passing through its center, is determined.     

Canonical Three-Body Angular Basis

 Three-body problems are basic for the quantum mechanics of molecular, atomic, or nuclear systems. We demonstrate that their variational solution for rotational states can be greatly simplified. A special choice of coordinates (hyperspherical) and of the kinematics (body-fixed coordinate frame) allows one to choose basis functions in a form that makes the angular coupling trivial. Received December 30, 1999; revised May 2, 2000; accepted for publication June 15, 2000     

Topological defects, geometric phases, and the angular momentum of light

Recent reports on the intriguing features of vector vortex bearing beams are analyzed using geometric phases in optics. It is argued that the spin redirection phase induced circular birefringence is the origin of topological phase singularities arising in the inhomogeneous polarization patterns. A unified picture of recent results is presented based on this proposition. Orbital angular momentum (OAM) shift within the light beam has exact equivalence with the angular momentum holonomy associated with the geometric phase consistent with our conjecture.     

Molecular bond formation in Na*+N2 energy transfer: Crossed beam study of atomic alignment and orientation

We report the first full analysis of collisionally induced atomic alignment and orientation for a molecular collision process. In an experiment with crossed supersonic beams of N₀ and laser excited Na(3² P _3/2) we have studied the dependence of angular and energy resolved differential quenching cross sections as a function of the linear and circular polarization of the exciting laser light. The anisotropies observed in the linear polarization data range up to 2∶1 when corrected for electron and nuclear spin relaxation. The maximum effect is found at small scattering angles and intermediate energy transfer where the cross section is also largest. The atomic alignment angle most favourable for quenching relates to the scattering angle and can be understood in a model picture in such a way that the (NaN₂)^* molecular system is formed at internuclear distances as low asR=10a ₀. The circular asymmetry is small but with significant structure and is attributed to interaction on different potential surfaces atR>10a ₀. Full analysis of the four measurable parameter is given in terms of the density matrix in a frame withz-axis perpendicular to collision plane which allows a clear understanding of the properties of atomic reflection symmetry and coherence of the scattering process.     

高功率法拉第隔离器多模退偏特性

理论分析了隔离器在高功率多模激光入射时的自退偏特性.结果表明:线性双折射致退偏与圆双折射致退偏均与入射光功率的平方成正比,线性双折射致退偏与光斑大小无关,而圆双折射致退偏随光斑半径的增大而减小.当光斑半径与旋转晶体半径相比很小时(R0/r0≥80)圆双折射引起的退偏大于线性双折射引起的退偏,当光斑半径接近旋转晶体半径(R0/r0≤3)时,与线性双折射引起的退偏相比,圆双折射引起的退偏可以忽略.对比单模激光入射,在同种条件下,多模入射使得线性双折射致退偏减小了0.4倍, 最小圆双折射致退偏减小为0.05倍.     

高功率法拉第隔离器多模退偏特性

理论分析了隔离器在高功率多模激光入射时的自退偏特性.结果表明：线性双折射致退偏与圆双折射致退偏均与入射光功率的平方成正比,线性双折射致退偏与光斑大小无关,而圆双折射致退偏随光斑半径的增大而减小.当光斑半径与旋转晶体半径相比很小时（R0/r0≥80）圆双折射引起的退偏大于线性双折射引起的退偏,当光斑半径接近旋转晶体半径（R0/r0≤3）时,与线性双折射引起的退偏相比,圆双折射引起的退偏可以忽略.对比单模激光入射,在同种条件下,多模入射使得线性双折射致退偏减小了0.4倍, 最小圆双折射致退偏减小为0.05倍.     

Manifestation of the second-order alignment in light scattering by polarized atoms

An expression for the cross section of light scattering by axisymmetrically aligned atomic systems is derived in a compact form. The cross section under consideration is proportional to the state multipole of the fourth rank. The effect of the second-order alignment determined by the fourth-rank state multipole on the polarization and the angular distribution of scattered light is investigated. The polarization of incident light can be arbitrary and, in the general case, is specified by the Stokes parameters. In particular, it is demonstrated that the second-order alignment cannot induce circular polarization of scattered light and does not influence the dissipation-induced effects of circular dichroism associated with the first-order alignment but leads to a change in the angular distribution and the degree of linear polarization of the scattered light.     

