This project is to create ultralow loss cavity optomechanics through optical dilution for use in white light cavity to reduce quantum noise in gravitational wave detectors.

Optical springs:  towards measurements below the standard quantum limit

We will be fabricating low noise resonators with international partners in Austria, Taiwan, Holland and France.  These resonators are designed to have a macroscopic mass suspended with nanoscale suspension, in order to achieve extremely low mechanical coupling. We can then use radiation pressure to achieve thermal noise free optomechanics.

Project

Optical springs are created by radiation pressure forces in optical cavities. This radiation pressure allows the stiffness and resonant frequencyFigure 1. An optical cavity with a %u201Ccat-flap%u201D resonator mirror design (the purple part is the coated mirror) of a mechanical resonator to be raised without adding extra mechanical coupling. Current techniques have managed to achieve a quality factor enhancement of approximately 50-fold. We aim to optimise the optical stiffening process by using a resonator with an extremely small mechanical stiffness provided by nanoscale suspension, thus allowing the majority of the restoring force to be provided by radiation pressure. We aim to eventually achieve a Q-factor enhancement of over 1000, with an ultimate Qf product of more than 1013. This is an extremely challenging task, which requires expertise in optical experimentation techniques, cavity locking and technical noise mitigation.

An opto-mechanical system as shown in Figure 1 has been designed.  The cat-flap resonator, shown in Figure 2, is trapped in a high power laser beam which provides the radiation pressure restoring force. This resonator is a highly customised component which requires extensive modelling, design and specialised fabrication. The project involves modelling this resonator to minimise unwanted mechanical modes in the bulk, suspension and dielectric mirror coatings, as well as losses through clamping, recoil and other means. The first iteration of the experiment aims to achieve an extremely high quality factor with the cat-flap resonator, while the second iteration aims to integrate this design into an optomechanical filter in an interferometer.

A working gravitational wave detector filter cavity has the potential of measuring macroscopic objects with resolution better than the “standard quantum limit” predicted by naïve application of quantum mechanics. This offers a new technique for improving gravitational wave sensitivity for signals in the frequency range of 100 Hz to 10 kHz. Successful trapping of the cat-flap resonator also opens new areas in macroscopic quantum mechanics by obtaining extremely high quality factors at relatively low frequencies, compared to other quantum optomechanics experiments.

Eligibility

Applicants should have excellent academic records and preferably an internationally peer reviewed paper. General UWA PhD entrance requirements can be found on the Future Students website.

Suggested reading

• Blair, D., Ju, L., Zhao, C., Wen, L., Chu, Q., Ma, Y., Page, M., Blair, C., Fang, Q., Miao, H., 'The development of ground based gravitational wave astronomy and opportunities for Australia-China collaboration', International Journal of Modern Physics A, 30, 28-29, pp. 1545019. (2015)
• Blair, D., Ju, L., Zhao, C.N., Wen, L.Q., Miao, H.X., Cai, R.G., Gao, J.R., Lin, X.C., Liu, D., Wu, L.A., Zhu, Z.H., Hammond, G., Paik, H.J., Fafone, V., Rocchi, A., Blair, C., Ma, Y.Q., Qin, J.Y., Page, M, 'The next detectors for gravitational wave astronomy', Science China: Physics, Mechanics and Astronomy, 58, 12, pp. 1-34.  (2015)
• Page, M., Ma, Y., Blair, D., Zhao, C., Ju, L., Pan, H.-W., Chao, S., Mitrofanov, V., Sadeghian, H., ‘Towards thermal noise free optomechanics’, arxiv.org/abs/1602.03621 (refereed version currently in submission process to Journal of Physics D: Applied Physics)
• Miao, H., Ma, Y., Zhao, C., Chen, Y., ‘Enhancing the bandwidth of gravitational wave detectors with unstable optomechanical filters’, Physical Review Letters, 115, 211104 (2015)
• Blair, D.G., Howell, E.J., Ju, L., Zhao, C., Advanced Gravitational Wave Detectors, Cambridge University Press, USA (2012)
• Corbitt, T., Chen, Y., Innerhofer, E., Müller-Ebhardt, H., Ottaway, D., Rehbein, H., Sigg, D., Whitcomb, S., Wipf, C., Mavalvala, N., ‘An All-Optical Trap for a Gram-Scale Mirror’, Physical Review Letters, 98, 150802 (2007)

This project is to investigate methods for suppressing and control parametric instabilities in very high power optical cavities in advanced gravitational wave detectors.

