Power spectral density analysis of optical substrates for gravitational-wave interferometry.
The power spectral density of surface-relief variations on polished optical surfaces across microscopic through to macroscopic spatial scales is calculated from measurements on substrates that are being produced for the Laser Interferometer Gravitational-Wave Observatory (LIGO). These spectra give a guide to the scattering properties of the surface, which in turn critically influence the performance of LIGO. Measurements obtained by use of a full-aperture interferometer and an interference microscope with two different objectives are combined to produce one-dimensional power spectral density representations of the surfaces across spatial frequencies ranging from 0.1 to 8000 cm(-1). These measurements from different instruments are in good agreement with an analytic power spectrum that varies as nu(-1.5), where nu is the spatial frequency. Some anomalies in the power spectral density spectra can be related to aspects of the polishing process.
Walsh
C J
CJ
Division of Telecommunications and Industrial Physics, Commonwealth Scientific and Industrial Research Organisation, PO Box 218, Lindfield 2070, Australia. chris.walsh@tip.csiro.au
Leistner
A J
AJ
Oreb
B F
BF