A kg-mass prototype demonstrator for DUAL gravitational wave detector: opto-mechanical excitation and cooling

TL;DR

This paper presents a prototype for a large-mass gravitational wave detector demonstrating opto-mechanical excitation, cooling, and key effects like back-action reduction, advancing the path toward quantum regime detection.

Contribution

It introduces a kg-scale prototype for gravitational wave detection with novel opto-mechanical effects and active cooling, bridging microscopic experiments to large-mass systems.

Findings

Reduction of local susceptibility via large-area interrogation

Observation of back-action reduction through mode interference

Active radiation-pressure cooling of a kg-scale oscillator

Abstract

The next generation of gravitational wave (gw) detectors is expected to fully enter into the quantum regime of force and displacement detection. With this aim, it is important to scale up the experiments on opto-mechanical effects from the microscopic regime to large mass systems and test the schemes that should be applied to reach the quantum regime of detection. In this work we present the experimental characterization of a prototype of massive gw detector, composed of two oscillators with a mass of the order of the kg, whose distance is read by a high finesse optical cavity. The mechanical response function is measured by exciting the oscillators though modulated radiation pressure. We demonstrate two effects crucial for the next generation of massive, cryogenic gw detectors (DUAL detectors): a) the reduction of the contribution of 'local' susceptibility thanks to an average over a large interrogation area. Such effect is measured on the photo-thermal response thanks to the first implementation of a folded-Fabry-Perot cavity; b) the 'back-action reduction' due to negative interference between acoustic modes. Moreover, we obtain the active cooling of an oscillation mode through radiation pressure, on the described mechanical device which is several orders of magnitude heavier than previously demonstrated radiation-pressure cooled systems.