Control of Parametric Instabilities 

This project investigates control strategies and novel uses for opto-mechanical interactions under the extreme conditions required to create parametric instability.

Project

The first detection of gravitational waves at Advanced LIGO was achieved with a circulating power of 100kW. One of the challenges to reach design sensitivity is to increase the circulating optical power inside the detectors to the design power of 800 kW.  A fundamental limitation on increasing the optical power is three-mode parametric instability, in which the carrier laser power is resonantly scattered into transverse optical modes by acoustic modes in the fused silica test masses. This causes exponential build-up of acoustic modes severely impacting the operation of the detector. Parametric instability in a free optical cavity was first observed in a small scale table top experiment in a UWA lab. 

Then we observed parametric instability in our 80m suspended cavity at the Gingin High Optical Power Facility.  Shortly afterward, the gravitational wave observatories in the USA also observed parametric instability in the 4km interferometer detector.  It is of importance we find effective control strategies to maintain stability within a cavity.  These interactions have also been demonstrated as precise metrology tools.  Students working on this project will work at the Gingin High Optical Power Test Facility and if required may travel to the gravitational wave detector sites worldwide.

Eligibility

Applicants should have excellent academic records and preferably an internationally peer reviewed paper. General UWA PhD entrance requirements can be found on the Future Students website.

Suggested reading

• Zhao, C., Ju, L., Fang, Q., Blair, C., Qin, J., Blair, D., Degallaix, J., Yamamoto, H., 'Parametric instability in long optical cavities and suppression by dynamic transverse mode frequency modulation', Physical Review D - Particles, Fields, Gravitation and Cosmology, 91, 9, pp. 092001-1 - 092001-8. (2015)
• Chen, X., Zhao, C., Danilishin, S., Ju, L., Blair, D., Wang, H., Vyatchanin, S.P., Molinelli, C., Kuhn, A., Gras, S., Briant, T., Cohadon, P.F., Heidmann, A., Roch-Jeune, I., Flaminio, R., Michel, C., Pinard, L., 'Observation of three-mode parametric instability', Physical Review A - Atomic, Molecular, and Optical Physics, 91, pp. 1-9. (2015)
• M. Evans, et.al., 'Observation of Parametric Instability in Advanced LIGO', Physics Review Letters, 114, 161102 ' 23 Apr (2015)
• Danilishin, S.L., Vyatchanin, S.P., Blair, D.G., Ju, L., Zhao, C., 'Time evolution of parametric instability in large-scale gravitational-wave interferometers', PHYSICAL REVIEW D, 90, 12, pp. 122008. (2014)

The advance of the next generation of airborne geophysical tools can uncover the deep Earth. State of the art gravity gradiometers and magnetometers are currently limited by aircraft motion and turbulence. In collaborating with industries, this project is to develop new vibration isolators and algorithms which will allow these instruments to image through increasing amounts of cover.

We are looking for hands-on undergrads and PhD students who are interested in exploration technology, mechanical systems and finite element modelling to participate in a University-Industry collaboration project.

Using Magnetometer based upon opto-acoustic sensors.

New technologies based on vibration isolation, innovative sensor concepts and low noise electronics can enable airborne surveys to discover minerals at greater depths.

Eligibility criteria

Applicants should have excellent academic records and preferably an internationally peer reviewed paper. General UWA PhD entrance requirements can be found on the Future Students website.

