2,335 research outputs found
Layered superconductors as negative-refractive-index metamaterials
We analyze the use of layered superconductors as anisotropic metamaterials.
Layered superconductors can have a negative refraction index in a wide
frequency range for arbitrary incident angles. Indeed, low-Tc (s-wave)
superconductors allow to produce artificial heterostructures with low losses
for T<<Tc. However, the real part of their in-plane effective permittivity is
very large. Moreover, even at low temperatures, layered high-Tc superconductors
have a large in-plane normal conductivity, producing large losses (due to
d-wave symmetry). Therefore, it is difficult to enhance the evanescent modes in
either low-Tc or high-Tc superconductors.Comment: 4 pages, 2 figure
Fabrication technologies for quantum cascade photonic-crystal microlasers
In this paper we describe the technological and fabrication methods necessary to incorporate both photonic and electronic-band engineering in order to create novel surface-emitting quantum cascade microcavity laser sources. This technology offers the promise of several innovative applications such as the miniaturization of QC lasers, and multi-wavelength two-dimensional laser arrays for spectroscopy, gas-sensing and imaging. This approach is not limited to light-emitting devices, and may be efficiently applied to the development of mid- and far-infrared normal-incidence detectors
Fabrication methods for a quantum cascade photonic crystal surface emitting laser
Conventional quantum cascade (QC) lasers are intrinsically edge-emitting devices with mode confinement achieved via a standard mesa stripe configuration. Surface emission in edge emitting QC lasers has therefore necessitated redirecting the waveguided laser emission using a second order grating. This paper describes the methods used to fabricate a 2D photonic crystal (PC) structure with or without a central defect superimposed on an electrically pumped QC laser structure with the goal of achieving direct surface emission. A successful systematic study of PC hole radius and spacing was performed using e-beam lithography. This PC method offers the promise of a number of interesting applications, including miniaturization and integration of QC lasers
Quantum cascade photonic crystal surface emitting injection laser
A surface emitting quantum cascade injection laser is presented. Direct surface emission is obtained by using a 2D photonic-band-gap structure that simultaneously acts as a microcavity. The approach may allow miniaturization and on-chip-integration of the devices
Nonlinear Micromechanical Casimir Oscillator
The Casimir force between uncharged metallic surfaces originates from quantum
mechanical zero point fluctuations of the electromagnetic field. We demonstrate
that this quantum electrodynamical effect has a profound influence on the
oscillatory behavior of microstructures when surfaces are in close proximity
(<= 100 nm). Frequency shifts, hysteretic behavior and bistability caused by
the Casimir force are observed in the frequency response of a periodically
driven micromachined torsional oscillator.Comment: 4 pages, 4 figures; added and rearranged references; added comments
on sensitivit
Horava-Lifshitz gravity: tighter constraints for the Kehagias-Sfetsos solution from new solar system data
We analytically work out the perturbation induced by the Kehagias-Sfetsos
(KS) space-time solution of the Horava-Lifshitz (HL) modified gravity at long
distances on the two-body range for a pair of test particles A and B orbiting
the same mass M. We apply our results to the most recently obtained
range-residuals \delta\rho for some planets of the solar system (Mercury, Mars,
Saturn) ranged from the Earth to effectively constrain the dimensionsless KS
parameter \psi_0 for the Sun. We obtain \psi_0 >= 7.2 x 10^-10 (Mercury),
\psi_0 >= 9 x 10^-12 (Mars), \psi_0 >= 1.7 x 10^-12 (Saturn). Such lower bounds
are tighter than other ones existing in literature by several orders of
magnitude. We also preliminarily obtain \psi_0 >= 8 x 10^-10 for the system
constituted by the S2 star orbiting the Supermassive Black Hole (SBH) in the
center of the Galaxy.Comment: LaTex2e, 15 pages, 1 table, 3 figures, 31 references. Version
matching the one at press in International Journal of Modern Physics D
(IJMPD
Precision measurement of the Casimir-Lifshitz force in a fluid
The Casimir force, which results from the confinement of the quantum
mechanical zero-point fluctuations of the electromagnetic fields, has received
significant attention in recent years for its effect on micro- and nano-scale
mechanical systems. With few exceptions, experimental observations have been
limited to conductive bodies interacting separated by vacuum or air. However,
interesting phenomena including repulsive forces are expected to exist in
certain circumstances between metals and dielectrics when the intervening
medium is not vacuum. In order to better understand the effect of the Casimir
force in such situations and to test the robustness of the generalized
Casimir-Lifshitz theory, we have performed the first precision measurements of
the Casimir force between two metals immersed in a fluid. For this situation,
the measured force is attractive and is approximately 80% smaller than the
force predicted by Casimir for ideal metals in vacuum. We present experimental
results and find them to be consistent with Lifshitz's theory.Comment: 6 pages, 3 figures. (version before final publication
Quantum codewords contradict local realism
Quantum codewords are highly entangled combinations of two-state systems. The
standard assumptions of local realism lead to logical contradictions similar to
those found by Bell, Kochen and Specker, Greenberger, Horne and Zeilinger, and
Mermin. The new contradictions have some noteworthy features that did not
appear in the older ones.Comment: 9 pages LaTeX, 1 figur
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