A Broadband Signal Recycling Scheme for Approaching the Quantum Limit from Optical Losses

TL;DR

This paper proposes a broadband signal recycling scheme using an active optomechanical filter to approach the quantum limit in gravitational-wave detectors, offering potential sensitivity improvements despite increased thermal noise susceptibility.

Contribution

It introduces a novel broadband signal recycling scheme with an active optomechanical filter, enhancing quantum-limited sensitivity compared to previous white light cavity methods.

Findings

Potential to approach quantum-limited sensitivity with reduced optical losses

Demonstrates advantages over previous white light cavity schemes

Identifies increased thermal noise as a key challenge

Abstract

Quantum noise limits the sensitivity of laser interferometric gravitational-wave detectors. Given the state-of-the-art optics, the optical losses define the lower bound of the best possible quantum-limited detector sensitivity. In this work, we come up with a broadband signal recycling scheme which gives potential solution to approaching this lower bound by converting the signal recycling cavity to be a broadband signal amplifier using an active optomechanical filter. We will show the difference and advantage of such a scheme compared with the previous white light cavity scheme using the optomechanical filter in [Phys.Rev.Lett.115.211104 (2015)]. The drawback is that the new scheme is more susceptible to the thermal noise of the mechanical oscillator.