Optical dispersive bistability in media with forced girotropy

In this paper the results of an analysis concerning the course of optical dispersive bistability in media with forced girotropy (the Faraday effect) are presented. It is shown that radiation transmitted through a non-linear Fabry-Perot cavity reveals, apart from bistability of the intensity, bistable states of polarization. The elliptically polarized transmission radiation changes bistably not only the value of proportion of the semiaxes of the polarization ellipse and the orientation angle of its major semi-axis, but also the direction of the rotation of its electric vector.     

Ultrafast time-resolved quantum beats in the polarization state of coherent emission from quantum wells

Dual-channel spectral interferometry is used to measure the ellipticity, the orientation of the polarization ellipse, and the sense of rotation of the four-wave-mixing signal from a GaAs-AlGaAs multiple quantum well. Each parameter is observed to oscillate dramatically at the heavy-hole-light-hole quantum beat frequency. During each beat period (in the strong quantum beat regime), the ellipticity oscillates twice between linear and almost-circular polarization, the orientation of the polarization ellipse rotates through a complete 180 degrees , and the sense of rotation changes from left- to right-circular polarization.     

Changes in the state of polarization of apertured stochastic electromagnetic modified Bessel–Gauss beams in free-space propagation

By using the generalized Huygens–Fresnel diffraction integral, the analytical expressions for the cross-spectral density matrix, spectral degree of polarization, orientation angle and degree of ellipticity of polarization ellipse of apertured stochastic electromagnetic modified Bessel–Gauss beams (MBGBs) through a paraxial optical ABCD system are derived, and used to study the changes in the state of polarization of apertured stochastic electromagnetic MBGBs propagating in free space. The invariance of the on-axis state of polarization of unapertured stochastic electromagnetic MBGBs propagating through paraxial optical ABCD systems is illustrated analytically and numerically. For apertured stochastic electromagnetic MBGBs, the on-axis spectral degree of polarization, orientation angle and degree of ellipticity of polarization ellipse increase with increasing propagation distance, and approach asymptotic values when the propagation distance is large enough. There is a uniform distribution region of the state of polarization around the center of the beams whose range decreases with increasing truncation parameter. In addition, the state of polarization of apertured stochastic electromagnetic MBGBs upon propagation can be modulated by controlling the truncation parameter.     

Polychromatic polarization singularities

Elliptical polarization can appear in only monochromatic optical fields. In polychromatic vector fields the polarization is a Lissajous figure, but in only commensurate fields do the figures have well-defined shapes; in other fields the shapes are undefined. Nonetheless, I show that a given paraxial polychromatic vector field has a coherency ellipse field associated with it that contains polarization singularities and stationary points that are surrogates for the corresponding critical points of the parent optical field.     

Specific features of the self-action of elliptically polarized light pulses and the formation of vector solitons in an isotropic medium with the anomalous frequency dispersion and the spatial dispersion of cubic nonlinearity

Numerical methods are used to study the effect of local and nonlocal nonlinear optical susceptibilities on the parameters of a soliton whose degree of ellipticity depends on time and that is formed at a distance of several dispersion lengths in a medium with the anomalous frequency dispersion. The rotation angle of the major axis of the polarization ellipse does not depend on time and linearly increases with an increasing propagation coordinate. If the tensor components of the local nonlinear susceptibility have opposite signs, the incident elliptically polarized pulse can propagate in the regime that involves the pulse splitting into components for which the absolute values of the electric-field degrees of ellipticity are close to unity. In this case, the electric-field vector at the center of the pulse rotates in the opposite direction with respect to the rotation at the edges.     

Strong polarization in the optical transmission through elliptical nanohole arrays

Strong polarization dependence is observed in the optical transmission through nanohole arrays in metals. It is shown that the degree of polarization is determined by the ellipticity and orientation of the holes; the polarization axis lies perpendicular to the broad edge of the ellipse. Furthermore, the depolarization ratio shows a squared dependence on the aspect ratio of the holes, which is discussed in terms of coupling into and out of the surface plasmon modes. The observed results will be useful for tailoring the polarization behavior of metallic nanophotonic elements in many applications, including surface plasmon enhanced optical sensing and ultrafast optical switching.     

