Communication with dynamically fluctuating states of light polarization

The fast, irregular, fluctuations of the state of polarization of light output from an erbium doper fiber ring laser are used to communicate digital information. The experiments illustrate the application of a dynamical encoding and information recovery scheme that is robust to perturbations of the communication channel, a standard single mode fiber. A fiber-optic polarization analyzer was used to measure and visualize the polarization dynamics at nanosecond time scales on the Poincaré sphere.     

Impact of spin-zero particle-photon interactions on light polarization in external magnetic fields

If the recent PVLAS results on polarization changes of a linearly polarized laser beam passing through a magnetic field are interpreted by an axion-like particle, it is almost certain that it is not a standard QCD axion. Considering this, we study the general effective interactions of photons with spin-zero particles without restricting the latter to be a pseudo-scalar or a scalar, i.e., a parity eigenstate. At the lowest order in effective field theory, there are two dimension-5 interactions, each of which has previously been treated separately for a pseudo-scalar or a scalar particle. By following the evolution in an external magnetic field of the system of spin-zero particles and photons, we compute the changes in light polarization and the transition probability for two experimental set-ups: one-way propagation and round-trip propagation. While the first may be relevant for astrophysical sources of spin-zero particles, the second applies to laboratory optical experiments like PVLAS. In the one-way propagation, interesting phenomena can occur for special configurations of polarization where, for instance, transition occurs but light polarization does not change. For the round-trip propagation, however, the standard results of polarization changes for a pseudoscalar or a scalar are only modified by a factor that depends on the relative strength of the two interactions.     

Influence of the spatial rotation of a polarization plane on the radiative friction force in light fields with polarization gradients

Simple atomic models (1/2→1/2 and 1/2→3/2 transitions) were taken as an example to consider, in the sub-Doppler cooling approximation, influence of the spatial rotation of a polarization plane on the radiative friction force at arbitrary field configurations of dimensionality D<1. Spatial gradients of the angles determining this rotation additionally contribute to the friction force. This contribution is comparable in magnitude with other forces if the detuning δ is on the order of the radiative relaxation constant γ. For the j→j+1 transitions, the contribution promotes sub-Doppler cooling at δ<0, whereas for the j→j transitions (half-integer j) it induces anisotropic heating and cooling processes.     

Impact of ultra-light particles on polarization of laser light in strong external fields

The recent results by the PVLAS group on possible changes of polarization of laser light in a transverse magnetic field are beyond the QED expectations by many orders of magnitude. If confirmed, they may indicate new physics associated with ultra-light particles. I describe here how the polarization of light is modified in an external magnetic field by interactions with a spin-zero particle of no definite parity. While the PVLAS-type experiments cannot tell such a particle from one with definite parity, the parity property could be studied in photon regeneration experiments if the polarization of the regenerated photons could be measured. This talk was based on my recent work.     

Impact of ultra-light particles on polarization of laser light in strong external fields

The recent results by the PVLAS group on possible changes of polarization of laser light in a transverse magnetic field are beyond the QED expectations by many orders of magnitude. If confirmed, they may indicate new physics associated with ultra-light particles. I describe here how the polarization of light is modified in an external magnetic field by interactions with a spin-zero particle of no definite parity. While the PVLAS-type experiments cannot tell such a particle from one with definite parity, the parity property could be studied in photon regeneration experiments if the polarization of the regenerated photons could be measured. This talk was based on my recent work.     

Coherence, polarization, and entanglement for classical light fields

We examine a classical version of entanglement between spatial and polarization degrees of freedom for classical light. We examine the relation between classical entanglement, polarization, and several recently introduced measures of coherence for vectorial waves. We show that there is no definite relation between quantum and classical entanglement.     

Polarization distributions and degree of polarization for quantum Gaussian light fields

We examine polarization properties of electromagnetic field states with Gaussian complex-amplitude distributions, such as quadrature coherent and squeezed states, thermal chaotic states, and two-mode squeezed vacuum states. We compute their polarization distribution and we apply to them diverse measures of degree of polarization and polarization fluctuations. This allows us to investigate the main properties of the degrees of polarization introduced so far.     

Intensity fluctuations and degree of polarization in three-dimensional thermal light fields

The normalized intensity fluctuations of arbitrary electromagnetic wave fields obeying Gaussian statistics are expressed in terms of the three-dimensional degree of polarization. This general formulation implies an important physical result concerning the polarization of planar fields and the dimensionality of the formalism. The results are expected to be particularly useful in intensity interferometry.     

Evidence for particle-shape sensitivity in the correlation between polarization states of light scattering

The cross correlation between polarization states of scattered laser speckle as a function of scattering angle is observed for a range of spherical and nonspherical particle suspensions. A variation in the degree of correlation between polarization states is observed, and this information is indicative of the particle shape. A comparison with a theoretical model for small particles is made, suggesting that variations in polarization correlation with angle originate from the nonisotropic polarizability of nonspheres. Experiments are also performed on large spheroids and random-shaped polydispersions, and the results indicate that the measurement method has significant potential for nonsphere detection and characterization.     

