Optical orientation by linearly polarized light in intersubband quantum-well transitions

The absorption of linearly polarized light in low-dimensional semiconductor structures is investigated. It is shown that the absorption under consideration can give rise to spin orientation of free carriers. A theory of this optical orientation by linearly polarized light is developed for resonant intersubband optical transitions in n-type quantum wells. It is demonstrated that, in the vicinity of the resonance, the optical orientation undergoes spectral inversion, namely, the electron spin orientation reverses sign with increasing frequency. This behavior can be accounted for by the spin-orbit subband splitting, which is linear in the wave vector, and by the energy and quasi-momentum conservation laws.     

光控二维光子晶体光开关

提出了一种调节液晶光子晶体光子带隙的方法。二维三角介质柱形光子晶体位于2块熔凝石英片之间,在介质柱之间填充各向同性排列的液晶,受偏振紫外光照射后,光诱导液晶分子定向排列,通过光诱导液晶分子取向改变液晶的折射率。数值模拟结果表明：通过外界光场控制所填充的向列相液晶分子的方向可以对这种二维三角形介质柱光子晶体的禁带结构进行调节。该可调光子晶体可控制波导中TM模和TE模的选择性传输,因而可应用于制作全光光开关。     

Variable optical attenuators with ability to independently control two orthogonal linearly polarized light amplitudes

New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator(MZM) to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude.Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthogonal linearly polarized light amplitudes.Experimental results demonstrate that more than 30 dB difference in slow-and fast-axis light power can be obtained by controlling an MZM input DC voltage, and over 24 dB independent power adjustment for light traveling on the slow and fast axes into a dual-polarization MZM.     

Pure spin current from one-photon absorption of linearly polarized light in noncentrosymmetric semiconductors

We show that one-photon absorption of linearly polarized light should produce pure spin currents in noncentrosymmetric semiconductors, including even bulk GaAs. We present 14x14 k.p model calculations of the effect in GaAs, including strain, and pseudopotential calculations of the effect in wurtzite CdSe.     

Passive magnetic shielded spin polarized electron source with optical electron polarimeter

A new GaAs(100) spin polarized electron source with an optical polarimeter, which is employed in the field of polarized electron and gas atom collision, is presented in detail. The apparatus is passive-magnetic-shielded by a box and a cylinder made of nickel--iron--molybdenum soft magnetic alloy without Helmholtz coil arrangement. And a uniformly distributed residual magnetic field of less than 5×10^-7,T is obtained near the collision area. The spin polarized electron beam is transmitted and focused onto collision point from photocathode by a set of electron optics with more than 25% transmission 95cm distance through an 1mm diameter aperture. Construction and operation of the apparatus, such as vacuum and magnetic shielding system, photocathode, laser optics, electron optics and polarimeter are discussed. The polarization of the spin polarized electron beam is determined to be 30.8\pm3.5% measured with a He optical polarimeter.     

Velocimetry microsensors driven by linearly polarized optical tweezers

We report on a new type of single-point velocimetry microsensor that can be positioned in microfluidic devices by use of optical tweezers. The flag-shaped microsensor is readily made by a low-cost two-photon polymerization technique. At rest the linearly polarized optical tweezer traps the microsensor at the focal point, and the flag-plate gets aligned in the polarization direction. Under a fluid flow, the plate rotates to an equilibrium angle that is used to measure the fluid velocity with a micrometer-size spatial resolution. Experimental results are in good agreement with theoretical calculations of optical and hydrodynamic torques on such a flag-shaped microsensor.     

Depolarization of linearly polarized light by a polycrystalline specimen

One of the methods in use for measuring the kinetics of isothermal crystallization of polymers is the recording of the depolarization of plane-polarized light by a microscope specimen. A relation between this depolarization and the volume fraction crystallized has been derived taking into account the polycrystalline nature of the specimen and assuming uniaxially birefringent crystallites. Uniform, all-directional increase in size of the crystallites would cause the depolarization to follow an Avrami-type equation with the Avrami exponent one unit “too high.” For spherulitic growth the correct Avrami exponent is found on the assumption that the birefringent entities in the spherulites do not increase in size but only in number. The depolarization by a polycrystalline specimen of uniform particle size is proportional to both specimen thickness and particle size. The derived relations are tested by random number calculation and their limits of reliability are indicated accordingly.     

Optimization of focusing of linearly polarized light

We show that, by adding a π-phase shift to one-half of a linearly polarized beam, the roles of the transversal and longitudinal field components of the focused beam are interchanged, resulting in better focusing of the longitudinal component in the direction perpendicular to the phase jump line. For this component the scheme produces a spot with FWHM >15% smaller than a spot generated with either linearly or radially polarized light for any NA. The scheme has a similar advantage when applied to circularly polarized light, and it holds for both a plane wave and a realistic case of a Gaussian incident beam. This technique may find applications when using recording media responsive to the longitudinal field only, particularly in read/write for optical storage where the resolution in one transverse dimension is most important.     

An approach to remove the background light based on linearly polarized light in the inter-satellite optical communications

In the inter-satellite optical communications, background light is an important factor that worsens the acquisition performance and tracking precision of the system. In general, optical filters are applied in eliminating background light. But the bandwidth of the optical filter is a bottleneck for improving the performance of the optical system further. We propose a new method for decreasing background light, in which linearly polarized light is employed as the beacon light. The theoretical model of acquisition probability is derived. Contrastive analysis is performed, among the system with the pure optical filter, the system using the linearly polarized light and the system with the circularly polarized light. Numerical simulations and experimental verification lead to the conclusion that acquisition probability of the system with linearly polarized light is greater than that of the other systems, and this approach is effective. This work can benefit the design of inter-satellite optical communication system.     

