  Thermal fluctuations of different origin in the substrate and in the coating
of optical mirrors produce phase noise in the reflected wave. This noise
determines the ultimate stabilization capability of high-Q cavities used as a
reference system. In particular this noise is significant in interferometric
laser gravitational wave antennas. It is shown that simple alteration of a
mirror multilayer coating may provide suppression of phase noise produced by
thermorefractive, thermoelastic, photothermal and thermoradiation induced
fluctuations in the coating.
