Development of signal-extraction scheme for Resonant Sideband Extraction

TL;DR

This paper presents a novel signal-extraction scheme for resonant sideband extraction in advanced gravitational-wave detectors, improving control robustness by using two sets of sidebands to diagonalize the sensing matrix.

Contribution

It introduces a new method employing dual sidebands to achieve a diagonalized sensing matrix for better cavity control in RSE configurations.

Findings

The scheme provides a diagonalized sensing matrix.

It enhances robustness of RSE cavity control.

The method effectively isolates control signals.

Abstract

As a future plan, an advanced gravitational-wave detector will employ an optical configuration of resonant sideband extraction (RSE), achieved with an additional mirror at the signal-detection port of the power-recycled Fabry-Perot Michelson interferometer. To control the complex coupled cavity system, one of the most important design issues is how to extract the longitudinal control signals of the cavities. We developed a new signal-extraction scheme which provides an appropriate sensing matrix. The new method uses two sets of sidebands: one of the sideband components satisfies the critical coupling ondition for the RSE interferometer and reaches the signal-extraction port, and the other sideband is completely reflected by the Michelson interferometer. They provide a diagonalized sensing matrix and enable the RSE control to be robust.