Separation of spin angular momentum in space-variant linearly polarized beam

We show that the spin angular momentum (SAM) flux in a space-variant linearly polarized beam can be separated in the focal plane. Such a beam carries only orbital angular momentum (OAM) and develops a net SAM flux upon focusing. The radial splitting of the SAM flux density is mediated by the phase vortex (or OAM) and can be controlled by the topological charge of the phase vortex. Optical trapping experiments verify the separation of the SAM flux density. The proposed approach enriches the manipulation of the angular momentum of light fields and inspires more designs of focus engineering, which would benefit optical micromanipulation of microscopic particles.     

非相对论线偏振激光下的J×B加热

利用解析的方法研究了非相对论线偏振激光与等离子体相互作用中的J×B加热吸收机理,建立了一种包含两类有质动力效应在内的自洽理论.探讨了密度轮廓修正下的J×B加热机理,给出了相应的吸收系数随激光场强度变化的关系曲线.研究发现,当激光场强度A0=20时,J×B加热所导致的吸收系数fabs约为2.8%.     

Coherent effects in multiple scattering of linearly polarized light

Comparing the stochastic Monte Carlo technique with the iteration procedure for solving the Bethe-Salpeter equation in the framework of numerical simulation, the time correlation function and the interference component of the coherent backscattering of a linearly polarized light wave in a multiply scattering medium are calculated. The results of the simulation agree well with theoretical results obtained by generalizing the Milne solution, as well as with experimental data.     

Second-order orientation effects in light scattering by polarized atoms

A compact expression is derived for the part of the cross section for light scattering by axisymmetrically polarized atomic systems proportional to the third-rank state multipole. The effect of the second-order orientation determined by this state multipole on the polarization and angular distribution of the scattered light is studied. The polarization of the incident light can be arbitrary and is specified by the Stokes parameters. A number of orientation effects in the scattering process are shown to be induced precisely by the second-order orientation. In particular, when nonpolarized light is scattered by an oriented atom, the scattering intensity in the perpendicular direction depends on the second-order orientation alone. The second-order orientation also preserves circular dichroism in the linear polarization of the forward-and back-scattered light.     

Dynamic study of compressed electron layer driven by linearly polarized laser

The dynamics of the compressed electron layer(CEL) are investigated when a linearly polarized(LP) laser pulse irradiates a plasma target. The turbulent motion of the CEL is investigated by a simple model, which is verified by particlein-cell(PIC) simulations. It is found that the compressed layer disperses in a few cycles of the laser duration, because the CEL comes back with a large velocity in the opposite direction of the laser incident. A larger wavelength laser can be used to tailor the proton beam by reducing the turbulence of the CEL in the region of the LP laser acceleration.     

Topological phase for spin systems in a linearly polarized RF field

The Permsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 3, pp. 342–344, March, 1991.     

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.     

All-fiber linearly polarized laser oscillator by fiber coiling loss control

In this paper,we demonstrate an all-fiber linearly polarized fiber laser oscillator.The single polarization of the oscillator is achieved through the careful designing of the active fiber coiling.The relationship between fiber coiling diameter and polarization extinction ratio and optical efficiency is studied,whose results lead to an optimized system.The thermal management of the oscillator is also refined,which allows the oscillator to reach a maximum output power of44.1 W with an optical-to-optical efficiency of 57.9%.A high average polarization extinction ratio of 21.6 d B is achieved during a 2-hour stability test.The oscillator also owns a narrow 3-d B bandwidth of 0.1 nm,as well as near-diffraction-limit beam quality of M~2~ 1.14.     

线性偏振光激发的错位表面等离子体激元纳米结构聚焦

利用扫描近场光学显微镜观测并分析了两种表面等离子体激元纳米结构对表面等离子体激元(SPP)的激发和聚焦现象.用线偏振光照射有半个周期相位差的环状沟槽结构与有半个周期位相差的环状狭缝结构,得到了单点的SPP聚焦.有限时域差分法的模拟结果验证了实验中观测的现象.这两种相位错位的表面等离子体激元纳米结构,突破了由于干涉导致的线偏振光不能得到单个聚焦点的限制.与采用径向偏振光激发而得到单个聚焦点的方法相比,线偏振光不需要聚焦,也不需要将光束中心对准纳米结构的几何中心即可得到单点聚焦。     

Field-free orientation of diatomic molecule via the linearly polarized resonant pulses

We propose a scheme to coherently control the field-free orientation of NO molecule whose rotational temperature is above 0 K. It is found that the maximum molecular orientation is affected by two factors: one is the sum of the population of M = 0 rotational states and the other is their distribution, however, their distribution plays a much more significant role in molecular orientation than the sum of their population. By adopting a series of linearly polarized pulses resonant with the rotational states, the distribution of M = 0 rotational states is well rearranged. Though the number of pulses used is small, a relatively high orientation degree can be obtained. This scheme provides a promising approach to the achievement of a good orientation effect.     

Nonlinear theory of scattering of linearly polarized electromagnetic waves by unmagnetized electron beam

The nonlinear dynamics of scattering of linearly polarized electromagnetic waves by an unmagnetized beam of nonrelativistic electrons is studied. General nonlinear equations are derived and linear scattering regimes are analyzed. For the case of high-density beams, the general nonlinear equations are reduced to a system containing only cubic nonlinearities. Analytic expressions are provided for the amplitudes of interacting waves and for typical process-development times.