Experimental demonstration of a Displacement noise Free Interferometry scheme for gravitational wave detectors showing displacement noise reduction at low frequencies

TL;DR

This paper experimentally demonstrates a novel interferometry scheme that significantly reduces displacement noise in gravitational wave detectors, especially at low frequencies, by using a detuned Fabry-Perot cavity to isolate signals.

Contribution

It provides the first experimental validation of a displacement noise free laser interferometry scheme for gravitational wave detection.

Findings

Displacement noise was reduced by a factor of 60 in the 10 Hz to 10 kHz range.

The scheme isolates gravitational wave signals from displacement noise using cavity signal combination.

Experimental results confirm the feasibility of the proposed noise reduction method.

Abstract

This paper reports an experimental demonstration of partial displacement noise free laser interferometry in the gravitational wave detection band. The used detuned Fabry-Perot cavity allows the isolation of the mimicked gravitational wave signal from the displacement noise on the cavities input mirror. By properly combining the reflected and transmitted signals from the cavity a reduction of the displacement noise was achieved. Our results represent the first experimental demonstration of this recently proposed displacement noise free laser interferometry scheme. Overall we show that the rejection ratio of the displacement noise to the gravitational wave signal was improved in the frequency range of 10 Hz to 10 kHz with a typical factor of 60.