Heating by optical absorption and the performance of interferometric gravitational-wave detectors

The ultimate sensitivity of interferometric gravitational-wave detectors requires extremely high light powers sensing the separation of test masses. Absorption of light at the optical components causes wave-front distortions via the thermally deformed substrates or via thermal lensing. The performance of thermally distorted interferometers is treated quantitatively, and the two schemes for increasing the optical path, the delay-line and Fabry-Pérot methods, are compared.