1,887 research outputs found
Optical realization of nonlinear quantum dynamics
In a cavity filled with a Kerr medium it is possible to generate the
superposition of coherent states, i.e. Schroodinger cat states may be realized
in this system. We show that such a medium may be mimicked by the propagation
of a conveniently shaped Gaussian beam in a GRIN device. This is attained by
introducing a second order correction to the paraxial propagation of the beam.
An additional result is that a Gaussian beam propagating in GRIN media, may
split into two Gaussian beams
The mid-infrared extinction law in the darkest cores of the Pipe Nebula
Context. The properties of dust grains, in particular their size
distribution, are expected to differ from the interstellar medium to the
high-density regions within molecular clouds. Aims. We measure the mid-infrared
extinction law produced by dense material in molecular cloud cores. Since the
extinction at these wavelengths is caused by dust, the extinction law in cores
should depart from that found in low-density environments if the dust grains
have different properties. Methods. We use the unbiased LINES method to measure
the slope of the reddening vectors in color-color diagrams. We derive the
mid-infrared extinction law toward the dense cores B59 and FeSt 1-457 in the
Pipe Nebula over a range of visual extinction between 10 and 50 magnitudes,
using a combination of Spitzer/IRAC, and ESO NTT/VLT data. Results. The
mid-infrared extinction law in both cores departs significantly from a
power-law between 3.6 and 8 micron, suggesting that these cores contain dust
with a considerable fraction of large dust grains. We find no evidence for a
dependence of the extinction law with column density up to 50 magnitudes of
visual extinction in these cores, and no evidence for a variation between our
result and those for other clouds at lower column densities reported elsewhere
in the literature. This suggests that either large grains are present even in
low column density regions, or that the existing dust models need to be revised
at mid-infrared wavelengths. We find a small but significant difference in the
extinction law of the two cores, that we tentatively associate with the onset
of star formation in B59.Comment: 8 pages, 6 figures. Accepted to A&
From Strong to Weak Coupling Regime in a Single GaN Microwire up to Room Temperature
Large bandgap semiconductor microwires constitute a very advantageous
alternative to planar microcavities in the context of room temperature strong
coupling regime between exciton and light. In this work we demonstrate that in
a GaN microwire, the strong coupling regime is achieved up to room temperature
with a large Rabi splitting of 125 meV never achieved before in a Nitride-based
photonic nanostructure. The demonstration relies on a method which doesn't
require any knowledge \'a priori on the photonic eigenmodes energy in the
microwire, i.e. the details of the microwire cross-section shape. Moreover,
using a heavily doped segment within the same microwire, we confirm
experimentally that free excitons provide the oscillator strength for this
strong coupling regime. The measured Rabi splitting to linewidth ratio of 15
matches state of the art planar Nitride-based microcavities, in spite of a much
simpler design and a less demanding fabrication process. These results show
that GaN microwires constitute a simpler and promising system to achieve
electrically pumped lasing in the strong coupling regime.Comment: 14 pages, 4 figure
- âŠ