19 research outputs found
Comparison of different sloshing speedmeters
By numerical simulation, we compare the performance of four speedmeter interferometer configurations with potential application in future gravitational wave detectors. In the absence of optical loss, all four configurations can be adjusted to yield the same sensitivity in a fair comparison. Once we introduce a degree of practicality in the form of lossy optics and mode mismatch, however, the situation changes: the sloshing Sagnac and the speedmeter of Purdue and Chen have almost identical performance showing smaller degradation from the ideal than the speedmeter of Freise and the speedmeter of Miao. In a further step, we show that there is a similar hierarchy in the degree of improvement obtained through the application of 10 dB squeezing to the lossy speedmeters. In this case, the sensitivity of each speedmeter improves, but it is greatest for the sloshing Sagnac and the speedmeter of Purdue and Chen, in particular in the lower part of the target frequency range
Local-Oscillator Noise Coupling in Balanced Homodyne Readout for Advanced Gravitational Wave Detectors
The second generation of interferometric gravitational wave detectors are
quickly approaching their design sensitivity. For the first time these
detectors will become limited by quantum back-action noise. Several back-action
evasion techniques have been proposed to further increase the detector
sensitivity. Since most proposals rely on a flexible readout of the full
amplitude- and phase-quadrature space of the output light field, balanced
homodyne detection is generally expected to replace the currently used DC
readout. Up to now, little investigation has been undertaken into how balanced
homodyne detection can be successfully transferred from its ubiquitous
application in table-top quantum optics experiments to large-scale
interferometers with suspended optics. Here we derive implementation
requirements with respect to local oscillator noise couplings and highlight
potential issues with the example of the Glasgow Sagnac Speed Meter experiment,
as well as for a future upgrade to the Advanced LIGO detectors.Comment: 7 pages, 5 figure
Waveguide grating mirror in a fully suspended 10 meter Fabry-Perot cavity
We report on the first demonstration of a fully suspended 10m Fabry-Perot
cavity incorporating a waveguide grating as the coupling mirror. The cavity was
kept on resonance by reading out the length fluctuations via the
Pound-Drever-Hall method and employing feedback to the laser frequency. From
the achieved finesse of 790 the grating reflectivity was determined to exceed
99.2% at the laser wavelength of 1064\,nm, which is in good agreement with
rigorous simulations. Our waveguide grating design was based on tantala and
fused silica and included a ~20nm thin etch stop layer made of Al2O3 that
allowed us to define the grating depth accurately during the fabrication
process. Demonstrating stable operation of a waveguide grating featuring high
reflectivity in a suspended low-noise cavity, our work paves the way for the
potential application of waveguide gratings as mirrors in high-precision
interferometry, for instance in future gravitational wave observatories
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
Effects of static and dynamic higher-order optical modes in balanced homodyne readout for future gravitational waves detectors
With the recent detection of Gravitational waves (GW), marking the start of the new field of GW astronomy, the push for building more sensitive laser-interferometric gravitational wave detectors (GWD) has never been stronger. Balanced homodyne detection (BHD) allows for a quantum noise (QN) limited readout of arbitrary light field quadratures, and has therefore been suggested as a vital building block for upgrades to Advanced LIGO and third generation observatories. In terms of the practical implementation of BHD, we develop a full framework for analyzing the static optical high order modes (HOMs) occurring in the BHD paths related to the misalignment or mode matching at the input and output ports of the laser interferometer. We find the effects of HOMs on the quantum noise limited sensitivity is independent of the actual interferometer configuration, e.g. Michelson and Sagnac interferometers are effected in the same way. We show that misalignment of the output ports of the interferometer (output misalignment) only effects the high frequency part of the quantum noise limited sensitivity (detection noise). However, at low frequencies, HOMs reduce the interferometer response and the radiation pressure noise (back action noise) by the same amount and hence the quantum noise limited sensitivity is not negatively effected in that frequency range. We show that the misalignment of laser into the interferometer (input misalignment) produces the same effect as output misalignment and additionally decreases the power inside the interferometer. We also analyze dynamic HOM effects, such as beam jitter created by the suspended mirrors of the BHD. Our analyses can be directly applied to any BHD implementation in a future GWD. Moreover, we apply our analytical techniques to the example of the speed meter proof of concept experiment under construction in Glasgow. We find that for our experimental parameters, the performance of our seismic isolation system in the BHD paths is compatible with the design sensitivity of the experiment
Demonstration of a switchable damping system to allow low-noise operation of high-Q low-mass suspension systems
Low mass suspension systems with high-Q pendulum stages are used to enable
quantum radiation pressure noise limited experiments. Utilising multiple
pendulum stages with vertical blade springs and materials with high quality
factors provides attenuation of seismic and thermal noise, however damping of
these high-Q pendulum systems in multiple degrees of freedom is essential for
practical implementation. Viscous damping such as eddy-current damping can be
employed but introduces displacement noise from force noise due to thermal
fluctuations in the damping system. In this paper we demonstrate a passive
damping system with adjustable damping strength as a solution for this problem
that can be used for low mass suspension systems without adding additional
displacement noise in science mode. We show a reduction of the damping factor
by a factor of 8 on a test suspension and provide a general optimisation for
this system.Comment: 5 pages, 5 figure
The 10m AEI prototype facility A brief overview
The AEI 10 m prototype interferometer facility is currently being constructed
at the Albert Einstein Institute in Hannover, Germany. It aims to perform
experiments for future gravitational wave detectors using advanced techniques.
Seismically isolated benches are planned to be interferometrically
interconnected and stabilized, forming a low-noise testbed inside a 100 m^3
ultra-high vacuum system. A well-stabilized high power laser will perform
differential position readout of 100 g test masses in a 10 m suspended
arm-cavity enhanced Michelson interferometer at the crossover of measurement
(shot) noise and backaction (quantum radiation pressure) noise, the so-called
Standard Quantum Limit (SQL). Such a sensitivity enables experiments in the
highly topical field of macroscopic quantum mechanics. In this article we
introduce the experimental facility and describe the methods employed,
technical details of subsystems will be covered in future papers
Comparison of different sloshing speedmeters
By numerical simulation, we compare the performance of four speedmeter interferometer configurations with potential application in future gravitational wave detectors. In the absence of optical loss, all four configurations can be adjusted to yield the same sensitivity in a fair comparison. Once we introduce a degree of practicality in the form of lossy optics and mode mismatch, however, the situation changes: the sloshing Sagnac and the speedmeter of Purdue and Chen have almost identical performance showing smaller degradation from the ideal than the speedmeter of Freise and the speedmeter of Miao. In a further step, we show that there is a similar hierarchy in the degree of improvement obtained through the application of 10 dB squeezing to the lossy speedmeters. In this case, the sensitivity of each speedmeter improves, but it is greatest for the sloshing Sagnac and the speedmeter of Purdue and Chen, in particular in the lower part of the target frequency range
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ISSN:0028-0836ISSN:1476-468