Search results for "polarization."
showing 10 items of 1842 documents
Unidirectional Spin Hall Magnetoresistance as a Tool for Probing the Interfacial Spin Polarization of Co2MnSi
2019
Materials with high spin polarization, such as Heusler compounds, are required for efficient spintronics. The authors propose an approach to probe the transport spin polarization at interfaces, using the recently discovered unidirectional spin Hall magnetoresistance. They show that insertion of thin Ag(001) layers clearly increases the interfacial spin polarization of the Heusler compound Co${}_{2}$MnSi, which is crucial for giant-magnetoresistance devices.
Doping dependence of spin dynamics of drifting electrons in GaAs bulks
2010
We study the effect of the impurity density on lifetimes and relaxation lengths of electron spins in the presence of a static electric field in a n-type GaAs bulk. The transport of electrons and the spin dynamics are simulated by using a semiclassical Monte Carlo approach, which takes into account the intravalley scattering mechanisms of warm electrons in the semiconductor material. Spin relaxation is considered through the D'yakonov-Perel mechanism, which is the dominant mechanism in III-V semiconductors. The evolution of spin polarization is analyzed by computing the lifetimes and depolarization lengths as a function of the doping density in the range 10^{13} - 10^{16} cm^{-3}, for differ…
Hyperpolarization of cis ‐ 15 N 2 ‐Azobenzene by Parahydrogen at Ultralow Magnetic Fields**
2021
The development of nuclear spins hyperpolarization, and the search for molecules that can be efficiently hyperpolarized is an active area in nuclear magnetic resonance. In this work we present a detailed study of SABRE SHEATH (signal amplification by reversible exchange in shield enabled alignment transfer to heteronuclei) experiments on 15 N2 -azobenzene. In SABRE SHEATH experiments the nuclear spins of the target are hyperpolarized through transfer of spin polarization from parahydrogen at ultralow fields during a reversible chemical process. Azobenzene exists in two isomers, trans and cis. We show that all nuclear spins in cis-azobenzene can be efficiently hyperpolarized by SABRE at suit…
On the Theory of Domain Structure of Disordered Ferroelectrics
2009
We present a comprehensive analysis of domain structure formation in ferroelectric phase of incipient ferroelectrics with off-center dipole impurities like KTaO 3 :Li, Nb,Na. Our analysis is carried out on the base of effective free energy of disordered ferroelectrics, derived by us earlier. This free energy permits to apply the standard approach to domain structure calculation. Using coupled system of Maxwell equations with those obtained by minimization of above free energy, we calculate the physical characteristics of domain structure as functions of impurity dipoles concentration n. Our theory can be easily generalized for arbitrary temperature and crystal shape including thin films.
Substantial enlargement of angular existence range for Dyakonov-like surface waves at semi-infinite metal-dielectric superlattice
2012
We investigated surface waves guided by the boundary of a semi-infinite layered metal-dielectric nanostructure cut normally to the layers and a semi-infinite dielectric material. Using the Floquet-Bloch formalism, we found that Dyakonov-like surface waves with hybrid polarization can propagate in dramatically enhanced angular range compared to conventional birefringent materials. Our numerical simulations for an Ag-GaAs stack in contact with glass show a low to moderate influence of losses. This research was funded by the Qatar National Research Fund under the project NPRP 09-462-1-074, by the Spanish Ministry of Economy and Competitiveness under the project TEC2009-11635, and by the Serbia…
Dynamic control of the operation regimes of a mode-locked fiber laser based on intracavity polarizing fibers: experimental and theoretical validation.
2012
[EN] An intracavity polarizing fiber is proposed to control the emission regime of a passively mode-locked fiber laser. Stable operation in self-starting high and low dispersion soliton mode-locking and 100 GHz multiwavelength regimes is demonstrated through numerical simulations and experimental validation. Mode-locking stability is ensured by a saturable absorber in the ring cavity. The effective selection of operation regime is dynamically carried out by controlling the intracavity polarization state.
Real-time polarimetric optical sensor using macroporous alumina membranes.
2013
We report on the demonstration of real-time refractive index sensing within 60 μm thick free-standing macroporous alumina membranes with pore diameters of 200 nm. The free-standing macroporous alumina membranes allow the analytes to flow through the pores for targeted delivery, resulting in fast sensing responses. The polarimetric measurement platform exploits the optical anisotropy of the membranes in monitoring the refractive index variations of the analytes that fill the pores, providing highly sensitive and real-time measurements. The experimental characterization of the membranes' birefringence at wavelengths of 808, 980, and 1500 nm showed a decrease in birefringence for shorter wavel…
Symmetry of valence states of Heusler compounds explored by linear dichroism in hard-x-ray photoelectron spectroscopy.
2011
This study reports on the linear dichroism in angular-resolved photoemission from the valence band of the Heusler compounds ${\mathrm{NiTi}}_{0.9}{\mathrm{Sc}}_{0.1}\mathrm{Sn}$ and NiMnSb. High-resolution photoelectron spectroscopy was performed with an excitation energy of $h\ensuremath{\nu}=7.938\text{ }\text{ }\mathrm{keV}$. The linear polarization of the photons was changed using an in-vacuum diamond phase retarder. The valence band spectra exhibit the typical structure expected from first-principles calculations of the electronic structure of these compounds. Noticeable linear dichroism is found in the valence band of both materials, and this allows for a symmetry analysis of the cont…
Parabolic pulse generation with active or passive dispersion decreasing optical fibers
2007
International audience; We experimentally demonstrate the possibility to generate parabolic pulses via a single dispersion decreasing optical fiber with normal dispersion. We numerically and experimentally investigate the influence of the dispersion profile, and we show that a hybrid configuration combining dispersion decrease and gain has several benefits on the parabolic generated pulses.
Transmission anisotropy in triple-film opal photonic crystals
2006
Summary form only given: For photonic crystals (PhCs) to have successful impact on advancement of optical circuits and realisation of various functionalities, the incorporation of artificial defects into 3D PhCs is necessary. Opal films represent a convenient approach to the realisation of 3D PhCs. Taking into account the limited flexibility of the self-assembly, the first steps can be studies of planar defects in opals and hetero-opals. Characterisation of heteroPhCs should include the investigation of the dispersion of photonic bandgaps (PBG). While the dispersion of low-order PBGs in opal films is well known, the high order PBGs were hardly studied so far owing to high requirements to th…