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.


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.



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,, `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)