Suggested reading

Sunderland, A., Blair, D.G., Ju, L., Golden, H., Torres, F., Chen, X., Lockwood, R., Wolfgram, P. 'High performance rotational vibration isolator', Review of Scientific Instruments, 84, 10, pp. 105111-1 - 105111-6. (2013)

The PhD student will develop new curriculum materials with the help of physicists and will work with a few selected school groups.

Measuring the effectiveness of teaching Einsteinian physics at an early age

The premise of this PhD project is that it is possible and, indeed, beneficial to begin to teach the concept of Einsteinian Physics at an early age.

Project

Since early in the twentieth century physicists have known that the geometry of the universe is the geometry of curved space, and that the quantum reality of the universe is weird and extraordinary. Both of these topics are seen as being "difficult" and have minimal coverage in school science curricula. Curved space gives rise to surprising phenomena like the effect of gravity on clocks, and errors in standard geometrical formulae. Despite knowing that Newtonian physics is strictly incorrect, the teaching of physics at school has remained Newtonian, with little recognition given to the discoveries which are now 100 years old, and which are essential for understanding space engineering and modern electronics. This project will test the following:

• The ability of primary school students to understand curved space geometry, and to understand that flat space geometry is a special case, but one which for most purposes is a very useful approximation.
• The ability of secondary students to understand basic concepts of both quantum mechanics and Einstein's relativity, while also understanding that Newtonian physics is a useful approximation.
• Whether this new approach to teaching physics helps to improve student attitudes to physics by presenting physics as a frontier of learning with many mysteries and problems still to be solved.

Eligibility

Applicants should have excellent academic records and preferably an internationally peer reviewed paper. General UWA PhD entrance requirements can be found on the Future Students website.

Suggested reading

• Pitts, M., Venville, G., Blair, D., Zadnik, M., 'An Exploratory Study to Investigate the Impact of an Enrichment Program on Aspects of Einsteinian Physics on Year 6 Students', RESEARCH IN SCIENCE EDUCATION, Online, pp. 26pp. (2014)
• Venville, G., Blair, D., Coward, D., Deshon, F., Gargano, M., Gondwe, M., Heary, A., Longnecker, N., Pitts, M., Zadnick, M. 2012, 'Research informed science enrichment programs at the Gravity Discovery Centre', TEACHING SCIENCE, 58, 1, pp. 33-39. (2012) Detail
• Hendry, M.A., Bradaschia, C., Audley, H., Barke, S., Blair, D.G., Christensen, N.L., Danzmann, K.V., Freise, A., Gerberding, O., Knispel, B., Lieser, M., Mandel, I., Moore, T.A., Stuver, A.L., Whiting, B.F., 'Education and public outreach on gravitational-wave astronomy', General Relativity and Gravitation, 46, 8, pp. 1-11. (2014)

This project uses the UWA 1m robotic Zadko Telescope to perform the following transient sky science:

• Search for optical transients in coincidence with gravitational wave candidates triggered from LIGO
• Earth orbiting space debris identification and tracking
• Multi-messenger astronomy: optical observations combined with the ANTARES neutrino detector and the gravitational wave observatory LIGO to search for coincident transient phenomena

Projects involve collaborators in France.

Project

During LIGO’s third observing run, the LIGO-Virgo Scientific Collaboration (LSC) have issued alerts about gravitational wave signals they have detected to the astronomy community in close to real time. Only five groups around the world take part in this ‘online’ search, where data from the LIGO and Virgo instruments is processed on-the-fly and alerts are issued within seconds of the data being processed.

One of the online search pipelines is the SPIIR (Summed Parallel Infinite Impulse Response) pipeline, developed and operated by scientists at UWA. SPIIR is one of the fastest of the five online pipelines. As the LSC prepares for O4, the SPIIR team is focussing on sending alerts about gravitational waves up to 30 seconds before objects like binary neutron stars finally merge. This will enable astronomers to catch neutron star mergers as they happen, rather than several hours later, and will reveal important insights about the physics of these objects.

