Abstract

Ion-beam milling of optical coatings and concurrent measurement of transmittance or reflectance has been shown to be a useful destructive characterization technique [1][2]. As the coating is gradually removed, an optical signal is obtained that reproduces the monitoring signal in reverse. During operation of this technique almost invariably an initial rapid change in signal level was detected, which was quite uncharacteristic of the gradual sputtering of the multilayer as a whole. This rapid change occurred even at flux levels that were established as too low to cause perceptible sputtering in a reasonable time. The effect was found to be due to rapid desorption of moisture within the coatings.

© 1984 Optical Society of America