Negative optical inertia for enhancing the sensitivity of future gravitational-wave detectors

TL;DR

This paper proposes using negative optical inertia via double optical spring to enhance gravitational-wave detector sensitivity, surpassing the Standard Quantum Limit over broad frequencies through signal amplification.

Contribution

It introduces a novel scheme employing negative optical inertia with double optical spring to improve detector sensitivity beyond the SQL.

Findings

The negative optical inertia effect can be achieved with appropriate parameters.

This scheme can surpass the Standard Quantum Limit over a broad frequency band.

Feasibility is demonstrated for implementation in future detectors.

Abstract

We consider enhancing the sensitivity of future gravitational-wave detectors by using double optical spring. When the power, detuning and bandwidth of the two carriers are chosen appropriately, the effect of the double optical spring can be described as a "negative inertia", which cancels the positive inertia of the test masses and thus increases their response to gravitational waves. This allows us to surpass the free-mass Standard Quantum Limit (SQL) over a broad frequency band, through signal amplification, rather than noise cancelation, which has been the case for all broadband SQL-beating schemes so far considered for gravitational-wave detectors. The merit of such signal amplification schemes lies in the fact that they are less susceptible to optical losses than noise cancelation schemes. We show that it is feasible to demonstrate such an effect with the {\it Gingin High Optical Power Test Facility}, and it can eventually be implemented in future advanced GW detectors.