Tip tilt suspensions
Second generation advanced gravitational wave detectors, such as Advanced LIGO, are in the process of being installed and constructed. These detectors consists of suspended optics forming a Michelson interferometer with fabry-perot cavities in each arm. The gravitational wave readout is done via ‘DC-readout’, which utilises suspended photo detectors behind a small fabry-perot cavity. This smaller cavity is used as a mode-cleaner, removing any stray light which do not contribute to the gravitational wave signal. Additional mode-matching and beam steering is required to direct the optical beam from the output of the large suspended interferometer into the smaller mode-cleaning cavity. These steering mirrors need to have isolation in 6 degrees of freedom, as well as being able to provide active beam steering for an active control and feedback system.
These suspended steering mirrors, the Tip-Tilt Suspensions (or Tip-Tilts for short), are designed and tested by the ANU Centre for Gravtational Physics. In partnership with Advanced LIGO, the ANU CGP is constructing and delivering multiple sets for incorporation into these second generation gravitational wave detectors.