Photomagnetization of polydomain magnetic insulators by circularly polarized light

A new effect of magnetization of magnetic insulators due to light absorption by magnetic ions is proposed. The estimates for an yttrium ion garnet crystal are made.     

Bloch oscillations for circularly polarized light

All previous investigations on the Bloch oscillations of waves focus on scalar waves. Here we demonstrate, for the first time, the existence of Bloch oscillations of vector fields for circularly polarized light (CPL) propagating through a designed liquid crystal structure. To obtain the Wannier-Stark ladder of the CPL, we have designed a cholesteric liquid crystal structure with spatially varying pitch. The Bloch oscillations of the CPL have been observed in such a structure by exact numerical simulations. We have also shown that such a phenomenon can be easily detected in time-resolved reflection experiments.     

光强连续可调的圆偏振光衰减器

利用1/4波片及偏光棱镜,设计了光强连续可调的圆偏振光衰减器,通过该器件可获得偏振度高且光强连续可调的圆偏振光.该衰减器解决了632.8 nm多膜氦氖激光器出射光为非完全自然光且偏振面随时间做随机变化导致实验误差的问题,为偏光信息测试系统提供了相对稳定的激光光源.     

High-density all-optical magnetic recording using a high-NA lens illuminated by circularly polarized pulse lights

We propose a method for high-density all-optical magnetic recording. Our analyses, based on the vector diffraction theory, show that owing to the inverse Faraday effect, circularly polarized laser pulses focused by a high numerical aperture (NA) lens can induce a small magnetization domain. For an example, the FWHM of the effective magnetization domain is 0.4646λ when NA=0.85. The magnetization direction is basically perpendicular to the surface of the optic-magneto film within the effective magnetization domain and the switching direction of magnetization can be controlled by the helicity of the incident circularly polarized light. These characteristics are useful to next-generation high-density all-optical magnetic storage.     

Propagation of circularly polarized light in media with large-scale inhomogeneities

Small-angle multiple scattering of circularly polarized waves in disordered systems composed of large (larger than the light wavelength) spherical particles is discussed. The equation for Stokes’s fourth parameter V — the difference between the intensities of the left-and right-hand polarized light — is shown to have the form similar to that of the scalar transport equation for intensity I, the only difference being the presence of an additional “non-small-angle” term responsible for depolarization. In the case of small-angle scattering, depolarizing collisions are relatively rare and, in contrast to the scalar case, the problem contains an additional spatial scale, namely the depolarization depth. The polarization degree and helicity of the scattered light are calculated for the case of purely elastic scattering and in the presence of absorption in the medium. For strong absorption, depolarization is shown to follow the transition to the asymptotic regime of wave propagation. The features appearing in strong (non-Born) single scattering are also discussed. Zh. éksp. Teor. Fiz. 115, 769–790 (March 1999)     

Vibrationally resolved K-shell photoionization of CO with circularly polarized light

Diffraction of a low energy (<4 eV) carbon-K-photoelectron wave that is created inside a CO molecule by absorption of a circularly polarized photon is investigated. The measurements resolve the vibrational states of the K-shell ionized CO+ molecule and display the photoelectron diffraction patterns in the molecular frame. These show significant variation for the different vibrational states. This effect is stronger than predicted by state-of-the-art theory. As this study is performed close to C-K-threshold and, therefore, far below the molecule's sigma-shape resonance, this surprisingly strong effect is not related to that resonance phenomenon.     

Heating of magnetic fluid systems driven by circularly polarized magnetic field

A theory is presented to calculate the heat dissipation of a magnetic suspension, a ferrofluid, driven by circularly polarized magnetic field. Theory is tested by in vitro experiments and it is shown that, regardless of the character of the relaxation process, linearly and circularly polarized magnetic field excitations, having the same root-mean-square magnitude, are equivalent in terms of heating efficiency.     

Spin- and angle-resolved photoelectron spectroscopy from solid surfaces with circularly polarized light

Spin-polarized photoemission with circularly polarized light represents a relatively new technique in surface science. It became feasible with the increased availability of circularly polarized light in the vacuum ultraviolet and soft X-ray regime, generated in dedicated synchrotron radiation facilities. Another important ingredient was the development of efficient electron spin polarization detectors. Supported by group theoretical considerations, this technique was first employed to study the process of optical spin orientation in single crystalline non-magnetic materials. In these samples, spin-dependent effects arise solely from spin-orbit coupling. The experiments revealed the strong influence of spin-orbit coupling on the details of the electronic band structure, such as the symmetry character of the electronic wave functions, hybridization phenomena, and the behavior of degeneracies. The results opened the way to a detailed understanding of the electronic structure and permit a rigorous test of both state-of-the-art bulk band theories and fully relativistic photoemission calculations. Since 1990, spin-polarized photoemission with circularly polarized light is also used to investigate ferromagnetic systems. These experiments led to the discovery of the counterpart of optical spin orientation in ferromagnets, namely, the magnetic dichroisms. Magnetic dichroism means that the spin-dependent photoexcitation from a ferromagnetically ordered system manifests itself already in the photoelectron intensity distributions. Because of this particular property, techniques based on magnetic dichroisms are currently receiving wide interest in the spectroscopic investigation of magnetic systems and phenomena.

The following article reviews the current status of the field of spin- and angle-resolved photoemission from solids using circularly polarized radiation. We survey the development of this technique over the last 10 years, covering its applications to both non-magnetic and ferromagnetic systems.     

