98,779 research outputs found
Large enhancement of deuteron polarization with frequency modulated microwaves
We report a large enhancement of 1.7 in deuteron polarization up to values of
0.6 due to frequency modulation of the polarizing microwaves in a two liters
polarized target using the method of dynamic nuclear polarization. This target
was used during a deep inelastic polarized muon-deuteron scattering experiment
at CERN. Measurements of the electron paramagnetic resonance absorption spectra
show that frequency modulation gives rise to additional microwave absorption in
the spectral wings. Although these results are not understood theoretically,
they may provide a useful testing ground for the deeper understanding of
dynamic nuclear polarization.Comment: 10 pages, including the figures coming in uuencoded compressed tar
files in poltar.uu, which also brings cernart.sty and crna12.sty files neede
A Scalar Wigner Theory for Polarized Light in Nonlinear Kerr Media
A scalar Wigner distribution function for describing polarized light is
proposed in analogy with the treatment of spin variables in quantum kinetic
theory. The formalism is applied to the propagation of circularly polarized
light in nonlinear Kerr media and an extended phase space evolution equation is
derived along with invariant quantities. We further consider modulation
instability as well as the extension to partially coherent fields.Comment: 6 page
Hysteresis effect in \nu=1 quantum Hall system under periodic electrostatic modulation
The effect of a one-dimensional periodic electrostatic modulation on quantum
Hall systems with filling factor \nu=1 is studied. We propose that, either when
the amplitude of the modulation potential or the tilt angle of the magnetic
field is varied, the system can undergo a first-order phase transition from a
fully spin-polarized homogeneous state to a partially spin-polarized
charge-density-wave state, and show hysteresis behavior of the spin
polarization. This is confirmed by our self-consistent numerical calculations
within the Hartree-Fock approximation. Finally we suggest that the \nu=1/3
fractional quantum Hall state may also show similar hysteresis behavior in the
presence of a periodic potential modulation.Comment: RevTeX, 4 page, 3 EPS figure
Tailoring Chirp in Spin-Lasers
The usefulness of semiconductor lasers is often limited by the undesired
frequency modulation, or chirp, a direct consequence of the intensity
modulation and carrier dependence of the refractive index in the gain medium.
In spin-lasers, realized by injecting, optically or electrically,
spin-polarized carriers, we elucidate paths to tailoring chirp. We provide a
generalized expression for chirp in spin-lasers and introduce modulation
schemes that could simultaneously eliminate chirp and enhance the bandwidth, as
compared to the conventional (spin-unpolarized) lasers.Comment: 4 pages, 3 figure
Spin Modulation in Semiconductor Lasers
We provide an analytic study of the dynamics of semiconductor lasers with
injection (pump) of spin-polarized electrons, previously considered in the
steady-state regime. Using complementary approaches of quasi-static and small
signal analyses, we elucidate how the spin modulation in semiconductor lasers
can improve performance, as compared to the conventional (spin-unpolarized)
counterparts. We reveal that the spin-polarized injection can lead to an
enhanced bandwidth and desirable switching properties of spin-lasers.Comment: 4 pages, 3 figure
Shape-dependent Depinning of a Domain Wall by a Magnetic Field and a Spin-Polarized Current
The effect of sample shape on the depinning of the domain wall (DW) driven by
an applied magnetic field or a spin-polarized current is studied theoretically.
The shape effect resulting from the modulation of the sample width (geometric
pinning) can essentially affect the DW depinning. We found a good agreement
between the ratios of the critical values of the magnetic field and the
spin-polarized current predicted by the theory and measured in the experiment.Comment: 9 pages, 5 figure
Tunable plasmon-enhanced birefringence in ribbon array of anisotropic 2D materials
We explore the far-field scattering properties of anisotropic 2D materials in
ribbon array configuration. Our study reveals the plasmon-enhanced linear
birefringence in these ultrathin metasurfaces, where linearly polarized
incident light can be scattered into its orthogonal polarization or be
converted into circular polarized light. We found wide modulation in both
amplitude and phase of the scattered light via tuning the operating frequency
or material's anisotropy and develop models to explain the observed scattering
behavior
Ballistic spin transport through electronic stub tuners: spin precession, selection, and square-wave transmission
Ballistic spin transport is studied through electronic tuners with double
stubs attached to them. The spins precess due to the spin-orbit interaction.
Injected polarized spins can exit the structure polarized in the opposite
direction. A nearly square-wave spin transmission, with values 1 and 0, can be
obtained using a periodic system of symmetric stubs and changing their length
or width. The gaps in the transmission can be widened using asymmetric stubs.
An additional modulation is obtained upon combining stub structures with
different values of the spin-orbit strength.Comment: 3 pages, 4 figure
A Sensitive Faraday Rotation Setup Using Triple Modulation
The utilization of polarized targets in scattering experiments has become a
common practice in many major accelerator laboratories. Noble gases are
especially suitable for such applications, since they can be easily
hyper-polarized using spin exchange or metastable pumping techniques. Polarized
helium-3 is a very popular target because it often serves as an effective
polarized neutron due to its simple nuclear structure. A favorite cell material
to generate and store polarized helium-3 is GE-180, a relatively dense
aluminosilicate glass. In this paper, we present a Faraday rotation method,
using a new triple modulation technique, where the measurement of the Verdet
constants of SF57 flint glass, pyrex glass, and air were tested. The
sensitivity obtained shows that this technique may be implemented in future
cell wall characterization and thickness measurements. We also discuss the
first ever extraction of the Verdet constant of GE-180 glass for four
wavelength values of 632 nm, 773 nm, 1500 nm, and 1547 nm, whereupon the
expected 1/{\lambda}^{2} dependence was observed.Comment: 4 pages, 2 figures Updated version for RSI submissio
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