71 research outputs found
Phase Control of Squeezed Vacuum States of Light in Gravitational Wave Detectors
Quantum noise will be the dominant noise source for the advanced laser
interferometric gravitational wave detectors currently under construction.
Squeezing-enhanced laser interferometers have been recently demonstrated as a
viable technique to reduce quantum noise. We propose two new methods of
generating an error signal for matching the longitudinal phase of squeezed
vacuum states of light to the phase of the laser interferometer output field.
Both provide a superior signal to the one used in previous demonstrations of
squeezing applied to a gravitational-wave detector. We demonstrate that the new
signals are less sensitive to misalignments and higher order modes, and result
in an improved stability of the squeezing level. The new signals also offer the
potential of reducing the overall rms phase noise and optical losses, each of
which would contribute to achieving a higher level of squeezing. The new error
signals are a pivotal development towards realizing the goal of 6 dB and more
of squeezing in advanced detectors and beyond
Terrestrial Laser Interferometers
Terrestrial laser interferometers for gravitational-wave detection made the
landmark first detection of gravitational waves in 2015. We provide an overview
of the history of how these laser interferometers prevailed as the most
promising technology in the search for gravitational waves. We describe their
working principles and their limitations, and provide examples of some of the
most important technologies that enabled their construction. We introduce each
of the four large-scale laser interferometer gravitational-wave detectors in
operation around the world today and provide a brief outlook for the future of
ground-based detectors.Comment: Invited chapter for "Handbook of Gravitational Wave Astronomy" (Eds.
C. Bambi, S. Katsanevas and K. Kokkotas; Springer Singapore, 2021
Status of advanced ground-based laser interferometers for gravitational-wave detection
Ground-based laser interferometers for gravitational-wave (GW) detection were
first constructed starting 20 years ago and as of 2010 collection of several
years' worth of science data at initial design sensitivities was completed.
Upgrades to the initial detectors together with construction of brand new
detectors are ongoing and feature advanced technologies to improve the
sensitivity to GWs. This conference proceeding provides an overview of the
common design features of ground-based laser interferometric GW detectors and
establishes the context for the status updates of each of the four
gravitational-wave detectors around the world: Advanced LIGO, Advanced Virgo,
GEO600 and KAGRA
An Experiment for Observing Quantum Gravity Phenomena using Twin Table-Top 3D Interferometers
Theories of quantum gravity based on the holographic principle predict the
existence of quantum fluctuations of distance measurements that accumulate and
exhibit correlations over macroscopic distances. This paper models an expected
signal due to this phenomenology, and details the design and estimated
sensitivity of co-located twin table-top 3D interferometers being built to
measure or constrain it. The experiment is estimated to be sensitive to
displacements in a frequency band between
1 and 250 MHz, surpassing previous experiments and enabling the possible
observation of quantum gravity phenomena. The experiment will also be sensitive
to MHz gravitational waves and various dark matter candidates.Comment: Accepted for publication in Classical and Quantum Gravit
Angular control of optical cavities in a radiation-pressure-dominated regime: the Enhanced LIGO case
We describe the angular sensing and control (ASC) of 4 km detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO). Enhanced LIGO, the culmination of the first generation LIGO detectors, operated between 2009 and 2010 with about 40 kW of laser power in the arm cavities. In this regime, radiation-pressure effects are significant and induce instabilities in the angular opto-mechanical transfer functions. Here we present and motivate the ASC design in this extreme case and present the results of its implementation in Enhanced LIGO. Highlights of the ASC performance are successful control of opto-mechanical torsional modes, relative mirror motions of ≤ 1×10^−7 rad rms, and limited impact on in-band strain sensitivity
Prospects for detecting gravitational waves at 5 Hz with ground-based detectors
We propose an upgrade to Advanced LIGO (aLIGO), named LIGO-LF, that focuses
on improving the sensitivity in the 5-30 Hz low-frequency band, and we explore
the upgrade's astrophysical applications. We present a comprehensive study of
the detector's technical noises and show that with technologies currently under
development, such as interferometrically sensed seismometers and
balanced-homodyne readout, LIGO-LF can reach the fundamental limits set by
quantum and thermal noises down to 5 Hz. These technologies are also directly
applicable to the future generation of detectors. We go on to consider this
upgrade's implications for the astrophysical output of an aLIGO-like detector.
A single LIGO-LF can detect mergers of stellar-mass black holes (BHs) out to a
redshift of z~6 and would be sensitive to intermediate-mass black holes up to
2000 M_\odot. The detection rate of merging BHs will increase by a factor of 18
compared to aLIGO. Additionally, for a given source the chirp mass and total
mass can be constrained 2 times better than aLIGO and the effective spin 3-5
times better than aLIGO. Furthermore, LIGO-LF enables the localization of
coalescing binary neutron stars with an uncertainty solid angle 10 times
smaller than that of aLIGO at 30 Hz, and 4 times smaller when the entire signal
is used. LIGO-LF also significantly enhances the probability of detecting other
astrophysical phenomena including the tidal excitation of neutron star r-modes
and the gravitational memory effects.Comment: 5 pages, 6 figures, published in PR
High-vacuum-compatible high-power Faraday isolators for gravitational-wave interferometers
Faraday isolators play a key role in the operation of large-scale gravitational-wave detectors. Second-generation gravitational-wave interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo will use high-average-power cw lasers (up to 200 W) requiring specially designed Faraday isolators that are immune to the effects resulting from the laser beam absorption–degraded isolation ratio, thermal lensing, and thermally induced beam steering. In this paper, we present a comprehensive study of Faraday isolators designed specifically for high-performance operation in high-power gravitational-wave interferometers
DC readout experiment in Enhanced LIGO
The two 4 km long gravitational wave detectors operated by the Laser
Interferometer Gravitational-wave Observatory (LIGO) were modified in 2008 to
read out the gravitational wave channel using the DC readout form of homodyne
detection and to include an optical filter cavity at the output of the
detector. As part of the upgrade to Enhanced LIGO, these modifications replaced
the radio-frequency (RF) heterodyne system used previously. We describe the
motivations for and the implementation of DC readout and the output mode
cleaner in Enhanced LIGO. We present characterizations of the system, including
measurements and models of the couplings of the noises from the laser source to
the gravitational wave readout channel. We show that noise couplings using DC
readout are improved over those for RF readout, and we find that the achieved
shot-noise-limited sensitivity is consistent with modeled results
Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers
We present the design and performance of the LIGO Input Optics subsystem as implemented for the sixth science run of the LIGO interferometers. The Initial LIGO Input Optics experienced thermal side effects when operating with 7 W input power. We designed, built, and implemented improved versions of the Input Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO interferometers, designed to run with 30 W input power. At four times the power of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved performance including better optical isolation, less thermal drift, minimal thermal lensing, and higher optical efficiency. The success of the Input Optics design fosters confidence for its ability to perform well in Advanced LIGO
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