Polarization singularity democracy: WYSIWYG

The canonical point singularity of elliptically polarized light is a C point, an isolated point of circular polarization surrounded by a field of polarization ellipses. The defining singular property of a C point is that the surrounding ellipses rotate about the point. It is shown that this rotation is seen only for a particular line of sight (LOS) and, conversely, that there exists a unique LOS for every ellipse along which the ellipse is seen as a singularity. It is also shown that changes in LOS can turn singularities into stationary points and vice versa. The democratic behavior of polarization singularities and stationary points is a consequence of the fundamental "what you see is what you get" property of ellipse fields. Simple experiments are proposed for observing this unusual property of elliptically polarized light.     

On the change in electromagnetic wave polarization in a smooth one-dimensionally inhomogeneous medium

Propagation of an electromagnetic wave in a smooth one-dimensionally inhomogeneous isotropic medium is considered in the second approximation of geometrical optics. The polarization evolution is studied extensively. It is known that in the first (Rytov) approximation of geometrical optics, there is only the rotation of the plane of polarization (with no change in the polarization shape and sign) for rays with torsion. In the case considered, both the shape of polarization ellipse and the sign of polarization change proportionally to the integral of the squared ray curvature even for plane rays. The effect is of nonlocal geometrical nature and can be described in terms of the generalized geometrical phase incursion between two linear polarizations.     

Observation of elliptical polarization rotation in a long twisted fiber

The intensity-dependent polarization rotation caused by the self-induced nonlinear birefringence in a long twisted fiber is studied numerically and experimentally. By using a 1 km length of twisted fiber, we show that the effect of ellipse rotation accumulates monotonically as if the fiber were perfectly isotropic. Such behavior cannot be observed in a typical nontwisted fiber with randomly varying birefringence and is a unique feature of the twisted fiber, in which the large circular birefringence plays an essential role of preserving the handedness of elliptical polarization. We demonstrate a novel Faraday-mirror configuration to ensure automatic polarization alignment, which is directly applicable to achieving a simple and stable intensity discriminator.     

Rotation of the polarization ellipse under multiple light scattering in disordered media

A study is performed of the multiple small-angle scattering of circularly polarized waves in random media with large-size transparent inhomogeneities that are less dense than the surrounding medium. In these conditions, a new effect is observed—rotation of the polarization ellipse of the multiply scattered light.     

Optical triangulation for dynamic gauging of cylindrical parts

The optical triangulation technique was applied to gauge cylindrical parts undergoing rotation. From the fabrication point of view, it may be assumed that the actual shape of cylindrical parts could be an ellipse. This deviation of shape from the desired circular cross-section and the departure of the actual rotation axis from the geometric axis of parts were dynamically monitored.     

Nonlinear ellipse rotation of high energy femtosecond optical pulses for pulse contrast enhancement

An argon filled hollow fiber with metal coating on the inner glass surface has been used for nonlinear ellipse rotation of femtosecond optical pulses at 800 nm. Pulse contrast can be achieved using this waveguide with higher transmission compared with a fused silica waveguide.     

Photonic density and nonreciprocal optical properties in chiral liquid crystals

Nonreciprocal optical properties of anisotropic (nano-film) heterostructures made of a cholesteric and nematic liquid crystal (CLC-NLC) layers are studied. Namely, a NLC-CLC (and CLC-NLC) structures are considered in which the NLC layer is a quarter-wave plate. The problem is exactly solvable by Ambartsumians’ modified layer addition and Mullers’ transfer-matrix methods. The peculiarities of the polarization dependent properties, such as the photonic density of states, reflection spectra, the polarization plane rotation and ellipticity spectra are investigated. It is shown that such a system canwork as a light modulator, an element for obtaining linearly polarized light with an electrically tunable polarization plane rotation, or a transformer of non-polarized source into linearly polarized light. The analysis of the optical properties in investigated structures can be used for design of perspective optical diodes, microlasers and multifunctional elements on chiral liquid crystals with electrically tunable polarization plane rotation and field controlled light polarization.     

