274 research outputs found
Squeezed-field injection for gravitational wave interferometers
In a recent table-top experiment, we demonstrated the compatibility of three advanced interferometer techniques for gravitational wave detection, namely power-recycling, detuned signal recycling and squeezed-field injection. The interferometer's signal-to-noise ratio was improved by up to 2.8 dB beyond the coherent state's shot-noise. This value was mainly limited by optical losses on the squeezed field. We present a detailed analysis of the optical losses in our experiment and provide an estimation of the possible nonclassical performance of a future squeezed-field enhanced GEO 600 detector
Triple Michelson Interferometer for a Third-Generation Gravitational Wave Detector
The upcoming European design study `Einstein gravitational-wave Telescope'
represents the first step towards a substantial, international effort for the
design of a third-generation interferometric gravitational wave detector. It is
generally believed that third-generation instruments might not be installed
into existing infrastructures but will provoke a new search for optimal
detector sites. Consequently, the detector design could be subject to fewer
constraints than the on-going design of the second generation instruments. In
particular, it will be prudent to investigate alternatives to the traditional
L-shaped Michelson interferometer. In this article, we review an old proposal
to use three Michelson interferometers in a triangular configuration. We use
this example of a triple Michelson interferometer to clarify the terminology
and will put this idea into the context of more recent research on
interferometer technologies. Furthermore the benefits of a triangular detector
will be used to motivate this design as a good starting point for a more
detailed research effort towards a third-generation gravitational wave
detector.Comment: Minor corrections to the main text and two additional appendices. 14
pages, 6 figure
Experimental characterization of frequency dependent squeezed light
We report on the demonstration of broadband squeezed laser beams that show a
frequency dependent orientation of the squeezing ellipse. Carrier frequency as
well as quadrature angle were stably locked to a reference laser beam at
1064nm. This frequency dependent squeezing was characterized in terms of noise
power spectra and contour plots of Wigner functions. The later were measured by
quantum state tomography. Our tomograph allowed a stable lock to a local
oscillator beam for arbitrary quadrature angles with one degree precision.
Frequency dependent orientations of the squeezing ellipse are necessary for
squeezed states of light to provide a broadband sensitivity improvement in
third generation gravitational wave interferometers. We consider the
application of our system to long baseline interferometers such as a future
squeezed light upgraded GEO600 detector.Comment: 8 pages, 8 figure
Observation of coherent transients in ultrashort chirped excitation of an undamped two-level system
The effects of Coherent excitation of a two level system with a linearly
chirped pulse are studied theoretically and experimentally (in Rb (5s - 5p)) in
the low field regime. The Coherent Transients are measured directly on the
excited state population on an ultrashort time scale. A sharp step corresponds
to the passage through resonance. It is followed by oscillations resulting from
interferences between off-resonant and resonant contributions. We finally show
the equivalence between this experiment and Fresnel diffraction by a sharp
edge.Comment: 4 pages, 4 figures, to appear in PR
Feasibility of measuring the Shapiro time delay over meter-scale distances
The time delay of light as it passes by a massive object, first calculated by
Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all
measurements of the Shapiro time delay have been made over solar-system
distance scales. We show that the new generation of kilometer-scale laser
interferometers being constructed as gravitational wave detectors, in
particular Advanced LIGO, will in principle be sensitive enough to measure
variations in the Shapiro time delay produced by a suitably designed rotating
object placed near the laser beam. We show that such an apparatus is feasible
(though not easy) to construct, present an example design, and calculate the
signal that would be detectable by Advanced LIGO. This offers the first
opportunity to measure space-time curvature effects on a laboratory distance
scale.Comment: 13 pages, 6 figures; v3 has updated instrumental noise curves plus a
few text edits; resubmitted to Classical and Quantum Gravit
A Femtosecond Neutron Source
The possibility to use the ultrashort ion bunches produced by circularly
polarized laser pulses to drive a source of fusion neutrons with sub-optical
cycle duration is discussed. A two-side irradiation of a thin foil deuterated
target produces two countermoving ion bunches, whose collision leads to an
ultrashort neutron burst. Using particle-in-cell simulations and analytical
modeling, it is evaluated that, for intensities of a few ,
more than neutrons per Joule may be produced within a time shorter than
one femtosecond. Another scheme based on a layered deuterium-tritium target is
outlined.Comment: 15 pages, 3 figure
Probing seed black holes using future gravitational-wave detectors
Identifying the properties of the first generation of seeds of massive black
holes is key to understanding the merger history and growth of galaxies.
