297 research outputs found
Electric-field multiplexing/demultiplexing of volume holograms in photorefractive media
We propose a new method of volume hologram multiplexing/demultiplexing in noncentrosymmetric media. Volume holograms may be multiplexed by tuning the material parameters of the recording medium (such as refractive index or lattice parameters) while keeping the external parameters (wavelength and angles) fixed. For example, an external dc electric field alters the index of refraction through the electro-optic effect, effectively changing the recording and reconstruction wavelengths in the storage medium. Then the storage of holograms at different fields, hence different indices of refraction, is closely related to wavelength multiplexing. We demonstrate this concept in a preliminary experiment by electrically multiplexing two volume holograms in a strontium barium niobate crystal
Anomalous enhancement of spin Hall conductivity in superconductor/normal metal junction
We propose a spin Hall device to induce a large spin Hall effect in a
superconductor/normal metal (SN) junction. The side jump and skew scattering
mechanisms are both taken into account to calculate the extrinsic spin Hall
conductivity in the normal metal. We find that both contributions are
anomalously enhanced when the voltage between the superconductor and the normal
metal approaches to the superconducting gap. This enhancement is attributed to
the resonant increase of the density of states in the normal metal at the Fermi
level. Our results demonstrate a novel way to control and amplify the spin Hall
conductivity by applying an external dc electric field, suggesting that a SN
junction has a potential application for a spintronic device with a large spin
Hall effect.Comment: 5 pages, 4 figures, To be published as a Rapid Communication in
Physical Review
Electric field excitation suppression in cold atoms
In this article, the atom excitation suppression is studied in two ways. The
first way of exploring the excitation suppression is by an external DC electric
field. The second way is to study the excitation suppression caused by electric
field generated by free charges, which are created by ionizing atoms. This
suppression is called Coulomb blockade. Here the Coulomb forces are created by
ions through ionizing atoms by a UV laser. The theory shows that the
interaction, which causes the suppression, is primarily caused by charge-dipole
interactions. Here the charge is the ion, and the dipole is an atom. In this
experiment, we use Rb atoms. The valence electron and the ion core are
the two poles of an electric dipole. The interaction potential energy between
the ion and the atom is proportional to , and the frequency
shift caused by this interaction is proportional to , where
is the distance between the ion and the dipole considered. This research can be
used for quantum information storage, remote control, creating hot plasmas
using cold atoms, as well as electronic devices.Comment: 12 pages, 7 figure
- …