Multi-color Cavity Metrology

TL;DR

This paper introduces a multi-color cavity metrology technique that enhances the control and stability of gravitational wave detectors by using harmonically related external fields, significantly reducing seismic disturbances.

Contribution

The paper presents a novel hierarchical control method using multi-color fields to improve lock acquisition and stability in gravitational wave interferometers.

Findings

Reduces seismic disturbance effects by four orders of magnitude.

Enhances the reliability and duty cycle of gravitational wave detectors.

Discusses potential to surpass quantum and thermal noise limits.

Abstract

Long baseline laser interferometers used for gravitational wave detection have proven to be very complicated to control. In order to have sufficient sensitivity to astrophysical gravitational waves, a set of multiple coupled optical cavities comprising the interferometer must be brought into resonance with the laser field. A set of multi-input, multi-output servos then lock these cavities into place via feedback control. This procedure, known as lock acquisition, has proven to be a vexing problem and has reduced greatly the reliability and duty factor of the past generation of laser interferometers. In this article, we describe a technique for bringing the interferometer from an uncontrolled state into resonance by using harmonically related external fields to provide a deterministic hierarchical control. This technique reduces the effect of the external seismic disturbances by four orders of magnitude and promises to greatly enhance the stability and reliability of the current generation of gravitational wave detector. The possibility for using multi-color techniques to overcome current quantum and thermal noise limits is also discussed.