As a student working with the SPIIR group, you will use the pipeline to learn more about the astrophysics of gravitational wave sources, and you will be responsible for running the pipeline in its ‘online’ configuration to send alerts about gravitational waves to the astronomy community, and using the pipeline to characterize the properties of merging compact objects.

Eligibility

Applicants should have excellent academic records and an undergraduate degree in physics or astronomy. General UWA PhD entrance requirements can be found on the Future Students website.

Suggested reading

LIGO website
GCN Notices
Hooper et al. 2012
Dr Qi Chu’s PhD thesis
Dr Shaun Hooper’s PhD thesis

Project

As we observe more and more compact object mergers (binary black hole mergers, binary neutron star mergers and neutron star-black hole mergers), we can begin to use statistics to probe many of the properties of the population of these objects.

Just one such key question we can begin to ask: ‘Is the population of binary black hole mergers distributed isotropically in the Universe?  Similar analysis of the distribution of Gamma-Ray bursts uncovered their cosmological origin and answers many important questions about the origin of these events, including their connection to host galaxies, the properties of their host galaxies and the different mechanisms that power short and long GRBs.

In this project, you will use Bayesian inference and develop methods to find answers to questions like ‘Are binary black holes distributed isotropically in the Universe?

Project

In 2017, a binary neutron star merger detected via gravitational waves was also observed across the electromagnetic spectrum. This event, known as GW170817, opened up many new possibilities for understanding the astrophysics of compact objects.

With a large number of events observed during LIGO’s 3rd observing run, it is now possible to search for any connection between these observed events, and electromagnetic transients. Of particular interest are the mysterious ‘fast radio bur

sts’, which at present have an unknown astrophysical origin.

In this project, you will use gravitational wave data and observations from radio and gamma-ray observatories to investigate the putative connection between short bursts of gravitational waves observed by LIGO and Virgo, fast radio bursts and gamma-ray bursts, both in archival data and in real time during the O4 observing run.

Eligibility

Applicants should have excellent academic records and an undergraduate degree in physics or astronomy. General UWA PhD entrance requirements can be found on the Future Students website.

Suggested reading

Project

Many areas of scientific research are now leveraging computational techniques such as machine learning to solve complex problems. Gravitational wave astronomy is no different, and many areas of gravitational wave discovery include problems that are well-suited to application of machine learning techniques.

Discovery of gravitational waves in time-series data is one such problem. Identification of peaks in signal-to-noise ratio time series and distinguishing between peaks that result from true gravitational wave signals and peaks that result from noise or glitches in the detectors is a problem ideally suited to machine learning applications, where real and simulated detector data can be used to train and verify the chosen algorithms.

Another problem suited to machine learning solutions is the localization of the source of gravitational waves. Accurate localization is a vital part of gravitational wave astronomy as it enables the rapid followup to detect electromagnetic counterparts, such as the kilonova associated with the neutron star merger GW170817. Neural networks can be used to rapidly produce accurate localizations of GW mergers.

Modern computer architecture can be used to reduce the latency (time between receiving GW data and the end of data processing to send alerts of GW events) of pipelines like SPIIR. GPU acceleration has already been used to improve the latency of SPIIR, and further refinement of the algorithms used in the pipeline can further reduce the pipeline’s latency. What’s more, many machine learning algorithms are well suited to implementation on GPU hardware, an ideal project for students interested in both optimization and machine learning.

In this project, you will use machine learning techniques and GPU acceleration to develop new and improved ways to detect and localize GWs in real time.

Eligibility

Applicants should have excellent academic records and an undergraduate degree in physics or astronomy is preferred. Applicants should have skills in programming or an interest in developing their programming skills. General UWA PhD entrance requirements can be found on the Future Students website.

Suggested reading

LIGO website
Chatterjee et al. 2019
Cuoco et al.  2020

For further information on any of the above projects, contact Prof. Linqing WEN linqing.wen@uwa.edu.au and Ruby Chan Ruby.Chan@uwa.edu.au