Observing the optical modes of parametric instability

TL;DR

This paper presents a real-time imaging technique for observing optical modes of parametric instability in laser cavities, which is crucial for controlling PI in gravitational wave detectors.

Contribution

The authors introduce the first method to image optical modes of PI in real time, aiding active control in high-power laser interferometers.

Findings

First images of optical modes of PI obtained

Technique enables real-time amplitude and phase imaging

Potential for improved active control strategies

Abstract

Parametric Instability (PI) is a phenomenon that results from resonant interactions between optical and acoustic modes of a laser cavity. This is problematic in gravitational wave interferometers where the high intra-cavity power and low mechanical loss mirror suspension systems create an environment where three mode PI will occur without intervention. We demonstrate a technique for real time imaging of the amplitude and phase of the optical modes of PI yielding the first ever images of this phenomenon which could form part of active control strategies for future detectors.