ORCID Profile
0000-0001-6726-3268
Current Organisation
The University of Western Australia Faculty of Science
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Publisher: AIP Publishing
Date: 12-2018
DOI: 10.1063/1.5049508
Abstract: Advanced gravitational wave detectors use suspended test masses to form optical resonant cavities for enhancing the detector sensitivity. These cavities store hundreds of kilowatts of coherent light and even higher optical power for future detectors. With such high optical power, the radiation pressure effect inside the cavity creates a sufficiently strong coupling between test masses whose dynamics are significantly altered. The dynamics of two independent nearly free masses become a coupled mechanical resonator system. The transfer function of the local control system used for controlling the test masses is modified by the radiation pressure effect. The changes in the transfer function of the local control systems can result in a new type of angular instability which occurs at only 1.3% of the Sidles-Sigg instability threshold power. We report the experimental results on a 74 m suspended cavity with a few kilowatts of circulating power, for which the power to mass ratio is comparable to the current Advanced LIGO. The radiation pressure effect on the test masses behaves like an additional optical feedback with respect to the local angular control, potentially making the mirror control system unstable. When the local angular control system is optimised for maximum stability margin, the instability threshold power increases from 4 kW to 29 kW. The system behaviour is consistent with our simulation, and the power dependent evolution of both the cavity soft and hard mode is observed. We show that this phenomenon is likely to significantly affect the proposed gravitational wave detectors that require very high optical power.
Publisher: The Optical Society
Date: 05-02-2014
DOI: 10.1364/AO.53.000841
Publisher: IOP Publishing
Date: 05-06-2017
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-06-2021
Abstract: Cooling objects to low temperature can increase the sensitivity of sensors and the operational performance of most devices. Removing most of the thermal vibrations—or phonons—such that the object reaches its motional quantum ground state has been achieved but typically with tiny, nanoscale objects. Using the suspended mirrors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) that form a 10-kg optomechanical oscillator, Whittle et al. demonstrate the ability to cool such a large-scale object to nearly the motional ground state. An upgrade to LIGO with such a modification could increase its sensitivity and range to gravitational waves but also extend studies of quantum mechanics to large-scale objects. Science , abh2634, this issue p. 1333
Publisher: AIP Publishing
Date: 05-2023
DOI: 10.1063/5.0140766
Abstract: Advanced LIGO and Advanced Virgo have detected gravitational waves from astronomical sources to open a new window on the Universe. To explore this new realm requires an exquisite level of detector sensitivity, meaning that the much stronger signal from instrumental and environmental noise must be rejected. Selected ex les of unwanted noise in Advanced LIGO are presented. The initial focus is on how the existence of this noise (characterized by particular frequencies or time intervals) was discovered. Then, a variety of methods are used to track down the source of the noise, e.g., a fault within the instruments or coupling from an external source. The ultimate goal of this effort is to mitigate the noise by either fixing equipment or by augmenting methods to suppress the coupling to the environment.
Location: Australia
No related grants have been discovered for Jian Liu.