Mergers between ~100 solar mass seed black holes generate gravitational waves
in the 0.1-10Hz band that lies between the sensitivity bands of existing
ground-based detectors and the planned space-based gravitational wave detector,
the Laser Interferometer Space Antenna (LISA). However, there are proposals for
more advanced detectors that will bridge this gap, including the third
generation ground-based Einstein Telescope and the space-based detector DECIGO.
In this paper we demonstrate that such future detectors should be able to
detect gravitational waves produced by the coalescence of the first generation
of light seed black-hole binaries and provide information on the evolution of
structure in that era. These observations will be complementary to those that
LISA will make of subsequent mergers between more massive black holes. We
compute the sensitivity of various future detectors to seed black-hole mergers,
and use this to explore the number and properties of the events that each
detector might see in three years of observation. For this calculation, we make
use of galaxy merger trees and two different seed black hole mass distributions
in order to construct the astrophysical population of events. We also consider
the accuracy with which networks of future ground-based detectors will be able
to measure the parameters of seed black hole mergers, in particular the
luminosity distance to the source. We show that distance precisions of ~30% are
achievable, which should be sufficient for us to say with confidence that the
sources are at high redshift.Comment: 14 pages, 6 figures, 2 tables, accepted for proceedings of 13th GWDAW
meetin
Probing multiphoton light-induced molecular potentials
The strong coupling between intense laser fields and valence electrons in molecules causes distortions of the potential energy hypersurfaces which determine the motion of the nuclei and influence possible reaction pathways. The coupling strength varies with the angle between the light electric field and valence orbital, and thereby adds another dimension to the effective molecular potential energy surface, leading to the emergence of light-induced conical intersections. Here, we demonstrate that multiphoton couplings can give rise to complex light-induced potential energy surfaces that govern molecular behavior. In the laser-induced dissociation of H2+, the simplest of molecules, we measure a strongly modulated angular distribution of protons which has escaped prior observation. Using two-color Floquet theory, we show that the modulations result from ultrafast dynamics on light-induced molecular potentials. These potentials are shaped by the amplitude, duration and phase of the dressing fields, allowing for manipulating the dissociation dynamics of small molecules
Coherent Control of Multiphoton Transitions with Femtosecond pulse shaping
We explore the effects of ultrafast shaped pulses for two-level systems that
do not have a single photon resonance by developing a multiphoton
density-matrix approach. We take advantage of the fact that the dynamics of the
intermediate virtual states are absent within our laser pulse timescales. Under
these conditions, the multiphoton results are similar to the single photon and
that it is possible to extend the single photon coherent control ideas to
develop multiphoton coherent control.Comment: 13 pages, 7 figures. submitted to PR
DC-readout of a signal-recycled gravitational wave detector
All first-generation large-scale gravitational wave detectors are operated at
the dark fringe and use a heterodyne readout employing radio frequency (RF)
modulation-demodulation techniques. However, the experience in the currently
running interferometers reveals several problems connected with a heterodyne
readout, of which phase noise of the RF modulation is the most serious one. A
homodyne detection scheme (DC-readout), using the highly stabilized and
filtered carrier light as local oscillator for the readout, is considered to be
a favourable alternative. Recently a DC-readout scheme was implemented on the
GEO 600 detector. We describe the results of first measurements and give a
comparison of the performance achieved with homodyne and heterodyne readout.
The implications of the combined use of DC-readout and signal-recycling are
considered.Comment: 11 page
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