From Faraday rotation to “Faraday oscillation”: Coherence effect between real and virtual excitons

This work provides the microscopic mechanisms responsible for circular birefringence changed into linear birefringence when the polarization of the excitons present in a semiconductor sample goes from circular to linear. This change shows up as Faraday rotation turning to “Faraday oscillation”: The probe polarization plane oscillates instead of rotates while the polarization goes from linear to elliptical and linear again. This oscillation, which reduces to zero when the probe polarization is parallel or perpendicular to the exciton polarization, comes from a non trivial coherence effect between real excitons present in the sample and virtual excitons coupled to unabsorbed photons. While Faraday rotation mainly follows from one single carrier exchange between composite excitons in the absence of Coulomb interaction, Faraday oscillation requires two Coulomb interactions plus a double carrier exchange, the virtual excitons coupled to the unabsorbed “in” and “out” photons being made with different electrons and holes, as nicely revealed by Shiva diagrams which visualize the many-body physics taking place in composite-exciton systems.     

The scattering of partially polarized light by oriented atoms

A compact expression is derived for the cross section of scattering of arbitrarily polarized light by oriented atomic systems, in which the dependence on the geometric parameters and on the Stokes parameters preassigning the state of partial polarization of incident radiation is explicitly separated. It is found that the cross section of any photoprocess accompanied by photon absorption (stimulated emission) contains the sum of the products of the circular and linear dichroisms of the process by the respective Stokes parameters. The effect of the atomic orientation and of the dissipation of light energy on the polarization singularities and angular distribution of scattered light is investigated. In particular, it is demonstrated that, in the case of an open dissipation channel, the angular distribution remains dependent on the atomic orientation even in the case of zero degree of circular polarization of scattered radiation.     

Sub-Doppler bandwidth atomic optical filter

We demonstrate what is to our knowledge the first atomic optical filter that uses velocity selection to achieve a passband width that is less than the Doppler width of the filtering transition. A narrow-linewidth pump laser is used to induce circular birefringence in a narrow velocity class of atoms in a dense potassium vapor for 694-nm light resonant with the 4P(3/2)-6S(1/2) transition. The filter displays a single 170-MHz passband at a peak transmittance of 9.5%. The bandwidth is an order of magnitude lower than that of previously demonstrated atomic optical filters.     

Unified description of angular distributions of target particles in light and heavy ion induced interactions in nuclear emulsions at high energies

Some investigations show that in light ion (LI) induced reactions, such as He, O, Ne, and Ar in nuclear emulsions (Em) at high energies, the angular distributions of the target particles show a wide structure around the polar angle ν≈ 60°. With heavy ions (HI) such as Kr and Au such a wide structure has not been observed. The experimental results on Mg--Em and Si--Em interactions also do not show such a wide structure in the angular distribution of the target particles. Using a multisource ideal gas model we uniformly describe the angular distributions of the target particles produced in LI--Em and HI--Em interactions. The result is not only in agreement with the mean trend, but also with the fluctuations of the experimental data. We conclude that the wide structure observed in LI--Em interactions may be the result of statistical fluctuations.     

Quasi-stationary states in a circular geometry

The quasi-stationary final states of decaying two-dimensional turbulence on a circular domain, with an initial flow field containing either no or a substantial amount of angular momentum, have been investigated numerically. The production of angular momentum is almost absent for these flows on a circular domain with a no-slip wall. Its presence or absence essentially determines the character of the quasi-stationary final state. Based on a minimum-enstrophy principle a diagram is constructed that provides insight into the development of the typical late-time flow patterns on a circular domain with a no-slip wall. The quasi-stationary final states found in the present numerical study can be understood based on the predictions from the minimum-enstrophy principle.     

Scattering of partially polarized light by aligned atoms

A compact expression for the cross section of scattering of an arbitrarily polarized light by aligned atomic systems is obtained, in which the dependence on the geometric parameters and the Stokes parameters specifying the state of partial polarization of the incident radiation is represented in explicit form. The effect of atomic alignment and the processes of dissipation of the light energy on the polarization specific features and the angular distribution of the scattered light is investigated. In particular, it is shown that, if a dissipative channel is accessible, the angular distribution and the degree of linear polarization of scattered light depend on the degree of circular polarization of the incident radiation η₂. Dissipative processes also induce the circular polarization of the light scattered by aligned atoms when η₂=0.     

