High-frequency Analysis of Diffraction from Baffes in Gravitational Wave Interferometers

Interferometric gravitational wave detectors rely on laser beam interference to measure the small distortions of space-time due to a gravitational wave. The extreme sensitivity of these detectors make them very vulnerable to noise from any spurious sources, including vibrations from the detector beam-pipe walls. Irises, or baffles, are accordingly placed along the laser beam path to intercept stray rays which may couple with the detector walls. These baffles are themselves possible sources of noise due to diffraction from their edge. In this paper an incremental theory of diffraction approach is presented for the accurate analysis of several baffle geometries, aimed at minimizing diffracted rays coupling back to the detector laser beam.