6,199 research outputs found
Stability of continuously pumped atom lasers
A multimode model of a continuously pumped atom laser is shown to be unstable
below a critical value of the scattering length. Above the critical scattering
length, the atom laser reaches a steady state, the stability of which increases
with pumping. Below this limit the laser does not reach a steady state. This
instability results from the competition between gain and loss for the excited
states of the lasing mode. It will determine a fundamental limit for the
linewidth of an atom laser beam.Comment: 4 page
Classical noise and flux: the limits of multi-state atom lasers
By direct comparison between experiment and theory, we show how the classical
noise on a multi-state atom laser beam increases with increasing flux. The
trade off between classical noise and flux is an important consideration in
precision interferometric measurement. We use periodic 10 microsecond
radio-frequency pulses to couple atoms out of an F=2 87Rb Bose-Einstein
condensate. The resulting atom laser beam has suprising structure which is
explained using three dimensional simulations of the five state
Gross-Pitaevskii equations.Comment: 4 pages, 3 figure
11 W narrow linewidth laser source at 780nm for laser cooling and manipulation of Rubidium
We present a narrow linewidth continuous laser source with over 11 Watts of
output power at 780nm, based on single-pass frequency doubling of an amplified
1560nm fibre laser with 36% efficiency. This source offers a combination of
high power, simplicity, mode quality and stability. Without any active
stabilization, the linewidth is measured to be below 10kHz. The fibre seed is
tunable over 60GHz, which allows access to the D2 transitions in 87Rb and 85Rb,
providing a viable high-power source for laser cooling as well as for
large-momentum-transfer beamsplitters in atom interferometry. Sources of this
type will pave the way for a new generation of high flux, high duty-cycle
degenerate quantum gas experiments.Comment: 5 pages, 3 figure
Flattening the Learning Curve: SOF as the Supported Command in the Irregular Warfare Environment
When the United States commits forces to a war, overseas contingency operations, or any other large-scale military effort that centers on conflict with belligerents other than another countrys armed military forces, Special Operations Forces (SOF) should be the supported command. Joint doctrine allows for support of such a concept, but that doctrine has not always been followed in practice. Consequently, this thesis argues for SOF being the supported command in an irregular warfare environment. By selecting the force specifically trained for the task at hand, the United States will dramatically reduce the time lost on the learning curve that results from relying predominantly on General Purpose Forces (GPF) commanders in all combat situations. Advocating for SOF being the supported command is not an argument for SOF only, but rather aims for a synergistic and truly unified approach that makes the best possible use of local national forces, partner nations, and GPF in an irregular warfare environment.http://archive.org/details/flatteninglearni109457395Major, United States Army,Major, United States Army,Major, United States Arm
Achieving peak brightness in an atom laser
In this paper we present experimental results and theory on the first
continuous (long pulse) Raman atom laser. The brightness that can be achieved
with this system is three orders of magnitude greater than has been previously
demonstrated in any other continuously outcoupled atom laser. In addition, the
energy linewidth of a continuous atom laser can be made arbitrarily narrow
compared to the mean field energy of a trapped condensate. We analyze the flux
and brightness of the atom laser with an analytic model that shows excellent
agreement with experiment with no adjustable parameters.Comment: 4 pages, 4 black and white figures, submitted to Physical Revie
A Bose-condensed, simultaneous dual species Mach-Zehnder atom interferometer
This paper presents the first realisation of a simultaneous Rb
-Rb Mach-Zehnder atom interferometer with Bose-condensed atoms. A number
of ambitious proposals for precise terrestrial and space based tests of the
Weak Equivalence Principle rely on such a system. This implementation utilises
hybrid magnetic-optical trapping to produce spatially overlapped condensates
with a duty cycle of 20s. A horizontal optical waveguide with co-linear Bragg
beamsplitters and mirrors is used to simultaneously address both isotopes in
the interferometer. We observe a non-linear phase shift on a non-interacting
Rb interferometer as a function of interferometer time, , which we
show arises from inter-isotope scattering with the co-incident Rb
interferometer. A discussion of implications for future experiments is given.Comment: 7 pages, 5 figures. The authors welcome comments and feedback on this
manuscrip
Superradiant scattering from a hydrodynamic vortex
We show that sound waves scattered from a hydrodynamic vortex may be
amplified. Such superradiant scattering follows from the physical analogy
between spinning black holes and hydrodynamic vortices. However a sonic horizon
analogous to the black hole event horizon does not exist unless the vortex
possesses a central drain, which is challenging to produce experimentally. In
the astrophysical domain, superradiance can occur even in the absence of an
event horizon: we show that in the hydrodynamic analogue, a drain is not
required and a vortex scatters sound superradiantly. Possible experimental
realization in dilute gas Bose-Einstein condensates is discussed.Comment: 10 pages, 1 figur
- …