Application of power spectral density to specify optical super-smooth surfaces

The power spectral density (PSD) is an appropriate way to specify the optical super-smooth surfaces. The reasons to characterize the super-smooth surfaces using the PSD are discussed. Some super-smooth mirror substrates obtained by different process methods are measured with an atomic force microscope (AFM). The measured optical surfaces are characterized by the PSD. The result shows that the PSD is of great guidance to the selection of manufacturing methods and process improvement.