Radiation Pressure Induced Instabilities in Laser Interferometric Detectors of Gravitational Waves

TL;DR

This paper investigates how radiation pressure at high laser powers causes mirror displacements and energy gain in gravitational wave detectors, potentially impacting their optimal operation.

Contribution

It reveals the role of time delay in radiation pressure effects, leading to mirror instabilities and energy gain, which are critical for next-generation interferometers.

Findings

Mirrors gain energy and swing with increasing amplitude.

Time delay causes the displacement and energy gain effects.

Implications for the operation of VIRGO and LIGO detectors.

Abstract

The large scale interferometric gravitational wave detectors consist of Fabry-Perot cavities operating at very high powers ranging from tens of kW to MW for next generations. The high powers may result in several nonlinear effects which would affect the performance of the detector. In this paper, we investigate the effects of radiation pressure, which tend to displace the mirrors from their resonant position resulting in the detuning of the cavity. We observe a remarkable effect, namely, that the freely hanging mirrors gain energy continuously and swing with increasing amplitude. It is found that the `time delay', that is, the time taken for the field to adjust to its instantaneous equilibrium value, when the mirrors are in motion, is responsible for this effect. This effect is likely to be important in the optimal operation of the full-scale interferometers such as VIRGO and LIGO.