LIGO Seminar

Squeezed states of light will offer an important future contribution to improving the sensitivity of interferometric gravitational wave detectors. As these detectors reach their design requirements and beyond, vacuum fluctuations at their dark ports will drive noise that will ultimately limit their sensitivity over the broader detection band. Higher laser power can be used to improve the signal to noise of quantum shot noise. However, in future gravitational wave detectors, limits to maximum attainable circulating laser power necessitate other approaches to addressing this problem. Squeezing to pre-correlate vacuum photons before entering the instrument is one way to improve on noise contributions without increase circulating power requirements.

The detection and application of squeezed vacuum to gravitational wave interferometers is particularly degraded by loss. In this seminar, I will present results and findings from a recently completed Australian National University prototype: a Glass cavity Optical Parametric Oscillator (GOPO) for the generation of vacuum squeezing under vacuum using a dually resonant bowtie configuration. The potential for producing squeezing directly within the vacuum envelope of LIGO offers a way of reducing loss from coupling squeezed states from outside the LIGO vacuum system. Scattered light is another issue for squeezed light injection, with the potential to couple environmental noise through parasitic interferences. Scattering along the input coupling path to the interferometer can be greatly reduced by Faraday isolators at the cost of degradation of squeezing by loss.

In this seminar I will also present a demonstration of a novel path modulation technique to frequency upshift scattered light contributions out of the detection band of interest whilst recovering vacuum squeezing in the audio band.

We plan to broadcast this talk using SeeVogh.