10,246 research outputs found
Atom Interferometry with up to 24-Photon-Momentum-Transfer Beam Splitters
We present up to 24-photon Bragg diffraction as a beam splitter in
light-pulse atom interferometers to achieve the largest splitting in momentum
space so far. Relative to the 2-photon processes used in the most sensitive
present interferometers, these large momentum transfer beam splitters increase
the phase shift 12-fold for Mach-Zehnder (MZ-) and 144-fold for Ramsey-Borde
(RB-) geometries. We achieve a high visibility of the interference fringes (up
to 52% for MZ or 36% for RB) and long pulse separation times that are possible
only in atomic fountain setups. As the atom's internal state is not changed,
important systematic effects can cancel.Comment: New introduction. 4 pages, 4 figure
Extended cavity diode lasers with tracked resonances
We present a painless, almost-free upgrade to present extended cavity diode
lasers (ECDLs), which improves the long term mode-hop free performance by
stabilizing the resonance of the internal cavity to the external cavity. This
stabilization is based on the observation that the frequency or amplitude noise
of the ECDL is lowest at the optimum laser diode temperature or injection
current. Thus, keeping the diode current at the level where the noise is lowest
ensures mode-hop free operation within one of the stable regions of the mode
chart, even if these should drift due to external influences. This method can
be applied directly to existing laser systems without modifying the optical
setup. We demonstrate the method in two ECDLs stabilized to vapor cells at 852
nm and 895 nm wavelength. We achieve long term mode-hop free operation and low
noise at low power consumption, even with an inexpensive non-antireflection
coated diode.Comment: 5 pages, 6 figure
Phase-Locked, Low-Noise, Frequency Agile Titanium: Sapphire Lasers for Simultaneous Atom Interferometers
We demonstrate phase lock of two >1.6W Titanium:sapphire lasers with a phase
noise of -138dBc/Hz at 1MHz from the carrier, using an intra-cavity
electro-optic phase modulator. The residual phase variance is 2.5 10^(-8)rad^2
integrated from 1Hz to 10kHz. Instantaneous offset frequency steps of up to
4MHz are achieved within 200ns. Simultaneous atom interferometers can make full
use of this ultra-low phase noise in differential measurements by suppressing
common influences from vibration of optics.Comment: Additional phase-noise data and references; to appear in Optics
Letters. 3 pages, 4 figure
Targets and Fisheries Management in the Asia and Pacific Region
Marine fisheries in the Asia and the Pacific
region play an important role in global,
regional and national economies. Many of the
fisheries in the region are over-exploited, both
biologically and economically.We focus on the
use of appropriate fishery targets, and the
importance of tying those targets to management
objectives to overcome the usual and
unwanted negative externalities that occur in
ocean fisheries, the ones that result in substantial
over-fishing. Of particular importance is
the use of a maximum economic yield target
for both short- and long-lived species.
Maximum economic yield, when combined
with appropriately designed marine protected
areas, or marine reserves, not only provides
maximum profitability and generally larger
and more �conservationist� stocks of fish, but it
also ensures a measure of resilience from stochastic
shocks that may negatively impact the
fishery. It remains the preferred target for most
fisheries in the Asia and Pacific region
Wave-packet treatment of neutrino oscillations and its implications on determining the neutrino mass hierarchy
We derive the neutrino flavor transition probabilities with the neutrino
treated as a wave packet. The decoherence and dispersion effects from the
wave-packet treatment show up as damping and phase-shifting of the plane-wave
neutrino oscillation patterns. If the energy uncertainty in the initial
neutrino wave packet is larger than around 0.01 of the neutrino energy, the
decoherence and dispersion effects would degrade the sensitivity of reactor
neutrino experiments to mass hierarchy measurement to lower than 3
confidence level
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