INTRODUCTION
The detection of gravitational waves started a new era of gravitational wave astronomy. It is the fastest growing field of astronomy as we discover more and more sources of gravitational waves across the universe. The improvement of detectors, and development of new detectors is crucial for the field to continue to advance.
 
Gravitational wave instrumentation research in Australia began at UWA, where we pioneered one of the world’s first high sensitivity resonant mass gravitational wave detectors. Today our research is focused on the development of advanced techniques to improve the sensitivity of gravitational wave detectors. Our team is part of the LIGO Scientific Collaboration (LSC) and contributed some key technologies towards the first detection of the gravitational waves. We are part of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav). Our research areas include precision measurement, quantum optics, high optical power suspended cavities, advanced vibration isolation techniques and control systems. The research is exploring exciting new physics phenomena and techniques that have applications beyond gravitational wave detectors, including quantum measurement technologies and airborne exploration devices.
 
We have exciting projects suitable for PhD and Master students. The GW experimental group is part of the national ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav). We are a vibrant, friendly and international group.  We welcome highly motivated students to join us.
 
THE PROJECTS:

1.     Optical Springs and Optical Dilution —Beating the Standard Quantum Limit

A specific area of research explores new concepts in amplification and measurement based on the interactions between optical photons and acoustic phonons. Devices based on this frontier of measurement technology require very low loss opto- mechanical systems in which light and sound (or mechanical vibration) interact very strongly without being contaminated by thermal fluctuations.
 
We are testing and inventing many novel opto-mechanical resonators, including nano- scale optical pendulums made from synthetic crystalline mirrors, others made from photonic and phononic crystals, and some made from ultrapure crystals of quartz. With these devices we observe and predict many new phenomena such as optical springs, optical dilution, optomechanically induced transparency, frequency dependent optical squeezing, negative dispersion and white light resonance. The phenomenon of white light resonance (that violates the normal theory of resonance) offers enormous opportunities for improving the sensitivity of gravitational wave detectors, which in turn will allow new astrophysical phenomena to be explored.
 
2.      High optical power experiments

We operate the large High Optical Power Facility at Gingin in beautiful bushland 80km from UWA. Here we study high optical power related phenomenon such as thermal lensing and parametric instability in gravitational wave detectors. We resonate laser light down 80m long optical cavities. The facility uses high performance vibration isolation systems and advanced digital control systems to study the physics of gravitational wave detectors.
 
Parametric instability (PI) is a phenomenon due to the interaction between the optical photons and phonons inside the large test mass mirrors. When certain conditions are met, the optical modes will resonantly drive the test mass acoustic mode via radiation pressure force. Leading to exponential ring up of the acoustic mode and thus disrupting the stable operation of gravitational wave detectors. Techniques developed by us enabled the LIGO gravitational wave detectors in the USA to be stabilised, thus enabling the first detection of gravitational waves in 2015.
 
Very high optical power warms up mirrors and changes their shape. A new project is harnessing the parametric instability phenomenon to measure acoustic vibrations of the mirrors and use the data to enable precise measurement of their temperature distribution. This in turn allows the mirror shape to be estimated and corrected by shining a pattern of CO2 laser light onto the mirrors.
 
3.      Silicon optical cavity for next generation detectors

There are worldwide effort to develop techniques for the next generation (3rd generation—3G) gravitational wave detectors with optical cavity arm lengths up to 40km. Silicon is one of the candidates for the 3G detectors test masses. It is transparent at 2 microns wavelength. We are currently developing the world’s first large scale silicon optical cavity and associated silicon optics to evaluate its performance at 2 microns wavelength.
 
The large scale silicon optical cavities use newly developed 2 micron laser technology, and mirrors made from crystalline films of gallium arsenide and aluminium gallium arsenide. We offer many projects that will investigate the quality of the crystalline mirrors, and the mechanical, thermal and optical performance of the high optical power cavity.  All the results will contribute to the development of the future detectors.
 
4.      Engineering-oriented projects 

Gravitational wave research requires engineering techniques beyond the level of normal engineering practice. In every area we have exciting projects that will extend your skills and give experience at the frontiers of current expertise.
  • We build novel vibration isolators using advanced materials such as glassy metals, that have performance measured in hundreds of decibels.
  • We use seismometers to measure and control seismic noise and ground deformation created by wind forces.
  • We aim to measure incoming seismic waves before they arrive at our instruments.
  • We build tilt sensors and feedback systems to actively suppress the floor tilts created by people walking.
  • We use our skills to build vibration isolation systems for improving the performance of airborne exploration instruments.
  • We build digital control systems using advanced control technology to make adaptive and intelligent controllers for maintaining our optical cavities and vibration isolators aligned and positioned at the sub-nanometer level
  • Another project focuses on improving the vacuum in our 80meter long vacuum pipes and understanding the effects that influence the residual gas content.

Scholarships:
UWA Postgraduate Research Scholarships are available for excellent students.
 
Group Contact:
Prof. Chunnong Zhao (chunnong.zhao@uwa.edu.au)
Prof. Li Ju (li.ju@uwa.edu.au)
http://www.gravity.uwa.edu.au/
​https://www.ozgrav.org/