Here is a brief summary of the current research activities going on in the group. A list of recent publications is also available.
The next generation of interferometric terrestial gravitational wave detectors is expected to be limited by quantum noise and quantum back-action effects in the peak sensitivity frequency band. This limit to acheivable sensitivity, called the standard quantum limit (SQL) is due by the quantum noise of the light in the interferometer. This is essentially the same situation as the Heisenberg microscope, where measurement of the position of a test mass by measuring the phase of light reflected from the mass causes perturbations of the masses momentum due to the radiation pressure of the incindent photons. We have performed experiments to demonstrate classical noise cancellation via opto-mechanical coupling and are beginning preliminary SQL interferometer work. Once the SQL has been observed we aim to demonstrate techniques to supress the effects of quantum noise for improving the sensitivity of gravitational wave detectors.
Squeezing at GW signal frequencies (10Hz-10kHz) could be used to reduce quantum noise in GW detectors. The quantum noise cancellation experiments on an SQL interferometer will also require locked squeezing at acoustic frequencies. Until recently squeezing had not been demonstrated below 50kHz. In early 2004 we demonstrated squeezing down to 200Hz using a degenerate Optical Parametric Oscillator. In collaboration with the ANU Quantum Optics group, the Quantum Measurement Group at MIT and Hannover University we are developing techniques and technology that will hopefully yield an unprecedented 10dB at 100 Hz. For more information please contact Sheon Chua.
In conjunction with LIGO, ACIGA is the only group outside the US providing code for the mission-critical LIGO Data Analysis System, LDAS. Our contributions range from atomic signal processing operations to sophisticated data conditioning tools, such as output-error model line prediction and removal, that will be used to prepare data for the stochastic, burst and other search codes. We also perform independent simulations of global networks of cooperative gravitational observatories to determine how to optimise future configurations.
This research has included the demonstration of a Variable Reflectivity Signal Mirror (VRSM) with Polarisation Control and an experimental demonstration of Resonant Sideband Extraction. More information will be available soon.
The High Power Test Facility in Gingin will study the effect of high circulating optical power on test mass coatings and substrates of a suspended cavity. To enable this study, longitudinal locking of a high power laser to the cavity, and automatic alignment to the cavity optical axis are required. We have designed and implemented the optical system and electronics for the feedback control for the Facility in Gingin. Longitudinal control is achieved with the Pound-Drever-Hall frequency locking technique, while autoalignment employs a technique involving wavefront sensing.
The detection of Gravitational Waves (GW) require unprecedented sensitivity. Over the last two decades, a host of techniques in various aspects of instrumentation has been developed to achieve this goal. These include techniques in longitudinal and alignment control; Fabry-Perot technologies; acoustic, mechanical and thermal isolation, laser stabilisation, and laser spectroscopy. At the Centre for Gravitational Physics, we have been actively exploring ways to transfer some of these technologies into promising industrial and commercial applications. Over the past year, we have had landmark successes in applying GW detection techniques in fibre-optic sensing (see below for example), as well as advanced spectroscopy for laser stabilisation. For more information contact Jong Chow.
Early in 2007 the Centre for Gravitational Physics at the ANU began a $1.2m ARC linkage project with a geophysical services company, Benthic Geotech Pty Ltd, to develop an all-optical, fibre acoustic array for the oil and gas industry. The multidiscipline team has combined sensitive digital interferometric techniques with conventional fibre technology, to create a world class multiplexed, all-optical array. The project is on track to deliver a multiplexed all-optical geophone array with sensitivity in the tens of nano-g, down to infrasonic frequencies. For more information contact Ian Littler.
