2,527 research outputs found
Gravitational Wave Experiments and Early Universe Cosmology
Gravitational-wave experiments with interferometers and with resonant masses
can search for stochastic backgrounds of gravitational waves of cosmological
origin. We review both experimental and theoretical aspects of the search for
these backgrounds. We give a pedagogical derivation of the various relations
that characterize the response of a detector to a stochastic background. We
discuss the sensitivities of the large interferometers under constructions
(LIGO, VIRGO, GEO600, TAMA300, AIGO) or planned (Avdanced LIGO, LISA) and of
the presently operating resonant bars, and we give the sensitivities for
various two-detectors correlations. We examine the existing limits on the
energy density in gravitational waves from nucleosynthesis, COBE and pulsars,
and their effects on theoretical predictions. We discuss general theoretical
principles for order-of-magnitude estimates of cosmological production
mechanisms, and then we turn to specific theoretical predictions from
inflation, string cosmology, phase transitions, cosmic strings and other
mechanisms. We finally compare with the stochastic backgrounds of astrophysical
origin.Comment: 99 pages, Latex, 17 figures. To appear in Physics Report. v4:
conceptual changes in sect. 7.
The next detectors for gravitational wave astronomy
This paper focuses on the next detectors for gravitational wave astronomy
which will be required after the current ground based detectors have completed
their initial observations, and probably achieved the first direct detection of
gravitational waves. The next detectors will need to have greater sensitivity,
while also enabling the world array of detectors to have improved angular
resolution to allow localisation of signal sources. Sect. 1 of this paper
begins by reviewing proposals for the next ground based detectors, and presents
an analysis of the sensitivity of an 8 km armlength detector, which is proposed
as a safe and cost-effective means to attain a 4-fold improvement in
sensitivity. The scientific benefits of creating a pair of such detectors in
China and Australia is emphasised. Sect. 2 of this paper discusses the high
performance suspension systems for test masses that will be an essential
component for future detectors, while sect. 3 discusses solutions to the
problem of Newtonian noise which arise from fluctuations in gravity gradient
forces acting on test masses. Such gravitational perturbations cannot be
shielded, and set limits to low frequency sensitivity unless measured and
suppressed. Sects. 4 and 5 address critical operational technologies that will
be ongoing issues in future detectors. Sect. 4 addresses the design of thermal
compensation systems needed in all high optical power interferometers operating
at room temperature. Parametric instability control is addressed in sect. 5.
Only recently proven to occur in Advanced LIGO, parametric instability
phenomenon brings both risks and opportunities for future detectors. The path
to future enhancements of detectors will come from quantum measurement
technologies. Sect. 6 focuses on the use of optomechanical devices for
obtaining enhanced sensitivity, while sect. 7 reviews a range of quantum
measurement options
同心円回析格子と位相変調干渉計を用いた軸受のラジアル アキシャル アンギュラモーションの同時測定法
国立大学法人長岡技術科学大
Ion-Exchanged Glass Waveguide Technology: A Review
We review the history and current status of ion exchanged glass waveguide technology. The background of ion exchange in glass and key developments in the first years of research are briefly described. An overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applications are discussed. Ion exchanged waveguide technology has served as an available platform for studies of general waveguide properties, integrated optics structures and devices, as well as applications. It is also a commercial fabrication technology for both passive and active waveguide components
Optical/IR from ground
Optical/infrared (O/IR) astronomy in the 1990's is reviewed. The following subject areas are included: research environment; science opportunities; technical development of the 1980's and opportunities for the 1990's; and ground-based O/IR astronomy outside the U.S. Recommendations are presented for: (1) large scale programs (Priority 1: a coordinated program for large O/IR telescopes); (2) medium scale programs (Priority 1: a coordinated program for high angular resolution; Priority 2: a new generation of 4-m class telescopes); (3) small scale programs (Priority 1: near-IR and optical all-sky surveys; Priority 2: a National Astrometric Facility); and (4) infrastructure issues (develop, purchase, and distribute optical CCDs and infrared arrays; a program to support large optics technology; a new generation of large filled aperture telescopes; a program to archive and disseminate astronomical databases; and a program for training new instrumentalists
Range-resolved optical interferometric signal processing
The ability to identify the range of an interferometric signal is very useful in interferometry,
allowing the suppression of parasitic signal components or permitting
several signal sources to be multiplexed. Two novel range-resolved optical interferometric
signal processing techniques, employing very different working principles,
are theoretically described and experimentally demonstrated in this thesis. The first
technique is based on code-division multiplexing (CDM), which is combined with
single-sideband signal processing, resulting in a technique that, unlike prior work,
only uses a single, regular electro-optic phase modulator to perform both range-based
signal identification and interferometric phase evaluation. The second approach
uses sinusoidal optical frequency modulation (SFM), induced by injection current
modulation of a diode laser, to introduce range-dependent carriers to determine phase
signals in interferometers of non-zero optical path difference. Here, a key innovation
is the application of a smooth window function, which, when used together with
a time-variant demodulation approach, allows optical path lengths of constituent
interferometers to be continuously and independently variable, subject to a minimum
separation, greatly increasing the practicality of the approach.
Both techniques are applied to fibre segment interferometry, where fibre segments
that act as long-gauge length interferometric sensors are formed between pairs of
partial in-fibre reflectors. Using a regular single-mode laser diode, six fibre segments
of length 12.5 cm are multiplexed with a quadrature bandwidth of 43 kHz and a phase
noise floor of 0.19 mrad
·
Hz
-0.5
using the SFM technique. In contrast, the 16.5 m
spatial resolution achieved with the CDM technique points towards its applicability
in medium-to-long range sensing. The SFM technique also allows high linearity,
with cyclic errors as low as 1 mrad demonstrated, and with modelling indicating
further room for improvement. Additionally, in an industrial measurement, the SFM
technique is applied to single-beam, multi-surface vibrometry, allowing simultaneous
differential measurements between two vibrating surfaces
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