We observed the effect of radiation pressure on the angular sensing and control system of the Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometer's core optics at LIGO Hanford Observatory. This is the first measurement of this effect in a complete gravitational wave interferometer. Only one of the two angular modes survives with feedback control, since the other mode is suppressed when the control gain is sufficiently large. We developed a mathematical model to understand the physics of the system. This model matches well the dynamics that we observe.
@article{arxiv.0909.0010,
title = {Angular instability due to radiation pressure in the LIGO gravitational wave detector},
author = {Eiichi Hirose and Keita Kawabe and Daniel Sigg and Rana Adhikari and Peter R. Saulson},
journal= {arXiv preprint arXiv:0909.0010},
year = {2015}
}