Effects of vacuum exposure on stress and spectral shift of high reflective coatings.

Coating stress and spectral shift are affected by changing from ambient to vacuum environments. This change can affect optical systems that are aligned in air and used in a vacuum or in a dry environment. Spectral shifts up to 3% and reflected wave-front changes up to 0.35 waves peak to valley are reported for conventional electron-beam deposition and ion-assisted deposition. Alternatively, ion-beam sputtered coatings have virtually no changes between different pressure environments.