Fabrication and measurement of optics for the laser interferometer gravitational wave observatory

The manufacture and testing of high-precision optical surfaces for the Laser Interferometer Gravitational Wave Observatory is described. Through the use of carefully shaped polishing laps made of a nondeformable polymer material coated on a rigid base, surfaces 250 mm in diameter with radii of curvature between 7 and 15 km were polished to an accuracy of several hundred meters in the curvature and with low values of waviness and microroughness. Metrology instrumentation used to measure the optical finish included a large-aperture digital interferometer calibrated to nanometer-level accuracy for measurements of curvature, astigmatism, and waviness and an interference microscope for measurements of microroughness. The power spectra of the data from both instruments were in good agreement.