A Rotating Quantum Vacuum

We investigate how a uniformly rotating frame is defined as the rest frame of an observer rotating with constant angular velocity around the z axis of an inertial frame. Assuming this frame to be a Lorentz one, we second quantize a free massless scalar field in the rotating frame and obtain that creation-annihilation operators of the field are not the same as those of an inertial frame. This leads to a new vacuum state—a rotating vacuum. After this, introducing an apparatus device coupled linearly with the field, we obtain that there is a strong correlation between the number of Trocheries-Takeno particles (in a given state) obtained via canonical quantization and the response function of the rotating detector. Finally, we analyze polarization effects in circular accelerators in the proper frame of the electron, making a connection with the inertial frame point of view.     

Light with a twist in its tail

Polarized light is a phenomenon familiar to anyone with a pair of polaroid sunglasses. Optical components that change the nature of the polarization from linear to circular are common in any undergraduate laboratory. Probably only physicists know that circularly polarized light carries with it an angular momentum that results from the spin of individual photons. Few physicists realize, however, that a light beam can also carry orbital angular momentum associated not with photon spin but with helical wavefronts. Beams of this type have been studied only over the last decade. In many instances orbital angular momentum behaves in a similar way to spin. But this is not always so: orbital angular momentum has its own distinctive properties and its own distinctive optical components. This article outlines the general behaviour of such beams; how they can be used to rotate microscopic particles; how they interact with nonlinear materials; the role they play in atom-light interactions and how the rotation of such beams results in a measurable frequency shift.     

Developable modes in vibrated thin plates

We investigate the normal modes of a developable cone singularity as observed in a circular sheet supported by a rigid circular frame and pushed at its center. When the center of the sheet is in addition submitted to a sinusoidal forcing, two types of bending modes, named here rolling and tilt modes, are parametrically excited. The rolling mode is an angular oscillation of the concave sector of the developable cone structure. If the amplitude of vibration is high enough, the rolling mode amplitude increases dramatically giving rise to both a continuous rotation of the concave sector and a material angular displacement of the sheet, similar to that produced by a moving wrinkle in a carpet.     

高功率隔离器单模与多模工作退偏特性

以传统结构隔离器为模型,应用琼斯理论,比较分析了单模与多模激光入射时高功率隔离器热致退偏特性。研究结果表明：高功率隔离器热致退偏可分为线性双折射致退偏与圆双折射致退偏;两种退偏均与入射激光功率的平方成正比;在光功率一定的条件下,线性双折射致退偏不随光斑半径的变化而变化,圆双折射致退偏随光斑半径的增大而减小;在其它条件相同的条件下,多模光场能够有效地降低隔离器热致退偏,多模时线性双折射致退偏仅为单模时退偏的60%,圆双折射致退偏也比单模时要小,减小幅度随光斑半径的增加而增加。     

高功率隔离器单模与多模工作退偏特性

以传统结构隔离器为模型,应用琼斯理论,比较分析了单模与多模激光入射时高功率隔离器热致退偏特性。研究结果表明:高功率隔离器热致退偏可分为线性双折射致退偏与圆双折射致退偏;两种退偏均与入射激光功率的平方成正比;在光功率一定的条件下,线性双折射致退偏不随光斑半径的变化而变化,圆双折射致退偏随光斑半径的增大而减小;在其它条件相同的条件下,多模光场能够有效地降低隔离器热致退偏,多模时线性双折射致退偏仅为单模时退偏的60%,圆双折射致退偏也比单模时要小,减小幅度随光斑半径的增加而增加。     

Effects of induced birefringence on Brillouin dynamic gratings in single-mode optical fibers

The effects of linear or circular birefringence on the operation of Brillouin dynamic grating are experimentally investigated where the birefringence is induced by bending or twisting a single-mode optical fiber, respectively. Experimental results show that the reflection spectrum of the dynamic grating in a 5 m fiber is split by bend-induced linear birefringence with the separation frequency dependent on the bending diameter, matching well with the theoretical model. Meanwhile, the spectrum is almost immune to circular birefringence induced by twist with a rate of up to 24 turns/m.