321 research outputs found
Proposal for an Integrated Raman-free Correlated Photon Source
We propose a dual-pump third-order nonlinear scheme for producing pairs of
correlated photons that is less susceptible to Raman noise than typical
spontaneous four wave mixing methods (SFWM). Beginning with the full multimode
Hamiltonian we derive a general expression for the joint spectral amplitude,
from which the probability of producing a pair of photons can be calculated. As
an example, we demonstrate that a probability of 0.028 pairs per pulse can be
achieved in an appropriately designed fused silica microfiber. As compared with
single pump SFWM in standard fiber, we calculate that our process shows
significant suppression of the spontaneous Raman scattering and an improvement
in the signal to noise ratio.Comment: 7 pages, 3 figures (two containing 2 subfigures
The Effects of an Integrated Space Support Node on Theater Air Combat
The Air Force requires a methodology to assess alternative means for providing integrated space support data, collected from imagery space platforms, to enhance overall theater warfighting capability. This research examines imagery systems supporting the warning, surveillance, and weather missions, alternative concepts to integrate this imagery data, and models their influence on air-to-ground and limited ground-to-air combat in five potential theaters of operation. These theaters were Northeast Asia, Southeast Asia, Southeast Europe, the Caribbean, and Central America. Influence diagram decision analysis techniques were used to identify and quantify the key variables within the three space-based mission areas effecting air combat planning and execution. The theater warfighter\u27s imagery requirements and air campaign planning theory were examined and linked to identify the affected air combat measures of effectiveness. The results of this research and air combat simulation reveals a significant increase in sortie effectiveness and lethality by incorporating space-based imagery support into theater conflict through acquiring and deploying an integrated space support center. The methodology provided can be tailored to include any number of theaters of conflict and modified to study other military space systems
Coherence in parametric fluorescence
We investigate spontaneous four wave mixing (SFWM) in a single-channel
side-coupled integrated spaced sequence of resonators (SCISSOR). Analytic
expressions for the number of photon pairs generated, as well as the biphoton
wave function (joint spectral amplitude) describing the pairs, are derived and
numerically computed for different pump pulse durations and numbers of ring
resonators. In the limit of a long input pump pulse, we show a strong analogy
between super-linear scaling of generation efficiency with respect to the
number of rings in the structure and Dicke superradiance. More generally, we
discuss in detail the factors that influence the shape of the biphoton wave
function, as well as the conditions for observing super-SFWM
Tuneable quantum interference in a 3D integrated circuit
Integrated photonics promises solutions to questions of stability,
complexity, and size in quantum optics. Advances in tunable and non-planar
integrated platforms, such laser-inscribed photonics, continue to bring the
realisation of quantum advantages in computation and metrology ever closer,
perhaps most easily seen in multi-path interferometry. Here we demonstrate
control of two-photon interference in a chip-scale 3D multi-path
interferometer, showing a reduced periodicity and enhanced visibility compared
to single photon measurements. Observed non-classical visibilities are widely
tunable, and explained well by theoretical predictions based on classical
measurements. With these predictions we extract a Fisher information
approaching a theoretical maximum, demonstrating the capability of the device
for quantum enhanced phase measurements.Comment: 11 pages, 24 figure
From Classical Four-Wave Mixing to Parametric Fluorescence in Silicon micro-ring resonators
Four-wave mixing can be stimulated or occur spontaneously. The first process
is intrinsically much stronger, and well understood through classical nonlinear
optics. The latter, also known as parametric fluorescence, can be explained
only in the framework of a quantum theory of light. We experimentally
demonstrate that, in a micro-ring resonator, there exists a simple relation
between the efficiencies of these two processes, which is independent of the
nonlinearity and size of the ring. In particular we show that the average power
generated by parametric fluorescence can be immediately estimated from a
classical FWM experiment. These results suggest that classical nonlinear
characterization of a photonic integrated structure can provide accurate
information on its nonlinear quantum properties.Comment: 4 pages, 3 figure
Absolute dimensions of eclipsing binaries. XVII. A metal-weak F-type system, perhaps with preference for Y = 0.23-0.24
V1130 Tau is a bright (m_V = 6.56), nearby (71 +/- 2 pc) detached system with
a circular orbit (P = 0.80d). The components are deformed with filling factors
above 0.9. Their masses and radii have been established to 0.6-0.7%. We derive
a [Fe/H] abundance of -0.25 +/- 0.10. The measured rotational velocities, 92.4
+/- 1.1 (primary) and 104.7 +/- 2.7 (secondary) km/s, are in fair agreement
with synchronization. The larger 1.39 Msun secondary component has evolved to
the middle of the main-sequence band and is slightly cooler than the 1.31 Msun
primary. Yonsai-Yale, BaSTI, and Granada evolutionary models for the observed
metal abundance and a 'normal' He content of Y = 0.25-0.26, marginally
reproduce the components at ages between 1.8 and 2.1 Gyr. All such models are,
however, systematically about 200 K hotter than observed and predict ages for
the more massive component, which are systematically higher than for the less
massive component. These trends can not be removed by adjusting the amount of
core overshoot or envelope convection level, or by including rotation in the
model calculations. They may be due to proximity effects in V1130 Tau, but on
the other hand, we find excellent agreement for 2.5-2.8 Gyr Granada models with
a slightly lower Y of 0.23-0.24. V1130 Tau is a valuable addition to the very
few well-studied 1-2 Msun binaries with component(s) in the upper half of the
main-sequence band, or beyond. The stars are not evolved enough to provide new
information on the dependence of core overshoot on mass (and abundance), but
might - together with a larger sample of well-detached systems - be useful for
further tuning of the helium enrichment law.Comment: Accepted for publication in Astronomy & Astrophysic
Generation of heralded single photons beyond 1100 nm by spontaneous four-wave mixing in a side-stressed femtosecond laser-written waveguide
We demonstrate a monolithically integrable heralded photon source in a
femtosecond laser direct written glass waveguide. The generation of photon
pairs with a wide wavelength separation requires a concomitant large
birefringence in the normal dispersion regime. Here, by incorporation of
side-stress tracks, we produce a waveguide with a birefringence of
and propagation loss as low as 0.21 dB/cm near 980~nm. We
measure photon pairs with 300~nm wavelength separation at an internal
generation rate exceeding /s. The second order correlations
indicate that the generated photon pairs are in a strongly non-classical
regime.Comment: 5 pages, 5 figure
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