Optical design of a high power mode-cleaner for AIGO

Laser beam geometry variations such as beam jitter and frequency fluctuations are a critical source of noise in the output signal of a laser interferometer gravitational wave detector. In order to minimise this noise a resonant vibration isolated optical filter or mode-cleaner is required. For advanced gravitational wave detectors such a mode-cleaner is required to be able to handle transmitted power similar to 100 W, and an internal circulating power of 45 kW. This paper addresses the design requirements of such a mode-cleaner. We characterise the mode-cleaner requirements and the effects of high laser power on the optics and its consequence on the suppression of higher order modes.