11,349 research outputs found
Nonlinearity in the Dark: Broadband Terahertz Generation with Extremely High Efficiency
Plasmonic metamaterials and metasurfaces offer new opportunities in
developing high performance terahertz emitters and detectors beyond the
limitations of conventional nonlinear materials. However, simple meta-atoms for
second-order nonlinear applications encounter fundamental trade-offs in the
necessary symmetry breaking and local-field enhancement due to radiation
damping that is inherent to the operating resonant mode and cannot be
controlled separately. Here we present a novel concept that eliminates this
restriction obstructing the improvement of terahertz generation efficiency in
nonlinear metasurfaces based on metallic nanoresonators. This is achieved by
combining a resonant dark-state metasurface, which locally drives nonlinear
nanoresonators in the near field, with a specific spatial symmetry that enables
destructive interference of the radiating linear moments of the nanoresonators,
and perfect absorption via simultaneous electric and magnetic critical coupling
of the pump radiation to the dark mode. Our proposal allows eliminating linear
radiation damping, while maintaining constructive interference and effective
radiation of the nonlinear components. We numerically demonstrate a giant
second-order nonlinear susceptibility around Hundred-Billionth m/V, a one order
improvement compared with the previously reported split-ring-resonator
metasurface, and correspondingly, a 2 orders of magnitude enhanced terahertz
energy extraction should be expected with our configuration under the same
conditions. Our study offers a paradigm of high efficiency tunable nonlinear
metadevices and paves the way to revolutionary terahertz technologies and
optoelectronic nanocircuitry.Comment: 6 pages, 4 figure
Linearly and Circularly Polarized Emission in Sagittarius A*
We perform general relativistic ray-tracing calculations of the transfer of
polarized synchrotron radiation through the relativistic accretion flow in
Sagittarius (Sgr) A*. Based on a two-temperature magneto-rotational-instability
(MRI) induced accretion mode, the birefringence effects are treated
self-consistently. By fitting the spectrum and polarization of Sgr A* from
millimeter to near-infrared bands, we are able to not only constrain the basic
parameters related to the MRI and the electron heating rate, but also limit the
orientation of the accretion torus. These constraints lead to unique
polarimetric images, which may be compared with future millimeter and
sub-millimeter VLBI observations. In combination with general relativistic MHD
simulations, the model has the potential to test the MRI with observations of
Sgr A*.Comment: 12 pages, 2 figures, ApJL accepte
Inflatable penile prosthesis in the radical prostatectomy patient: a review [version 1; referees: 2 approved]
In the population of patients with prostate cancer, survivorship has come to the forefront of continuity-of-care. In addition to urinary control, erectile function is a significant issue after radical pelvic surgery. Penile prosthesis surgery remains an excellent option for restoring erectile function to those for whom more conservative measures have failed. This review article outlines the anatomical, surgical and post-operative consideration involved in the placement of a penile prosthesis in this special patient population
Current-induced Spin Polarization in Two-Dimensional Hole Gas
We investigate the current-induced spin polarization in the two-dimensional
hole gas (2DHG) with the structure inversion asymmetry. By using the
perturbation theory, we re-derive the effective -cubic Rashba Hamiltonian
for 2DHG and the generalized spin operators accordingly. Then based on the
linear response theory we calculate the current-induced spin polarization both
analytically and numerically with the disorder effect considered. We have found
that, quite different from the two-dimensional electron gas, the spin
polarization in 2DHG depends linearly on Fermi energy in the low doping regime,
and with increasing Fermi energy, the spin polarization may be suppressed and
even changes its sign. We predict a pronounced peak of the spin polarization in
2DHG once the Fermi level is somewhere between minimum points of two spin-split
branches of the lowest light-hole subband. We discuss the possibility of
measurements in experiments as regards the temperature and the width of quantum
wells.Comment: 13 pages, 8 figures, submitted to PR
The 3D-tomography of the nano-clusters formed by Fe-coating and annealing of diamond films for enhancing their surface electron field emitters
[[abstract]]The Fe-coating and H2-annealed processes markedly increased the conductivity and enhanced the surface electron field emission (s-EFE) properties for the diamondfilms. The enhancement on the s-EFE properties for the diamondfilms is presumably owing to the formation of nano-graphite clusters on the surface of the films via the Fe-to-diamond interaction. However, the extent of enhancement varied with the granular structure of the diamondfilms. For the microcrystalline (MCD)films, the s-EFE process can be turned on at (E0)MCD = 1.9 V/μm, achieving a large s-EFE current density of (Je)MCD = 315 μA/cm2 at an applied field of 8.8 V/μm. These s-EFE properties are markedly better than those for Fe-coated/annealed ultrananocrystalline diamond(UNCD)films with (E0)UNCD = 2.0 V/μm and (Je)UNCD = 120 μA/cm2. The transmission electron microscopy showed that the nano-graphite clusters formed an interconnected network for MCDfilms that facilitated the electron transport more markedly, as compared with the isolated nano-graphitic clusters formed at the surface of the UNCDfilms. Therefore, the Fe-coating/annealing processes improved the s-EFE properties for the MCDfilms more markedly than that for the UNCDfilms. The understanding on the distribution of the nano-clusters is of critical importance in elucidating the authentic factor that influences the s-EFE properties of the diamondfilms. Such an understanding is possible only through the 3D-tomographic investigations.[[journaltype]]國外[[ispeerreviewed]]Y[[booktype]]電子版[[countrycodes]]US
Study of Decays with Polarization in Perturbative QCD Approach
The , decays are useful to determine the CKM
angle . Their polarization fractions are also interesting since
the polarization puzzle of the decay. We study these decays in
the perturbative QCD approach based on factorization.
After calculating of the non-factorizable and annihilation type
contributions, in addition to the conventional factorizable contributions, we
find that the contributions from the annihilation diagrams are crucial. They
give dominant contribution to the strong phases and suppress the longitudinal
polarizations. Our results agree with the current existing data. We also
predict a sizable direct CP asymmetries in , , and decays, which can be tested by the
oncoming measurements in the B factory experiments.Comment: 15 pages, latex, including 4 figure
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