Measurement of optical rotation and phase retardance of optical samples with depolarization effects using linearly and circularly polarized probe lights

This paper presents an experimental technique for measuring the optical rotation, depolarization, and phase retardance of optical samples. In the proposed approach, the optical properties of the sample are derived using a Stokes–Mueller matrix formalism in conjunction with linearly and circularly polarized probe lights. For a compound sample comprising a half-wave plate positioned in front of glucose solutions with concentrations ranging from 0 to 1.2 g/dl, the average normalized error in the measured rotation angle is determined to be 3.11% when using a linearly polarized light. The average surviving linear and circular polarization fractions of the glucose solutions are determined to be 1.0252 and 0.9945. The average normalized error in the measured retardance of the half-wave plate is 3.45%. When measuring a compound sample comprising a half-wave plate positioned in front of the scattered glucose solutions with turbidities from 0% to 50% by the addition of milk, experimental results show that the induced rotation angle increased as the turbidity increased, whereas both surviving linear and circular polarization fractions decreased as the turbidity increased. The effect of the turbidity on rotation angle is more significant than that on both surviving linear and circular polarization fractions. The average normalized error in the measured retardance of the half-wave plate is 1.43%. Consequently, a simplified geometry of the polarimeter is proposed to independently estimate the rotation angle, surviving linear and circular polarization fractions, and retardance from the derived viable algorithm.     

电流变液的旋光与椭偏光行为

本文研究了电流变液(ER流体)的旋光行为及椭偏光行为.激光束垂直于电场方向,利用HeNe激光器对SiO₂、Si₃N₄和硅油组成的ER流体进行测量.发现电流变液样品存在旋光现象,且对于同一种浓度的ER流体,随着电场强度的增大,旋光角度增大.在同一电场强度下,旋光角度随着浓度的增大而增大.当浓度大于某一值c₀时,旋光角度开始减小,在不同电场强度下,透过电流变液的椭圆偏振光性质不发生改变,且随着电场强度的增大,透射光强度随之增大.电流变液的旋光行为及椭偏光行为起因于在电场作用下ER流体由各向同性的液体转变为各向异性的液体.     

Nonlinear Kerr effect in magnetic crystals

The reflection of an intense light wave from the boundary of a semiinfinite magnetic crystal is investigated theoretically. Expressions are obtained for the rotation angle of the polarization ellipse and the degree of ellipticity of the reflected wave as a function of the polarization of the incident radiation. The physical wave-interaction mechanisms that give rise to this effect are established. Fiz. Tverd. Tela (St. Petersburg) 41, 656–659 (April 1999)     

Separability of amplitude,phase and polarization information in the Jones calculus

The two-component Jones vector is cast in a form that achieves the separation of the information on the polarization ellipse from that on the amplitude and phase of the light wave. The shape, sense of rotation and orientation of the elliptic vibration of the electric field are described by the complex polarization variable χ while the amplitude a (size) and temporal phase ? of that vibration are described by the complex amplitude A = aexp(i?). The transformation of the complex amplitude of the wave A after passing through an optical system leads to a complex-amplitude transfer function (CATF) which is a nonanalytic function of the complex polarization variable χ. The CATF is, in turn, separable into polarization-dependent (real) amplitude and phase transfer functions (ATF and PHTF). Together with the polarization transfer function PTF (the transformation of χ), the ATF and PHTF provide a useful set of tools that complement the well-known Jones calculus.     

道威棱镜的偏振特性及偏振补偿研究

为了避免机载光电吊舱中共口径光学系统内部由于道威棱镜旋转引起的激光照射脉冲偏振态的变化,利用琼斯矩阵对道威棱镜的偏振特性与四分之一波片、半波片补偿道威棱镜旋转引起的激光脉冲偏振态变化进行了理论分析和实验验证。结果表明:线偏振的激光脉冲通过旋转一定角度的道威棱镜时,激光脉冲偏振态变为椭圆偏振,偏振态发生变化;而激光脉冲首先通过旋转一定角度的四分之一波片与半波片时,可使通过道威棱镜系统的激光脉冲偏振态保持不变,且两波片旋转角度与道威棱镜旋转角度之间存在一种非线性关系。采用偏振补偿方法可有效避免机载共口径光学系统中道威棱镜引起的激光脉冲偏振态变化,提高激光脉冲能量利用率,降低激光脉冲后向散射抑制难度。     

Polarization effect produced by the magnetooptical phenomena

The possibility of simultaneous measurement of the Faraday rotation and magnetic induced circular dichroism is discussed. The linearly polarized radiation under the action of the two mentioned phenomena is transformed into elliptically polarized one. The relation between parameters of the polarization ellipse and the parameters of the two studied phenomena is found.