Manipulation of spin dephasing in InAs quantum wires

The spin dephasing due to the Rashba spin-orbit coupling, especially its dependence on the direction of the electric field is studied in InAs quantum wire. We find that the spin dephasing is strongly affected by the angle of Rashba effective magnetic field and the applied magnetic field. The nonlinearity in spin dephasing time versus the direction of the electric field shows a potential evenue to manipulate the spin lifetime in spintronic device. Moreover, we figure out a quantity that can well represent the inhomogeneous broadening of the system which may help us to understand the many-body spin dephasing due to the Rashba effect.Comment: 4 pages, 3 figure

Spin dynamics in high-mobility two-dimensional electron systems

Understanding the spin dynamics in semiconductor heterostructures is highly important for future semiconductor spintronic devices. In high-mobility two-dimensional electron systems (2DES), the spin lifetime strongly depends on the initial degree of spin polarization due to the electron-electron interaction. The Hartree-Fock (HF) term of the Coulomb interaction acts like an effective out-of-plane magnetic field and thus reduces the spin-flip rate. By time-resolved Faraday rotation (TRFR) techniques, we demonstrate that the spin lifetime is increased by an order of magnitude as the initial spin polarization degree is raised from the low-polarization limit to several percent. We perform control experiments to decouple the excitation density in the sample from the spin polarization degree and investigate the interplay of the internal HF field and an external perpendicular magnetic field. The lifetime of spins oriented in the plane of a [001]-grown 2DES is strongly anisotropic if the Rashba and Dresselhaus spin-orbit fields are of the same order of magnitude. This anisotropy, which stems from the interference of the Rashba and the Dresselhaus spin-orbit fields, is highly density-dependent: as the electron density is increased, the kubic Dresselhaus term becomes dominant and reduces the anisotropy.Comment: 13 pages, 6 figure

Spin-dependent hole quantum transport in Aharonov-Bohm ring structure: possible schemes for spin filter

We study the Aharonov-Bohm (AB) effect in two-dimensional mesoscopic frame in hole systems. We show that differing from the AB effect in electron systems, due to the presence of both the heavy hole and the light hole, the conductances not only show the normal spin-unresolved AB oscillations, but also become spin-separated. Some schemes for spin filter based on the abundant interference characteristics are proposed.Comment: 4 pages, 5 figures. Phys. Lett. A, 2005, in pres

Random distributed feedback Raman fiber laser with polarized pumping

In this letter, the polarization properties of a random fiber laser operating via Raman gain and random distributed feedback owing to Rayleigh scattering are investigated for the first time. Using polarized pump, the partially polarized generation is obtained with a generation spectrum exhibiting discrete narrow spectral features contrary to the smooth spectrum observed for the depolarized pump. The threshold, output power, degree of polarization and the state of polarization (SOP) of the lasing can be significantly influenced by the SOP of the pump. Fine narrow spectral components are also sensitive to the SOP of the pump wave. Furthermore, we found that random lasing's longitudinal power distributions are different in the case of polarized and depolarized pumping that results in considerable reduction of the generation slope efficiency for the polarized radiation. Our results indicate that polarization effects play an important role on the performance of the random fiber laser. This work improves the understanding of the physics of random lasing in fibers and makes a step forward towards the establishment of the vector model of random fiber lasers

Spin oscillations in transient diffusion of a spin pulse in n-type semiconductor quantum wells

By studying the time and spatial evolution of a pulse of the spin polarization in $n$-type semiconductor quantum wells, we highlight the importance of the off-diagonal spin coherence in spin diffusion and transport. Spin oscillations and spin polarization reverse along the the direction of spin diffusion in the absence of the applied magnetic field are predicted from our investigation.Comment: 5 pages, 4 figures, accepted for publication in PR

Novel Correspondence-based Approach for Consistent Human Skeleton Extraction

This paper presents a novel base-points-driven shape correspondence (BSC) approach to extract skeletons of articulated objects from 3D mesh shapes. The skeleton extraction based on BSC approach is more accurate than the traditional direct skeleton extraction methods. Since 3D shapes provide more geometric information, BSC offers the consistent information between the source shape and the target shapes. In this paper, we first extract the skeleton from a template shape such as the source shape automatically. Then, the skeletons of the target shapes of different poses are generated based on the correspondence relationship with source shape. The accuracy of the proposed method is demonstrated by presenting a comprehensive performance evaluation on multiple benchmark datasets. The results of the proposed approach can be applied to various applications such as skeleton-driven animation, shape segmentation and human motion analysis

