Extreme-ultraviolet thin-film interference in an Al-Mg-Al multiple-layer transmission filter

Thin-film interference has been observed in the transmittance of a filter consisting of 263.5-nm-thick magnesium with a 32.2-nm-thick aluminum layer on each side. The transmittance, measured by synchrotron radiation, has an oscillatory behavior in the 25-70-nm wavelength range. On the basis of the calculation of the transmittance, the oscillatory behavior results from interference associated with the relatively transmissive magnesium and aluminum layers and the reflection from the oxidized aluminum surface layers. The bandpass performance of magnesium and aluminum layers deposited on a silicon photodiode detector is presented.