Rotational frequency shifts for electromagnetic fields of arbitrary states of coherence and polarization

The rotational frequency shift is studied for fields of arbitrary states of coherence and polarization. It is shown that the power spectrum of the field in the rotating frame is influenced both by the degree of polarization and the degree of coherence. Examples for some model field classes are given.     

Near-field characteristics of highly non-paraxial subwavelength optical fields with hybrid states of polarization

The vectorial structure of an optical field with hybrid states of polarization(So P) in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial So P of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions.     

Biphotons,squeezing, and new states of light in polarization quantum optics

The concept of squeezing is discussed for multimode quantum light beams with consideration of polarization using the polarization gaugeSU (2) invariance of free electromagnetic fields. We separate the polarization and biphoton degrees of freedom from other ones, and consider uncertainty relations characterizing polarization and biphoton observables. As a consequence, we obtain a new classification of polarization states of light within quantum optics. We also discuss briefly some interrelations of our analysis with experiments related to some fundamental problems of physics.     

光的偏振对热光关联成像的影响

根据完全偏振光的不同偏振态和部分偏振光的不同偏振度对二阶关联函数的影响,利用统计光学理论研究了光的不同偏振性质对关联成像的可见度和信噪比的影响.研究表明,光的偏振对热光关联成像的影响体现在部分偏振光的不同偏振度上,关联成像的可见度是偏振度的二次函数,由二阶关联函数方法得到的信噪比随着偏振度增大而提高,而利用减去背景项的二阶关联函数以及二阶相干度方法得到的信噪比均与偏振度无关. 关键词： 关联成像 偏振 可见度 信噪比     

Three-dimensional polarization control in microscopy

We propose an approach to optical microscopy that enables full control over the three-dimensional polarization vector at the focal spot of a high-numerical-aperture lens. The input field to the lens is linearly polarized and no polarization optics are needed. This technique utilizes the azimuthal spatial degree of freedom of the input field. We find that only a small set of low-order azimuthal spatial harmonics contributes to the focused field on axis, and a simple transformation exists between the linear vector space of these harmonics and the three-dimensional polarization-vector space. Controlling the relative complex weights of these azimuthal harmonics produces any desired three-dimensional state of polarization.     

On the polarization of non-paraxial transverse fields

On the basis of a plane-wave spectrum representation, the polarization features of a transverse quasimonochromatic non-paraxial field have been studied. A relationship has been established between the polarization characteristics in the near field and the coherence and symmetry properties of the beam in the far field.     

Random error of determining light scattering matrix elements at various polarization states of probing radiation

Using the method of mathematical modeling, we consider the transformation of a random error of light intensity measurement into an error of determining elements of the light scattering matrix. We consider a device in which the polarization properties of probing radiation change depending on the setting of the phase plate and polarization analysis of scattered radiation is performed while the second phase plate located ahead of a stationary analyzer is rotated. A set of settings of the first phase plate has been revealed, which provides a minimum random error in determining the scattered light matrix elements. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 520–523, July–August, 2000.     

Band-gap modulations of armchair silicene nanoribbons by transverse electric fields

Under external transverse electronic fields, the structure and electronic properties of the silicene nanoribbon with armchair edge (ASiNR) are studied. We find that the electric properties are modified by a transverse electric field. As affected by a transverse electric field, the band gap varies with increasing absolute value of the field strength. All the results can be explained using the Stark quadratic effect.     

Three-fermion bound states on the light front

We investigate the stability of the relativistic three-fermion system with a zero-range force in the light front form. In particular, introducing an invariant cut-off, we study the dependence of the bound state on the coupling strength also for cases where the two-fermion system is unbound. The relativistic Thomas collapse is discussed by solving the fully coupled integral equation system. Furthermore, we explicitly investigate the ground state mass of the three-fermion system and compare to previous simplified calculations.     

Manifestation of the polarization incoherence of light in polarization self-action effects

On the basis of the beam tensor formalism proposed by F. I. Fedorov, the theory of polarization selfaction of radiation in isotropic resonant media is extended to the case of partial elliptic polarization of an electromagnetic wave. The influence of the degree of radiation polarization on the known polarization self-action effects is demonstrated and the self-polarization (depolarization) of light is predicted.     

在与原子相互作用中光偏振态的量子描述及其演化

应用偏振光的量子理论和斯托克斯算符研究了无克尔媒质和存在克尔媒质情况下，光在与原子相互作用过程中偏振态的演化.研究了偏振光中斯托克斯参量的涨落及其压缩的非经典行为.偏振椭圆、量子光学中的偏振度和斯托克斯参量的信噪比也得到了讨论.结果表明斯托克斯参量及其涨落在时间演化中呈现出被调制的振荡，这些振荡表现出间歇地崩塌和恢复.在与原子的相互作用过程中，光的偏振椭圆不随时间变化，但偏振度却随时间出现振荡.克尔媒质对这些振荡演化有很大影响. 关键词： 斯托克斯算符 斯托克斯参量 量子偏振态 量子涨落