High resolution optical time-domain reflectometry based on correlation utilizing an all-fiber chaotic source

We propose a high-resolution optical time domain reflectometry (OTDR) based on an all-fiber supercontinuum source. The source simply consists of a laser with moderate power and a section of fiber which has a zero dispersion wavelength near the laser's central wavelength. Spectrum and time domain properties of the source are investigated, showing that the source has great capability in nonlinear optics, such as correlation OTDR. We analyze one of the key factors limiting the operational range of such an OTDR, i.e., sampling time. Finally, we experimentally demonstrate a correlation OTDR with 25km sensing range and 5.3cm spatial resolution, as a verification of theoretical analysis

Long-range and high-resolution correlation optical time-domain reflectometry utilizing an all optical chaotic source

A high resolution optical time domain reflectometry (OTDR) based on an all-fiber chaotic source is demonstrated. We analyze the key factors limiting the operational range of such an OTDR, e.g., integral Rayleigh backscattering and the fiber loss, which degrade the optical signal to noise ratio at the receiver side, and then the guideline for counter-act such signal fading is discussed. The experimentally demonstrated correlation OTDR presents ability of 100km sensing range and 8.2cm spatial resolution (1.2 million resolved points), as a verification of the theoretical analysis. To the best of our knowledge, this is the first time that correlation OTDR measurement is performed over such a long distance with such high precision

Spin-orbit coupling in bulk GaAs

We study the spin-orbit coupling in the whole Brillouin zone for GaAs using both the $sp^3s^{\ast}d^5$ and $sp^3s^{\ast}$ nearest-neighbor tight-binding models. In the $\Gamma$-valley, the spin splitting obtained is in good agreement with experimental data. We then further explicitly present the coefficients of the spin splitting in GaAs $L$ and $X$ valleys. These results are important to the realization of spintronic device and the investigation of spin dynamics far away from equilibrium.Comment: 8 pages, 3 figures, Physica E, in pres

Preparation, Properties, and Microstructure of Graphite Powder-Containing Conductive Concrete

Conductive concrete not only retains the advantages of ordinary concrete but also possesses high electrical conductivity. It can be applied to snow and ice control on the roads. In preparing the conductive concrete, sand as the conductive fine aggregate was replaced with graphite powder. Its properties and microstructure were also investigated. The conductive concrete strength is shown to decrease with a graphite powder ratio. The conductive concrete resistivity goes down with the powder fineness and content; the temperature grows after electrification, and the concrete exhibits a high heating effect. Graphite powder exerts little influence on the hydration products of the concrete. With an increase in the content and fineness of graphite powder, its filling efficiency becomes rather helpful to form the conductive path.Проводящий бетон не только сохраняет преимущества обычного бетона, но и имеет высокую электропроводность; может использоваться для удаления снега и плавления льда на дорогах. Для получения такого бетона применялся вместо песка в качестве проводящего мелкого заполнителя графитовый порошок. Исследуются свойства и микроструктура бетона. Установлено, что прочность бетона уменьшается с увеличением содержания графитового порошка. Электрическое удельное сопротивление бетона уменьшается с увеличением мелкости и содержания графитового порошка; температура повышается после электризации, и бетон проявляет высокий нагревательный эффект. Графитовый порошок оказывает незначительное влияние на продукты гидратации проводящего бетона. С увеличением содержания и мелкости графитового порошка увеличивается положительный эффект заполнения графитовым порошком для формирования проводящей дорожки.Електропровідний бетон не тільки зберігає переваги звичайного бетону, але і має високу електропровідність; може використовуватися для видалення снігу та плавлення льоду на дорогах. Для отримання такого бетону застосовувався замість піску в якості провідного дрібний заповнювач графітовий порошок. Досліджуються властивості і мікроструктура бетону. Встановлено, що міцність бетону зменшується зі збільшенням вмісту графітового порошку. Електричний питомий опір бетону зменшується зі збільшенням дрібноту і змісту графітового порошку; температура підвищується після електризації, і бетон проявляє високий нагрівальний ефект. Графітовий порошок має незначний вплив на продукти гідратації проводить бетону. Зі збільшенням вмісту і дрібноту графітового порошку збільшується позитивний ефект заповнення графітовим порошком для формування провідної доріжк