Different approaches to improve the wavefront of low-loss mirrors used in the Virgo gravitational wave antenna

Several experimental techniques have been developed and tested to improve the wavefront of low-loss mirrors used in the Virgo program. The most elaborated one, called ‘Corrective Coating Treatment’, allows us to reach an R.M.S. wavefront of 1.5 nm at 633 nm on 100-mm diameter high reflectivity mirrors. The next development will be to make the same correction at 1064 nm, wavelength of the Virgo interferometer, on very large silica substrates 350 mm diameter.. q1999 Elsevier Science B.V. All rights reserved