Zerodur Polishing Process for High Surface Quality and High Efficiency*

Zerodur [1] is a glass-ceramic composite of technical importance in applications where temperature instabilites influence optical and mechanical performance. For example, it has been extensively used for earthbound and spaceborne telescope mirror substrates. Polished Zerodur surfaces of high quality have been required for laser gyro mirrors. Recent studies of optics in high power laser applications have indicated that the polished surface quality of substrates affects performance of high reflection coatings [2,3]. Thus, the interest in improving Zerodur polished surface quality has become more general. Beyond eliminating subsurface damage, high quality surfaces are produced by reducing the amount of hydrated material redeposited on the surface during polishing [4]. With the proper control of polishing parameters, such surfaces exhibit roughnesses of <1Å rms. It has been our goal to study Zerodur polishing to recommend a high surface quality polishing process which could be easily adapted to standard planetary continuous polishing machines and spindles. This summary contains information on a polishing process developed at LLNL which reproducibly provides high quality polished Zerodur surfaces at very high polishing efficiencies. A continuation of work is planned to more fully understand the polishing behaviors.