Diffusion of circularly polarized light in a disordered medium with large-scale inhomogeneities

It is shown that in the presence of diffusion of electromagnetic waves in random media containing large discrete scatterers, circular polarization can persist even after the radiation flux is isotropized. For scattering exactly in the backward direction, this effect is manifested as an increase in the interference contribution to the cross-polarized component of the intensity as the size of the scatterers increases. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 21–26 (10 July 1998)     

Coherent trapping of a three-level atom in a circularly polarized light

Using semiclassical theory, we study coherent trapping of a three-level atom, where the atom possesses a momentum of its center-of-mass motion and is irradiated only by a classical circularly polarized electromagnetic wave. We find that if the atom is initially in a coherent trapping state of it, under the zero- or first-order approximation, the atom is absolutely or nearly in the state hereafter.     

Spin polarization of photoelectrons from solid cesium by circularly polarized light

The spin polarization of photoelectrons excited in cesium metal by circularly polarized light is discussed using group theoretical methods. Calculations of the spin polarization have been performed for direct transitions at the-point and between, and states. The results suggest that photoelectrons excited in monocrystalline Cs could have a high degree of spin polarization which depends both on the wave vector of the electrons and on the energy of the absorbed photon. Measurement of this polarization should allow the spin-orbit splitting of different energy bands to be determined.     

Backscattering of linearly and circularly polarized light in randomly inhomogeneous media

The scattering of linearly or circularly polarized light from a semibounded randomly inhomogeneous medium is considered. A new technique for simulating the electromagnetic radiation transport using the Monte Carlo method is proposed, which makes it possible to avoid cumbersome calculation of Muller matrices. Expressions are obtained for the co- and cross-polarized components of backscattered light for incident light of arbitrary polarization. The coherent and incoherent backscattering components are calculated for arbitrary combinations of incident and scattered light polarizations. It is shown that the main contribution to coherent backscattering is from the co- and cross-polarized components for linearly and circularly polarized light, respectively. The backscattering from an optically active random medium is calculated.     

磁光光纤Bragg光栅中圆偏振光的非线性传输特性

提出了磁光光纤Bragg光栅的理论模型,给出了圆偏振光在磁光光纤光栅中传播的非线性耦合模方程. 研究表明,在磁光光纤Bragg光栅中,光栅引起正反传播方向的导波光发生耦合,法拉第效应引起磁圆双折射效应,而非线性效应则将左旋和右旋圆偏振光耦合在一起,它们的共同作用可使双稳态状态发生反转、非线性光控光开关阈值功率降低. 与传统光纤光栅相比,利用左旋和右旋磁圆偏振光之间的交叉相位调制实现的脉冲整形具有磁光偏置可调特性,为基于磁光光纤光栅的动态灵活全光3R再生器的研制提供了理论基础. 关键词： 磁光光纤Bragg光栅 圆偏振光 脉冲整形     

Monoenergetic ion beam generation by driving ion solitary waves with circularly polarized laser light

Experimental data from the Trident Laser facility is presented showing quasimonoenergetic carbon ions from nm-scaled foil targets with an energy spread of as low as ±15% at 35?MeV. These results and high-resolution kinetic simulations show laser acceleration of quasimonoenergetic ion beams by the generation of ion solitons with circularly polarized laser pulses (500?fs, λ=1054 nm). The conversion efficiency into monoenergetic ions is increased by an order of magnitude compared with previous experimental results, representing an important step towards applications such as ion fast ignition.     

Optics of circularly polarized light waves in one-dimensional magneto-photonic crystals: Theory

A theory is presented for propagation of electromagnetic waves through one-dimensional magnetic Bragg structures (magneto-photonic crystals). Within the self-consistent Green-function technique the transfer matrices and magneto-optical characteristics are derived in terms of circularly polarized waves propagating in periodical arrays of alternating magnetic and dielectric layers. For finite-thickness magneto-photonic crystals, the Faraday rotation and other magneto-optical responses are demonstrated to change considerably in the spectral range of stop-bands, the magnetic modulation of the in-plane reflection intensity being essentially enhanced.     

Three-photon ionization of the potassium atom by linearly and circularly polarized light

The measurement and calculation results of the dependence of the three-photon ionization process of potassium atoms by linearly and circularly polarized light within the frequencies from 16300 to 16600 cm^-1 are presented. The experimental data do not confirm the predictions of perturbation theory on the existence of a window of nonlinear transparency for circularly polarized light.     

Time-resolved backscattering of circularly and linearly polarized light in a turbid medium

Time-resolved backscattering profiles of circularly and linearly polarized light were measured from a turbid medium composed of small and large polystyrene sphere particles in water. It is shown that, based on the measurements of the time-resolved backscattered copolarized and cross-polarized components of the incident polarized light, either linearly or circularly polarized light can be used to effectively image an object that is deep inside a turbid medium composed of small particles, depending on the depolarization properties of the object itself. For large particles such as in tissue, fog, and clouds, the experimentally observed polarization memory effect on the backscattering temporal profiles suggests that a significant improvement in the image contrast can be achieved by use of circularly polarized light.     

Dynamic Hall effect driven by circularly polarized light in a graphene layer

We report the observation of the circular ac Hall effect where the current is solely driven by the crossed ac electric and magnetic fields of circularly polarized radiation. Illuminating an unbiased monolayer sheet of graphene with circularly polarized terahertz radiation at room temperature generates--under oblique incidence--an electric current perpendicular to the plane of incidence, whose sign is reversed by switching the radiation helicity. Alike the classical dc Hall effect, the voltage is caused by crossed E and B fields which are, however rotating with the light's frequency.